Process for removing SOx and NOx compounds from gas streams

摘要

Gas streams containing SOx and/or NOx compounds are treated in an absorption-regeneration process for removal of the SOx and/or NOx compounds. The process in one embodiment removes SOx compounds from a stack gas or other feed gas stream by (1) absorbing the SOx into a novel aqueous liquid absorbent comprising formic acid and an alkanolamine containing a tertiary amine functional group and (2) regenerating the absorbent when spent by subjecting the spent absorbent to an elevated temperature above that utilized for absorption of said SOx, said elevated temperature being sufficient to convert a substantial proportion of the dissolved SOx to elemental sulfur and/or H2S. If NOx compounds are present in the stack gas stream, they may also be removed, NO2 being removed without modification of the process for removing SOx compounds, and NO by providing in the absorbent an iron (II) chelate, such as a chelate of ferrous ion with ethylenediaminetetraacetic acid. Regeneration of the spent absorbent containing absorbed NO is accomplished under conditions similar to those employed for spent absorbents containing absorbed SOx compounds. During regeneration, the dissolved SOx compounds are converted to hydrogen sulfide and/or sulfur and the dissolved NOx compounds are converted to nitrogen. The invention is most useful for removing SO2 from gas streams.