Sodium-limestone double alkali flue gas desulfurization process with improved limestone utilization

摘要

A method for improving utilization of limestone in a sodium-limestone double alkali flue gas desulfurization process. Spent alkaline absorber solution, containing sodium sulfite and sodium bisulfite, is diverted for regeneration treatment in a series of stirred tank reactors, where it is contacted with the limestone regenerating agent. Dilute slurry from the last reactor is concentrated in a thickener, and the concentrated underflow slurry from the thickener is then treated further in an after-reactor circuit. Since the thickener underflow slurry contains residual unreacted limestone, the slurry is contacted with a side stream of spent alkaline absorber solution in the after-reactor circuit to promote further reaction of residual limestone before the solids are separated and discarded.