PROCESS FOR SIMULTANEOUS EXTRACTION OF SO2 AND NOX CONTAINED IN WASTE GASES

摘要

Process for simultaneous extraction of SO2 and NOx contained in waste gases in one or several stages by a wet method. The purpose of the invention is to improve such a process so that it can be performed at a relatively small cost, obtaining in addition values which are much lower than the maximum values specified by the authorities. For this purpose, the SO2 absorbed during the process, which is precipitated by lime in the form of solid CaSO3/CaSO4 x 2H2O is no longer oxidized by an oxidizer to become CaSO4 x 2H2O but is added in the solid state to the flow of washing liquid of a prewashing stage for the purpose of oxidizing the quantity of CaSO3 by the oxygen of the waste gas supply, the washing solution having a pH of between 2 and 2.5. The solid matter is transferred to the washer or to the washing basin of the prewashing stage and maintained in contact with the washing liquid at a corresponding pH value (pH 1 to 1.5) until the release of the appropriate quantity of SO2 required for the simultaneous washing reaction of SO2/NOx in the washer.