At present, a large number of different methods for cleaning gases from technical pollution have been developed and tested in industry: NOx, SO2, H2S, NH3, carbon monoxide, various organic and inorganic substances.

We describe these basic methods and indicate their advantages and disadvantages.

a) absorption method.

Absorption is the process of dissolving a gaseous component in a liquid solvent. Absorption systems are divided into aqueous and non-aqueous. In the second case, usually low-volatile organic liquids are used. The liquid is used for absorption only once, or it is regenerated, releasing the contaminant in its pure form. Schemes with a single use of the absorber are used in cases where absorption leads directly to the receipt of the finished product or intermediate. Examples include:

production of mineral acids (absorption of SO3 in the production of sulfuric acid, absorption

oxides of nitrogen in the production of nitric acid),

obtaining salts (absorption of nitrogen oxides by alkaline solutions to obtain nitrite-nitrate lye, absorption by aqueous solutions of lime or limestone to obtain

calcium sulfate)

other substances (absorption of NH3 by water to obtain ammonia water, etc.).

Schemes with repeated use of the absorber (cyclic processes) are more widespread. They are used for trapping hydrocarbons, purification of flue gases from thermal power plants from SO2, purification of ventilation gases from hydrogen sulfide by the iron-soda method with the production of elemental sulfur, monoethanolamine gas purification from CO2 in the nitrogen industry.

Depending on the method of creating the phase contact surface, there are surface, bubbling and spraying absorption apparatuses.

In the first group of devices, the contact surface between the phases is a liquid mirror or the surface of a fluid film of liquid. This also includes packing absorbents, in which the liquid flows down over the surface of the packing loaded into them from bodies of various shapes. In the second group of absorbents, the contact surface increases due to the distribution of gas flows into liquid in the form of bubbles and jets. Bubbling is carried out by passing gas through a liquid-filled apparatus or in column-type apparatuses with plates of various shapes.

In the third group, the contact surface is created by spraying a liquid into a mass of gas. The contact surface and the efficiency of the process as a whole is determined by the dispersion

sprayed liquid.

Packed (surface) and bubbling tray absorbers are most widely used. For the effective use of aqueous absorption media, the removed component must be well soluble in the absorption medium and often chemically interact with water, as, for example, in gas purification from HCl, HF, NH3, NO2. For the absorption of gases with lower solubility (SO2, Cl2, H2S), alkaline solutions based on NaOH or Ca(OH)2 are used. Additives of chemical reagents in many cases increase the efficiency of absorption due to the occurrence of chemical reactions in the film. To purify gases from hydrocarbons, this method is used much less frequently in practice, which is primarily due to the high cost of absorbents. The general disadvantages of absorption methods are the formation of liquid effluents and the bulkiness of the instrumentation.

b) Adsorption method.

The adsorption method is one of the most common means of protecting the air basin from pollution. In the United States alone, tens of thousands of adsorption systems have been introduced and successfully operated. The main industrial adsorbents are activated carbons, complex oxides and impregnated sorbents. Activated carbon (AC) is neutral with respect to polar and nonpolar molecules of adsorbed compounds. It is less selective than many other sorbents and is one of the few suitable for use in wet gas streams. Activated carbon is used, in particular, to purify gases from foul-smelling substances, recover solvents, etc.

Oxide adsorbents (OA) have a higher selectivity with respect to polar molecules due to their own inhomogeneous distribution of the electric potential. Their disadvantage is the decrease in efficiency in the presence of moisture. The OA class includes silica gels, synthetic zeolites, aluminum oxide.

The following main methods for implementing adsorption purification processes can be distinguished:

After adsorption, desorption is carried out and the trapped components are recovered for reuse. In this way, various solvents, carbon disulfide in the production of artificial fibers and a number of other impurities are captured.

After adsorption, impurities are not disposed of, but are subjected to thermal or catalytic afterburning. This method is used to clean off gases of chemical-pharmaceutical and paint-and-lacquer enterprises, the food industry and a number of other industries. This type of adsorption treatment is economically justified at low concentrations of pollutants and (or) multicomponent pollutants.

After cleaning, the adsorbent is not regenerated, but subjected, for example, to burial or incineration together with the strongly chemisorbed pollutant. This method is suitable when using cheap adsorbents.

For the desorption of impurities, heating of the adsorbent, evacuation, purging with an inert gas, and displacement of impurities with a more easily adsorbed substance, for example, water vapor, are used. Recently, special attention has been paid to the desorption of impurities by evacuation, and they can often be easily disposed of.

A variety of equipment has been developed for carrying out adsorption processes. The most common adsorbers with a fixed bed of granular or honeycomb adsorbent. The continuity of the processes of adsorption and regeneration of the adsorbent is ensured by the use of apparatuses with a fluidized bed.

In recent years, fibrous sorption-active materials have been increasingly used. Not much different from granular adsorbents in terms of their capacitive characteristics, they are significantly superior to them in a number of other indicators. For example, they are distinguished by a higher chemical and thermal stability, uniformity of the porous structure, a significant volume of micropores and a higher mass transfer coefficient (10-100 times higher than that of sorption materials). Installations using fibrous materials take up a much smaller footprint. The mass of the adsorbent when using fibrous materials is less than when using AC by 15-100 times, and the mass of the apparatus is 10 times less. The layer resistance does not exceed 100 Pa.

It is also possible to improve the technical and economic indicators of existing processes by optimally organizing the desorption stage, for example, by means of a programmed temperature rise.

It should be noted the efficiency of cleaning on activated carbons of a honeycomb (cellular) structure, which have improved hydraulic characteristics. Such sorbents can be obtained by applying certain compositions with AC powder to a foamed synthetic resin or by foaming a mixture of a given composition containing AC, as well as by burning out a filler from a mixture containing AC together with a binder.

Another direction for improving adsorption cleaning methods is the development of new modifications of adsorbents - silica gels and zeolites, which have increased thermal and mechanical strength. However, the hydrophilicity of these adsorbents makes their application difficult.

The most widespread are adsorption methods for extracting solvents from exhaust gases, including organochlorine ones. This is due to the high efficiency of the gas purification process (95-99%), the absence of chemical reactions for the formation of secondary pollutants, the quick payback of recovery plants (usually 2-3 years) due to the reuse of solvents and the long (up to 10 years) service life of AC. Active work is underway on the adsorption extraction of sulfur and nitrogen oxides from gases.

Adsorption methods are one of the most common methods of gas purification in industry. Their use allows a number of valuable compounds to be returned to production. At concentrations of impurities in gases of more than 2-5 mg / m3. cleaning is even cost-effective. The main disadvantage of the adsorption method is the high energy consumption of the stages of desorption and subsequent separation, which greatly complicates its application for multicomponent mixtures.

c) Thermal afterburning.

Afterburning is a method of neutralizing gases by thermal oxidation of various harmful substances, mainly organic, into practically harmless or less harmful, mainly CO2 and H2O. Typical afterburning temperatures for most compounds lie in the range of 750-1200 degrees C. The use of thermal afterburning methods makes it possible to achieve 99% gas purification.

When considering the possibility and expediency of thermal neutralization, it is necessary to take into account the nature of the resulting combustion products. Combustion products of gases containing sulfur, halogen, and phosphorus compounds can exceed the initial gas emission in terms of toxicity. In this case, additional cleaning is required. Thermal afterburning is very effective in neutralizing gases containing toxic substances in the form of solid inclusions of organic origin (soot, carbon particles, wood dust, etc.).

The most important factors determining the expediency of thermal neutralization are the energy (fuel) costs for providing high temperatures in the reaction zone, the calorific value of the neutralized impurities, the possibility of preheating the gases to be purified. Increasing the concentration of afterburning impurities leads to a significant reduction in fuel consumption. In some cases, the process can proceed in an autothermal mode, i.e., the operating mode is maintained only due to the heat of the reaction of deep oxidation of harmful impurities and preliminary heating of the initial mixture with neutralized exhaust gases.

The fundamental difficulty in using thermal afterburning is the formation of secondary pollutants, such as nitrogen oxides, chlorine, SO2, etc.

Thermal methods are widely used to purify exhaust gases from toxic combustible compounds. Afterburning plants developed in recent years are characterized by compactness and low energy consumption. The use of thermal methods is effective for afterburning dust of multicomponent and dusty exhaust gases.

G). thermocatalytic methods.

Catalytic gas cleaning methods are versatile. With their help, it is possible to release gases from oxides of sulfur and nitrogen, various organic compounds, carbon monoxide and other toxic impurities. Catalytic methods make it possible to convert harmful impurities into harmless, less harmful and even beneficial ones. They make it possible to process multicomponent gases with low initial concentrations of harmful impurities, to achieve high degrees of purification, to conduct the process continuously, and to avoid the formation of secondary pollutants. The use of catalytic methods is most often limited by the difficulty of finding and fabricating catalysts suitable for long-term operation and sufficiently cheap. Heterogeneous catalytic conversion of gaseous impurities is carried out in a reactor loaded with a solid catalyst in the form of porous granules, rings, balls or blocks with a structure close to honeycomb. Chemical transformation occurs on the developed inner surface of the catalysts, reaching 1000 sq. m. / G.

A wide variety of substances serve as effective catalysts that are used in practice - from minerals, which are used almost without any pretreatment, and simple massive metals to complex compounds of a given composition and structure. Typically, catalytic activity is exhibited by solids with ionic or metallic bonds, which have strong interatomic fields. One of the main requirements for a catalyst is the stability of its structure under the reaction conditions. For example, metals should not be converted into inactive compounds during the reaction.

Modern neutralization catalysts are characterized by high activity and selectivity, mechanical strength and resistance to poisons and temperatures. Industrial catalysts made in the form of rings and honeycomb blocks have low hydrodynamic resistance and high external specific surface.

The most widespread are catalytic methods for neutralizing exhaust gases in a fixed catalyst bed. Two fundamentally different methods of implementing the gas cleaning process can be distinguished - in stationary and in artificially created non-stationary modes.

1. Stationary method.

Acceptable for practice, the rates of chemical reactions are achieved on most cheap industrial catalysts at a temperature of 200-600 degrees C. After preliminary purification from dust (up to 20 mg / m 3) and various catalytic poisons (As, Cl2, etc.), gases usually have significantly lower temperature.

Heating of gases to the required temperatures can be carried out by introducing hot flue gases or using an electric heater. After passing through the catalyst layer, the purified gases are released into the atmosphere, which requires significant energy consumption. It is possible to achieve a reduction in energy consumption if the heat of the exhaust gases is used to heat the gases entering the treatment. For heating, recuperative tubular heat exchangers are usually used.

Under certain conditions, when the concentration of combustible impurities in the exhaust gases exceeds 4-5 g / m 3, the implementation of the process according to the scheme with a heat exchanger makes it possible to do without additional costs.

Such devices can work effectively only at constant concentrations (flow rates) or when using perfect automatic process control systems.

These difficulties can be overcome by carrying out gas cleaning in a non-stationary mode.

2. Non-stationary method (reverse process).

The reverse process provides for a periodic change in the direction of filtration of the gas mixture in the catalyst bed using special valves. The process proceeds as follows. The catalyst bed is preheated to a temperature at which the catalytic process proceeds at a high rate. After that, purified gas is fed into the apparatus at a low temperature, at which the rate of chemical transformation is negligible. From direct contact with a solid material, the gas heats up, and a catalytic reaction begins to proceed at a noticeable rate in the catalyst layer. The layer of solid material (catalyst), giving off heat to the gas, is gradually cooled to a temperature equal to the temperature of the gas at the inlet. Since heat is released during the reaction, the temperature in the layer may exceed the temperature of the initial heating. A thermal wave is formed in the reactor, which moves in the direction of filtration of the reaction mixture, i.e. in the direction of exit from the layer. Periodic switching of the direction of gas supply to the opposite one makes it possible to keep the thermal wave within the layer for as long as desired.

The advantage of this method is the stability of operation with fluctuating concentrations of combustible mixtures and the absence of heat exchangers.

The main direction in the development of thermal catalytic methods is the creation of cheap catalysts that operate efficiently at low temperatures and are resistant to various poisons, as well as the development of energy-saving technological processes with low capital costs for equipment. Thermal catalytic methods are most widely used in the purification of gases from nitrogen oxides, the neutralization and utilization of various sulfur compounds, the neutralization of organic compounds and CO.

For concentrations below 1 g / m3. and large volumes of purified gases, the use of the thermal catalytic method requires high energy consumption, as well as a large amount of catalyst.

e). ozone methods.

