Processing aqueous effluent liquors from degasification or gasification of coal

摘要

The aqueous effluent liquors from gasification or de- gasification of coal are extracted with a water-insoluble solvent and the extract is processed to recover the solvent. The aqueous residue is treated to remove NH.sub.3 in a driving-off column. The invention adds the steps ofPP(a) removing part of the overhead product of the driving-off column as uncondensed vapors;PP(b) transferring the vapors from (a) to a scrubbing column, in steps condensing water, small amounts of ammonia and all acid gases in the upper part of said scrubbing column, and withdrawing pure ammonia overhead;PP(c) withdrawing the condensate which contains all acid gases from the upper portion of the scrubbing column, transferring the condensate to a separate reboiler, and heating the transferred condensate in said reboiler;PP(d) feeding cold water at a low rate to the top of the scrubbing column;P P(e) withdrawing the sump product of the scrubbing column, transferring it into a pressurized de-acidification column, and withdrawing therefrom overhead under pressure the acid gases H.sub.2 S and CO.sub.2 ; andPP(f) recycling to the stripping column the sump product of the pressurized de-acidification column consisting of a solution high in ammonia content.