All methods of producing nitrogen in industry are based on the separation of atmospheric air, which is the most accessible raw material and contains about 75% of the target product. Other methods are characterized by high unit costs and are used mainly in research laboratories. In industry, nitrogen is obtained both for own needs and for sale. From air separation plants, the finished gas is supplied directly to consumers or pumped into cylinders for storage and transportation.

Nitrogen production in industry is carried out according to three technologies:

• cryogenic;
• membrane;
• adsorption.

We offer 5 types of equipment

Cryogenic production

The method consists in fractional evaporation of liquefied air and is based on the difference in the boiling points of its components. The process takes place in several stages:

• The air is compressed in a compressor unit with simultaneous heat extraction released during compression.
• Before getting nitrogen from liquefied air remove water and carbon dioxide which become solid and precipitate.
• After the pressure is reduced, the mixture begins to boil, and its temperature drops to -196 °C. Nitrogen, oxygen and noble gases are sequentially evaporated.

Cryogenic production of nitrogen in industry is justified at a significant expense, as well as with high requirements for its composition. The purity of the final product reaches 99.9999%. Energy-intensive and overall equipment is highly complex, requires professional training of maintenance and technological personnel.

Membrane separation of nitrogen

Technical nitrogen in liquid and gaseous state is obtained from atmospheric air. The substance is a fairly common chemical element. The Earth's atmosphere is 75% nitrogen, but in its pure form, it is unsuitable for breathing. Nevertheless, hundreds of processes take place in the human body, the speed and quality of which are affected by this substance. For example, nitrogen is part of hemoglobin, amino acids and proteins. In addition, it is found in the cells of plants and animals.

A gas molecule contains two atoms that are very tightly bonded. In order for nitrogen to become part of a chemical compound, this bond must be broken or weakened, and this is quite difficult. Much easier is the reverse process of nitrogen release from various compounds. The combustion reaction always proceeds with the formation of free gas.

A rich source of nitrogen is Chilean nitrate (sodium nitrite). At the beginning of the 19th century, fertilizers and gunpowder were obtained from it. Over time, mineral reserves decreased, and the need for nitrates only increased. At the beginning of the 20th century, nitrogen was obtained from atmospheric air and bound into ammonia. To do this, it was necessary to apply high temperature, pressure and introduce catalysts into the reaction. Since then, the issue of obtaining nitrogen has received a new solution, since the atmosphere is its inexhaustible source.

Due to its inert and other properties, this gas has found application in:

• development of coal seams;
• well drilling;
• product packaging;
• firefighting;
• high-temperature processing of metals, etc.



Physical characteristics of the substance

Under normal conditions (at an atmospheric pressure of 760 mm Hg and a temperature of 0 ° C), the substance is an odorless and colorless gas that is poorly soluble in water. It does not react with other elements except for lithium. When heated, nitrogen acquires the ability to dissociate into atoms and creates various chemical compounds. Its reaction with hydrogen is most in demand, as a result of which ammonia is obtained, which is used for the manufacture of fertilizers, coolant, synthetic fibers, etc. Gaseous nitrogen is fire and explosion-proof, and it also prevents decay and oxidation. The substance is non-toxic, therefore it does not have a dangerous effect on the environment. But with prolonged inhalation, it causes oxygen deficiency and suffocation.

When cooled to -195.8 ° C, nitrogen turns into a liquid resembling ordinary water in appearance. The boiling point of this substance is somewhat lower than that of oxygen. Therefore, when liquid air is heated, nitrogen begins to evaporate first. This property underlies the modern principle of production of a chemical product. Repeated repetition of liquefaction and boiling makes it possible to obtain nitrogen and oxygen in the desired concentration. This process is called rectification.

If nitrogen in a liquid state, the volume of which is 1 liter, is heated to + 20 ° C, it will evaporate and form 700 liters of gas. Therefore, the substance is stored in special open-type containers with vacuum insulation or in cryogenic pressure vessels.

Subsequent cooling of nitrogen to -209.86°C transforms it into a solid state of aggregation. Large white crystals are obtained. Upon subsequent contact with air, the snow-like mass absorbs oxygen and melts.



industrial production

Currently, three technologies are mainly used to produce inert nitrogen, based on the separation of atmospheric air:

• cryogenic;
• membrane;
• adsorption.

Separating cryogenic plants operate on the principle of air liquefaction. First, it is compressed by a compressor, then it passes through heat exchangers and expands in an expander. As a result, the cooled air becomes a liquid. Due to the different boiling point of oxygen and nitrogen, they separate. The process is repeated many times on special distillation plates. It ends with obtaining the purest oxygen, argon and nitrogen. This method is most effective for large enterprises due to the significant dimensions of the system, the complexity of its start-up and maintenance. The advantage of the method is that it is possible to obtain nitrogen of the highest purity, both liquid and gaseous, in any quantity. In this case, the energy consumption for the manufacture of 1 liter of the substance is 0.4-1.6 kW / h (depending on the technological scheme of the installation).

Membrane gas separation technology began to be used in the 70s of the last century. The high cost-effectiveness and efficiency of this method has served as a worthy alternative to cryogenic and adsorption methods for obtaining pure nitrogen. Today, the plants use the latest generation of high performance membranes. Now this is not a film, but thousands of hollow fibers, on which a selective layer is applied. There are no moving components in the installation, so the duration of its operation without breakdowns is significantly increased. The filtered air is fed into the system. Oxygen passes freely through it, and nitrogen is removed under pressure through the opposite side of the membrane and sent to the accumulator. With the help of these plants, a substance with a purity of up to 99.95% is produced. Thus, the production of nitrogen from atmospheric air is carried out. The limited purity of the resulting nitrogen does not allow the use of this method by large manufacturers with large needs for high-purity nitrogen.