Ozone methods are used to neutralize flue gases from SO2 (NOx) and deodorize gas emissions from industrial enterprises. The introduction of ozone accelerates the oxidation of NO to NO2 and SO2 to SO3. After the formation of NO2 and SO3, ammonia is introduced into the flue gases and a mixture of the formed complex fertilizers (ammonium sulfate and nitrate) is isolated. .4 - 0.9 sec. Energy consumption for gas purification by the ozone method is estimated at 4-4.5% of the equivalent capacity of the power unit, which is, apparently, the main reason that hinders the industrial application of this method.

The use of ozone for the deodorization of gas emissions is based on the oxidative decomposition of foul-smelling substances. In one group of methods, ozone is injected directly into the gases to be purified, in the other, the gases are washed with pre-ozonized water. The subsequent passage of the ozonized gas through a layer of activated carbon or its supply to the catalyst is also used. With the introduction of ozone and the subsequent passage of gas through the catalyst, the temperature of transformation of substances such as amines, acetaldehyde, hydrogen sulfide, etc. decreases to 60-80 degrees C. Both Pt/Al2O3 and supported oxides of copper, cobalt, and iron are used as a catalyst. The main application of ozone deodorization methods is found in the purification of gases that are released during the processing of raw materials of animal origin in meat (fat) plants and in everyday life.

e). biochemical methods.

Biochemical purification methods are based on the ability of microorganisms to destroy and transform various compounds. The decomposition of substances occurs under the action of enzymes produced by microorganisms in the environment of the gases to be purified. With frequent changes in the gas composition, microorganisms do not have time to adapt to produce new enzymes, and the degree of destruction of harmful impurities becomes incomplete. Therefore, biochemical systems are most suitable for cleaning gases of constant composition.

Biochemical gas cleaning is carried out either in biofilters or in bioscrubbers. In biofilters, the gas to be purified is passed through a layer of packing irrigated with water, which creates humidity sufficient to support the vital activity of microorganisms. The surface of the nozzle is covered with a biologically active biofilm (BP) of microorganisms.

BP microorganisms in the course of their life activity absorb and destroy substances contained in the gaseous medium, resulting in an increase in their mass. The cleaning efficiency is largely determined by the mass transfer from the gas phase to the BP and the uniform distribution of gas in the packing layer. Such filters are used, for example, for air deodorization. In this case, the gas stream being cleaned is filtered in co-current conditions with an irrigated liquid containing nutrients. After the filter, the liquid enters the settling tanks and then re-supplied for irrigation.

Currently, biofilters are used to purify exhaust gases from ammonia, phenol, cresol, formaldehyde, organic solvents of paint and drying lines, hydrogen sulfide, methyl mercaptan and other organic sulfur compounds.

The disadvantages of biochemical methods include, firstly, the low rate of biochemical reactions, which increases the dimensions of the equipment; secondly, the specificity (high selectivity) of strains of microorganisms, which makes it difficult to process multicomponent mixtures; thirdly, the complexity of processing mixtures of variable composition.

and). Plasma chemical methods.

The plasma-chemical method is based on passing an air mixture with harmful impurities through a high-voltage discharge. As a rule, ozonizers based on barrier, corona or sliding discharges, or pulsed high-frequency discharges on electrostatic precipitators are used. Air with impurities passing through the low-temperature plasma is bombarded by electrons and ions. As a result, atomic oxygen, ozone, hydroxyl groups, excited molecules and atoms are formed in the gaseous medium, which participate in plasma-chemical reactions with harmful impurities. The main directions for the application of this method are to remove SO2, NOx and organic compounds. The use of ammonia, when neutralizing SO2 and NOx, gives powdered fertilizers (NH4)2SO4 and NH4NH3 at the outlet after the reactor, which are filtered.

The disadvantages of this method are:

insufficiently complete decomposition of harmful substances to water and carbon dioxide, in the case of oxidation of organic components, at acceptable discharge energies

the presence of residual ozone, which must be decomposed thermally or catalytically

significant dependence on dust concentration when using ozone generators with the use of a barrier discharge.

3) Plasma catalytic method

This is a fairly new purification method that uses two well-known methods - plasma-chemical and catalytic. Installations based on this method consist of two stages. The first is a plasma-chemical reactor (ozonator), the second is a catalytic reactor. Gaseous pollutants, passing through the high-voltage discharge zone in gas-discharge cells and interacting with electrosynthesis products, are destroyed and converted into harmless compounds, up to CO2 and H2O. The depth of conversion (purification) depends on the value of the specific energy released in the reaction zone. After the plasma-chemical reactor, the air is subjected to final fine purification in a catalytic reactor. The ozone synthesized in the gas discharge of the plasma-chemical reactor enters the catalyst, where it immediately decomposes into active atomic and molecular oxygen. Remains of pollutants (active radicals, excited atoms and molecules) that are not destroyed in the plasma-chemical reactor are destroyed on the catalyst due to deep oxidation with oxygen.

The advantage of this method is the use of catalytic reactions at temperatures lower (40-100 degrees C) than with the thermal catalytic method, which leads to an increase in the service life of catalysts, as well as to lower energy costs (at concentrations of harmful substances up to 0.5 g/ m cube).

The disadvantages of this method are:

large dependence on dust concentration, the need for pre-treatment to a concentration of 3-5 mg/m3,

at high concentrations of harmful substances (over 1 g/m3), the cost of equipment and operating costs exceed the corresponding costs in comparison with the thermal catalytic method

i) Photocatalytic method.

The photocatalytic method for the oxidation of organic compounds is currently being widely studied and developed. Basically, catalysts based on TiO2 are used, which are irradiated with ultraviolet light. Known household air purifiers of the Japanese company "Daikin" using this method. The disadvantage of this method is the clogging of the catalyst with the reaction products. To solve this problem, the introduction of ozone into the mixture to be purified is used; however, this technology is applicable to a limited composition of organic compounds and at low concentrations.

Introduction

3.2 Calculation of the mist eliminator

Conclusion

Introduction

The rapid growth of the human population and its scientific and technical equipment have radically changed the situation on Earth. If in the recent past all human activity manifested itself negatively only in limited, albeit numerous, territories, and the impact force was incomparably less than the powerful circulation of substances in nature, now the scales of natural and anthropogenic processes have become comparable, and the ratio between them continues to change with acceleration towards an increase in the power of anthropogenic influence on the biosphere.

The relevance of this topic is as follows: atmospheric air is a vital component of the environment. Hazardous pollutants, getting into the atmospheric air, are transported over long distances. As they settle, they get into the soil, water, thereby polluting them.

This has a great adverse effect on the flora and fauna. Pollution is harmful to human health.

Humanity is in mortal danger. And this danger lies in catastrophically rapid climate change, air, water and soil pollution, the emergence of new diseases, the extinction of hundreds of thousands of species of animals and plants - the first threats of an impending threat.

The danger of unpredictable changes in the stable state of the biosphere, to which natural communities and species, including man himself, are historically adapted, is so great while maintaining the usual ways of managing that the current generations of people inhabiting the Earth have faced the task of urgently improving all aspects of their lives in accordance with the need preservation of the existing circulation of substances and energy in the biosphere. In addition, the widespread pollution of our environment with a variety of substances, sometimes completely alien to the normal existence of the human body, poses a serious danger to our health and the well-being of future generations.

The purpose of this course is to consider methods for cleaning atmospheric air.

To achieve this goal, it is necessary to solve the following tasks:

classify the air purification system;

consider cleaning methods;

show cleaning efficiency in a variety of conditions.

The object of this study is the methods and means of protecting the atmosphere.

Subject The present study is air purification using a mist eliminator.

Work structure. The course project consists of an introduction, three chapters, divided into paragraphs, a conclusion and a list of references. The work is placed on forty pages.

1. General characteristics of atmospheric pollution (on the example of the Astrakhan region)

1.1 Condition and quality of atmospheric air in the Astrakhan region

Main Geophysical Observatory named after Voikova annually conducts research on air measurements with the help of the Federal State Meteorological Service "Roshydromet" in 260 cities of Russia. According to the results of the research, a so-called priority list of cities with the highest level of air pollution is compiled. Compared to last year, the "black list" has changed significantly. It included Volgograd, Stavropol, Rostov-on-Don, and the capital of the Southern Federal District was in the top ten of this list.

According to the regional center for hydrometeorology, Astrakhan is not yet in danger of being blacklisted. Of course, the Astrakhan region cannot be classified as one of the cleanest cities, but the situation there is quite stable. Over the past five years, the level of air pollution has not changed significantly and even has a downward trend for some pollutants. Air quality control is systematic.

In the Astrakhan region, there are eight stationary monitoring posts for monitoring the state of the environment, which are located both in the city and in the region, primarily in the area of ​​influence of the Astrakhan gas complex, in the city of Narimanov, the settlement of Dosang and the settlement of Aksaraisky. Every day, the laboratory examines 10 harmful substances, and also takes samples for heavy metals and benzapyrene, which are sent to NPO Typhoon, Obninsk. The priority air pollutants in the Astrakhan region are: nitrogen dioxide, sulfur dioxide, formaldehyde, carbon monoxide, dust, soot, aromatic hydrocarbons. None of these highly contaminated components, i.e. more than 5 MPC, in Astrakhan and the region has not been observed for many years.

Many different harmful substances are emitted into the atmosphere, so a general indicator of air pollution by several substances is needed. This is the Air Pollution Index (API). Within five years, the API in Astrakhan fluctuates from 1 to 7 (moreover, an indicator of less than 5 is considered low, and from 5 to 7 - increased). But it still remains low.

Favorable meteorological conditions and the implementation of active environmental protection measures contributed to the reduction of emissions. Along with LLC Astrakhangazprom, the largest contribution to air pollution is made by thermal power plants (in particular, CHPP-2), the fuel industry, the production of building materials, as well as road, rail and water transport. Thus, emissions of pollutants into the atmosphere last year amounted to 119 thousand tons, and more than 23 thousand tons fall on the share of vehicles, which says a lot. More than 85,000 vehicles are currently registered in Astrakhan, and this number is growing by an average of 15 percent every year. Considering the condition of our roads and the general congestion of city roads with various types of vehicles, the negative impact of vehicles has become one of the most acute social problems.

A significant contribution to air pollution is made by city dumps and unauthorized accumulations of garbage, which are often simply burned. Each landfill is a chemical mine that releases dangerous poisons into the atmosphere. Unfavorable meteorological conditions contribute to high air pollution. The situation is aggravated in summer with high air temperature and calm weather. Calm weather in the city contributes to the stagnation of air and the accumulation of harmful impurities in it. But the wind is not always good. With horizontal transfer of air masses, trans-regional transfer of emissions of harmful substances to the Astrakhan region from neighboring regions and Kazakhstan is possible. Despite the shortage of funds, the administrations of the city and the region constantly pay attention to monitoring the implementation of environmental protection measures. Two years ago, a territorial center for environmental monitoring was opened, located in the building of the Main Directorate of Natural Resources and Environmental Protection of the Ministry of Natural Resources of the Russian Federation for the Astrakhan Region, two posts for monitoring atmospheric air pollution were built on the territory of Astrakhangazprom LLC and in the city of Narimanov.

1.2 Sources of air pollution

The main sources of atmospheric air pollution - Astrakhangazprom LLC , OOO Astrakhanenergo . The main sources of pollution of water bodies are housing and communal services in Astrakhan, maritime transport

In the region, there is a low quality of return waters discharged into open water bodies by enterprises - nature users. The most frequently observed excess for such ingredients as ammonium nitrogen, nitrite nitrogen, nitrate nitrogen, petroleum products, iron, copper. Discharges from 26 enterprises, 43 sewerage and water treatment facilities, 4 fish farms, 6 storm drains were checked.

118.5 thousand tons of pollutants entered the atmosphere from stationary sources, including 9.2 thousand tons in Astrakhan.

The main pollutant of the air basin of the region is the enterprise LLC "Astrakhangazprom - its emissions are 102 thousand tons or 86% of the regional volume. Increase in gross emissions of pollutants into the atmosphere at the enterprise Astrakhangazprom LLC by 3.2 thousand tons compared to 2002 due to an increase in the volume of formation gas processing.

According to the inventory of waste disposal and storage facilities in the city and 439 settlements of the Astrakhan region, more than 440 waste dumps were identified, of which about 300 were unauthorized, 7 waste landfills, including 6 solid waste landfills and 1 industrial waste landfill. The total area of ​​land occupied by landfills is 634 hectares, by landfills - 65 hectares. Of the total number of unauthorized dumps in Astrakhan, there are 91 dumps. The total area of ​​land occupied by unauthorized waste dumps is 182.4 ha, including 63.0 ha in Astrakhan.

