Today, sulfuric acid is produced mainly by two industrial methods: contact and nitrous. The contact method is more progressive and in Russia it is used more widely than nitrous, that is, tower.
The production of sulfuric acid begins with the firing of sulfur materials, for example, iron pyrites. In special pyritic furnaces, the so-called calcining gas is obtained, which contains about 9% sulfur dioxide. This stage is the same for both the contact and nitrous methods.
Next, it is necessary to oxidize the resulting sulfur dioxide into sulfur. However, it must first be cleaned of a number of impurities that interfere with the further process. The fired gas is cleaned of dust in electrostatic precipitators or in cyclone devices, and then it is fed to a device containing solid contact masses, where sulfur dioxide SO 2 is oxidized to sulfuric anhydride SO 3 .
This exothermic reaction is reversible - an increase in temperature leads to decomposition of the formed sulfuric anhydride. On the other hand, with decreasing temperature, the rate of the direct reaction is very small. Therefore, the temperature in the contact apparatus is maintained within 480 ° C, by adjusting its speed of passage of the gas mixture.
Subsequently, in the contact method, sulfuric acid is formed by combining sulfuric anhydride with water.
The nitrous method is characterized in that sulfur dioxide is oxidized by nitrogen oxides. The production of sulfuric acid by this method is triggered by the formation of sulfur dioxide during the interaction of sulfur dioxide from the calcining gas with water. Subsequently, the resulting sulfuric acid is oxidized with nitric acid, which leads to the formation of nitric monoxide and sulfuric acid.
This reaction mixture is fed to a special tower. At the same time, by regulating the gas flow, they achieve that in the gas mixture entering the absorption tower, nitrogen dioxide and monoxide are contained in a ratio of 1: 1, which is necessary to obtain nitrous anhydride.
Finally, the interaction of sulfuric acid and nitrous anhydride produces NOHSO 4 - nitrosyl sulfuric acid.
The resulting nitrosylsulfuric acid is fed into the production tower, where it decomposes with water and releases nitrous anhydride:
2NOHSO 4 + H 2 O = N 2 O 3 + 2H 2 SO 4,
which oxidizes the sulfuric acid formed in the tower.
Nitric oxide released as a result of the reaction returns to the oxidation tower again and enters a new cycle.
At present, in Russia, the production of sulfuric acid is carried out mainly by the contact method. The nitrous method is rarely used.
The use of sulfuric acid is very wide and diverse.
Most of it goes to the production of chemical fibers and mineral fertilizers, it is necessary in the production of drugs and dyes. Ethyl and other alcohols, detergents and pesticides are obtained with the help of sulfuric acid.
Its solutions are used in the textile, food industry, in nitration processes and for the production of explosives. Battery sulfuric acid serves as an electrolyte for pouring into lead batteries, which are widely used in transport.