Process for the removal of sulfur oxides from waste gases

Claim 1

In a process for removing sulfur dioxide from a gaseous sulfur dioxide-containing feed by means of a lean aqueous sulfite-containing solution in a gas scrubbing zone, said lean solution comprising regenerated sulfite-containing solution and makeup solution by: a. introducing the lean solution into the scrubbing zone; b. introducing the feed into the scrubbing zone and into contact with the lean solution to form a fat solution and a resulting gas having a sulfur dioxide content which is less than the sulfur dioxide content of the feed gas; c. withdrawing the resulting gas from the gas scrubbing zone; d. withdrawing the fat solution from the gas scrubbing zone; e. passing the withdrawn fat solution into a stripping zone and forming gaseous sulfur dioxide and said regenerated solution by stripping said fat solution; f. withdrawing said sulfur dioxide gas from the stripping zone; and g. withdrawing the regenerated solution from the stripping zone and forming said lean solution by adding makeup solution, said makeup solution being aqueous alkaline caustic selected from the group consisting of alkali metal hydroxide, carbonate and mixtures thereof; the improvement which comprises scrubbing said resulting gas with at least a portion of said makeup solution prior to said addition, said scrubbing being effected by employing at least sufficient of said makeup solution to maintain the process in balance and to provide a degree of gas scrubbing corresponding to at least a single tray in a tray-type gas scrubbing tower, thereby reducing the sulfur dioxide content of the resulting effluent gas stream to a value less than about 75 ppm.