Unauthorized landfills contain household solid waste, waste from dwellings generated by the population, industrial consumption waste similar to household waste, street garbage, selectively construction waste and scrap metal.

The amount of waste accumulated at authorized landfills is 282.2 thousand tons, unauthorized - 47.7 thousand tons, at landfills for solid waste and production waste 2677 thousand tons.

On the territory of the city of Astrakhan, 30.8 thousand tons of waste have been accumulated at unauthorized dumps. In the Pravoberezhnaya part of the city, a tense environmental situation has again been created due to the lack of space for the disposal of solid industrial and domestic waste. A similar situation in the next 1-2 years may develop in the Left-bank part of the city, since the existing solid waste landfill, located in the village. Funtovo, Privolzhsky district, can accept waste until 2006.

An unfavorable environmental situation has developed with the disposal of liquid sewage and household wastewater from cesspools in the non-sewered part of the city, which are currently located on sludge (drain) maps of the southern treatment facilities for biological sewage treatment. At this time, their liquidation and the construction of drain pumping stations are required in accordance with the requirements of building codes and regulations.

The main sources of air pollution are industrial, transport and domestic emissions.

Every year, the industry and transport of the Astrakhan region emit about 200 thousand tons of pollutants into the atmosphere. This means that, on average, up to 200 kg of pollution falls on one inhabitant of the region. A significant part of emissions into the atmosphere of the region (about 60%) is accounted for by the Astrakhangazprom enterprise.

In order to protect people and other organisms from the effects of pollutants, maximum allowable concentrations (MACs) of pollutants in the natural environment are set.

In recent years, atmospheric emissions of pollutants from industrial enterprises have been declining. This is due to the decline in production at the enterprises of the city of Astrakhan and some improvement in the work of the enterprise "Astrakhangazprom" in environmental matters. But at the same time, the amount of pollutants entering the atmosphere from mobile sources - vehicles is increasing.

Pollutants entering the air, as a rule, are not characteristic of its composition or have an insignificant content in natural conditions. These are substances such as: sulfur dioxide, hydrogen, soot, ammonia, nitrogen oxides, formaldehyde and other volatile organic substances. Carbon dioxide is also a pollutant, since an increase in its content in the atmospheric air causes a "greenhouse effect" - a warming of the Earth's climate.

Any increase in the capacity of industrial enterprises will lead to an increase in air pollution. At present, the most acceptable way to reduce environmental pollution by emissions from industrial enterprises is the use of dust-collecting and gas-cleaning equipment.

The state of the air environment is influenced by public utilities. In cold winters, air pollution from these industries increases.

In recent years, accidental emissions of pollutants by the Astrakhangazprom and Astrakhanbumprom enterprises have been a powerful source of atmospheric air pollution. At the same time, methane, hydrogen sulfide (H2S), mercaptans, nitrogen oxides (NO, NO2), soot, but most of all sulfur dioxide, entered the air environment. Meanwhile, the increased content of sulfur and nitrogen compounds in the atmosphere causes acid precipitation. This has become a big environmental problem, both for the Astrakhan region and the country as a whole.

Motor transport is one of the main, and often the main source of air pollution. Therefore, the use of various devices that reduce the intake of pollutants with exhaust gases can reduce air pollution. In developed countries, such devices are now widely used - catalysts that provide more complete combustion of fuel and partial capture of pollutants. An important measure to reduce toxic emissions from vehicles is the replacement of additives containing toxic lead in gasoline with less toxic ones and the use of unleaded gasoline. All gasoline produced at the Astrakhangazprom enterprise is produced without additives containing lead, which significantly reduces environmental pollution by this hazardous substance.

In our country, the use of automotive catalysts is not mandatory, so they are not used on domestic cars. In recent years, many old imported cars have appeared on the roads of Russia, the use of which in foreign countries without catalysts is prohibited. This significantly worsened the quality of atmospheric air on the streets of many cities, including Astrakhan.

1.3 Human activity as a factor of environmental impact

The protection of the atmosphere includes constant monitoring not only of its condition, but also of the organization of the work of enterprises and vehicles. Every year in the Astrakhan region, the "Clean Air" operation is carried out, during which car enterprises, car service stations, cars on highways are checked for toxicity and smoke. Then measures are developed to reduce air pollution: diagnostic posts are created, equipped with modern control devices, sites for repair, adjustment of engines, and others are organized.

According to the Department of Information of the Astrakhan Region Administration, in order to reduce air pollution in the 8-kilometer specially controlled zone of the Astrakhan gas complex and develop a network for monitoring the state of air in the city of Astrakhan and the region, a number of relevant measures should be taken by a decree of the acting head of the regional administration. The management of OOO "Astrakhangazprom" was proposed to develop a set of air protection measures that would provide for the organization of a sanitary protection zone with the mandatory resettlement of its inhabitants. In addition, OAO Gazprom will be offered to take measures to reduce specific emissions into the atmosphere and improve the environmental friendliness of its products. The Astrakhan Center for Hydrometeorology and Environmental Monitoring was proposed to develop and implement methodological recommendations for predicting a high level of pollution of the boundary layer of the atmosphere in the area of ​​the AGC and the city of Narimanov, as well as for regulating emissions. Next year, observations of the ecological state of the atmospheric air may also be carried out in Akhtubinsk and Znamensk.

purification air mist eliminator pollution

One of the most urgent for the Astrakhan region is the environmental problem. It is connected, first of all, with air emissions from cars and the gas complex, as well as water pollution. Recently, the index of air pollution from the AGPZ in Aksaraysk has noticeably decreased. However, the concentration of harmful gases in the atmosphere remains quite high, especially in the area of ​​the city of Narimanov.

Indicators of drinking water pollution in the Astrakhan region are lower than in other regions of the Russian Federation, as evidenced by drinking water samples. However, the distribution of chemicals along the rivers persists. Particularly acute is the problem associated with treatment facilities and sewers. These objects do not function well. As a result, water after the flood stagnates, rots, forming a focus of diseases.

These tasks should be solved by local governments, developing new projects and attracting funds. For example, the problem of processing waste from enterprises and building a waste processing plant in our region is growing. It needs to be solved. However, according to the Department of Natural Resources of the Ministry of Natural Resources of Russia for the Astrakhan Region, the waters of the Lower Volga are characterized as moderately polluted. However, the amount of purified water increases very slowly.

As of December 31, 2012, the network of specially protected natural areas of the Astrakhan region consisted of two state nature reserves, four state nature reserves, three biological reserves and 35 natural monuments.

In general, the state of natural complexes existing on the territory of the SPNA region in the past year was satisfactory. However, there is a need to survey the territories of some natural monuments in order to make a decision on the advisability of their reorganization due to the loss by them to a large extent of the main protected natural objects and complexes and nature protection functions. As before, fires continue to pose a serious threat to the natural complexes of protected areas. The issue of streamlining the residence of citizens and their grazing of personal livestock on the territory of the Stepnoy State Nature Reserve remained unresolved.

In 2012, the ecological and toxicological situation in the river. The Volga and its delta were characterized by the stabilization of indicators of oil, phenol, detergent pollution and such metals as cadmium, nickel, cobalt. The most unfavorable situation was observed on the watercourses of the Belinsky Bank and in the river. Volga in the city, where increased concentrations of all HMs were noted. The waters of the Volga-Caspian canal have a high level of oil pollution.

When conducting hydrobiological monitoring in 2012, it was found that the water area of ​​the Volga-Akhtuba floodplain, according to the classification of surface water quality, is assessed as transitional from “weakly” to “moderately polluted”. In general, the toxicological situation in the Caspian Sea was relatively favorable for hydrobionts.

2. Methods and means of protecting atmospheric air

2.1 Classification of atmospheric air purification methods

Mechanical Methods

Mechanical Methods based on the use of gravity, inertial forces, centrifugal forces, diffusion, capture, etc. This group of methods includes: inertial dust collection, wet dust collection, filtration.

Inertial dust collection is based on the fact that solid particles and drops fall out of a dusty gas stream when its direction changes sharply. The most widespread are inertial dust collectors, which are designed to capture large fractions of dust larger than 50 microns, and cyclones used to remove ash from flue gases and dry (wood, asbestos-cement, metal) dust with a particle size of 25-30 microns from the air, rotary dust collectors designed to purify the air of working premises .

Rice. 1 Small dust collector

The principle of operation of a cyclone - one of the most common dust-cleaning devices - is based on the use of centrifugal force arising from the rotational-translational movement of a gas flow: centrifugal force throws dust particles to the walls of the cyclone body, then dust particles, flowing down the walls, fall into the hopper, and the cleaned gas through the exhaust pipe located along the axis of the cyclone is emitted into the atmosphere or supplied to the consumer. Cyclones make up the largest group of eco-technical equipment - more than 90% of the total number of dust collectors used in industry. They capture more than 80% of the total mass of dust captured by all devices

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Rice. 2. Battery cyclone: a- scheme ( 1 - pipe branch; 2 - distribution chamber;

3 - guide elements; 4 - dust collector; 5 - camera;

6 - pipe branch); b- cyclone at the boiler depot

Wet dust collection is based on washing a dusty gas stream with a liquid supplied in the form of spray or mist.

The operation of wet gas scrubbers is based on the capture of dust particles by liquid, which carries them away from the apparatus in the form of sludge. The process of dust capture in wet dust collectors is facilitated by the condensation effect - the coarsening of dust particles due to the condensation of water vapor on them. Since the dust cleaning process in these devices is usually accompanied by the absorption and cooling of gases, they are used both as heat exchangers and for cleaning gaseous components. Usually, water is used as the irrigating liquid, if chemical treatment is not required. Wet gas scrubbers are often used as a preliminary stage before other types of apparatuses.

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Rice. 3. Rotary dust collector: 1 - spiral casing; 2 - gate required to direct polluted air into the cyclone; 3 - cyclone for final settling of solid particles

Wet gas scrubbers are called foam scrubbers and scrubbers, they are divided into hollow and packed, centrifugal, dynamic, turbulent. Scrubbers (Fig. 15) remove particles larger than 10 µm, and foam scrubbers trap particles up to 2 µm in size. They are used in areas for painting products and applying polymer coatings in closed air handling systems. The cleaning effect is 90-99%.

Rice. 4. Hollow scrubber

1 - frame; 2 - irrigation system

Filtration based on passing a dusty gas stream through the filter material. Filtration is used for ultra-fine purification of atmospheric air from wood, asbestos-cement, abrasive dust, ash, soot, metal particles, their oxides, anhydrides. Depending on the filter material, filters are usually divided into fabric, fibrous, porous and granular (from bulk materials). In fabric filters, not only fabrics are used, but also non-woven materials, such as felt or felt. Cotton fabric filters are used to filter neutral and alkaline gases at relatively low temperatures. Fibrous filters use stuffed layers of natural or synthetic fibers, slag wool, shavings of metals or polymeric materials, as well as formed layers (filter paper, cardboard). Synthetic and glass fiber filters are widely used. They have high thermal stability and mechanical strength. The most common filtration dust collectors are bag filters, which are a bag stretched over a tubular frame. To purify air from mists of acids, alkalis, oils and other liquids, fibrous filters are used - mist eliminators that trap particles smaller than 3 microns in size, the principle of which is based on the deposition of drops on the surface of the fibers, followed by the liquid draining under the action of gravity. The cleaning efficiency is 90-99%.

Rice. 5. Multi-section bag filter:

Distribution box for gas supply; 2 - sleeves for dust settling; 3 - shaking device; 4 - auger for removing settled dust; 5 - collector for the release of purified gas to the atmosphere.

Rice. 6. Cyclone filtering unit at the boiler depot

Physical Methods

Physical methods are based on the use of electric and electrostatic fields, cooling, condensation and crystallization processes. Electrostatic gas cleaning is carried out in vertical and horizontal electrostatic precipitators, it is based on the electrification of polluting particles up to 0.1 microns in size and their release from the gas under the influence of an electric field (up to 50 kV) created by special electrodes.

Electrostatic precipitators - one - or two-section devices of a rectangular shape (Fig. 18). The bodies of the devices are steel, covered with thermal insulation from the outside. The active zone of electrostatic precipitators consists of collecting electrodes (flat sheets made of plate elements of a special profile) and corona electrodes (tubular frames in which corona elements are stretched). The distance between adjacent collecting electrodes (300 mm) is also the width of a single gas passage. Removal of trapped dust from the electrodes - mechanical, by periodically shaking them with hammer blows

According to the method of removing particles deposited on the electrodes, dry and wet electrostatic precipitators are distinguished. Dry electrostatic precipitators are used to remove dry dust, and wet ones are used to purify gases from acid vapors: sulfuric, hydrochloric, nitric. The cleaning effect is 97-99%.

