Ammonia production process. Modern ammonia production process

Ammonia- a light, colorless gas with an unpleasant, pungent odor. It is very important for the chemical industry, since it contains a nitrogen atom and three hydrogen atoms. Ammonia is used mainly for the production of nitrogen-containing fertilizers, ammonium sulfate and urea, for the production of explosives, polymers and other products; ammonia is also used in medicine.

Ammonia production in industry not a simple, labor-intensive and expensive process based on its synthesis from hydrogen and nitrogen using a catalyst, high temperature and under pressure. Oxide activated Potassium and aluminum sponge iron is used as a catalyst. Industrial plants for the synthesis of ammonia are based on the circulation of gases. It looks like this: the reacted mixture of gases, which contains ammonia, is cooled and condensation and separation of ammonia occurs, and nitrogen and hydrogen, which did not react, are mixed with a new portion of gases and again supplied to the catalyst.

Let us consider this process of industrial synthesis of ammonia, which occurs in several stages, in more detail. At the first stage, sulfur is removed from natural gas using technical device desulfurizer. At the second stage, the process of methane conversion is carried out at a temperature of 800 degrees Celsius on a nickel catalyst: Formed after this hydrogen reaction is suitable For the synthesis of ammonia, air containing nitrogen is supplied to the reactor. At this stage partial combustion of carbon also occurs after its interaction with oxygen, which is also contained in the air: 2 H2O + O2->H2O (steam).

The result of this stage production is to obtain a mixture of water vapor and oxides of carbon (secondary) and nitrogen. The third stage takes place in two processes. The so-called “shift” process takes place in two “shift” reactors. In the first, Fe3O4 catalyst is used and the reaction occurs at high temperatures, order 400 degrees Celsius. The second reactor uses a more productive copper catalyst and operates at a lower temperature. The fourth stage includes purification of the gas mixture from carbon monoxide (IV).

This cleaning is carried out by washing the gas mixture alkaline solution, which absorbs the oxide. The reaction 2 H2O + O2H2O (steam) is reversible and after the third stage, approximately 0.5% carbon monoxide remains in the gas mixture. This amount is enough to ruin the iron catalyst. At the fourth stage, carbon monoxide (II) is eliminated by converting hydrogen into methane on a nickel catalyst at temperatures of 400 degrees Celsius: CO + 3H2 -> CH4 + H2O

Gas mixture, which approximately contains? 74.5% hydrogen and 25.5% nitrogen are subjected to compression. Compression leads to a rapid increase in the temperature of the mixture. After compression, the mixture is cooled to 350 degrees Celsius. This process is described with the reaction: N2 + 3H2 - 2NH3 ^ + 45.9 kJ. (Gerber process)

Related articles:

	Building gypsum, which consists of dense rocks of gypsum, is produced using three main operations. First, the gypsum stone is crushed, then the resulting raw materials are ground, and...
	Chemical waste is waste from the chemical industry that contains harmful substances posing a threat to humans due to their toxic effects on the body. The chemical industry is a branch of industry dealing...

Ammonia (NH 3) is a compound of nitrogen and hydrogen. This light gas with a pungent odor. The production of ammonia in industry and laboratories is necessary for the production of fertilizers, polymers, nitric acid and other substances.

In industry

Ammonia is industrially produced from nitrogen by combining it with hydrogen. Nitrogen is taken from the air, hydrogen from water. The method was first developed by the German chemist Fritz Haber. The industrial method for producing ammonia began to be called the Haber process.

The reaction occurs with a decrease in volume and release of energy in the form of heat:

3H 2 + N 2 → 2NH 3 + Q.

The reaction is reversible, so several conditions must be met. At high pressure and low temperatures, the volume of ammonia produced increases. However, low temperatures slow down the reaction rate, and increasing the temperature increases the rate of the reverse reaction.

