Ammonia compounds. Ammonia production in industry

DEFINITION

Ammonia- hydrogen nitride.

Formula – NH 3. Molar mass – 17 g/mol.

Physical properties of ammonia

Ammonia (NH 3) is a colorless gas with a pungent odor (the smell of “ammonia”), lighter than air, highly soluble in water (one volume of water will dissolve up to 700 volumes of ammonia). The concentrated ammonia solution contains 25% (mass) ammonia and has a density of 0.91 g/cm 3 .

The bonds between atoms in the ammonia molecule are covalent. General view of the AB 3 molecule. All valence orbitals of the nitrogen atom enter into hybridization, therefore, the type of hybridization of the ammonia molecule is sp 3. Ammonia has a geometric structure of the AB 3 E type - a trigonal pyramid (Fig. 1).

Rice. 1. The structure of the ammonia molecule.

Chemical properties of ammonia

Chemically, ammonia is quite active: it reacts with many substances. The oxidation degree of nitrogen in ammonia “-3” is minimal, so ammonia exhibits only reducing properties.

When ammonia is heated with halogens, heavy metal oxides and oxygen, nitrogen is formed:

2NH 3 + 3Br 2 = N 2 + 6HBr

2NH 3 + 3CuO = 3Cu + N 2 + 3H 2 O

4NH 3 +3O 2 = 2N 2 + 6H 2 O

In the presence of a catalyst, ammonia can be oxidized to nitrogen oxide (II):

4NH 3 + 5O 2 = 4NO + 6H 2 O (catalyst - platinum)

Unlike hydrogen compounds of non-metals of groups VI and VII, ammonia does not exhibit acidic properties. However, hydrogen atoms in its molecule are still capable of being replaced by metal atoms. When hydrogen is completely replaced by a metal, compounds called nitrides are formed, which can also be obtained by direct interaction of nitrogen with the metal at high temperatures.

The main properties of ammonia are due to the presence of a lone pair of electrons on the nitrogen atom. A solution of ammonia in water is alkaline:

NH 3 + H 2 O ↔ NH 4 OH ↔ NH 4 + + OH —

When ammonia interacts with acids, ammonium salts are formed, which decompose when heated:

NH 3 + HCl = NH 4 Cl

NH 4 Cl = NH 3 + HCl (when heated)

Ammonia production

There are industrial and laboratory methods for producing ammonia. In the laboratory, ammonia is obtained by the action of alkalis on solutions of ammonium salts when heated:

NH 4 Cl + KOH = NH 3 + KCl + H 2 O

NH 4 + + OH - = NH 3 + H 2 O

This reaction is qualitative for ammonium ions.

Application of ammonia

Ammonia production is one of the most important technological processes worldwide. About 100 million tons of ammonia are produced annually in the world. Ammonia is released in liquid form or in the form of a 25% aqueous solution - ammonia water. The main areas of use of ammonia are the production of nitric acid (subsequent production of nitrogen-containing mineral fertilizers), ammonium salts, urea, hexamine, synthetic fibers (nylon and nylon). Ammonia is used as a refrigerant in industrial refrigeration units and as a bleaching agent in the cleaning and dyeing of cotton, wool and silk.

Examples of problem solving

EXAMPLE 1

– the average incapacitating concentration (ICt50) ensures the incapacitation of 50% of those affected;

– average threshold concentration (PCt50) – causes initial symptoms of damage in 50% of affected people (g min/m3);

– average lethal dose (LDt50) when administered into the stomach – leads to the death of 50% of the affected individuals with a single injection into the stomach (mg/kg).

To assess the degree of toxicity of hazardous chemicals with skin-resorptive action, the values ​​of the average lethal toxodose (LDt50) and the average threshold toxodose (PDt50) are used. Units of measurement – ​​g/person, mg/person, ml/kg.

The average lethal dose with a single application to the skin leads to the death of 50% of those affected.