Rice. 7. Single-zone electrostatic precipitator with transverse gas flow

- precipitation electrodes; 2 - corona electrodes

Physical and chemical methods

Physico-chemical methods are based on the physico-chemical interactions of pollutants with cleaning agents. These methods include: absorption, chemisorption, adsorption, catalytic method, thermal method .

Absorption is based on the separation of a gas-air mixture into its constituent parts by absorbing one or more gas components of this mixture with a liquid absorbent (absorbent). Water is used to remove ammonia, hydrogen chloride and hydrogen fluoride from emissions. Sulfuric acid is used to remove aromatic hydrocarbons. Currently, the most widely used absorbers are scrubbers-absorbers.

Rice. 8. Irrigated scrubber-absorber with nozzle:

Nozzle; 2 - sprinkler

Adsorption is based on the extraction of mixtures of harmful impurities from gases with the help of solid adsorbents. Most widely used as an adsorbent activated carbon is used, in addition, there are sorbents such as activated alumina, silica gel, activated alumina, synthetic zeolites. Some adsorbents are impregnated with reagents that increase the efficiency of adsorption and turn a harmful impurity into a harmless one due to chemisorption occurring on the surface of the adsorbent. The main treatment equipment are vertical, horizontal, scrubbers - adsorbers.

Chemisorption is based on the absorption of gases and vapors by liquid and solid absorbers with the formation of chemical compounds. This method is used to remove hydrogen sulfide and nitrogen oxides from emissions. Scrubbers are used as treatment equipment, and arsenic-oxalic and ethanolamine solutions are chemical absorbers.

catalytic method purification consists in the selective acceleration of a chemical reaction and the transformation of a pollutant into a harmless substance. To reduce the toxicity of exhaust gases, catalytic converters are used, in which polluted air is passed over a catalyst, most often aluminum oxide. With the help of such purification equipment, it is possible to purify the air from carbon monoxide, hydrocarbons, nitrogen oxides. In liquid neutralizers, 10% aqueous solutions of Na are used to reduce the content of aldehydes and nitrogen oxides. 2SO 3or NaHSO 4 with the addition of 0.5% basic reagent to prevent premature oxidation. This method can achieve complete purification of gases from aldehydes, and the content of nitrogen oxides is reduced by 70%.

Rice. 9. Catalytic Converter: 1 - frame; 2 - reactor;

3 - grid; 4 - thermal insulation; 5 - catalyst; 6 - flange

The thermal method is based on afterburning and thermal destruction of harmful substances in emissions. It is used when harmful impurities in emissions are combustible. This method is used to clean emissions from paint and impregnation areas. Thermal and fire neutralization systems provide cleaning efficiency up to 99%.

biological method

Under natural conditions, microelement aerosols can be removed from the surface of leaves by rain, wind, or together with a layer of cuticular wax. In addition, removal occurs due to the absorption of trace elements by leaves, followed by translocation. The removal of aerosols from leaves by rain depends on the nature of the leaf surface and the characteristics of trace elements.

All plants show the ability to selectively extract chemical elements. Under environmental conditions of complex geochemical composition, plants have developed mechanisms for actively absorbing elements involved in life processes and removing toxic excesses of other elements.

In plants, during evolution and during life, mechanisms are developed that lead to adaptation and insensitivity to changes in the chemical balance in the environment. Therefore, plant responses to trace elements in soil and ambient air must always be considered for the specific soil-plant system.

Above-ground parts of plants are collectors of all atmospheric pollutants. The chemical composition of urban plants can serve as an indicator for identifying contaminated areas.

The treatment facilities of industrial enterprises do not yet allow completely freeing production waste from harmful impurities. Therefore, an additional method of air purification is biological. The role of a biological filter is played by vegetation, primarily woody. Unrestrained exploitation and deforestation, expansion of agricultural crops reduce the productivity of the green filter, both in terms of area and time. It is known that agrocenoses, even the highest yielding ones, are inferior to natural forest phytocenoses in terms of total annual biological productivity in similar environmental conditions. Consequently, photosynthetic activity also decreases, providing the necessary balance of CO 2and about 2in the atmosphere and the binding of atmospheric pollutants. The problem of preserving the "green lungs" of the planet and their biospheric function is quite acute.

The research results indicate the important role of woody plants in the process of removing gaseous impurities from the atmospheric air. At the same time, many believe that the main way to reduce the level of air pollution is technological (filters, traps), and the biological method can only be considered as an additional, auxiliary one.

Terrestrial organs of plants actively respond to an increase in the concentration of chemical elements in the soil, accumulating them above the level necessary to ensure normal growth and development of plants. Plants can absorb and metabolize sulfur dioxide, nitrogen oxides, ammonia, similar to the assimilation of carbon dioxide by leaves. Under conditions of increased content of these gases in the atmosphere, a significant increase in the content of nitrogen and sulfur occurs in the tissues.

The absorption capacity of plantations depends on the composition of the species, density, quality class, age, assimilation surface of tree crowns, and the duration of vegetation. Woody plants have the highest absorption capacity. They are followed by local weeds, flower plants and turf grasses as absorption capacity decreases. In phytocenoses, gases are absorbed not only by vegetation, but also by soil, water, litter, the surface of tree trunks and branches, and other elements. The influence of vehicle exhaust gases on the species and quantitative composition of the forest ground cover was studied. As a result, it was found that on all test plots, ivy-shaped boudra was most widespread in the forest ground cover.

The role of individual components of the ecosystem in the absorption of pollutants can only be determined experimentally. Under natural conditions, the distribution of the pollutant in the ecosystem depends on the nature of air pollution and the translocation processes of the ingredient in the ecosystem, both under the influence of biological processes and environmental conditions.

The absorption of the pollutant by plants and individual elements of ecosystems is influenced by environmental factors. Under optimal conditions for phytocenosis (increased light and air humidity, temperature +25.30°C), the absorption of harmful gases by plants is also better expressed. In unfavorable conditions for phytocenosis, the absorption of gases by vegetation decreases and the role of soil increases.

Forest green spaces can be considered as an industrial phytofilter designed to neutralize atmospheric pollutants. The criterion for the effectiveness of its work should be the ability to reduce the level of air pollution to the maximum permissible concentrations.

2.2 Classification of air purification systems and their parameters

According to the state of aggregation, air pollutants are divided into dust, mists and gas-vapour impurities. Industrial emissions containing suspended solids or liquids are two-phase systems. The continuous phase in the system is gases, and the dispersed phase is solid particles or liquid droplets.

Air purification systems from dust are divided into four groups: dry and wet dust collectors, as well as electrostatic precipitators and filters.

The choice of type of dust collector depends on the nature of the dust (on the size of dust particles and its properties; dry, fibrous, sticky dust, etc.), the value of this dust and the required degree of purification.

Dry dust collectors

Gravity dust collectors. The simplest type of dust collectors are dust settling chambers related to gravity dust collectors. Their action is based on the fact that the speed of the flow of dusty air entering the chamber and expanding in it decreases, as a result of which the solid particles in it are deposited under the influence of their own weight.

To improve the efficiency of cleaning and reduce the time of sedimentation of dust particles, i.e. reducing the length of the chamber, it is divided into a number of channels or labyrinths are arranged. Due to their bulkiness, all these cameras were not widely used. The cleaning efficiency in labyrinth chambers reaches 55-60%.

Inertial dust collectors. Dry inertial dust collectors include cyclones, jet rotary dust collectors of the rotoklon type, etc.

Cyclones. Cyclones are dust collectors in which dust is collected as a result of inertial separation /

The cleaned air, entering the upper cylindrical part of the cyclone tangentially and rotating, descends from the annular space formed by the cyclone body and the exhaust pipe into the conical part and, continuing to rotate, rises, leaving through the exhaust pipe. In this case, both in the descending and ascending vortex flow of the cyclone, there is a continuous change in the direction of the flow velocity, and therefore the speed of particles moving in the flow does not coincide with the flow speed at any given time. Aerodynamic forces, which arise under the influence of the difference in the speeds of air movement towards dust particles, bend the particle trajectories. They reach the walls of the cyclone, i.e. separated from the flow, those particles whose weight is large enough.

Under the influence of gravity, radial flow, turbulence, a decrease in the cyclone taper angle and other hydrodynamic factors, the separated particles descend into the conical part of the cyclone or into the hopper attached to it.

Cyclones are widely used to clean dust from ventilation emissions, and are also widely used in many industries (mining, ceramics, energy, etc.).

The cyclones of NIIOGaz, SIOT and LIEOT are especially widespread.

The efficiency of air purification in a cyclone depends on the dispersed composition of dust, the mass of individual dust particles, the speed of air movement in the inlet pipe, on the design and dimensions of the cyclone (the smaller the diameter of the cyclone, the higher its efficiency).

Cyclones can be installed both on suction and discharge.

Cyclones that purify air containing damp dust (for example, in foundries) should be installed in heated rooms, otherwise freezing of dust and failure of the cyclones are possible.

Of the various designs of cyclones, cyclones TsN (TsN-11, TsN-15, TsN-15u, TsN-24), SIOT and vtsniiot are most widely used.

On the basis of an assessment of the indicators of the operation of cyclones - efficiency, economy and convenience of layout - the cyclone TsN-11 was approved by the State Construction Committee of the USSR as a unified dust collector.

In the cyclone TsN-11 NIIOGaz increased efficiency. Dusty air enters the tangentially located inlet pipe. Rotating in the cylindrical part of the body, dust particles released from the air fall into the hopper. Dust is removed from the hopper through its lower opening. The purified air enters the volute through the exhaust pipe and is removed from the cyclone into the atmosphere. Cyclone TsN-11 of NIIOGaz is produced with and without a snail.

If it is necessary to clean a significant amount of dusty air, it is recommended to install several smaller cyclones instead of one large cyclone. So, with an air flow rate of more than 5500 m 3/h it is recommended to arrange TsN-11 cyclones in groups of 2, 4, 6.8, 10, 12 and 14 cyclones.

Relative characteristics of cyclones with aerodynamic resistance of 981 Pa (100 kgf/m 2) and the same throughput.

Cyclones designed by NIIOGaz of the TsN series can be used to capture ash from flue gases of solid fuel boilers, dry dust from the air in the aspiration systems of grinding plants, dust from dryers and from the air of pneumatic transport systems with an initial dust content of 0.3 to 400 g / m 3. NIIOGaz cyclones should not be installed for cleaning sticky, explosive and fibrous dust.

The design of the SIOT cyclone is characterized by the absence of a cylindrical part and the triangular shape of the inlet pipe.

Cyclones SIOT can be used to clean the air from dry, non-coalescing, non-fibrous dust. These cyclones produce seven numbers (No. 1-7) with a throughput from 1500 to 10,000 m3 /h

VTsNIIOT cyclones are used for medium air purification from dry non-coalescing non-fibrous dust and for air purification from abrasive dust. They can also be used for sticking dust such as soot and talc. To increase the efficiency of dust settling and to prevent dust from being stirred up and carried away from the dust receiving hopper, there is an internal cone at the bottom of the cyclone.

Spiral-conical cyclones of NIIOGaz SDK-TsN-33 and SK-TsN-34 belong to devices with high aerodynamic resistance and can be installed only in cases where aerodynamic resistance is not standardized at the maximum degree of purification.

Cyclones L AND OT No. 1 are manufactured both in right and left execution. For a right-hand cyclone, the air moves clockwise (if you look at the Cyclone from above), and for a left-hand cyclone, it moves counterclockwise. Cyclones L AND OT can be installed both on suction and discharge.

In the woodworking industry, cyclones of Giprodrev, Giprodrevprom and cyclones of the Klaipeda OEKDM type are used to capture wood waste. The Klaipeda OEKDM cyclone can be used to capture chips, sawdust, dust and wood waste in woodworking factories and particle board production workshops. The cyclone installed on the discharge can be either right-hand or left-hand execution. All wood waste cyclones should be grounded during installation.

Rotary jet dust collectors of the rotoclone type. A rotary dust collector is a fan that, at the same time as moving air, cleans it of dust. Air purification occurs under the action of centrifugal forces arising from the rotation of the impeller.