The necessary conditions for carrying out the reaction were experimentally found:

• temperature- 500°C;
• pressure- 350 atm;
• catalyst- iron oxide Fe 3 O 4 (magnetite) with admixtures of oxides of silver, potassium, calcium and other substances.

Under these conditions, the resulting gas contains 30% ammonia. To avoid a reverse reaction, the substance is quickly cooled. At low temperatures, the resulting gas turns into a liquid. Unspent gases - nitrogen and hydrogen - are returned back to the synthesis column. This method helps to quickly obtain large volumes of ammonia, using raw materials as much as possible.

Rice. 1. Production of ammonia industrially.

To find the right catalyst, 20 thousand different substances were tried.

In the laboratory

To obtain ammonia in the laboratory, the reaction of alkalis with ammonium salts is used:

NH 4 Cl + NaOH → NH 3 + NaCl + H 2 O

Ammonia can also be obtained in the laboratory from ammonium chloride heated together with slaked lime, or by decomposition of ammonium hydroxide:

• 2NH 4 Cl + Ca(OH) 2 → CaCl 2 + 2NH 3 + 2H 2 O;
• NH 4 OH ↔ NH 3 + H 2 O.

Rice. 2. Obtaining ammonia in the laboratory.

Ammonia can be completely dried using a mixture of lime and sodium hydroxide, through which the resulting gas is passed. For the same purpose, liquid ammonia is mixed with sodium metal and subjected to distillation.

Ammonia is lighter than air, so to collect it, the test tube is held upside down.

Application

Ammonia is used in various industries:

• in agriculture - for the production of nitrogen-containing fertilizers;
• in industry - for the production of polymers, explosives, artificial ice;
• in chemistry - for the production of nitric acid, soda;
• in medicine - as ammonia.

Rice. 3. Fertilizer production.

What have we learned?

Ammonia is produced industrially and in the laboratory. For production on an industrial scale, nitrogen and hydrogen are used. Mixing under high temperature, pressure and under the influence of a catalyst, simple substances form ammonia. To prevent the reaction at high temperatures from going into reverse side, the gas is cooled. In the laboratory, ammonia is obtained by reacting ammonium salts with alkalis, slaked lime, or by decomposing ammonium hydroxide. Ammonia is used in the chemical industry, agriculture, medicine, and chemistry.

Test on the topic

Evaluation of the report

Average rating: 4.2. Total ratings received: 263.

1) 4FeS 2 + 11O 2 → 2Fe 2 O 3 + 8SO 2

2) 2SO 2 + O 2 V 2 O 5 → 2SO 3

3) nSO 3 + H 2 SO 4 → H 2 SO 4 nSO 3 (oleum)

Crushed, purified, wet pyrite (sulfur pyrite) is poured into the kiln on top for firing in " fluidized bed". Air enriched with oxygen is passed from below (counterflow principle).
Furnace gas comes out of the furnace, the composition of which is: SO 2, O 2, water vapor (the pyrite was wet) and tiny particles of cinder (iron oxide). The gas is purified from impurities of solid particles (in a cyclone and an electric precipitator) and water vapor (in a drying tower).
In a contact apparatus, sulfur dioxide is oxidized using a V 2 O 5 catalyst (vanadium pentoxide) to increase the reaction rate. The process of oxidation of one oxide to another is reversible. Therefore, optimal conditions for the direct reaction to occur are selected - high blood pressure(since the direct reaction occurs with a decrease in the total volume) and the temperature is not higher than 500 C (since the reaction is exothermic).

In the absorption tower, sulfur oxide (VI) is absorbed by concentrated sulfuric acid.
Absorption by water is not used, because sulfur oxide dissolves in water with the release of a large amount of heat, so the resulting sulfuric acid boils and turns into steam. To prevent the formation of sulfuric acid fog, use 98% concentrated sulfuric acid. Sulfur oxide dissolves very well in such an acid, forming oleum: H 2 SO 4 nSO 3

Industrial production of ammonia

A nitrogen-hydrogen mixture is first prepared. Hydrogen is produced by methane conversion (from natural gas):

CH 4 + H 2 O(g) → CO + ZN 2 - Q

2CH 4 + O 2 → 2CO + 4H 2 + Q

CO + H 2 O (g) → CO 2 + H 2 + Q

Nitrogen is obtained from liquid air.