Physico-chemical properties of ammonia

When assessing the potential danger of chemicals, it is necessary to take into account not only toxic, but also physicochemical properties that characterize their behavior in the atmosphere, on the ground and in water. In particular, the most important physical parameter that determines the behavior of toxic substances of inhalation action during emissions (spills) is the maximum concentration of its vapors in the air. In industrial toxicology, an indicator is used that takes into account both the toxic properties and volatility of substances - the coefficient of possibility of inhalation poisoning (CVIO). This coefficient is equal to the ratio of the maximum possible vapor concentration of a substance at 200C to its lethal concentration (Table A. 4.1)

In some of its properties (boiling point -33 °C, critical temperature -132 °C) ammonia is similar to chlorine. Just like chlorine, ammonia can be conveniently stored in liquefied form. The dependences of vapor pressure - temperature and the fraction of instantly evaporating liquid in the adiabatic approximation, temperature for ammonia and chlorine are very close. However, ammonia is mainly transported as a chilled liquid (in refrigerated trucks). Note that in the United States there are pipelines through which ammonia is transported across the country.

Industrial significance of ammonia and its areas of application

In terms of production volumes, ammonia occupies one of the first places. About 100 million tons of this compound are produced annually worldwide. Ammonia is used to produce nitric acid (HNO3), which is used to make fertilizers and many other products; nitrogen-containing salts [(NH4)2SO4, NH4NO3, NaNO3, Ca(NO3)2], urea, hydrocyanic acid.

Ammonia is also used in the production of soda using the ammonia method, in organic synthesis, and for the preparation of aqueous solutions (ammonia), which find various uses in the chemical industry and medicine. Liquid ammonia, as well as its aqueous solutions, are used as liquid fertilizers. Ammonia is a good solvent for a large class of nitrogen-containing compounds. Large amounts of ammonia are used for ammoniation of superphosphate.

Evaporation of ammonia occurs with the absorption of a significant amount of heat from the environment. Therefore, ammonia is also used as a cheap refrigerant in industrial refrigeration units. In this case, liquid ammonia must meet the requirements of GOST 6221 - 90 “Technical liquid ammonia”. Liquid technical ammonia grade A is used as a refrigerant. The water content should not exceed 0.1%.

Ammonia is also used to produce synthetic fibers, such as nylon and nylon. In light industry it is used in cleaning and dyeing cotton, wool and silk. In the petrochemical industry, ammonia is used to neutralize acid waste, and in the natural rubber industry, ammonia helps preserve latex as it travels from plantation to factory. In the steel industry, ammonia is used for nitriding - saturating the surface layers of steel with nitrogen, which significantly increases its hardness.

General rules for the design and safe operation of ammonia refrigeration units

General concepts about refrigeration units

Refrigeration system is a set of parts containing refrigerant and communicating with each other, forming one closed refrigeration circuit for circulating refrigerant for the purpose of supplying and removing heat.

Refrigeration unit – units, components and other components of the refrigeration system and all equipment necessary for their operation.

Absorption (or adsorption) refrigeration system is a system in which cold is produced as a result of refrigerant evaporation; The absorber (adsorber) absorbs refrigerant vapor, which is subsequently released from it when heated with an increase in partial pressure and then condenses under this pressure during cooling.

Refrigerant (refrigerant) is a working medium used in a refrigeration system that absorbs heat at low temperatures and pressures and releases heat at higher temperatures and pressures. This process is accompanied by a change in the aggregate state of the working environment.

Coolant is any liquid used to transfer heat without changing its state of aggregation.

Requirements for the hardware design of refrigeration units

1) The refrigeration unit must be equipped with devices that prevent drops of liquid ammonia from entering the suction cavity of the compressors.

2) The evaporator unit for cooling the coolant must include a device for separating liquid droplets from the vapor-liquid ammonia mixture and returning the separated liquid to the evaporator.

3) To separate the liquid phase from the moving vapor-liquid mixture in refrigeration systems with direct cooling, circulation (or protective) receivers are provided for each boiling point, combining the functions of a liquid separator. It is allowed to provide for these purposes separate liquid separators connected by pipelines to circulation (protective) receivers that do not combine the functions of a liquid separator.

4) The geometric volume of circulation receivers with a riser, combining the functions of a liquid separator, for each boiling point in pump circuits with lower and upper ammonia supply to cooling devices should be calculated using the formulas given in.

5) For emergency (repair) removal of liquid ammonia from cooling devices, apparatus, vessels and blocks, as well as to remove condensate when thawing cooling devices with hot vapors, it is necessary to provide a drainage receiver designed to receive ammonia from the most ammonia-intensive apparatus, vessel or block.

6) The geometric volume of the drainage receiver should be taken from the condition of filling it no more than 80%.