At those enterprises where high-purity nitrogen is in demand in large volumes, an installation is used to separate gas mixtures using adsorbents. Structurally, it consists of two columns. Each of them contains a substance that selectively absorbs a gas mixture. The operation of nitrogen production plants requires atmospheric air and electricity.

Initially, the air enters the compressor, where it is compressed. Then it is fed into the receiver, which equalizes its pressure. Since the air should not contain water vapor, dust, carbon dioxide, nitrogen oxides, acetylene, and other impurities, it is filtered. The main stage of the adsorption separation of the gas mixture begins. A stream of air is passed through a single column of carbon molecular sieves as long as they are able to absorb oxygen. After that, the surface of the adsorbent must be cleaned, that is, regenerated, by depressurizing or raising the temperature. And the air is sent to the second column. At this time, nitrogen passes through the unit and accumulates in the receiver. The duration of the adsorption and regeneration cycles is only a few minutes. The purity of nitrogen produced by this technology is 99.9995%.

Advantages of adsorption plants:

• quick start and stop;
• possibility of remote control;
• high separating ability;
• low power consumption;
• the possibility of operational readjustment;
• automatic mode control;
• low maintenance costs.

Gas Applications

Today, this product is in demand in many industries: gas, food, metallurgical. However, large-scale nitrogen production is relevant specifically for the petrochemical industry. The main area of ​​application is the manufacture of the acid of the same name and other fertilizers for agriculture. In engineering, nitrogen is used to cool various equipment and units. It creates an inert environment when pumping flammable liquids.

In the pharmaceutical industry, nitrogen is used to transport chemical raw materials, protect tanks, and package medicines. In electronics, it prevents oxidation during the semiconductor manufacturing process.

In the food industry, liquid nitrogen is used as a cooling and freezing element. In gaseous form, it is used to create an inert environment when bottling non-carbonated drinks and oils, as well as to produce propellant for spray cans.

The most effective method of extinguishing fires is nitrogen fire extinguishing. Evaporating, the substance quickly displaces the oxygen required to sustain combustion, and the fire dies out. The nitrogen is then rapidly vented out of the room, saving valuables that could be damaged by foam, powder or water.

In medicine, cells and organs are preserved with the help of cryogenic preservation. In addition, liquid nitrogen destroys the affected areas of tissue.



Storage and safety

Nitrogen in a liquid state is transported by road in special cryogenic vessels or tanks. The gaseous substance is delivered to consumers in compressed form in black cylinders. Nitrogen is stored in Dewar vessels with double walls, between which there is a vacuum. In order to reduce heat transfer, the surfaces are made mirror-like due to a layer of silver. Dewar vessels can be of different sizes. Containers holding tens of liters are made of metal. In such a vessel, the substance can be stored for several weeks.

Short-term contact of the skin with liquid nitrogen does not pose a serious danger, since an air cushion with low thermal conductivity is formed at the point of contact. It is she who protects the tissue from injury. Prolonged contact of nitrogen with the skin, eyes or mucous membranes causes severe damage. In case of contact with the substance, the affected area must be immediately washed with plenty of water.

When nitrogen evaporates, it accumulates at the floor level of the working room due to the low temperature and higher density than air. Unnoticed by a person, a high concentration of a substance is created, and the amount of oxygen decreases. This affects the general well-being: the rhythm of breathing is disturbed and the pulse quickens. With a severe outcome of the situation, consciousness is upset and the ability to move is lost. The danger lies in the fact that poisoning occurs unnoticed by a person, the victim is not aware of the seriousness of the situation. Therefore, rooms in which nitrogen is produced or used must be equipped with a reliable ventilation system.

Modern air separation plants

Sovremennye gazovye tekhnologii company proposes to refuse to purchase this substance, organizing its independent production. In this case, the cost of the resulting nitrogen is 10-20 times less than purchased. Should your facility require its own source of nitrogen, our experts will acquaint you with the specifications of the available plants. We will help you make the best choice of units, organize their delivery, installation, commissioning and commissioning.

Produce nitrogen yourself - send an application for equipment from the pages of our website!

Nitrogen

NITROGEN-A; m.[French] azote from Greek. an- - not-, without- and zōtikos - giving life]. A chemical element (N), a colorless and odorless gas that does not support respiration and combustion (makes up the main part of the air by volume and mass, is one of the main plant nutrients).

◁ Nitrogen, th, th. Ah acid. Ah, fertilizers. Nitrogenous, th, th. Ah acid.

nitrogen

(lat. Nitrogenium), a chemical element of group V of the periodic system. Name from Greek. a... is a negative prefix, and zōē is life (does not support breathing and burning). Free nitrogen consists of 2-atomic molecules (N 2); colorless and odorless gas; density 1.25 g/l, t pl -210ºC, t kip -195.8ºC. It is chemically very inert, but reacts with complex compounds of transition metals. The main component of air (78.09% of the volume), the separation of which produces industrial nitrogen (more than 3/4 goes to the synthesis of ammonia). It is used as an inert medium for many technological processes; liquid nitrogen - refrigerant. Nitrogen is one of the main biogenic elements that is part of proteins and nucleic acids.

