Production for sulfur dioxide containing gas by spraying a waste liquor containing a sulfur acid and an ammonium salt into a reactor in the presence of molecular oxygen at a temperature of 850.degree. C. to 1,150.degree. C.
This application is a continuation of application Ser. No. 724,303, filed Feb. 6, 1968, now U.S. Pat. No. 3,549,320 issued Dec. 22, 1970, and said application is a division of application Ser. No. 349,536 filed Mar. 3, 1964, now U.S. Pat. No. 3,419,601 issued Dec. 31, 1968.
A process for decomposing ammonium thiocyanate and equivalent compounds comprising mixing the compounds with molten ammonium sulfate at atmospheric pressure and about 310.degree. C. The compounds decompose giving off carbon dioxide, sulfur dioxide, ammonia and sulfur and leave a residue of ammonia salts but no organic materials.
In a process of concentrating an aqueous solution of ammonium sulfate and burning resultant concentrate at 850.degree.-1250.degree.C to form a combustion gas containing SO.sub.2, the improvement which comprises: Conducting said concentrating by passing said combustion gas in direct contact with said aqueous solution of ammonium sulfate to evaporate water from said solution. If the concentrate is a slurry, it can be sent in total to the combustion step or it can be centrifuged with a recycle of mother liquor to the concentrating step. The evaporation can also be conducted so that substantially dry ammonium sulfate is obtained.
In a process which comprises scrubbing an SO.sub.2 -containing gas with an aqueous ammonia solution to form ammonium sulfite and ammonium bisulfite as reaction products, neutralizing said reaction products with sulfuric acid to form SO.sub.2 and aqueous ammonium sulfate, and concentrating the resultant aqueous ammonium sulfate by evaporation, the improvement which comprises: A. heating the concentrated aqueous ammonium sulfate to a temperature of 900.degree.-1250.degree.C in a combustion chamber burning a carbon or sulfur containing fuel, in the presence of sufficient oxygen to maintain an oxygen content of 1-10 vol % in the gas exiting from the combustion chamber, to form a hot split gas consisting essentially of sulfur dioxide, sulfur trioxide, molecular nitrogen, molecular oxygen and water vapor; and B. heat exchanging the hot split gas with the aqueous ammonium sulfate to evaporate the aqueous ammonium sulfate to a concentrate having a water content of less than 55 wt. %, thereby cooling said hot split gas. The split gas can be furhter worked up for any purpose which an SO.sub.2 -containing gas is suitable, e.g., for the production of sulfuric acid.
Process for working up the scrubbing solution obtained during the scrubbing of SO.sub.2 -containing waste gases, which can also contain SO.sub.3, with the use of ammonia, by evaporation in direct heat exchange with hot cracked gas to a water content of between 15 and 55% by weight, cracking of the thus-evaporated mixture at temperatures of between 900.degree. and 1250.degree. C. with the concomitant combustion of a carbon- and/or sulfur-containing fuel to an SO.sub.2 -containing gas, and processing of the cracked gas, after utilization for evaporation purposes, by contact oxidation to sulfuric acid in accordance with U.S. patent application Ser. 284,709 filed Aug. 30, 1972, characterized in that the scrubbing solution is mixed, prior to or during the evaporation, with a quantity of sulfuric acid sufficient for the liberation of SO.sub.2 from 0-83% of the sulfite and/or bisulfite present in the solution.
Process for regenerating spent acid is improved by using oxygen-enriched air for combustion, recycling stack gases, and preheating spent acid and air fed to the furnace.
