Abstract: An improved apparatus and process are disclosed for the removal of sulfur oxides such as sulfur dioxide from waste gas streams. The process comprises scrubbing the waste gas with a circulating aqueous sodium sulfite/sodium bisulfite absorption solution at a relatively low pH followed by subjecting a portion of the circulating absorption solution to an improved multi-stage regeneration procedure wherein lime is employed to regenerate sulfite from bisulfite. The bleed from the scrubbing step which is subjected to regneration has a low pH and hence can dissolve more lime thereby increasing the lime utilization efficiency. In the regeneration procedure, a lime slurry is separated into a slurry of coarser lime particles and a second portion which contains very fine lime particles. The main regeneration is accomplished by adding the coarse lime slurry to the scrubber bleed. Due to the low pH in this reaction, not all the bisulfite is regenerated to sulfite.