NITROGEN

AZOT (lat. Nitrogenium - giving rise to saltpeter), N (read "en"), a chemical element of the second period of the VA group of the periodic system, atomic number 7, atomic mass 14.0067. In its free form, it is a colorless, odorless and tasteless gas, poorly soluble in water. It consists of diatomic N 2 molecules with high strength. Refers to non-metals.
Natural nitrogen consists of stable nuclides (cm. NUCLIDE) 14 N (mixture content 99.635% by mass) and 15 N. Outer electron layer configuration 2 s 2 2p 3 . The radius of the neutral nitrogen atom is 0.074 nm, the radius of the ions: N 3- - 0.132, N 3+ - 0.030 and N 5+ - 0.027 nm. The successive ionization energies of a neutral nitrogen atom are 14.53, 29.60, 47.45, 77.47, and 97.89 eV, respectively. On the Pauling scale, the electronegativity of nitrogen is 3.05.
Discovery history
It was discovered in 1772 by the Scottish scientist D. Rutherford as a gas unsuitable for breathing and combustion (“suffocating air”) as part of the products of burning coal, sulfur and phosphorus and, unlike CO 2, is not absorbed by an alkali solution. Soon the French chemist A. L. Lavoisier (cm. Lavoisier Antoine Laurent) came to the conclusion that the "suffocating" gas is part of the atmospheric air, and proposed the name "azote" for it (from the Greek azoos - lifeless). In 1784 the English physicist and chemist G. Cavendish (cm. Cavendish Henry) established the presence of nitrogen in saltpeter (hence the Latin name for nitrogen, proposed in 1790 by the French chemist J. Chantal).
Being in nature
In nature, free (molecular) nitrogen is part of atmospheric air (in the air 78.09% by volume and 75.6% by mass of nitrogen), and in bound form it is part of two nitrates: sodium NaNO 3 (found in Chile, hence name Chilean saltpeter (cm. CHILEAN NITER)) and potassium KNO 3 (found in India, hence the name Indian saltpeter) - and a number of other compounds. In terms of prevalence in the earth's crust, nitrogen occupies the 17th place, it accounts for 0.0019% of the earth's crust by mass. Despite its name, nitrogen is present in all living organisms (1-3% by dry weight), being the most important biogenic element. (cm. BIOGENIC ELEMENTS). It is part of the molecules of proteins, nucleic acids, coenzymes, hemoglobin, chlorophyll and many other biologically active substances. Some so-called nitrogen-fixing microorganisms are able to assimilate molecular nitrogen from the air, converting it into compounds available for use by other organisms (see Nitrogen fixation (cm. NITROGEN FIXATION)). The transformation of nitrogen compounds in living cells is an essential part of the metabolism of all organisms.
Receipt
In industry, nitrogen is obtained from the air. To do this, the air is first cooled, liquefied, and liquid air is subjected to distillation (distillation). The boiling point of nitrogen is slightly lower (-195.8 °C) than the other component of air - oxygen (-182.9 °C), therefore, when liquid air is carefully heated, nitrogen evaporates first. Gaseous nitrogen is supplied to consumers in compressed form (150 atm. or 15 MPa) in black cylinders with a yellow inscription "nitrogen". Store liquid nitrogen in Dewar flasks (cm. DEWAR VESSEL).
In the laboratory, pure (“chemical”) nitrogen is obtained by adding a saturated solution of ammonium chloride NH 4 Cl to solid sodium nitrite NaNO 2 when heated:
NaNO 2 + NH 4 Cl \u003d NaCl + N 2 + 2H 2 O.
You can also heat solid ammonium nitrite:
NH 4 NO 2 \u003d N 2 + 2H 2 O.
Physical and chemical properties
The density of gaseous nitrogen at 0 ° C is 1.25046 g / dm 3, liquid nitrogen (at the boiling point) - 0.808 kg / dm 3. Gaseous nitrogen at normal pressure at -195.8 °C turns into a colorless liquid, and at -210.0 °C - into a white solid. In the solid state, it exists in the form of two polymorphic modifications: below -237.54 ° C, a form with a cubic lattice is stable, above - with a hexagonal one.
The critical temperature of nitrogen is –146.95 °C, the critical pressure is 3.9 MPa, the triple point lies at a temperature of –210.0 °C and a pressure of 125.03 hPa, from which it follows that nitrogen at room temperature is not at any, even very high pressure, cannot be liquefied.
The heat of vaporization of liquid nitrogen is 199.3 kJ/kg (at the boiling point), the heat of fusion of nitrogen is 25.5 kJ/kg (at –210 °C).
The binding energy of atoms in the N 2 molecule is very high and amounts to 941.6 kJ / mol. The distance between the centers of atoms in a molecule is 0.110 nm. This indicates that the bond between the nitrogen atoms is triple. The high strength of the N 2 molecule can be explained in terms of the molecular orbital method. The energy scheme of the filling of molecular orbitals in the N 2 molecule shows that only the binding s- and p-orbitals are filled with electrons in it. The nitrogen molecule is non-magnetic (diamagnetic).
Due to the high strength of the N 2 molecule, the processes of decomposition of various nitrogen compounds (including the infamous explosive hexogen (cm. HEXOGEN)) when heated, hit, etc., lead to the formation of N 2 molecules. Since the volume of the resulting gas is much larger than the volume of the original explosive, an explosion thunders.
Chemically, nitrogen is rather inert and only reacts with the metal lithium at room temperature. (cm. LITHIUM) with the formation of solid lithium nitride Li 3 N. In compounds, it exhibits various degrees of oxidation (from –3 to +5). Forms ammonia with hydrogen (cm. AMMONIA) NH3. Hydrazine is obtained indirectly (not from simple substances) (cm. HYDRAZINE) N 2 H 4 and nitrous acid HN 3 . Salts of this acid are azides (cm. AZIDES). Lead azide Pb (N 3) 2 decomposes on impact, so it is used as a detonator, for example, in cartridge primers.
Several nitrogen oxides are known (cm. NITROGEN OXIDES). Nitrogen does not directly react with halogens; NF 3, NCl 3, NBr 3 and NI 3, as well as several oxyhalides (compounds that, in addition to nitrogen, include atoms of both halogen and oxygen, for example, NOF 3) were obtained indirectly.
Nitrogen halides are unstable and easily decompose when heated (some - during storage) into simple substances. So, NI 3 precipitates when draining aqueous solutions of ammonia and iodine tincture. Already with a slight shock, a dry NI 3 explodes:
2NI 3 = N 2 + 3I 2 .
Nitrogen does not react with sulfur, carbon, phosphorus, silicon and some other non-metals.
When heated, nitrogen reacts with magnesium and alkaline earth metals, and salt-like nitrides of the general formula M 3 N 2 appear, which decompose with water to form the corresponding hydroxides and ammonia, for example:
Ca 3 N 2 + 6H 2 O \u003d 3Ca (OH) 2 + 2NH 3.
Alkali metal nitrides behave similarly. The interaction of nitrogen with transition metals leads to the formation of solid metal-like nitrides of various compositions. For example, when iron and nitrogen react, iron nitrides of the composition Fe 2 N and Fe 4 N are formed. When nitrogen is heated with acetylene C 2 H 2, hydrogen cyanide HCN can be obtained.
Of the complex inorganic compounds of nitrogen, nitric acid is the most important. (cm. NITRIC ACID) HNO 3, its salts are nitrates (cm. NITRATE), and nitrous acid HNO 2 and its nitrite salts (cm. NITRITES).
Application
In industry, nitrogen gas is mainly used to produce ammonia. (cm. AMMONIA). As a chemically inert gas, nitrogen is used to provide an inert environment in various chemical and metallurgical processes, when pumping flammable liquids. Liquid nitrogen is widely used as a refrigerant (cm. REFRIGERANT), it is used in medicine, especially in cosmetology. Nitrogen mineral fertilizers play an important role in maintaining soil fertility. (cm. MINERAL FERTILIZERS).