In the turbocharger, the mixture is compressed to the required pressure of 25·10 6 Pa. In the synthesis column, gases react at 450-500 °C in the presence of a catalyst (porous iron with admixtures of Al 2 O 3 and K 2 O):
N 2 + 3H 2 ↔ 2NH 3 + 92 kJ (yield 10-20% ammonia)

The resulting ammonia is separated from unreacted nitrogen and hydrogen by liquefaction in a refrigerator, returning the unreacted nitrogen-hydrogen mixture to the synthesis column.
The process is continuous, circulating.

Application: production nitrogen fertilizers, explosives, plastics, etc.

Production of methyl alcohol

Before the industrial development of the catalytic method of production, methanol was obtained by dry distillation of wood (hence its name “wood alcohol”). IN given time this method is of secondary importance.

Modern way:

Raw materials: synthesis gas - a mixture of carbon monoxide (II) with hydrogen (1:2).

Auxiliary materials: catalysts (ZnO and CuO).

Basic chemical process: synthesis gas at a temperature of 250 °C and a pressure of 7 MPa is converted catalytically into methanol:

CO + 2H 2 ↔ CH3OH + Q

Peculiarities technological process: when the gas mixture passes through the catalyst layer, 10-15% methanol is formed, which is condensed, and the unreacted mixture is mixed with a fresh portion of synthesis gas and, after heating, is again sent to the catalyst layer (circulation). The overall yield is 85%.

The conditions for the synthesis of methanol and ammonia at medium pressure are similar, and the raw materials ( natural gas) common to both processes. Therefore, most often the production of methanol and ammonia is combined (nitrogen-fertilizer plants).

Ammonia –N.H. 3

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.

1. Molecule structure

The ammonia molecule has the shape of a trigonal pyramid with a nitrogen atom at the apex. Three unpaired p-electrons of the nitrogen atom participate in the formation of polar covalent bonds with the 1s-electrons of three hydrogen atoms (N−H bonds), the fourth pair of outer electrons is lone, it can form a donor-acceptor bond with a hydrogen ion, forming an ammonium ion NH 4 + .

View chemical bond: covalent polar, three singleσ - sigma N-H bonds

2. Physical properties ammonia

Under normal conditions, it is a colorless gas with a sharp characteristic odor (the smell of ammonia), almost twice as light as air, and poisonous.According to its physiological effect on the body, it belongs to the group of substances with asphyxiating and neurotropic effects, capable of causing toxic pulmonary edema and severe damage if inhaled. nervous system. Ammonia vapors strongly irritate the mucous membranes of the eyes and respiratory organs, as well as the skin. This is what we perceive 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. The solubility of NH 3 in water is extremely high - about 1200 volumes (at 0 °C) or 700 volumes (at 20 °C) per volume of water.

3.

4. Chemical properties ammonia

Ammonia is characterized by the following reactions:

1. with a change in the oxidation state of the nitrogen atom (oxidation reaction)
2. without changing the oxidation state of the nitrogen atom (addition)

5. Application of ammonia

In terms of production volumes, ammonia occupies one of the first places; Every year, about 100 million tons of this compound are produced worldwide. Ammonia is available in liquid form or in the form of an aqueous solution - ammonia water, which usually contains 25% NH 3. Huge quantities of ammonia are further used to produce nitric acid which goes to fertilizer production and many other products. Ammonia water is also used directly as fertilizer, and sometimes fields are watered directly from tanks with liquid ammonia. From ammonia receive various ammonium salts, urea, methenamine. His also used as a cheap refrigerant in industrial refrigeration units.