7) The geometric volume of linear receivers of refrigeration units should be no more than 30% of the total geometric volume of the cooling devices of the premises, the ammonia part of technological devices and evaporators.

8) For refrigeration machines with dosed ammonia charging, a linear receiver is not provided.

Hydrogen, under normal conditions, is a colorless gas with a sharp characteristic odor (the smell of ammonia)

• Halogens (chlorine, iodine) form dangerous explosives with ammonia - nitrogen halides (nitrogen chloride, nitrogen iodide).

• Ammonia reacts with halogenated alkanes through nucleophilic addition, forming a substituted ammonium ion (method for producing amines):

• It produces amides with carboxylic acids, their anhydrides, acid halides, esters and other derivatives. With aldehydes and ketones - Schiff bases, which can be reduced to the corresponding amines (reductive amination).

• At 1000 °C, ammonia reacts with coal, forming hydrocyanic acid HCN and partially decomposing into nitrogen and hydrogen. It can also react with methane, forming the same hydrocyanic acid:

History of the name

Ammonia (in European languages ​​its name sounds like “ammoniac”) owes its name to the oasis of Ammon in North Africa, located at the crossroads of caravan routes. In hot climates, urea (NH 2) 2 CO, contained in animal waste products, decomposes especially quickly. One of the decomposition products is ammonia. According to other sources, ammonia got its name from the ancient Egyptian word Amonian. This was the name given to people who worshiped the god Amon. During their rituals, they sniffed ammonia NH 4 Cl, which, when heated, evaporates ammonia.

Liquid ammonia

Liquid ammonia, although to a small extent, dissociates into ions (autoprotolysis), which shows its similarity to water:

The self-ionization constant of liquid ammonia at −50 °C is approximately 10 −33 (mol/l)².

The metal amides resulting from the reaction with ammonia contain a negative ion NH 2 −, which is also formed during the self-ionization of ammonia. Thus, metal amides are analogues of hydroxides. The reaction rate increases when going from Li to Cs. The reaction is significantly accelerated in the presence of even small impurities of H 2 O.

Metal-ammonia solutions have metallic electrical conductivity; in them, metal atoms decompose into positive ions and solvated electrons surrounded by NH 3 molecules. Metal-ammonia solutions, which contain free electrons, are the strongest reducing agents.

Complexation

Due to their electron-donating properties, NH 3 molecules can enter complex compounds as ligands. Thus, the introduction of excess ammonia into solutions of d-metal salts leads to the formation of their amino complexes:

Complexation is usually accompanied by a change in the color of the solution. So, in the first reaction, the blue color (CuSO 4) turns into dark blue (the color of the complex), and in the second reaction the color changes from green (Ni(NO 3) 2) to blue-violet. The strongest complexes with NH 3 are formed by chromium and cobalt in the oxidation state +3.

Biological role

Ammonia is the end product of nitrogen metabolism in the body of humans and animals. It is formed during the metabolism of proteins, amino acids and other nitrogenous compounds. It is highly toxic to the body, so most of the ammonia during the ornithine cycle is converted by the liver into a more harmless and less toxic compound - carbamide (urea). The urea is then excreted by the kidneys, and some of the urea may be converted by the liver or kidneys back to ammonia.

Ammonia can also be used by the liver for the reverse process - resynthesis of amino acids from ammonia and keto analogues of amino acids. This process is called "reductive amination". Thus, aspartic acid is obtained from oxaloacetic acid, glutamic acid is obtained from α-ketoglutaric acid, etc.

Physiological action

According to its physiological effect on the body, it belongs to the group of substances with asphyxiating and neurotropic effects, which, if inhaled, can cause toxic pulmonary edema and severe damage to the nervous system. Ammonia has both local and resorptive effects.

Ammonia vapors strongly irritate the mucous membranes of the eyes and respiratory organs, as well as the skin. This is what a person perceives as a pungent odor. Ammonia vapors cause excessive lacrimation, eye pain, chemical burns of the conjunctiva and cornea, loss of vision, coughing attacks, redness and itching of the skin. When liquefied ammonia and its solutions come into contact with the skin, a burning sensation occurs, and a chemical burn with blisters and ulcerations is possible. In addition, liquefied ammonia absorbs heat when it evaporates, and when it comes into contact with the skin, frostbite of varying degrees occurs. The smell of ammonia is felt at a concentration of 37 mg/m³.