The dusty air enters the rotary dust collector of the rotoclone type through the suction port. When the centrifugal wheel rotates, the dust-air mixture moves along the interblade channels and, under the action of inertia forces and Coriolis forces, dust particles are pressed against the surface of the wheel disk and the surfaces of the incoming blades. Dust with a small amount of air (3-5%) enters through the gap between the housing and the wheel disk into the annular receiver. From the receiver, the dust is sent through the nozzle to the bunker, where it settles. The air from the hopper through the hole again returns to the dust collector. The purified air enters the volute of the casing and leaves the dust collector through the discharge opening.

Rotary dust collectors are highly efficient in capturing dust particles with a size of at least 8 microns (83%), and when capturing dust particles with a size of more than 20 microns, their efficiency reaches 97%.

With the rotary dust separation method, the dust retention effect can be increased by using a water film. In this case, a centrifugal fan can be used to clean the air.

Wet dust collectors

Inertial dust collectors. Wet inertial dust collectors include centrifugal scrubbers, washing cyclones, Venturi dust collectors, etc.

The operating principle of the VTI centrifugal scrubber is as follows. Dust-laden air is introduced into the scrubber by an obliquely located branch pipe, in which the flushing device is located. The air flow with wetted and enlarged dust particles at a speed of 15 - 23 m/s enters tangentially into the housing. A water film flows down the walls of the housing from top to bottom, supplied by an irrigation tube through nozzles installed tangentially to the inner surface of the cylinder. This film washes away the separating dust from the walls down. The sludge is collected in a cone and enters the sludge trap through a cone pipe (hydraulic seal).

Purified air is discharged into the atmosphere through the volute and the outlet pipe.

The degree of purification in the scrubber ranges from 86 to 99% and increases with an increase in the specific gravity of dust, air velocity in the inlet pipe and with a decrease in the diameter of the body.

The VTI centrifugal scrubber is used in exhaust ventilation systems for air purification from quartz, coke, coal, lime, abrasive dust, etc.

In the SIOT cyclone-washer, dust is captured as a result of its deposition on the wetted inner surface of the housing walls under the action of inertia forces and due to air washing with water sprayed in the inlet pipe by an air stream. Water is supplied to the cyclone in the inlet pipe and on the bottom of the water distributor, which is located in the upper part of the cyclone. The cyclone-washer consists of a body, inlet and outlet pipes, as well as a untwist. To maintain a constant water pressure required for air washing, the cyclone-washer is supplied with a water pressure tank with a ball valve.

Cyclone-washers are used to clean the air from various types of dust, except for cementing and fibrous. They should be installed in suction.

The action of the Venturi dust collector (turbulent washer) is based on the use of the energy of the gas stream to atomize the injected water. The gas flow having a high degree of turbulence promotes particle coagulation. Large liquid droplets containing dust particles are easily captured in wet cyclones installed after the Venturi tube, droplet cyclones, etc.

The advantage of the Venturi tube with water supply to the neck is the possibility of coarsening dust particles to a size of 10 microns as a result of their collisions with liquid drops, which explains the high degree of purification, reaching 99.9%.

Fluid droplets downstream from the venturi can be trapped in a wet dust collector or in powerful electrical filters. Venturi dust collector units may contain one or more pipes. Coagulation of dust particles in a Venturi tube as a result of coagulation occurs under the influence of inertial forces of particle motion, Brownian motion, turbulent and polarization diffusion, electrostatic forces, and to a large extent under the influence of water vapor condensation that occurs during adiabatic gas expansion.

The cleaning efficiency also depends to a large extent on the speed of gas movement. An increase in the droplet diameter with an increase in the specific water flow leads to an increase in the resistance of the Venturi tubes and an increase in the efficiency of their work. Water consumption in large pipes can reach 0.5-I kg/m3 .

With all their advantages, Venturi pipes have a significant drawback - a large aerodynamic resistance of the dust and gas path - 10,000 Pa (1000 kgf / m 3and more), and consequently, a large energy consumption.

Venturi dust collectors are used mainly for gas purification at enterprises of the metallurgical, chemical and other industries, as well as for trapping dust from ventilation emissions.

Foam dust collectors. Foam gas cleaners PGS-LTI and PGP-LTI are used as foam dust collectors. Foam scrubbers are used to remove dust from neutral gases with temperatures up to 100 ° C, which do not form crystallizing salts during washing with water, clogging the holes of the gratings or deposited on the surfaces of the apparatus. Purified gases must have a density of at least 0.6 kg/m 3and high initial dustiness. The degree of purification with a particle size of 15-20 microns is 96-90%, with a particle size of 3-5 microns it drops to 80%.

Wet dust collectors should be installed in heated rooms to avoid their failure in the winter season. It is necessary to periodically check the compliance of the flow rate and distribution of water for individual nozzles or nozzles according to passport data.

Fabric dust collectors

When using fabric dust collectors, the degree of air purification can be 99% or more. When passing dusty air through the fabric, the dust contained in it is retained in the pores of the filter material or on a layer of dust accumulating on its surface.

Fabric dust collectors according to the shape of the filtering surface are sleeve and frame. As a filtering material, cotton fabrics, filter cloth, nylon, wool, nitron, lavsan, fiberglass and various nets are used.

Fabric bag dust collectors are widely used for capturing fine and coarse dust fractions.

Bag dust collectors are manufactured as single and double. Single baghouses consist of four, six, eight, or ten sections, while double baghouses have twice the number of sections. In each section, 14 fabric sleeves in three rows are installed in a checkerboard pattern. The area of ​​the filtering surface of each sleeve is 2 m 2, and one section - 28 m2 .

To avoid moisture condensation on the fabric and the walls of the sleeves, when installing dust collectors, the temperature and humidity of the air to be cleaned should be taken into account. Sleeve dust collector RFG consists of a body, a hopper, a gas distribution box, filter sleeves, a cover with a mechanism for shaking the sleeves and switching throttle valves, a purified air collector 6, a fan for blowing the sleeves, a sinter for unloading dust and a sluice gate.

The cleaned air is supplied by an air duct to the inlet flange of the gas distribution box of the bunker (from the front or rear end side of the dust collector) and descends under the influence of the guide partition into the lower part of the bunker, where it turns 180° and enters the sleeves. Passing through the fabric of the sleeves, the air is cleaned of dust that settles on the inner surface of the sleeves. The purified air enters the inter-hose space of the sections and further into the collector intended for it.

Tissue regeneration is carried out by simultaneous shaking of the sleeves and their back blowing. In this case, the regenerated section is disconnected from the purified air collector.

Each half of the dual dust collector has its own shaking and valve switching mechanism. Shaking and switching the valves to purge is carried out by an electric motor through a gearbox. The duration of shaking of one section is 1 min, while the duration of the filtration process is 9 min, and the entire working cycle is 10 min.

To purge the sleeves, a fan mounted on the same shaft with an electric motor is used. Only one section is purged at a time. Purge air enters the section from the purge air collector, passes through the fabric of the sleeves in the direction opposite to the flow of the air to be cleaned, and enters the internal cavity of the sleeves. In the process of tissue regeneration, dust from the surface of the sleeves is dumped into the hopper, and from the latter it is transported by a screw to the sluice gate, through which it is removed.

Permissible load of dusty air per 1 m 2the filtering material and the total throughput of the dust collector depend on the dispersed composition of the dust and the initial dust content of the air and can be determined according to the Santekhproekt GPI.

Of the other fabric dust collectors, suction bag filters PV are currently used. K-30. FVK-60, FVK-90, FV-30, FV-45, FV-60, FV-90; bag filters FR-10, FRM1-6. FRM1-8, FRMIO, etc.

Electric dust collectors

The efficiency of an electric dust collector depends on the properties of the gas (air) to be cleaned and the dust to be captured, dust contamination of the collecting and corona electrodes, the electrical parameters of the dust collector, the speed of gas movement and the uniformity of its distribution in the electric field.

In electric dust collectors, dust particles contained in the air acquire a charge and are deposited on the collecting electrodes. These processes take place in an electric field formed by two electrodes with opposite charges. One of the electrodes is also a precipitator.

The acquisition of an electric charge by dust particles in an electric dust collector is caused both by their bombardment with ions under the influence of an electric field - dust particles larger than 1 micron, and by the fact that ions come into contact with them (thermal - Brownian motion of molecules) - dust particles smaller than 1 micron.

The limiting charge of particles larger than 1 μm is proportional to the electric field strength and the square of the particle radius.

Each section of the electric dust collector has an electric field 8.5 m high with a cross section of 2.8X4.3 m. The speed of vertical movement of dusty air is 1.75-2 m/s. Capacity of one section 75,000-100,000 m 3/h of cleaned air.

Collecting electrodes, made in the form of metal plates, rest on the beams of the housing. The system of corona electrodes is a frame of pipes with horizontal wires stretched between them made of wire with a cross section of 4X4 ​​mm. The rods on which the corona electrode frames are suspended pass through the insulators.

To remove dust from the collecting and corona electrodes, shaking mechanisms are provided. When the electrodes are shaken, the dust falls along the dust troughs into the collection bins, from where it is removed.

Electricity consumption of this dust collector is 0.2 kW per 1000 m 3/h of cleaned air. Resistance 98 Pa (10 kgf/m 2). When combined with a DVP dust collector with battery cyclones, its efficiency reaches 98%.

Air filters can be divided into three classes, of which class I filters trap dust particles of all sizes (with a lower limit of the air purification efficiency of 99%), class II filters - particles larger than 1 micron (with an efficiency of 85%), and filters III class - particles ranging in size from 10 to 50 microns (with an efficiency of 60%).

Class I filters (fibrous) trap dust particles of all sizes as a result of diffusion and contact, as well as large particles as a result of their engagement with the fibers filling the filter.

In class II filters (fibrous with thicker fibers), particles smaller than 1 micron are not completely retained. Larger particles are effectively retained as a result of mechanical engagement and inertia. The retention of particles larger than 4-5 microns in dry filters of this class is ineffective.

In class III filters filled with thicker fibers, wire, perforated and zigzag sheets, etc., the inertial effect mainly acts. To reduce pores and channels in the filling of filters, the latter are wetted.

The efficiency and resistance of filters within each of the classes are not the same.

3. Air purification using a mist eliminator

3.1 General characteristics of the mist eliminator

To capture fog, fibrous and mesh filters-fog eliminators and wet electrostatic precipitators are used. The principle of operation of fibrous mist filters is based on the capture of liquid particles by fibers when mist is passed through the fibrous layer. Upon contact with the surface of the fiber, the trapped particles coalesce and form a film of liquid that moves inside the layer of fibers and then breaks up into individual droplets that are removed from the filter.

Advantages of filters: high efficiency of capture (including fine mist), reliability in operation, simplicity of design, installation and maintenance.

Disadvantages: the possibility of rapid overgrowing with a significant content of solid particles in the fog or the formation of insoluble salts due to the interaction of water hardness salts with gases (CO2, SO2, HF, etc.).

The movement of the trapped liquid in the filter occurs under the action of gravitational, aerodynamic and capillary forces, it depends on the structure of the fibrous layer (fiber diameter, porosity and degree of uniformity of the layer, the location of the fibers in the layer), the filtration rate, the wettability of the fibers, the physical properties of the liquid and gas. In this case, the higher the packing density of the layer and the smaller the diameter of the fibers, the more liquid is retained in it.

Fiber mist eliminators

Fiber mist eliminators are divided into low speed and high speed. Both are a set of filter elements. The filter elements of the low-velocity mist eliminator include two coaxially arranged cylindrical wire meshes with a diameter of 3.2 mm, welded to the bottom and inlet pipe. The space between the grids is filled with a thin fiber with a diameter of 5 to 20 microns with a packing density of 100-400 kg / m3 and a layer thickness of 0.03 to 0.10 m. The fibers are made from special glasses or polypropylene, polyesters, polyvinyl chloride, fluoroplast and other materials .

The filter elements are mounted on the tube sheet in the column body (up to 50-70 elements). Mist eliminators operate at gas velocity vg<0,2 м/с и имеют производительность до 180000 м3/ч.

High-speed mist eliminators are made in the form of flat elements filled with propylene felts. They can be used to capture acid mist (H2SO4, HC1, HF, H3PO4) and concentrated alkalis. Felts are produced from fibers with a diameter of 20, 30, 50 and 70 microns.