Ammonia is also used for producing synthetic fibers, for example, nylon and nylon. In light industry he 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. Ammonia is also used in the production of soda using the Solvay method. In the steel industry, ammonia is used for nitriding - saturating the surface layers of steel with nitrogen, which significantly increases its hardness.

Doctors use aqueous solutions ammonia (ammonia) in everyday practice: cotton wool soaked in ammonia, brings a person out of a fainting state. Ammonia in this dose is not dangerous for humans.

EXERCISES

Simulator No. 1 "Ammonia combustion"

Simulator No. 2 "Chemical properties of ammonia"

ASSIGNMENT TASKS

№1. Carry out transformations according to the scheme:

a) Nitrogen → Ammonia → Nitric oxide (II)

b) Ammonium nitrate → Ammonia → Nitrogen

c) Ammonia → Ammonium Chloride → Ammonia → Ammonium Sulfate

The nitrogen industry today is one of the leading industries. The use of ammonia has expanded to refrigeration (R717, medical or agriculture(fertilizers).

Primary attention is paid specifically to the production of nitrogen fertilizers (and therefore their bases, including ammonia, the demand for which has increased by 20% over the past two decades).

But ammonia production is characterized, first of all, by its high energy intensity. The whole history of this production is the struggle to reduce the energy used (mechanical, thermal, electrical).

The synthesis of ammonia is revealed by the formula:

N2 + 3H2 = 2NH3 + Q

The reaction is exothermic, reversible, with a decrease in volume. Since the reaction is exothermic, lowering the temperature will shift the equilibrium towards the formation of ammonia, but will decrease significantly. Ammonia production must take place at high temperatures (synthesis takes place at 500 degrees Celsius). An increase in t° will lead to Pressure from 15 to 100 MPa allows you to counteract the influence of temperature (low pressure - from 10 to 15 MPa, medium pressure - from 25 to 30 MPa, high pressure - over 50 MPa). Of these, the average is preferable.

The catalyst is used with the addition of calcium, silicon, potassium, and aluminum oxides.

Harmful impurities (water, hydrogen sulfide) negatively affect the reaction rate, poisoning the catalyst, thereby reducing its activity and reducing its service life. This means that the hydrogen sulfide mixture must undergo thorough cleaning. But even after purification, only part of this mixture turns into ammonia. Therefore, the remaining unreacted fraction is sent back to the reactor.

How is ammonia produced?

An already prepared mixture of three parts hydrogen and one part nitrogen is fed into the pipeline. It passes through a turbocharger, where it is compressed to the above pressure, and is sent to a synthesis column with a catalyst on built-in shelves. The process, as we found out, is highly exothermic. The released heat heats up the nitrogen-hydrogen mixture. About 25 percent of ammonia and unreacted nitrogen and hydrogen come out of the column. The entire composition goes into the refrigerator, where the mixture is cooled. Ammonia becomes liquid under pressure. Now the separator comes into operation, the task of which is to separate the ammonia into a collection at the bottom and the unreacted mixture, which is returned back to the column. Thanks to this circulation, the nitrogen-hydrogen mixture is used by 95 percent. Liquid ammonia is transported through an ammonia pipeline to a special warehouse.

All devices used in production are as sealed as possible, which eliminates leakage. Only the energy of the exothermic reactions occurring inside is used. The scheme is closed, low-waste. Costs are reduced thanks to a continuous and automated process.

Ammonia production cannot but affect environment. Gas emissions, including ammonia, carbon and nitrogen oxides and other impurities, are inevitable. Low-grade heat is released. Water is discharged after flushing the cooling systems and the reactor itself.

Therefore, ammonia production must include catalytic purification with the presence of a reducing gas. Quantity reduction waste water can be achieved by replacing with turbochargers. Low-grade heat can be utilized by introducing high-potential heat. However, this will increase pollution from flue gases.

An energy technology scheme that includes a steam-gas cycle, where both the heat of steam and fuel combustion products are used, will simultaneously increase production efficiency and reduce emissions.