encyclopedic Dictionary. 2009 .

Synonyms:

See what "nitrogen" is in other dictionaries:

- (N) chemical element, gas, colorless, tasteless and odorless; is 4/5 (79%) of air; beats weight 0.972; atomic weight 14; condenses into a liquid at 140°C. and a pressure of 200 atmospheres; component of many plant and animal substances. Dictionary… … Dictionary of foreign words of the Russian language

NITROGEN- NITROGEN, chem. element, char. N (French AZ), serial number 7, at. V. 14.008; boiling point 195.7°; 1 l A. at 0 ° and 760 mm pressure. weighs 1.2508 g [lat. Nitrogenium ("giving rise to saltpeter"), German. Stickstoff ("suffocating ... ... Big Medical Encyclopedia

- (lat. Nitrogenium) N, a chemical element of group V of the periodic system, atomic number 7, atomic mass 14.0067. The name is from the Greek a negative prefix and zoe life (does not support breathing and burning). Free nitrogen consists of 2 atomic ... ... Big Encyclopedic Dictionary

nitrogen- a m. azote m. Arab. 1787. Lexis.1. alchemy The first matter of metals is metallic mercury. Sl. 18. Paracelsus set off to the end of the world, offering everyone for a very reasonable price his Laudanum and his Azoth, to heal all possible ... ... Historical Dictionary of Gallicisms of the Russian Language

- (Nitrogenium), N, a chemical element of group V of the periodic system, atomic number 7, atomic mass 14.0067; gas, boiling point 195.80 shS. Nitrogen is the main component of air (78.09% by volume), is part of all living organisms (in the human body ... ... Modern Encyclopedia

Nitrogen- (Nitrogenium), N, a chemical element of group V of the periodic system, atomic number 7, atomic mass 14.0067; gas, bp 195.80 °С. Nitrogen is the main component of air (78.09% by volume), is part of all living organisms (in the human body ... ... Illustrated Encyclopedic Dictionary

- (chemical sign N, atomic weight 14) one of the chemical elements; a colorless gas that has neither smell nor taste; very slightly soluble in water. Its specific gravity is 0.972. Pictet in Geneva and Calheta in Paris managed to condense nitrogen by subjecting it to high pressure... Encyclopedia of Brockhaus and Efron

N (lat. Nitrogenium * a. nitrogen; n. Stickstoff; f. azote, nitrogene; and. nitrogeno), chem. element of group V periodic. systems of Mendeleev, at.s. 7, at. m. 14.0067. Opened in 1772 researcher D. Rutherford. Under normal conditions A.… … Geological Encyclopedia

Husband, chem. base, the main element of saltpeter; saltpeter, saltpeter, saltpeter; it is also the main, in quantity, component of our air (nitrogen 79 volumes, oxygen 21). Nitrogenous, nitric, nitric, containing nitrogen. Chemists distinguish... Dahl's Explanatory Dictionary

Organogen, nitrogen Dictionary of Russian synonyms. nitrogen n., number of synonyms: 8 gas (55) non-metal ... Synonym dictionary

Nitrogen It is a gas that extinguishes a flame because it does not burn and does not support combustion. It is obtained by fractional distillation of liquid air, stored under pressure in steel cylinders. Nitrogen is used mainly for the production of ammonia and calcium cyanamide, and ... ... Official terminology

Books

• Chemistry tests. nitrogen and phosphorus. Carbon and silicon. Metals. Grade 9 To the textbook of G.E. Rudzitis. Federal State Educational Standard, Borovskikh Tatyana Anatolyevna, This manual is fully consistent with the federal state educational standard (second generation). The manual includes tests covering 3 topics of the textbook by G. E. Rudzitis, ... Category: Handbooks, tests, collections of problems in chemistry Series: Teaching kit Publisher:

The plant for nitrogen production is a complex of equipment, with the help of which nitrogen is concentrated from the atmospheric air. The maximum nitrogen concentration at the outlet is 99.9999%. This indicator can be adjusted depending on the purpose of the gas.