The most commonly used two-stage installations (with filters of different design), which can be of two types. In the first type of installations, the head filter is designed to trap large particles and reduce the concentration of fog. The second filter is used to remove fine particles. In installations of the second type, the first filter serves as an agglomerator, in which particles of all sizes are deposited, and the trapped liquid is carried out by a stream of gases in the form of large droplets entering the second filter-spray trap. Sprinkler filters use felts made of fibers with a diameter of 70 microns. At a filtration rate of 1.5-1.7 m/s, the resistance is 0.5 kPa, and the cleaning efficiency for particles larger than 3 µm is close to 100%.

To purify the air from mists, acids, alkalis, oils and other liquids, fibrous filters are used, the principle of which is based on the deposition of drops on the surface of the pores, followed by their flow under the action of gravitational forces. In the space between two cylinders made of nets, a fibrous filter material is placed. The liquid deposited on the filter material flows through the hydraulic seal into the receiving device. Fastening to the body of the mist eliminator is carried out by flanges.

Felt, lavsan, polypropylene and other materials with a thickness of 5…15 cm are used as the material of the filter element. The efficiency of mist eliminators for particle sizes less than 3 microns can reach 0.99.

Dry electrostatic precipitators are also used to capture acid mists.

Fiber mist eliminators are divided into low speed and high speed. Both are a set of filter elements. The filter elements of the low-velocity mist eliminator include two coaxially arranged cylindrical wire meshes with a diameter of 3.2 mm, welded to the bottom and inlet pipe. The space between the grids is filled with a thin fiber with a diameter of 5 to 20 microns with a packing density of 100-400 kg/m 3and layer thickness from 0.03 to 0.10 m. Fibers are made from special glasses or polypropylene, polyesters, polyvinyl chloride, fluoroplast and other materials.

The filter elements are mounted on the tube sheet in the column body (up to 50-70 elements).

High-speed mist eliminators are made in the form of flat elements filled with propylene felts. They can be used to capture acid mist (H2SO4, HC1, HF, H3PO4) and concentrated alkalis.

The most commonly used two-stage installations (with filters of different design), which can be of two types. In the first type of installations, the head filter is designed to trap large particles and reduce the concentration of fog. The second filter is used to remove fine particles. In installations of the second type, the first filter serves as an agglomerator, in which particles of all sizes are deposited, and the trapped liquid is carried out by a stream of gases in the form of large droplets entering the second filter-spray trap. Sprinkler filters use felts made of fibers with a diameter of 70 microns. At a filtration rate of 1.5-1.7 m/s, the resistance is 0.5 kPa. and the cleaning efficiency for particles larger than 3 µm is close to 100%.

Filters for cleaning suction air from chromic and sulfuric acid mist particles have a capacity of 2 to 60 thousand m3/h. At a filtration rate of 3-3.5 m/s, the cleaning efficiency is 96-99.5%, the resistance of the filters is 150-500 Pa.

To trap oil, filters with a rotating cylindrical filter element have been developed, which ensures efficient and continuous regeneration of the layer from the trapped oil. The performance of such filters is from 500 to 1500 m3/h, the cleaning efficiency is 85-94%.

To remove coarse impurities from splashes, drop eliminators are used, consisting of packages of knitted metal meshes made of alloyed steels, titanium-based alloys and other corrosion-resistant materials. Grids (with a wire diameter of 0.2-0.3 mm) are corrugated and placed in packages with a thickness of 50 to 300 mm and installed in a column as separators. To increase the efficiency of mist collection, two stages of mesh separators are provided. Separators work effectively at a vapor concentration in gases of not more than 100-120 g/m 3. Grids can also be made of PTFE and polypropylene.

Wet electrostatic precipitators are used to capture acid mist. According to the principle of operation, they do not differ from dry electrostatic precipitators.

3.2 Calculation of the mist eliminator

Calculation of a pressure granular filter

Initial data:

Q= 250 m 3/h;

Loose wash mode B;

Diameters of standard filters D, mm: 700, 1000, 1500, 2000, 2600, 3000, 3400;

B - washing with water:

water supply rate i\u003d 12 l / (s? M2 );

duration of water supply t= 20 min.

Granular filters are used for deep purification of water from fine particles, as well as for post-treatment of wastewater after biological or physico-chemical treatment.

Filters with a granular layer are divided into slow (filtering speed up to 0.3 m/h) and high-speed (fast - 2-15 m/h and ultra-fast - more than 25 m/h), open and closed (pressure), with a fine-grained filter load (particle size 0.4 mm), medium-grained (0.4-0.8 mm) and coarse-grained (more than 0.8 mm), single-layer and multi-layer, vertical and horizontal.

The height of the layer in open filters is 1-2 m, in closed ones it is 0.5-1 m. The water pressure in closed filters is created by pumps.

The most widely used filter materials: quartz sand, crushed anthracite, ceramic chips and others.

Washing filters, as a rule, is carried out with purified water (filtrate), supplying it from the bottom up. In this case, the grains of the load pass into a suspended state and are freed from adhering particles of contaminants. Air-water washing can be carried out, in which the granular layer is first blown with air to loosen, and then water is supplied.

The scheme of a vertical pressure granular filter is shown in fig. 9.

The filter consists of a cylindrical housing 1, a lower distribution device 2, an upper distribution device 3 and a layer of filter material 4 placed inside the housing. Outside the filter there are pipelines for supplying and discharging water and compressed air.

The lower distribution device 2 is designed to ensure uniform collection of purified water and uniform distribution of loosening water and compressed air over the cross-sectional area of ​​the filter.

The upper distribution device 3 is designed to supply the filter and uniformly distribute the treated water over the cross-sectional area, as well as to remove wash water from the filter.

The switchgear consists of a vertical manifold and radially arranged perforated distribution pipes.

Frame; 2 - lower switchgear; 3 - top switchgear; 4 - layer of granular filter material

Rice. 9. Scheme of a vertical pressure granular filter

Preparation of the bulk filter for operation consists in washing the layer of the filtering load from retained contaminants. For good flushing, it is necessary that the grains of the filter material are in suspension. In this case, it is necessary to create such conditions under which the grains of the filtering material collide with each other and there would be a complete rubbing off of adhering contaminants from their surface.

The filter material is washed with an upward flow of water, which is fed into the filter through the lower distribution device 2. A necessary condition for washing is the expansion of the volume of the filter material layer by 40–50%, which allows the grains of the filter material to move freely in the water flow.

The particles of contaminants flying off the surface of the filter grains, together with the upward flow of water, are removed from the filter through the upper distribution device 3.

The necessary expansion of the filter layer is achieved at an appropriate water flow rate, which is characterized by the washing intensity.

The quality of washing is controlled by analyzing samples of water leaving the filter for turbidity.

To improve the quality of washing, compressed air is supplied to the filter through the lower distribution device. The filter layer is treated with compressed air for 3-5 minutes before the wash water is fed into the filter.

At the end of the washing, the cloudy filtrate is discharged either into the drain or into the wash water reuse tank.

During the operation of the filter, water is supplied through the upper distributor 2 to a layer of granular filter material 4, passes through it and is collected and discharged from the filter into a common collector using the lower distributor 3.

When the transparency of the filtrate decreases, as well as when the maximum allowable pressure drop across the filter material layer is reached, the filter is switched off for washing.

With plant capacity up to 70 m 3/h at least three filters are installed, over 70 m 3/h - at least four filters.

Approximately required total filtration area F, m 2, in normal operation is defined as follows:

where Q- performance of the filtration plant for clarified water, m3/h;

v- allowable filtration rate, in normal operation v= 5 m/h;

? - coefficient taking into account water consumption for own needs, is taken ? = 1,1.

Filtration area f, m2, each filter is determined from the equation:

where a- number of filters, minimum number of filters a = 2.

The filter diameter is determined D, m

Water volume V, m3, for one cleaning of the clarification filter is equal to

where i and t- respectively, the intensity (l / (s?m2) and duration (min) of loosening filter washing, depending on the type of washing adopted (water or air)

Average hourly water consumption for own needs q, m3/h, equal to

where n- the number of washes per day of the clarification filter, we accept n = 2.

For the selected standard filters, the filtering speed is determined

If the filtration rate exceeds the allowed ( v= 5 m/h), it is necessary to increase the diameter or the number of installed filters.

Conclusion

The assessment and forecast of the chemical state of the surface atmosphere, associated with the natural processes of its pollution, differs significantly from the assessment and forecast of the quality of this natural environment, due to anthropogenic processes. Volcanic and fluid activity of the Earth, other natural phenomena cannot be controlled. We can only talk about minimizing the consequences of the negative impact, which is possible only in the case of a deep understanding of the functioning of natural systems of different hierarchical levels, and, above all, the Earth as a planet. It is necessary to take into account the interaction of numerous factors that change in time and space. The main factors include not only the internal activity of the Earth, but also its connections with the Sun and space. Therefore, thinking in "simple images" when assessing and predicting the state of the surface atmosphere is unacceptable and dangerous.

Anthropogenic processes of air pollution in most cases are manageable.

Environmental practice in Russia and abroad has shown that its failures are associated with incomplete consideration of negative impacts, inability to select and evaluate the main factors and consequences, low efficiency of using the results of field and theoretical environmental studies in decision-making, insufficient development of methods for quantifying the consequences of surface air pollution and other life-supporting natural environments.

All developed countries have laws on the protection of atmospheric air. They are periodically revised to take into account new air quality requirements and new data on the toxicity and behavior of pollutants in the air basin. In the United States, the fourth version of the Clean Air Act is now being discussed. The fight is between environmentalists and companies with no economic interest in improving air quality. The Government of the Russian Federation has developed a draft law on the protection of atmospheric air, which is currently being discussed. Improving air quality in Russia is of great social and economic importance.

This is due to many reasons, and, above all, the unfavorable state of the air basin of megacities, large cities and industrial centers, where the bulk of the skilled and able-bodied population lives.

It is easy to formulate a formula for the quality of life in such a protracted ecological crisis: hygienically clean air, clean water, high-quality agricultural products, recreational security for the needs of the population. It is more difficult to realize this quality of life in the presence of an economic crisis and limited financial resources. In such a formulation of the question, research and practical measures are needed, which form the basis of the "greening" of social production.

The environmental strategy, first of all, implies a reasonable environmentally sound technological and technical policy. This policy can be formulated briefly: to produce more with less, i.e. save resources, use them with the greatest effect, improve and quickly change technologies, introduce and expand recycling. In other words, a strategy of preventive environmental measures should be provided, which consists in the introduction of the most advanced technologies in the restructuring of the economy, providing energy and resource saving, opening up opportunities for improving and rapidly changing technologies, introducing recycling and minimizing waste. At the same time, the concentration of efforts should be aimed at developing the production of consumer goods and increasing the share of consumption. On the whole, the Russian economy should reduce as much as possible the energy and resource intensity of the gross national product and the consumption of energy and resources per capita. The market system itself and competition should facilitate the implementation of this strategy.

The protection of nature is the task of our century, a problem that has become a social one. Again and again we hear about the danger threatening the environment, but still many of us consider them an unpleasant, but inevitable product of civilization and believe that we will still have time to cope with all the difficulties that have come to light. However, human impact on the environment has taken on alarming proportions. To fundamentally improve the situation, purposeful and thoughtful actions will be needed. A responsible and efficient policy towards the environment will be possible only if we accumulate reliable data on the current state of the environment, substantiated knowledge about the interaction of important environmental factors, if we develop new methods to reduce and prevent the harm caused to Nature by Man.

List of used literature

1. Butorina M.V., Vorobyov P.V., Dmitrieva A.P. and other Engineering ecology and environmental management. - M.: Logos, 2008.

Garin V.M., Klenova I.A., Kolesnikov V.I. Ecology for technical universities. - Rostov n / a: Phoenix, 2009.384 p.

Eremichev I.A. Fundamentals of environmental law. Tutorial. - M.: Center for Legal Literature "Shield", 2009.

Engineering Ecology: Textbook / Ed. prof.V.T. Medvedev. - M.: Gardariki, 2008.

Engineering ecology and environmental management: Textbook / Edited by N.I. Ivanova, I.M. Fadina. - M.: Logos, 2009.

Lukanin V.N., Trofimenko Yu.V. Industrial and transport ecology. Moscow: Higher school, 2009.

Environmental protection. / Edited by G.V. Duganov. - Kyiv: "Vyscha school, 2009.

Rodzevich N.N., Pashkang K.V. Protection and transformation of nature. - M.: Education, 2009.

Stepanovskikh A.S. Environmental protection. - M.: UNITI-DANA, 2000.559 p.

City Ecology: Textbook. / Ed. F.V. Stromberg. - K .: Libra, 2008.

