Abstract: In a process for the production of phthalic anhydride comprising a stage of catalytic oxidation of a mixture of o-xylene or naphthalene and air, a stage of separation of the crude phthalic anhydride from the reaction gas by cooling, and a stage of purification of the crude phthalic anhydride by rectification under vacuum, said vacuum being maintained by at least one jet pump, the improvement which comprises employing compressed air as the operating medium for said jet pump, and recycling resultant compressed air loaded with the exhaust gas to a process gas upstream of the phthalic anhydride separation stage, said process gas being any gas leading to the separation stage, preferably the gas between the oxidation stage and the separation stage.

Abstract: An improved process for the production of concentrated sulfuric acid from H.sub.2 O- and SO.sub.2 -containing gases by the oxidation of the SO.sub.2 thereof in a plurality of contact stages while lowering the temperature of the gases, thereby condensing the sulfuric acid therefrom, comprises cooling a portion of the sulfur dioxide-containing gases exiting from a combustion or cracking furnace by contacting them with cooling water, the water vapor contained in the gases thereby being partially condensed-out or separated-off. The resulting cooled gases with reduced steam content are recycled into the furnace and, by the selection of the cooling temperature of the recycled gas, the H.sub.2 O/SO.sub.2 mol ratio in the combustion or cracking gases is adjusted within the range of from 1.0 to 1.25, and the remaining portion of the sulfur dioxide-containing gases, i.e., those which are not recycled, is fed to contact oxidation stages.

Abstract: A process for utilization of the reaction heat generated by the catalytic oxidation of o-xylene with air to phthalic anhydride in a tubular reactor, which heat is partially carried away from the reactor by the reaction gas and partially by fused salt used as a cooling medium. Water is heated by heat exchange with the hot reaction gas, evaporated by heat exchange with the fused salt and the steam is superheated and expanded in a condensation turbine coupled with the feed air compressor. The hot reaction gas is used successively to heat, or evaporate, a heat carrier liquid serving for the heating of the phthalic anhydride distillation, and the pressurized water. Low pressure steam can be generated by heat exchange of pressurized water with the reaction gas and used for heating the feed air and/or o-xylene.

Abstract: In accordance with the invention sulfur dioxide in sulfur dioxide-containing gases is converted under selective conditions to provide elemental sulfur in an efficient and economically-acceptable manner for present day industrial operations. The conversion involves the thermal reduction of sulfur dioxide in a zone at relatively moderate temperatures maintained by the combustion of carbonaceous fuel in the zone to provide elemental sulfur and to provide a gaseous thermal reduction effluent which is acceptable for further processing to recover additional sulfur values therefrom.

Abstract: Sulfur dioxide in sulfur dioxide-containing gases is thermally reduced at relatively moderate temperatures under reducing conditions provided by the incomplete combustion of hydrocarbon to produce elemental sulfur. Elemental sulfur can be recovered from the effluent gases from the thermal reduction and the effluent gases may be treated by conventional catalytic processes to recover additional elemental sulfur from the remaining sulfur values.

Abstract: A furnace chamber of substantially circular cross section having a ceiling and a side wall, a burner positioned adjacent said ceiling and substantially evenly spaced from said side wall, a plurality of ultrasonic atomizer assemblies positioned around said burner in a concentric pattern adjacent said ceiling, each of said ultrasonic atomizer assemblies including: (a) means for converting a feed stream of the waste sulfuric acid into a coarse spray, and (b) means for further atomizing the coarse spray by passing it through a field of ultrasonic sound, and a gas flow constricting means transversing said chamber and spaced from said ceiling in a distance of about 1 to 4 times the length of the diameter of said chamber.

Abstract: There is disclosed a process and apparatus for the thermal treatment of crude phthalic anhydride. The process is conducted in a system with an inner chamber and outer chamber positioned therearound and the chambers have a common wall. The outer chamber may be divided into a plurality of sub-chambers and the flow of the phthalic anhydride undergoing treatment may be substantially reversed in successive ones of the sub-chambers. The system provides for more efficient use of heat and equipment.

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: Elemental sulfur is recovered from ammonium salts of sulfuric oxyacids (e.g. ammonium sulfate, ammonium hydrogen sulfite, and ammonium sulfite) by passing the salt (e.g. in aqueous solution) and a hydrogenous reducing agent (e.g. sewer gas or coal gas) through a reaction chamber maintained at 800.degree. to 1300.degree. C. so as to yield a product gas containing molecular nitrogen, steam, and vaporous sulfur, and then cooling the product gas to 125.degree. to 325.degree. C. so as to condense at least a portion of the sulfur, which is then recovered.

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: 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.