adsorption generator

Production takes place by supplying compressed air under pressure, which is pumped by a screw air compressor. The generator is equipped with a filtration system and a dryer. In this case, the air dryer can be either a refrigeration type or an adsorption type, depending on the purpose and the required nitrogen concentration. In the production process, compressed air passes through coarse and fine cleaning and a dryer, while reaching a dew point of + 3C and an air class that complies with ISO 8573-1:2010-1.4.1. Then the air is supplied after multi-stage filtration to the generator. At the output of nitrogen equipment, we get ready-made gas under pressure up to 10 bar. The station consists of two columns containing adsorbent to absorb the corresponding type of gas. Once every 8-15 years, the adsorbent needs to be replaced, depending on the operating conditions.
Advantages of adsorption type nitrogen generators:

• a large resource of work;
• quick start/stop;
• ease of operation;
• compactness;
• high reliability;
• operator control during operation is not required;
• full automation;
• the possibility of remote control through the General Gas website.

Membrane generator

Separation of gases occurs due to the gas separation membrane. The filtered air passes through the membrane module. The flow passes through thousands of selective fibers. Nitrogen exits from the reverse side of the membrane, and oxygen exits through its walls.

Nitrogen production involves the qualified installation of the entire range of equipment that requires compliance with safety standards.

The nitrogen production equipment manufactured by General Gas uses components from certified manufacturers and is tested to meet the high quality and safety standards of industrial units.

This equipment allows achieving high energy efficiency in the production of nitrogen, which is used in various industries:

• electronic;
• food;
• metalworking;
• pharmaceutical;
• metallurgical;
• oil and gas;
• petrochemical and chemical.

By purchasing equipment for nitrogen production in our company, you get favorable prices, a guarantee, fast delivery and installation.

How to choose equipment for nitrogen production?

In order to choose the type of air separation unit, you need to understand what they are:

To obtain industrial gases from atmospheric air, there are currently three types of air separation units (ASUs):

• Air separation plants of cryogenic type.
• Air separation plants of adsorption type.
• Membrane air separation plants.

ASU of a cryogenic type is a set of equipment that performs sequential processing and cooling of atmospheric air to cryogenic temperatures and subsequent separation by rectification into components: oxygen, nitrogen, argon, krypton, xenon.

Cryogenic ASUs are subdivided:

• Small = 30 ÷ 300 m³/h;
• Medium = 300 ÷ 3000 m³/h;
• High > 3000 m³/h;

Adsorption-type ASU is a set of equipment that separates atmospheric air by passing it through a molecular sieve, which, by its structure, can trap gas molecules. Adsorption ASPs are designed to obtain the main separation products in the gaseous state:

• Oxygen;
• Nitrogen.

The performance of adsorption plants is not limited and depends on the number of modules used, but there are limitations on the concentration (purity) of separation products:

• Outlet oxygen gas concentration up to 98%
• Outlet nitrogen gas concentration up to 99.9995%

Membrane ASP is a set of equipment that separates compressed air by passing it through membrane modules, in which separation into the main components takes place: nitrogen and oxygen. Membrane ASPs are designed to obtain separation products in the gaseous state. The performance of membrane plants depends on the number of membrane modules used.

• The concentration of gaseous oxygen at the outlet is up to 90%.
• The concentration of gaseous nitrogen at the outlet is up to 99.5%.

Also, to obtain gaseous gases at the place of consumption, cryogenic gasifiers are used, which, in turn, convert the liquid cryo-product (nitrogen, oxygen or argon) into a gaseous state.

In which case, what ASP should be used to obtain NITROGEN?

In order to select a VRU, you need to know the following parameters:

• Consumption of gaseous nitrogen m³/h;
• Nitrogen pressure, Bar;
• Nitrogen concentration, % or residual oxygen content;
• Peak consumption, number of "peaks", duration and frequency;
• Installation location option (outdoors, indoors…);
• Existing communications;
• Distance from the object;
• Schedule of work (consumption);
• Availability of staff.

Let's look at a visual graph:

On the chart:

1. Delivery in cylinders
2. Delivery in liquid or bottles
3. Liquid delivery
4. Cryogenic ASUs

The choice of a nitrogen source is a complex and demanding task; the efficiency of production processes and the cost of the final product depend on the correct choice.

At the moment, the market for adsorption nitrogen generators is rapidly developing and in areas where gaseous nitrogen is required, this type of generator shows the lowest cost of production nitrogen, which is ~ 0.3 kW per 1 meter of cubic nitrogen.

^ 9.1 General information about nitrogen

Nitrogen - from the Greek "lifeless", colorless gas without color and smell, atomic weight 14.0.

In 1772 nitrogen was discovered by the Scot Rutherford. Nitrogen does not exist in the free state in nature. A. Lavoisier in 1787 established that the air contains "vital" (supporting respiration and combustion, that is, oxygen) and "suffocating" gases. In 1785 G. Cavendish showed that nitrogen is part of saltpeter. Later, they found out the inertness of nitrogen in the free state and its important property in compounds with other elements, i.e. in a bound state. Nitrogen is the fourth most abundant (after hydrogen, helium and oxygen) element of the solar system.

Nitrogen is one of the most abundant elements on earth. Mostly concentrated in the atmosphere. In the composition of the air, it is more than 78%. Natural nitrogen compounds are sodium nitrates, usually found in deserts (Chile, Central Asia). Coal contains 1-2.5% nitrogen.

Nitrogen is essential for the life of living organisms. Living proteins contain 16-17% nitrogen.

^ 9.2 Physical and chemical properties

Nitrogen is slightly lighter than air ? =1,2506 kg/m 3 under normal conditions).

Melting point -209.86º WITH, boiling -195.8 є WITH.

Nitrogen is difficult to liquefy.

Critical parameters: t kr\u003d -174.1ºС, p kr =34,6 kg/m 2 .