Application

Ammonia is one of the most important products of the chemical industry; its annual global production reaches 150 million tons. Mainly used for the production of nitrogen fertilizers (ammonium nitrate and sulfate, urea), explosives and polymers, nitric acid, soda (using the ammonia method) and other chemical industry products. Liquid ammonia is used as a solvent.

Consumption rates per ton of ammonia

To produce one ton of ammonia in Russia, an average of 1200 nm³ of natural gas is consumed, in Europe - 900 nm³.

The Belarusian Grodno Azot consumes 1,200 nm³ of natural gas per ton of ammonia; after modernization, the consumption is expected to decrease to 876 nm³.

Ukrainian producers consume from 750 nm³ to 1170 nm³ of natural gas per ton of ammonia.

UHDE technology claims consumption of 6.7 - 7.4 Gcal of energy resources per ton of ammonia.

Ammonia in medicine

For insect bites, ammonia is used externally in the form of lotions. A 10% aqueous solution of ammonia is known as ammonia.

Possible side effects: with prolonged exposure (inhalation use), ammonia can cause a reflex cessation of breathing.

Local use is contraindicated for dermatitis, eczema, other skin diseases, as well as for open traumatic injuries to the skin.

In case of accidental damage to the mucous membrane of the eye, rinse with water (15 minutes every 10 minutes) or 5% boric acid solution. Oils and ointments are not used. If the nose and throat are affected, use a 0.5% solution of citric acid or natural juices. If taken orally, drink water, fruit juice, milk, preferably a 0.5% solution of citric acid or a 1% solution of acetic acid until the contents of the stomach are completely neutralized.

Interaction with other drugs is unknown.

Ammonia producers

Ammonia producers in Russia

Russia accounts for about 9% of global ammonia production. Russia is one of the world's largest exporters of ammonia. About 25% of total ammonia production is exported, which is about 16% of world exports.

Ammonia producers in Ukraine

• Jupiter's clouds are made of ammonia.

See also

Notes

Links

• //
• // Encyclopedic Dictionary of Brockhaus and Efron: In 86 volumes (82 volumes and 4 additional ones). - St. Petersburg. , 1890-1907.
• // Encyclopedic Dictionary of Brockhaus and Efron: In 86 volumes (82 volumes and 4 additional ones). - St. Petersburg. , 1890-1907.
• // Encyclopedic Dictionary of Brockhaus and Efron: In 86 volumes (82 volumes and 4 additional ones). - St. Petersburg. , 1890-1907.

Literature

• Akhmetov N. S. General and inorganic chemistry. - M.: Higher School, 2001.

Properties of ammonia NH 3 (gas) at atmospheric pressure

Ammonia (NH 3) is a toxic flammable gaseous substance that has the property of forming an explosive mixture upon contact with air.

At normal pressure and room temperature it exists in the form of a gas. For use in production and transportation, ammonia (nitride) is liquefied.

Technical ammonia is used as the main raw material in the production of a large number of substances containing and used in various industries: mineral fertilizers, and hydrocyanic acids, in general organic synthesis, etc.

The table shows the density and thermophysical properties of ammonia in the gaseous state depending on temperature at a pressure of 760 mmHg. The properties of ammonia are indicated at temperatures from -23 to 627 °C.

The table shows the following properties of ammonia:

• ammonia density, kg/m3;
• thermal conductivity coefficient, W/(m deg);
• dynamic viscosity, ;
• Prandtl number.

The table shows that the properties of ammonia depend significantly on temperature. So, As temperature increases, the density of ammonia decreases, and Prandtl number; other characteristics of this gas increase their values.

For example, at temperature 27°C(300 K) ammonia has a density equal to 0.715 kg/m 3, and when heated to 627°C (900 K), the density of ammonia decreases to a value of 0.233 kg/m 3.

The density of ammonia at room temperature and normal atmospheric pressure is significantly lower under these conditions.

Note: Be careful! The thermal conductivity of ammonia in the table is indicated to the power of 10 3. Don't forget to divide by 1000.

Properties of ammonia (dry saturated steam)

The table shows the thermophysical properties of dry saturated ammonia depending on temperature.
Properties are given in the temperature range from -70 to 70 °C.

