SU882918A1 - Method of sulfuring acid production - Google Patents

Description

The invention relates to a technique for producing sulfuric acid by the nitrous method. The known nitrous method of producing sulfuric acid is carried out on the basis of the roasting gas, which enters the process at 350-400 ° C and contains on average 9% 50/2 and 9% Oft, 80% NQ and 2% H2P, including stages denitration of production acid, oxidation and absorption of tl3 The disadvantage of this method is significant emissions of nitrogen oxides and sulfur dioxide into the atmosphere with exhaust gas, which leads to an increase in the consumption of nitric acid in the process of obtaining sulfuric acid, as well as poisoning of the environment with the indicated toxic oxides acid gases. The purpose of the invention is to reduce the loss of nitrogen oxides and eliminate emissions of toxic impurities into the atmosphere. The goal is to achieve that the purification of waste gases is accomplished by passing them through the adsorbent junction, followed by desorption of the absorbed oxides of nitrogen and sulfur dioxide with firing gas, which is then returned to the process. The drawing shows a diagram of the proposed method. The circuit contains block 1, including the 1st stage of hydrolysis, oxidation and absorption; adsorbers 2 and gas blowers 3 and 4. The process is carried out as follows. The firing gas contains an average of 9% S02. 9% O / g., At 350-400 ° C, enters unit 1, which includes the stages of denitration of production acid, oxidation and absorption. At the stage of hydrolysis, in production towers (there are usually two of them) from the top, towards the motion of the roasting gas, water and off-stream acid, as well as nitrosylsulfuric acid, obtained at the last stage of the process, the absorption stage, are supplied for irrigation. Under the influence of high temp. Peru-E roaster gas and dilution of the acid with water, hydrolysis of nitrosylsulfuric acid occurs with the formation of .. At the same time, the absorption of S OO by water and the formation reaction in what phase occurs.

Partially oxidation of S0, j and formation occurs in the gas phase. From the first tower, the hydrolysis stages are withdrawn as a finished product, and from the second tower N, 50. as absorbent for the final stage of the process, the absorption stage. The resulting nitric oxide is poorly soluble. It is dasorbed from the acid and oxidized with oxygen in the oxidation stage (usually one tower). Oxidation is accompanied by lowering the heat transfer agent by combining nitric oxide and nitrogen dioxide molecules to form, which is then absorbed at the absorption stage with sulfuric acid, which is fed for irrigation to the towers operating in series (usually two). The resulting nitrosylsulfuric acid is directed to the hydrolysis step, and the spent roasting gas is sent to the exhaust pipe in the form of so-called exhaust gas (off-gas).

Exhaust gas containing nitrogen oxides and sulfur oxides (target components) coming out of block 1 is directed to the adsorption stage 2 to adsorbents (the diagram shows 3 adscopically heated toxic gases from the exhaust gases. The purified gas stream is thrown into the atmosphere.

While one of the adsorbers 2 is in the process of adsorption (simultaneous absorption of nitrogen oxides and sulfuric anhydride by the adsorbent layer), in others, respectively, desorption steps are performed (separation of nitrogen oxides and sulfur dioxide from the adsorbent layer) and the adsorbent is cooled, i.e. the adsorbent is regenerated. Once in the apparatus, where the pulverisation process takes place, a layer of the target component will slip past the adsorbent layer, the exhaust gas to the apparatus is automatically stopped and the exhaust gas flow is switched to the second apparatus, in which the adsorbent has already been regenerated. The desorption is carried out by part of the roasting gas supplied to unit 1, at 35 О-4 00 ° С (here you can use the clinoptilolite type zeolite from domestic deposits).

I At the outlet of the apparatus, the desorbing gas comprises nitrogen oxides and sulfur dioxide separated from the layer of adsorbent, which by the gas blower 3 is sent to the beginning of the process before block 1 to the common firing gas feed line. In order to cool the adsorbent layer, after desorption, a portion of the purified gas is passed through the adsorbent layer (shown in dotted lines in the diagram) taken from

purified gas and having a temperature of about b. The gas exhausted during the cooling stage of the adsorbent by the gas blower 4 is directed to the clean gas line. After the adsorbent is regenerated, exhaust gas from block 1 is again supplied to the adsorber for adsorption deep purification from nitrogen and sulfur oxides, and the other two adsorbents automatically switch to the desorption and cooling stages. These stages in the apparatuses are sequentially repeated to carry out continuous purification of the exhaust gas.

An example. Exhaust gas,

5 containing 0.5% 50 and 0.2%

N0

with a temperature of 25 ° C is fed into the adsorber with a fixed bed gsbsorbent granular 3-4 mm with a speed of 0.5 m / s,

Acid-resistant adsorbents, natural zeolites from various deposits, which have the same adsorption capacity for these substances, are used for purification from these substances. For example, the dynamic activity of clinoptilolite in the Hekordzula deposit of the Georgian SSR is at 25 ° C relative to SO. 20 mg / g, and with respect to nitrogen oxides 22 mg / g. Its density is 800 kg / m.

After the target component has slipped past the adsorbent layer, the gas supply to this unit is automatically stopped and the exhaust gas flow is switched to the second unit, where the adsorbent has already been regenerated. And in the first adsorber, the spent adsorbent is blown through with part of the calcining gas, even at a speed of 0.5 m / s, and then subjected to cooling. The desorption and cooling time of the adsorbent is 7.8 i. While in one adsorber there is adsorption of 502 and nitrogen oxides before breakthrough for 8 hours, in the other - its regeneration during the same time. The cooling of the adsorbent layer can be carried out in its upper part to 120 ° C, since for clinoptilolite the adsorption activity decreases slightly. At the exit from the desorbirukhdium apparatus, the gas contains oxides of nitrogen and sulfur dioxide, separated from the layer of adsorbent, which are directed by the gas blower to the beginning of the process.

Thus, nitrogen oxides and sulfur dioxide are completely removed from the effluent gas and returned to the beginning of the process, which entails a reduction in the consumption of valuable nitric acid and the production of additional sulfuric acid and the elimination of harmful emissions of nitrogen oxides and sulfur dioxide into the atmosphere.

Claims (1)

Invention Formula A method for producing sulfuric acid from a roasting gas using the nitrous method, which includes the stages of denitration of production acid, oxidation, absorption of nitrogen oxides and purification of exhaust gases, characterized in that, in order to reduce losses of nitrogen oxides and eliminate emissions of toxic impurities into the atmosphere This is accomplished by passing them through an adsorbent bed, followed by desorption of the absorbed oxides of nitrogen and sulfur dioxide with firing gas, which is then returned to the beginning of the process. Sources of information taken into account in the examination 1. A.G.Amelin. Sulfur technology acid. M., Himi, 1971, p. 3230 325. About gas 7ir Exhaust gas