Density of liquid nitrogen ? and =808 kg/m 3 .

It is less soluble in water than oxygen.

Nitrogen reacts only with active metals (lithium, calcium, magnesium). With other elements - only at high temperature and the presence of a catalyst, including with hydrogen, forming NH 3 - ammonia.

Nitrogen does not harm the environment and is non-toxic. But a long stay in a gassed room is harmful to humans, and breathing in an environment with an oxygen content of less than 19% is life-threatening.

1. 
   ^ Obtaining nitrogen from the air

The main mass of atmospheric air is nitrogen (78.1%), so it is obvious that it is most rational to obtain nitrogen from the air.

Three methods of nitrogen production are currently used in industry: low-temperature separation, adsorption and membrane technologies.

^ Low temperature (cryogenic) technology the separation of air into components (nitrogen, oxygen, argon and other gases) is based on the difference in the boiling (or liquefaction) temperatures of nitrogen and oxygen during deep cooling of the air.

Liquefaction of nitrogen and oxygen under industrial conditions is carried out in expander plants. Pre-compressed and cooled air expands in an expander (piston or turbo expander) to a temperature of -192º WITH at which air is completely liquefied and becomes a colorless liquid. If liquid air is now slightly heated
(up to -183ºC), then nitrogen will evaporate from it, and oxygen will remain in the form of a liquid. This process is called air rectification. A detailed technological process is discussed in the section on oxygen. It should be noted that both nitrogen and oxygen are simultaneously produced at these plants, which can then be used for various purposes, in various technological lines.

These installations are high-performance, but complex in design, stationary and energy-intensive. They are used in industries with a high consumption of nitrogen, such as ammonia production.

Adsorption The technology is based on adsorption - the absorption of substances in a gaseous or liquid state by the surface of solid or liquid bodies (adsorbents), most often solid ones.

An adsorber is an adsorption apparatus in which a gas mixture passes through a layer of a porous adsorbent and the necessary substances are extracted from it. Adsorbers are of periodic and continuous action.

Such devices have a small capacity and are not used for nitrogen production on an industrial scale.

^ Membrane technology (use of molecular sieves). The principle of nitrogen production using this technology is based on the separation of nitrogen molecules from pre-cleaned compressed air pumped through the so-called membrane unit (or generator).

The membranes have the property of selective permeability - a progressive, efficient method with low energy consumption.

The essence of membrane technology is the separation of the gas mixture due to the difference in partial pressures on the outer and inner surfaces of the polyfiber membrane. Each component has its own characteristic penetration rate, which depends on its ability to dissolve in the membrane and penetrate through it. "Fast" gases (H 2 , CO 2 , O 2 , He, etc.) quickly penetrate through the polymer membrane. "Slow" gases (CO, N 2, CH 4, etc.) weakly penetrate the membrane and are discharged outside. The mixture of gases passing through the membrane is called permeate .

The diagram of the nitrogen generator is shown in Figure 9.1. The membrane separating unit is a cylindrical cartridge, inside which is a bundle of tubular polyfiber membranes.

Figure 9.1 - Membrane cartridge and membrane

With the help of such devices, it is possible to obtain nitrogen with a purity of 90 to 99.9% in fairly large quantities: from 1500 to 5000 m 3 /hour .

The emergence of membrane technologies has led to rapid progress in the development of air separation equipment and technology. The main advantage of membrane technology: low energy consumption, low parameters, compactness and mobility of plants contribute to its ever wider application.

The areas of use of various nitrogen production plants are shown in Fig. 9.2.




Figure 9.2 - Applications of various nitrogen plants

9.4 Process membrane plants for nitrogen production

With the use of the membrane method for producing nitrogen, in recent years a number of leading companies have created quite simple industrial plants. The schematic diagram of the installation is shown in Figure 9.3.

The air sucked in from the atmosphere is compressed in a piston or screw compressor station to a certain optimum gas separation pressure.



Compr. Membrane preparation unit

air station block

Figure 9.3 - Nitrogen production scheme using this technology:

F - filter; K - compressor; FS - filter-separator;

OS - dehumidifier; V / O - moisture separator

When choosing the required pressure, a compromise is sought: at low pressures it is easier, higher reliability, but very large dimensions of the devices, especially the membrane unit. And the cost of membrane modules is very high. At high pressures, there may be problems with strength and reliability.

The air compressed in the compressor enters the air preparation unit, where it is cooled, cleaned of liquid droplets (water, oil), mechanical impurities and dried. The air prepared in this way enters the membrane unit, where it is separated into consumer nitrogen and permeate (a mixture of oxygen, water vapor, hydrogen argon, etc.), which is released into the atmosphere. As you can see, the installation is environmentally friendly, does not harm the environment. In cases where stationary membrane plants are used at industrial enterprises, permeate as an oxygen-enriched air mixture can be usefully used, for example, for blowing in various types of combustion devices.

Using this technology, it is possible to obtain nitrogen with a concentration of 99.9%, but usually a purity of 90-98% is sufficient for technological applications.

The average cost of one liter of nitrogen is 50% cheaper than that obtained by the traditional low-temperature (cryogenic) method.

Nitrogen is produced directly at the place of its consumption in the required quantity. There are no storage and transportation costs at all.

This technology has indisputable advantages, including: compactness, mobility of the station, air separation takes place in a static apparatus, and not in an expander machine, the possibility of deep regulation, etc. The disadvantage is the high cost of membrane modules and the requirement for a high degree of purification of the air supplied to the modules . The last requirement is tough for compressors. Lubricated piston compressors and conventional oil-filled screw compressors are not acceptable.

The oil-free condition is satisfied by the so-called "dry" (lubrication-free) reciprocating and screw compressors. Such compressors exist. Structurally, they are much more complicated than usual and much more expensive.

