Abstract: In a process for manufacturing a lactam which includes rearranging a cycloalkanone-oxime with sulfuric acid to form the lactam, neutralizing the rearrangement mixture with ammonia to form ammonium sulfate, and separating the lactam and the ammonium sulfate, the improvement which comprises:A. heating at least a portion of the ammonium sulfate to a temperature of 240.degree. - 460.degree. C to form ammonia and ammonium bisulfate;B. separating the ammonia from the ammonium bisulfate;C. recycling the ammonia to neutralize the rearrangement mixture;D. burning the ammonium bisulfate at a temperature of 850.degree. - 1250.degree. C to form an SO.sub.2 -containing gas;E. oxidizing the SO.sub.2 -containing gas to form sulfuric acid; andF. recycling the sulfuric acid to the rearrangement stage.

Abstract: In a process for manufacturing a lactam which includes rearranging a cycloalkanone-oxime with sulfuric acid to form said lactam, neutralizing the rearrangement mixture with ammonia to form ammonium sulfate, and separating said lactam and said ammonium sulfate, the improvement which comprises:A. forming the ammonium sulfate into finely divided particles;B. burning the particles at a temperature of 850.degree. - 1250.degree. C. to form an SO.sub.2 -containing gas;C. oxidizing the SO.sub.2 -containing gas to form sulfuric acid; andD. recycling at least a portion of the sulfuric acid to the cycloalkanone-oxime rearrangement step.No external source of sulfuric acid is required. A portion of the SO.sub.2 -containing gas can be used for the manufacture of hydroxylamine sulfate, in which case no external source of SO.sub.2 need be required.

Abstract: 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; andB. 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.

Abstract: 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.

Abstract: 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.

Abstract: Scrubbing solutions containing ammonium salts of weak acids are mixed with sufficient sulfuric acid to react with all the salts; the resultant solutions are evaporated by direct heat exchange with a hot SO.sub.2 -containing combustion gas to a 40-78% water content and combusted at 800.degree.-1,250.degree.C to produce the SO.sub.2 -containing combustion gas used in the evaporation step. The SO.sub.2 in the combustion gas can be processed in a conventional manner.