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Comment

Sources of pollution

The main contributor to indoor air pollution is dust. It consists of microscopic textile fibers, fungal and mold spores, skin particles, bacteria, plant pollen, street soot, small mites and their metabolic products. Half of it consists of the strongest allergens that can cause allergic rhinitis, eye inflammation, cough, skin irritation and even asthma.

In addition to dust, air pollution occurs through kitchen fumes, consisting of tiny drops of fat and creating an unpleasant specific smell in the apartment.

• Smoking, or rather, tobacco smoke, which may not disappear for several weeks, is another important factor in air toxicity.
• The air quality in your home also depends on the area in which you live. The sources of its pollution are often finishing materials, with the help of which the apartment was improved, as well as substances emitted from the walls of houses and low-quality furniture, building materials from chipboard.
• Mercury vapor is also a common phenomenon that can be observed in apartments. Usually the cause is a broken thermometer.
• The action of toxins on the body occurs gradually. Poisoning occurs as a result of their constant exposure. Toxins enter our body through the mouth, but mostly with the inhaled air.

The list of toxins and harmful substances in the air can be continued for a long time. But the main point should be clear to everyone: the air in the apartment needs constant cleaning. How it's done? We will talk about this further.

Purification of gaseous emissions from dust or fog is carried out in practice in devices of various designs, which can be divided into four main groups:

1. mechanical dust collectors (dust settling or dust settling chambers, inertial dust and spray collectors, cyclones and multicyclones). Apparatuses of this group are usually used for preliminary purification of gases;
2. wet dust collectors (hollow, packed or bubbling scrubbers, foam apparatus, Venturi tubes, etc.). These devices are more efficient than dry dust collectors;
3. filters (fibrous, cellular, with bulk layers of granular material, oil, etc.). The most common bag filters;
4. electrostatic precipitators - devices for fine gas cleaning - trap particles with a size of 0.01 microns. The efficiency of the electrostatic precipitator can reach 99.9%.

Usually, the required degree of purification can only be achieved by a combined installation, which includes several devices of the same or different types.

Cleaning methods

One of the urgent problems today is air purification from various kinds of pollutants. Just from their physical and chemical properties it is necessary to proceed when choosing one or another cleaning method. Consider the main modern methods of removing pollutants from the air.

mechanical cleaning

The essence of this method lies in the mechanical filtration of particles during the passage of air through special materials, the pores of which are able to pass the air flow, but at the same time retain the pollutant. The speed and efficiency of filtration depends on the size of the pores and cells of the filter material. The larger the size, the faster the cleaning process, but its efficiency is lower at the same time. Therefore, before choosing this cleaning method, it is necessary to study the dispersion of pollutants in the environment in which it will be applied. This will allow cleaning within the required degree of efficiency and in a minimum period of time.

absorption method

Absorption is the process of dissolving a gaseous component in a liquid solvent. Absorption systems are divided into aqueous and non-aqueous. In the second case, usually low-volatile organic liquids are used. The liquid is used for absorption only once, or it is regenerated, releasing the contaminant in its pure form. Schemes with a single use of the absorber are used in cases where absorption leads directly to the receipt of the finished product or intermediate.

Examples include:

• production of mineral acids (SO3 absorption in the production of sulfuric acid, absorption of nitrogen oxides in the production of nitric acid);
• obtaining salts (absorption of nitrogen oxides by alkaline solutions to obtain nitrite-nitrate liquors, absorption by aqueous solutions of lime or limestone to obtain calcium sulfate);
• other substances (absorption of NH3 by water to obtain ammonia water, etc.).

Schemes with repeated use of the absorber (cyclic processes) are more widespread. They are used for capturing hydrocarbons, purification of flue gases from thermal power plants from SO2, purification of ventilation gases from hydrogen sulfide by the iron-soda method with the production of elemental sulfur, monoethanolamine purification of gases from CO2 in the nitrogen industry.

Depending on the method of creating the phase contact surface, there are surface, bubbling and spraying absorption apparatuses.

• In the first group of devices, the contact surface between the phases is a liquid mirror or the surface of a fluid film of liquid. This also includes packing absorbents, in which the liquid flows down over the surface of the packing loaded into them from bodies of various shapes.
• In the second group of absorbents, the contact surface increases due to the distribution of gas flows into liquid in the form of bubbles and jets. Bubbling is carried out by passing gas through a liquid-filled apparatus or in column-type apparatuses with plates of various shapes.
• In the third group, the contact surface is created by spraying a liquid into a mass of gas. The contact surface and the efficiency of the process as a whole is determined by the dispersion of the sprayed liquid.

Packed (surface) and bubbling disc absorbers are most widely used. For the effective use of aqueous absorption media, the component to be removed must be highly soluble in the absorption medium and often chemically interact with water, as, for example, in the purification of gases from HCl, HF, NH3, NO2. For the absorption of gases with lower solubility (SO2, Cl2, H2S), alkaline solutions based on NaOH or Ca(OH)2 are used. Additives of chemical reagents in many cases increase the efficiency of absorption due to the occurrence of chemical reactions in the film. To purify gases from hydrocarbons, this method is used much less frequently in practice, which is primarily due to the high cost of absorbents. The general disadvantages of absorption methods are the formation of liquid effluents and the bulkiness of the instrumentation.

Electric cleaning method

This method is applicable to fine particles. In electric filters, an electric field is created, when passing through which the particle is charged and deposited on the electrode. The main advantages of this method are its high efficiency, simplicity of design, ease of operation - there is no need for periodic replacement of cleaning elements.

adsorption method

Based on chemical purification from gaseous pollutants. Air comes into contact with the surface of activated carbon, during which pollutants are deposited on it. This method is mainly applicable to the removal of unpleasant odors and harmful substances. The downside is the need for a systematic replacement of the filter element.

The following main methods for implementing adsorption purification processes can be distinguished:

• After adsorption, desorption is carried out and the trapped components are recovered for reuse. In this way, various solvents, carbon disulfide in the production of artificial fibers and a number of other impurities are captured.
• After adsorption, impurities are not disposed of, but are subjected to thermal or catalytic afterburning. This method is used to clean off gases of chemical-pharmaceutical and paint-and-lacquer enterprises, the food industry and a number of other industries. This type of adsorption treatment is economically justified at low concentrations of pollutants and (or) multicomponent pollutants.
• After cleaning, the adsorbent is not regenerated, but subjected, for example, to burial or incineration together with the strongly chemisorbed pollutant. This method is suitable when using cheap adsorbents.

Photocatalytic cleaning

It is one of the most promising and effective cleaning methods today. Its main advantage is the decomposition of hazardous and harmful substances into harmless water, carbon dioxide and oxygen. The interaction of the catalyst and the ultraviolet lamp leads to interaction at the molecular level of contaminants and the surface of the catalyst. Photocatalytic filters are absolutely harmless and do not require replacement of cleaning elements, which makes their use safe and very profitable.

Thermal afterburning

Afterburning is a method of neutralizing gases by thermal oxidation of various harmful substances, mainly organic, into practically harmless or less harmful, mainly CO2 and H2O. Typical post-combustion temperatures for most compounds are in the range of 750-1200°C. The use of thermal afterburning methods makes it possible to achieve 99% gas purification.

When considering the possibility and expediency of thermal neutralization, it is necessary to take into account the nature of the resulting combustion products. Combustion products of gases containing sulfur, halogen, and phosphorus compounds can exceed the initial gas emission in terms of toxicity. In this case, additional cleaning is required. Thermal afterburning is very effective in neutralizing gases containing toxic substances in the form of solid inclusions of organic origin (soot, carbon particles, wood dust, etc.).

The most important factors determining the expediency of thermal neutralization are the energy (fuel) costs for providing high temperatures in the reaction zone, the calorific value of the neutralized impurities, the possibility of preheating the gases to be purified. Increasing the concentration of afterburning impurities leads to a significant reduction in fuel consumption. In some cases, the process can proceed in an autothermal mode, i.e., the operating mode is maintained only due to the heat of the reaction of deep oxidation of harmful impurities and preliminary heating of the initial mixture with neutralized exhaust gases.

The fundamental difficulty in using thermal afterburning is the formation of secondary pollutants, such as nitrogen oxides, chlorine, SO2, etc.

Thermal methods are widely used to purify exhaust gases from toxic combustible compounds. Afterburning plants developed in recent years are characterized by compactness and low energy consumption. The use of thermal methods is effective for afterburning dust of multicomponent and dusty exhaust gases.

flushing method

It is carried out by flushing the gas (air) flow with liquid (water). Principle of operation: liquid (water) introduced into the gas (air) flow moves at high speed, breaks up into small drops, finely dispersed suspension) envelops suspension particles (liquid fraction and suspension merge), as a result, coarse suspensions are guaranteed to be captured by the flushing dust collector. Design: Structurally, washing dust collectors are represented by scrubbers, wet dust collectors, high-speed dust collectors, in which liquid moves at high speed, and foam dust collectors, in which gas in the form of small bubbles passes through a layer of liquid (water).

Plasma chemical methods

The plasma-chemical method is based on passing an air mixture with harmful impurities through a high-voltage discharge. As a rule, ozonizers based on barrier, corona or sliding discharges, or pulsed high-frequency discharges on electrostatic precipitators are used. Air with impurities passing through the low-temperature plasma is bombarded by electrons and ions. As a result, atomic oxygen, ozone, hydroxyl groups, excited molecules and atoms are formed in the gaseous medium, which participate in plasma-chemical reactions with harmful impurities. The main directions for the application of this method are to remove SO2, NOx and organic compounds. The use of ammonia, when neutralizing SO2 and NOx, gives powdered fertilizers (NH4)2SO4 and NH4NH3 at the outlet after the reactor, which are filtered.

The disadvantages of this method are:

• insufficiently complete decomposition of harmful substances to water and carbon dioxide, in the case of oxidation of organic components, at acceptable discharge energies
• the presence of residual ozone, which must be decomposed thermally or catalytically
• significant dependence on dust concentration when using ozone generators with the use of a barrier discharge.

Gravity method

Based on the gravitational settling of moisture and (or) suspended particles. Operating principle: the gas (air) flow enters the expanding settling chamber (capacity) of the gravitational dust collector, in which the flow rate slows down and, under the influence of gravity, droplet moisture and (or) suspended particles are deposited.

Design: Structurally, the sedimentation chambers of gravitational dust collectors can be of direct-flow, labyrinth and shelf type. Efficiency: the gravitational method of gas cleaning allows you to capture large suspensions.

Plasma catalytic method

This is a fairly new purification method that uses two well-known methods - plasma-chemical and catalytic. Installations based on this method consist of two stages. The first is a plasma-chemical reactor (ozonator), the second is a catalytic reactor. Gaseous pollutants, passing through the high-voltage discharge zone in gas-discharge cells and interacting with electrosynthesis products, are destroyed and converted into harmless compounds, up to CO2 and H2O. The depth of conversion (purification) depends on the value of the specific energy released in the reaction zone. After the plasma-chemical reactor, the air is subjected to final fine purification in a catalytic reactor. The ozone synthesized in the gas discharge of the plasma-chemical reactor enters the catalyst, where it immediately decomposes into active atomic and molecular oxygen. Remains of pollutants (active radicals, excited atoms and molecules) that are not destroyed in the plasma-chemical reactor are destroyed on the catalyst due to deep oxidation with oxygen.

The advantage of this method is the use of catalytic reactions at temperatures lower (40-100 °C) than with the thermal catalytic method, which leads to an increase in the service life of catalysts, as well as to lower energy costs (at concentrations of harmful substances up to 0.5 g/m³ .).

The disadvantages of this method are:

• high dependence on dust concentration, the need for pre-treatment to a concentration of 3-5 mg/m³,
• at high concentrations of harmful substances (over 1 g/m³), the cost of equipment and operating costs exceed the corresponding costs in comparison with the thermal catalytic method

centrifugal method

It is based on the inertial settling of moisture and (or) suspended particles due to the creation of a centrifugal force in the field of gas flow and suspension. The centrifugal method of gas purification refers to inertial methods of gas (air) purification. Operating principle: the gas (air) flow is directed to a centrifugal dust collector in which, by changing the direction of movement of gas (air) with moisture and suspended particles, as a rule, in a spiral, the gas is cleaned. The density of the suspension is several times greater than the density of the gas (air) and it continues to move by inertia in the same direction and is separated from the gas (air). Due to the movement of gas in a spiral, a centrifugal force is created, which is many times greater than the force of gravity. Design: Structurally, centrifugal dust collectors are represented by cyclones. Efficiency: relatively fine dust is deposited, with a particle size of 10 - 20 microns.