In reciprocating "dry" compressors, the design of seals becomes more complicated, the use of special materials, etc. is required.

Screw "dry" compressors have a significantly lower degree of pressure increase in one housing than oil-filled ones, because no cooling oil injection
(? = 2-3 vs 8-10). They are more bulky. The requirement for a guarantee gap between the screws reduces the volumetric efficiency of the compressor.

In some cases, oil-filled screw compressors are used at the first stage of compression, and then, after cleaning and air separation, a “dry” reciprocating booster compressor is used.

At such plants, in addition to the main technological operation - obtaining nitrogen from air, the following operations are performed simultaneously:

Enrichment of air with oxygen (permeate);

Air drying.

^ 9.5 Nitrogen-membrane compressor stations

Complex installations of this kind are usually made mobile on cars or trailers, which allows you to quickly deliver it to the place of use.

An example is the nitrogen membrane screw mobile station AMVP-15/0.7 o C with a nitrogen capacity of 15 mm 3 /min and a pressure of 0.7 MPa, nitrogen concentration up to 97%. Developed at VNIIkompressormash (Sumy) in 2003.

All equipment is mounted in a car trailer 12 m long, which consists of three main blocks (Fig. 9.4).




Figure 9.4 - Mobile station AMVP

The station is controlled by a microprocessor system.

Drive - electric motor, piston compressor
2 stage, dry. Subsequently, dry compression screw blocks were used. Taking into account the mobility requirements, the station uses an air-cooled compressed air system.

The stations were successfully used to extinguish fires in the mines of Donbass. To localize and extinguish an underground fire, the station supplied nitrogen to the combustion zone to create an oxygen-depleted atmosphere.

Other applications of nitrogen membrane stations include:

– for the arrangement of oil and gas wells, repair and testing of pipelines in the oil and gas industry. This unit is equipped with a diesel drive, is not connected to power lines, can operate in any conditions of the north, the power of the station is 250 kW, the weight is 9.3 tons, the length is 6 m;

- to ensure long-term storage of grain, vegetables, by creating an inert environment without the use of chemicals, which slows down their breathing. The shelf life increases by 2-3 times, without loss of condition even at +20 - 25 єС;

– in the nuclear power industry – for purging the cooling jackets of NPP turbogenerators.

^ 9.6 Nitrogen applications

The bulk of the extracted free nitrogen is used for the industrial production of ammonia, which is then processed into nitric acid, fertilizers, and explosives. It is very expensive to obtain commercially pure nitrogen in separation plants in large quantities. Therefore, in such industries, not technically pure nitrogen is used, obtained, for example, by rectification of air, but directly atmospheric air. Such technology will be discussed in the next topic “Technologies for the production and use of ammonia”.

Free nitrogen is used in many industries:

- as an inert medium when testing devices and machines, such as compressors (works by VNIIkompressormash on the creation of a PC and a central committee of the SVD) (Fig. 9.5);

- for purging pipe apparatuses and other equipment operating on explosive gases (oil and gas industry) during repairs, tests before filling with gas;

- as a "buffer" locking medium when sealing machines and apparatuses operating on hazardous gases, a mixture of which with a small amount of nitrogen is permissible according to the conditions of the technological process;

- used as a pulse gas in the instrumentation and A systems of installations operating on hazardous gases (for elements of pneumatic automation, when it is impossible to use electroautomatic devices due to a possible spark);

- increasing the productivity of gas and oil wells by gas-pulse action using a nitrogen generator - a vessel filled with nitrogen at a very high pressure, which creates a local explosion around the intake part of the well, forming many cracks and channels in the solid formation.

Nitrogen is also widely used in engineering technology.

^ Nitriding (nitriding) – saturation of the surface of metal parts in order to increase hardness, wear resistance, fatigue limit, corrosion resistance.

Nitriding of steels takes place in sealed furnaces at 500 - 650ºC in an ammonia environment. The process is lengthy. To obtain a layer with a thickness of 0.2 - 0.4 mm, 20 - 50 hours are required. Increasing the temperature speeds up the process, but the hardness decreases.



Figure 9.5 - Scheme of the installation for testing PC and

Central Committee SVD on nitrogen

Nitriding is used mainly for alloyed steels, especially chromium-aluminum alloys, as well as steels containing tungsten and molybdenum. Titanium alloys are also nitrided, but at 850-950º WITH in a pure nitrogen environment.

The ability for deep cooling determines the use of liquid nitrogen in various refrigeration units, in mechanical engineering for assembly - disassembly of joints with a large interference fit, as well as in cryotherapy in medicine.

For technological needs, nitrogen is obtained at local or centralized nitrogen stations.

Nitrogen is stored in gas holders, containers, cylinders.

It is usually transported in a liquid state, in Dewar vessels with vacuum thermal insulation. The color of nitrogen vessels is black.

^ Security questions for topic 9

1 Name the main properties of nitrogen that are practically important for technology.

2 Name the industrial methods for obtaining nitrogen, their advantages, disadvantages, applications.

3 What is the essence of the low-temperature method of air separation to produce nitrogen?

4 What is the essence of the membrane nitrogen plant, explain its operation.

5 Give a diagram of a membrane nitrogen plant, explain its operation.

6 What are the requirements for nitrogen compression in membrane compressors? Which compressors meet these requirements.

7 What does "dry" compressors mean? What are the features of their device?

8 What are the applications of free nitrogen in the national economy?

9 Why is nitrogen used in engineering technology?

10 What are the features of storage, transportation and labeling of nitrogen vessels?

Bibliography

1. Atroshchenko V.I. Bound nitrogen technology course / V.I. Atroshchenko and others. -M.-L.: Chemistry, 1968.

2. Reference book of the nitrogen operator. -M.-L.: Chemistry, 1969. - Vol. I and II.

3. Glizmanenko D.L. Obtaining oxygen / D.L. Glizmanenko - M.: Chemistry, 1972.–752p.

Theme 10^ OXYGEN AND ITS APPLICATIONS

10.1 General information about oxygen

The role of oxygen in our life and production activities cannot be overestimated. Without oxygen, there is no life. Its main property is the ability to oxidize. Combustion is the most important oxidative process. Even the ancient Chinese, and later Leonardo da Vinci (1452-1519), believed that the air contains a component that is consumed during combustion.

