SU910110A3 - Process for purifying off gases from sulphur oxides - Google Patents

Abstract

1407028 Removing sulphur oxides from gases MITSUBISHI JUKOGYO KK 22 Nov 1972 [22 Nov 1971] 54005/72 Heading C1A SO 2 and SO 3 are removed from gas streams containing more than 2% by vol. O 2 by scrubbing the stream with an aqueous suspension of pulverized slag containing Ca as the major constituent and having a pH in the range 1À5-4À0. The aqueous suspension may contain 6% by wt. pulverized slag comprising Ca 2 Al 2 SiO 7 (40% by wt. CaO) and having an average particle size of 60 Á. The slag is derived from blast furnaces, converters or open hearth furnaces. The solid reaction product, principally CaSO 4 . 2H 2 O may be removed by filtration. The gas stream may be the exhaust from an oil-burning boiler or an internal combustion engine.

Description

The invention relates to methods for purifying waste gases from sulfur oxides to can be used in the chemical and metallurgical industries. A known method for the absorption of sulfur dioxide from flue gases is by passing them through an aqueous suspension with a pH of 89 finely divided siliceous material, for example, slag from the melting point fl. The disadvantage of this method is the low absorptive capacity of the suspension, since the absorbed sulfur dioxide in the aqueous medium contains sulfuric acid, which absorbs almost no components of the suspension and is not oxidized to sulfuric acid. The equilibrium data of O over the solution, sulfuric acid reaches 1OOO ppm, at pH 4 n, the process of absorbing S O from the exhaust gases is stopped when the content in the gas is p, 1% - 90 .. There is also a known method for cleaning the exhaust gases from sulfur oxides absorbed (due to their aqueous suspension of limestone (iesvest) method) pH less than 6. The disadvantage of this method is due to the insufficient oxidation rate of calcium sulfate obtained in the absorption of sulfate, which limits the absorptive capacity of the suspension and increases the volume circulating in the system ps This also complicates the instrumentation of the process. The purpose of iaofetenia is to simplify the process while simultaneously obtaining calcium sulfate as a commercial product. This goal is achieved by absorbing sulfur oxides by aqueous, suspension of domain or converter or open-hearth slag at pH suspension 1.5-4, O. Highly scS and the oxidation of sulfurous acid to sulfuric acid is ensured by the catalytic action of grains and earths produced during the decomposition

The caustic salt of Caj AgjOu, which is the main component of the slag. In the course of the process, sulfuric acid reacts with alumina and is consumed for the further decomposition of the bacon. At the same time, the pH of the absorbing suspension is maintained in the range of 1.5-4.0, which provides BI with a low degree of gas purification from 50 and at the same time view the extraction of slag from the slag, with calcium sulphate obtained in the process as a by-product.

Example. Exhaust gases in the amount of 2OOO, which had composition,%: 902. 0.07; Odd ten; Soa. 7; v.79.93, at 55 ° C, is introduced into the work absorber, irrigated with an aqueous suspension of blast-furnace slag, which has a composition in the CBO-I,%: 6iO2.33,7; , 7 AEiO 15.9 G T 1 02. 1.4; MIO 0.4; CaO 39.9; M 3.7.

The average particle size of the slag in the suspension is 6O microns The pH of the suspension is maintained at 3 by adjusting the concentration of slag in the suspension, which is about 6% by weight.

The degree of absorption gOj is 9O%.

The precipitate recovered from the treated suspension contains 67.2% calcium sulfate.

Claims (2)

1. Patent. England Me 13O5750, class C 1 A, 17, O9.7O .. 2. Cole A. L. and Risen (|) Eld F. F., Gas Cleaning, M., Nedra, 1968, p. 162-164 (prototype).