SO2 scrubbing downstream of combustion plants with crude gypsum as the end product

摘要

It known to scrub out SO2 from the dirty gas stream downstream of fossil-fuelled combustion plants by means of an aqueous solution enriched with lime. The aim is to free from gaseous pollutants the dirty gas loaded with SO2 and/or NOx and other acidic constituents and to achieve gypsum as the end product. Since coal having a very high chlorine content interferes with the actual scrubbing process for scrubbing out SO2 and/or NOx, it is known to provide a so-called prescrubber in order to scrub out the acidic constituents HCl, HF, etc. before the actual SO2 and/or NOx scrubbing. The salt load produced in the prescrubber generally must not be transferred to the rivers or the outfall but must be concentrated by evaporation and supplied to other applications or else to a special landfill. The gypsum produced must frequently be furnished with an additional chloride addition or, depending on the chloride content loading, be fed to a further processing. In order to further improve the purification process overall, according to the invention it is proposed that the crude gas scrubbing is carried out in a prescrubber (2) which is operated at an acidic pH in which chlorides are scrubbed out of the dirty gas stream, and downstream of a scrubber (2) is provided a secondary scrubber (3) in which SO2 and/or NOx are scrubbed, the absorption media for scrubbing SO2 and NOx being fed to the secondary scrubber (3) and the ... Original abstract incomplete. <IMAGE>