Oxygen was discovered at the beginning of the 18th century. by the Dutch inventor K. Drebbel, who used it for his submarine, keeping a deep secret.

Lomonosov M.V. in 1756, he proved that combustion-oxidation is the addition of a part from the air to the substance, and not from the fiery matter, as was previously thought. The French chemist V. Lavoisier gave the element its name and developed the theory of combustion and oxidation. Pure oxygen was isolated by the Swede N. Scheele in 1770 by heating saltpeter, magnesium nitrate, etc.

Oxygen is the most abundant element in nature by weight. Its content by weight is:

In the air 23 %;

In water 86 %;

In the earth's crust 47 %.

The main mass of oxygen is contained in a bound state mainly in the earth's atmosphere.

^ 10.2 Properties of oxygen

10.2.1 Physical properties

Oxygen is a colorless gas, odorless and tasteless.

Atomic weight 16.

Thickening (liquefaction) temperature - 182,98 o C at atmospheric pressure, a pale blue liquid is formed.

curing temperature - 218,7 about C, blue crystals are formed.

Critical temperature - 118,84 about C .

critical pressure 49.71 atm.

Gas density (at 760 mm Hg, 0 o C) ? =0.00143 g/cm.

Density of liquid oxygen (- 182.98 C) ?=1,1321 g/cm .

Density of solid oxygen (-252.5 C)?=1.4256 g/cm .

Under the action of ultraviolet rays, it breaks down into atoms.

In a quiet discharge, ozone is formed - O 3 .

Good absorbers are noble metals and charcoal.

Oxygen in any state of aggregation has a magnetic susceptibility, i.e. its particles are attracted to the magnetic poles.

Oxygen is highly soluble in organic solvents (gasoline, acetone, ether).

^ 10.2.2 Chemical properties

Oxygen forms compounds with all chemical elements except noble gases. Reacts directly with all elements except halogens and precious metals. The rate of the oxidation reaction depends on the nature of the oxidized substance, temperature and mixing conditions. The higher the temperature, the faster the oxidation reaction. For example, hydrogen at room temperature practically does not react with oxygen, and at t=700-800 o C its mixture with oxygen explodes.

Reaction accelerators are catalysts. An excellent catalyst is water.

Combustible gases form highly explosive mixtures with oxygen, and their vapors are capable of being oxidized upon contact with pure oxygen, and under certain conditions, spontaneously ignite with an explosion. With an increase in pressure and temperature, the risk of self-ignition and explosion of mixtures of combustible substances with oxygen increases. Ignition in a closed space of porous combustible substances (coal dust, pressed peat, wool) impregnated with liquid oxygen is accompanied by an explosion of great destructive power.

1. 
   ^ Oxygen production technology

Oxygen can be obtained: 1) by chemical means;
2) water electrolysis; 3) air separation by deep cooling method.

Industrial production of oxygen is carried out by deep cooling, compression and distillation (separation into components) in special installations. A typical setup is shown in fig. 10.1. These units use compressors to supply compressed air.

Rectification- the process of separating liquid air into liquid oxygen and gaseous nitrogen, carried out in special apparatus - reactor columns.

At the bottom of the column, the air is pre-separated into enriched air containing 40%O 2 and liquid nitrogen (97-98%), collected in the pockets of the condenser.

Enriched air is fed to the top of the column, where the final distillation takes place to obtain
99-99.5%O 2 And 97-98%N 2 . The energy consumption for the production of 1 nm 3 of technical oxygen is 0.65-1.5 kWh.

Deep cooling plants are used to produce liquid oxygen using pressure
180-200atm and further expansion in a piston expander or low-pressure air (6 atm) with expansion in a turbo-expander (method of Academician P.L. Kapitsa).


Figure 10.1 - Scheme of a distillation plant for the production of liquid oxygen

The Kapitza cycle refrigeration cycle based on the use of low pressure air and obtaining the necessary cold only by expanding this air in an air turbine (expander) with the performance of external work. The scheme of the installation implementing such a cycle is shown in Fig. 10.2



Figure 10.2 - Scheme of the Kapitza cycle to obtain

liquid air:

1 - turbocharger; 2 - regenerators; 3 – turbo expander;

4 - capacitor

The features of the cycle are:

Not high air compression (up to 0.6 - 0.7 MPa) in the compressor;

Use of cold air from the condenser in a regenerative heat exchanger;

Expansion of compressed air in a turbo expander;

This cycle was developed back in 1930 and is widely used in practice due to its high energy efficiency.

From liquefied air, oxygen and nitrogen are obtained by rectification.

Along with getting ABOUT 2 And N 2 in installations of deep cooling, the gases contained in the air are also obtained: argon, neon, krypton, xenon.

Today, installations with a capacity of 1000 before
20,000 m 3 /hour oxygen. At the same time, regenerators are used as heat exchangers, which makes it possible to compress the main amount of air only up to 4.5-5.5 atm, which reduces the total specific consumption for the production of gaseous oxygen to 0.45-0.55 kWh.

There is a whole branch of the national economy - the oxygen industry, which produces technical oxygen as a marketable product, and technological oxygen (ie, for own needs, for example, in steel mills).