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 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.