| 摘要 |
<p>1376404 Sulphuric acid, sulphur dioxide CHEMIEBAU DR A ZIEREN GmbH & CO KG 29 March 1972 [31 Aug 1971] 14711/72 Heading C1A The sulphur content of a wash solution obtained by scrubbing SO 2 containing gases with aqueous ammonia is obtained and the nitrogen content of the solution rendered ecologically innocuous by mixing the wash solution, which contains ammonium sulphite, bisulphite, and optionally sulphate if the gas scrubbed contained SO 3 , with a quantity of sulphuric acid at least sufficient to liberate all the SO 2 from the sulphite and bisulphite content of the wash solution, and the resulting ammonium sulphate containing liquor is evaporated by direct heat-exchange with hot split gas, obtained as hereinafter explained, to a water content of from 15 to 55% by weight, and the concentrated mixture so obtained is heated at a temperature of 900‹ to 1250‹ C. with the simultaneous combustion of a carbon and/or sulphur containing fuel to form an SO 2 containing split gas which hot split gas is used for the evaporation and thereafter its SO 2 content is converted to sulphuric acid using the contact process. After being used for the evaporation the hot split gas may be washed before being subjected to the contact process and the wash solution to be treated by the process of invention is mixed with the H 2 SO 4 -containing wash acid from washing the split-gas to liberate its SO 2 content. Alternatively, a portion of the product acid from the contact process may be used to acidify the ammoniacal wash liquors being treated, to liberate their SO 2 content. The wash solution being treated and the acidifying sulphuric acid may be sprayed into a tower through which the hot split-gas flows upwardly. The SO 2 liberated from the ammonium salt content of the used wash liquor being acidified may be separated from the accompanying aqueous solutions and added to the split gas after it has been used for evaporation. The water content of the ammonium sulphate containing liquor may be reduced to 25 to 50 wt. per cent in the evaporating step. The concentrated liquor may be split at a temperature of 1000‹ to 1100‹C. using a residence time of 0À3 to 15 sees. in the splitting chamber. The splitting step may be carried out so that the oxygen content of the gases leaving the splitting chamber is from 2 to 10 vol. per cent. The SO 2 containing gas used for the present process may be tail-gas from a sulphuric acid plant or flue gas from the combustion of a sulphur containing fuel.</p> |