Do not forget about elementary methods of cleaning the air from dust, such as wet cleaning, regular ventilation, maintaining the optimal level of humidity and temperature. At the same time, periodically get rid of accumulations in the room of a large amount of rubbish and unnecessary items that are “dust collectors” and do not carry any useful functions.

All cleaning methods are divided into regenerative and destructive. The former allow the emission components to be returned to production, the latter transform these components into less harmful ones.

Methods for cleaning gas emissions can be divided into the type of component being processed(cleaning from aerosols - from dust and fog, cleaning from acidic and neutral gases, and so on).

· Electrical cleaning methods.

With this cleaning method, the gas flow is sent to the electrostatic precipitator, where it passes in the space between two electrodes - corona and precipitation. Dust particles are charged, move to the collecting electrode, and are discharged on it. This method can be used to purify dust with a resistivity of 100 to 100 million ohm*m. Dusts with lower resistivity are immediately discharged and fly away, while dusts with higher resistivity form a dense insulating layer on the collecting electrode, sharply reducing the degree of purification. The electric cleaning method can remove not only dust, but also mists. Cleaning of electrostatic precipitators is carried out by washing off the dust with water, vibration or using a hammer-impact mechanism.

· Various wet methods.

Use of foam apparatus, scrubbers.

The following methods are used for gas purification:

· Adsorption.

That is, the absorption of a gas (in our case) component by a solid substance. Active carbons of various grades, zeolites, silica gel and other substances are used as adsorbents (absorbers). Adsorption is a reliable method that allows achieving high degrees of purification; moreover, it is a regenerative method, that is, the captured valuable component can be returned back to production. Applied periodic and continuous adsorption. In the first case, upon reaching the full adsorption capacity of the adsorbent, the gas flow is sent to another adsorber, and the adsorbent is regenerated - for this, stripping with live steam or hot gas is used. Then a valuable component can be obtained from the condensate (if live steam was used for regeneration); for this purpose, rectification, extraction or settling is used (the latter is possible in the case of mutual insolubility of water and a valuable component). With continuous adsorption, the adsorbent layer is constantly moving: part of it works for absorption, and part is regenerated. This, of course, contributes to the attrition of the adsorbent. In the case of a sufficient cost of the regenerated component, the use of adsorption can be beneficial. For example, recently (in the spring of 2001), a calculation of the xylene recovery section for one of the cable plants showed that the payback period would be less than a year. At the same time, 600 tons of xylene, which annually fell into the atmosphere, will be returned to production.

· Absorption.

That is, the absorption of gases by a liquid. This method is based either on the process of dissolution of gas components in a liquid (physical adsorption), or on dissolution together with a chemical reaction - chemical adsorption (for example, the absorption of an acid gas by a solution with an alkaline reaction). This method is also regenerative; a valuable component can be isolated from the resulting solution (when chemical adsorption is used, this is not always possible). In any case, the water is purified and at least partially returned to the circulating water supply system.

· thermal methods.

They are destructive. With sufficient calorific value of the exhaust gas, it can be burned directly (everyone has seen flares on which associated gas burns), catalytic oxidation can be used, or (if the calorific value of the gas is low) it can be used as blast gas in furnaces. The components resulting from thermal decomposition should be less hazardous to the environment than the original component (for example, organic compounds can be oxidized to carbon dioxide and water - if there are no other elements than oxygen, carbon and hydrogen). This method achieves a high degree of purification, but can be expensive, especially if additional fuel is used.

· Various chemical cleaning methods.

Typically associated with the use of catalysts. Such, for example, is the catalytic reduction of nitrogen oxides from vehicle exhaust gases (in general, the mechanism of this reaction is described by the scheme:

C n H m + NO x + CO -----> CO 2 + H 2 O + N 2,

where platinum, palladium, ruthenium or other substances are used as the catalyst kt). The methods may require the use of reagents and expensive catalysts.

· Biological cleaning.

For the decomposition of pollutants, specially selected cultures of microorganisms are used. The method is distinguished by low costs (few reagents are used and they are cheap, the main thing is that microorganisms are alive and reproduce themselves, using pollution as food), a sufficiently high degree of purification, but in our country, unlike the West, unfortunately, it has not yet received wide distribution. .

· Air ions - tiny liquid or solid particles, positively or negatively charged. The effect of negative (light air ions) is especially favorable. They are rightly called the vitamins of the air.

The mechanism of action of negative air ions on particles suspended in the air is as follows. Negative air ions charge (or recharge) the dust and microflora in the air to a certain potential, in proportion to their radius. Charged dust particles or microorganisms begin to move along the electric field lines towards the opposite (positively) charged pole, i.e. to the ground, to the walls and ceiling. If we express in length the gravitational forces and the electrical forces acting on fine dust, then it can be easily seen that the electrical forces exceed the gravitational forces by thousands of times. This makes it possible, at will, to strictly direct the movement of a cloud of fine dust and thus purify the air in a given place. In the absence of an electric field and the diffuse movement of negative air ions between each moving air ion and the positively charged ground (floor), lines of force arise along which this air ion moves along with a particle of dust or a bacterium. Microorganisms that have settled on the surface of the floor, ceiling and walls can be periodically removed.

Bioremediation of the atmosphere

Bioremediation of the atmosphere is a complex of methods for cleaning the atmosphere with the help of microorganisms.

Cyanobacteria:

Researchers from the School of Engineering and Applied Sciences. Henry Samueli at the University of California at Los Angeles was genetically modified cyanobacteria(blue-green algae), which are now able to absorb CO2 and produce liquid isobutane fuel, which has great potential as an alternative to gasoline. The reaction takes place under the action of solar energy through photosynthesis. The new method has two advantages. First, the volume of greenhouse gases is reduced due to the utilization of CO2. Secondly, the resulting liquid fuel can be used in the current energy infrastructure, including in most cars. Using cyanobacteria Synechoccus elongatus, the researchers genetically increased the amount of the carbon dioxide-capturing enzyme. Then, genes from other microorganisms were introduced that allowed them to absorb CO2 and sunlight. As a result, the bacteria produce isobuteraldehyde gas.

Biofiltration:

Biofiltration is the most economically advantageous and the most mature technology for cleaning exhaust gases. It can be successfully used to protect the atmosphere in food, tobacco, oil refining industries, wastewater treatment plants, as well as in agriculture.

Institute of Biochemistry. A. N. Bakha RAS (INBI) is the leader of the Russian market in the field of biological methods for cleaning industrial ventilation emissions from vapors of volatile organic compounds (VOCs). It has developed a unique microbiological technology BIOREACTOR, which compares favorably with existing methods in terms of its technical parameters, capital and operating costs. The basis of BIOREACTOR technology is a consortium of natural immobilized microorganisms, specially selected and adapted for highly efficient (80-99%) degradation of various VOCs, such as aromatic hydrocarbons, carbonyl, C1-, organochlorine and many other compounds. The BIOREACTOR is also effective in removing unpleasant odors. The method is based on the microbiological utilization of harmful organic substances with the formation of carbon dioxide and water by specially selected non-toxic strains of microorganisms (destructors of pollution), tested and registered in the prescribed manner. The method is implemented in a new highly efficient biofiltration plant that provides effective continuous purification of exhaust gas-air emissions from various organic contaminants: phenol, xylene, toluene, formaldehyde, cyclohexane, white spirit, ethyl acetate, gasoline, butanol, etc.

The installation includes:

Bioabsorber, - auxiliary equipment - circulation pump, valve,

Tank (100l) for brine, instrumentation, heat exchanger, tail fan.

The unit in working condition (with liquid) weighs approx. 6.0 t, has dimensions of 4 * 3.5 * 3 m (indoors) and an installed power of 4 kW.

Development benefits. The biofiltration plant has the following main advantages:

High efficiency of cleaning gas-air emissions (from 92 to 99%),

Low operating energy consumption up to 0.3 kW*h/m 3 ,

High productivity in terms of the gas flow to be cleaned (10-20 thousand / m 3 * h),

Low aerodynamic resistance to gas flow (100-200 Pa),

Easy maintenance, long, reliable and safe operation.

The scientific and technical development has been worked out in an industrial version.

· Biological products MICROZYM(TM) ODOR TRIT:

Biological product - odor neutralizer, acting on the principle of neutralization of volatile compounds. The biological product is a complex of biological extracts of plant origin that enter into biochemical reactions with a wide range of volatile compounds from chemical ones: acetone, phenols, to organic ones: mercaptans, hydrogen sulfide, ammonia, and as a result of the reaction destroy volatile compounds and neutralize odors caused by these volatile compounds. The biological product does not mask the smell with the help of fragrances or fragrances, but destroys the smell by naturally cleaning the air from volatile compounds. The result of the action of the drug Odor Treat is an acceptable level of odor (intensity of 1-2 points) without foreign odors (flavors, fragrances).



The study of the causes and types of air pollution, the consequences of pollution. Familiarization with the methods of air purification and forecasting its condition for the future.

2 Key points

The air shell of our planet - the atmosphere - protects living organisms from the harmful effects of ultraviolet radiation from the Sun and hard cosmic radiation. It also protects the Earth from meteorites and space dust.

The atmosphere maintains heat balance. Atmospheric air is a source of respiration for humans, animals, and the synthesis of chemicals. It is a material for cooling a variety of industrial and transport installations, as well as a medium into which human, animal and plant waste is thrown.

It is known that a person can live without food for about five weeks, without water for about five days, and without air - he will not live even five minutes. A person's need for clean air ranges from 5 to 10 l / min, or 12 ... 15 kg / day.

Humanity is at the bottom of a large ocean of air. The most studied part of the atmosphere extends from sea level to an altitude of 100 m. In general, the atmosphere is divided into several spheres: troposphere, lithosphere, stratosphere, mesosphere, ionosphere (thermosphere), exosphere. The boundaries between spheres are called pauses. According to the chemical composition, the Earth's atmosphere is divided into the lower one (up to 100 km high) and the upper one - the heterosphere, which has a heterogeneous chemical composition. In addition to gases in the atmosphere, various aerosols are present - dust-like or water particles that are in a gaseous medium in a suspended state. They can be both natural and man-made.

Troposphere(gr. troops - turnover + sphere) - this is the surface lower part of the atmosphere in which most living organisms exist, including humans. More than 80% of the mass of the entire atmosphere is concentrated in this sphere, its power (height above the earth's surface) is determined by the intensity of vertical air flows, which depend on the temperature of the earth's surface. In this regard, at the equator it reaches a height of 16 ... 18 km, in the middle latitudes - up to 10 ... 11 km, and at the poles - up to 8 km. A regular decrease in air temperature depending on the height by an average of 0.6°C for every 100 m was revealed.

The troposphere contains most of the cosmic and anthropogenic dust, water vapor, oxygen, inert gases and nitrogen. It is practically transparent to short-wave solar radiation. At the same time, water vapor, ozone, carbon dioxide, which are in the atmosphere, quite strongly absorb the thermal (long-wave) radiation of the planet, resulting in a certain heating of the troposphere. This leads to vertical movement of air currents, condensation of water vapor, formation of clouds and precipitation.

At sea level, the composition of atmospheric air is as follows: 78% nitrogen, 21% oxygen, an insignificant part of inert gases, carbon dioxide, methane, hydrogen.

Stratosphere(lat. stratum - ball + sphere) - located above the troposphere at an altitude of 50 ... 55 km. The temperature circle of its upper boundary is rising due to the presence of ozone.

Mesosphere(gr. mesos - middle + sphere) - the upper boundary of this layer is fixed at an altitude of 80 km. Its main feature is a sharp drop in temperature (down to -75...-90°C) near the upper boundary. The so-called silvery clouds, which consist of ice crystals, are observed here.

Ionosphere (thermosphere)(gr. thermo - heat + sphere) - reaches a height of 800 km. It has an inherent significant increase in temperature (more than + 1000 ° C). Under the influence of ultraviolet radiation from the sun, the gases of the atmosphere are in an ionized state. This is associated with the emergence of aurora and the glow of gases. The ionosphere has the properties of multiple reflection of radio waves, which provides long-range radio communications on Earth.

Exosphere(gr. exo - outside, externally + sphere) - spreads from a height of 800 km to a height of 2000 ... 3000 km. Temperatures here reach +2000 °С and more. Important is the fact that the velocity of gases is approaching the critical value of 11.2 km/s. The composition is dominated by hydrogen and helium atoms, which form around our planet, the so-called crown, which reaches a height of 20 thousand km.