The table shows the following properties of ammonia vapor:

• ammonia density, kg/m3;
• heat of phase transition, kJ/kg;
• specific heat capacity, kJ/(kg deg);
• thermal diffusivity, m 2 /s;
• dynamic viscosity, Pa s;
• kinematic viscosity, m 2 /s;
• Prandtl number.

The properties of ammonia are highly dependent on temperature. There is a direct relationship between temperature and pressure of saturated ammonia vapor.
The density of saturated ammonia vapor increases significantly. Thermal diffusivity and viscosity values ​​decrease. The thermal conductivity of saturated ammonia vapor in the table is indicated to the power of 10 4. Don't forget to divide by 10000.

Properties of liquid ammonia in a saturated state

The table shows the thermophysical properties of saturated ammonia liquid depending on temperature.
The properties of ammonia in a saturated liquid state are given in the temperature range from -70 to 70 °C.

The table shows the following properties of liquid ammonia:

• saturated vapor pressure, MPa;
• ammonia density, kg/m3;
• specific heat capacity, kJ/(kg deg);
• thermal conductivity, W/(m deg);
• thermal diffusivity, m 2 /s;
• dynamic viscosity, Pa s;
• kinematic viscosity, m 2 /s;
• surface tension coefficient, N/m;
• Prandtl number.

The density of ammonia in the liquid state is less dependent on temperature than the density of its vapor. Only dynamic viscosity decreases significantly with increasing temperature of liquid ammonia.

Thermal conductivity of ammonia in liquid and gaseous states

The table shows the thermal conductivity of ammonia in liquid and gaseous states depending on temperature and pressure.
The thermal conductivity of ammonia (dimension W/(m deg)) is indicated in the temperature range from 27 to 327 °C and pressure from 1 to 1000 atmospheres.

The thermal conductivity of ammonia in the table is indicated to the power of 10 3. Don't forget to divide by 1000.
Thermal conductivity values ​​above the line are indicated for liquid ammonia, the thermal conductivity of which decreases with increasing temperature.

The thermal conductivity of ammonia gas increases when heated. An increase in pressure leads to an increase in the thermal conductivity value for both liquid and gaseous ammonia.

The following table shows thermal conductivity of ammonia at low temperatures and atmospheric pressure.

on the saturation line depending on temperature is shown in the table below. It should be noted that the thermal conductivity of liquid ammonia decreases when heated.

Note: Be careful! The thermal conductivity of ammonia in the tables is indicated to the power of 10 3. Don't forget to divide by 1000.

Ammonia. The molecules of this gas have the shape of a pyramid, at one of the vertices of which there is a nitrogen atom. They are formed through hydrogen bonds and are characterized by strong polarity. This explains the unusual nature of ammonia: its melting point is about -80 degrees. It dissolves well in water, alcohols and other organic solvents.

Application of ammonia

Ammonia plays an important role in industry. It is used to produce nitrogen fertilizers used in agriculture, nitric acid and even explosives. Ammonia, widely used by doctors, is also produced using ammonia. The pungent odor of this gas irritates the nasal mucosa and stimulates respiratory functions. Ammonia is used for fainting or alcohol poisoning. There is also external use of ammonia in medicine. It is an excellent antiseptic that surgeons use to treat their hands before operations.

Ammonia, as a product of the decomposition of ammonia, is used in metal soldering. At high temperatures, ammonia is produced from ammonia, which protects the metal from the formation of an oxide film.

Ammonia poisoning

Ammonia is a toxic substance. Poisoning with this gas often occurs at work, which is accompanied by suffocation, delirium and severe agitation. How to help a person who finds himself in such a situation? First you need to rinse his eyes with water and put on a gauze bandage, previously soaked in a weak solution of citric acid. Then it is necessary to remove it outside the area where there is a high concentration of ammonia. Poisoning is possible at a concentration of about 350 mg/m³.

If ammonia comes into contact with your skin, immediately rinse the affected areas with water. Depending on the amount of ammonia exposed to the skin, severe redness or chemical burns with blisters may occur.

Strict fire safety measures have been introduced at factories where ammonia is produced. The fact is that a mixture of ammonia and air is highly flammable. Containers where it is stored can easily explode when heated.

Chemical properties of ammonia

Ammonia reacts with many acids. As a result of this interaction, various ammonium salts are obtained. When reacting with polybasic acids, two types of salts are obtained (depending on the number of moles of ammonia).