Combustion Engineering, Inc.

Philip C Rader

Stephen L Goodstine

Madanamohana R Gogineni

Dante Frabotta

Robert W Hanson

Wilfred R Roczniak

In the process of scrubbing flue gas to remove pollutants therefrom by contacting the flue gas with an aqueous reactant mixture of water and pollutant absorbent, water soluble chloride impurities present in the flue gas and make-up water tend to build-up as the supernatent liquor from the spent reactant mixture dewatering cycle is recycled for mixing with unreacted pollutant absorbent to form additional reactant mixture for contacting with the pollutant laden gas. The build-up of chlorides in the reactant mixture is controlled by passing a purge stream of the chloride containing liquor in contact with a hot drying gas so as to evaporate the water and crystallize the chloride impurities in the purge stream. The crystallized particles of chloride salt are then removed from the drying gas as a dry solid.

Process for limiting chloride buildup in SO.sub.2 scrubber slurry

An SO.sub.2 flue gas scrubbing system wherein a calcium compound is dissolved in water and recirculated in contact with the flue gases. Calcium sulfite and sulfate formed in this process are also recirculated. A stream of the slurry passing to waste is separated based on the rate of settling of the constituents so that calcium sulfate and undissolved calcium compound is returned to the recirculating system with the calcium sulfite being sent to waste.

Flue gas scrubbing system

Gases containing SO.sub.2 from a furnace are contacted in the scrubbing zone of a scrubber with an aqueous scrubbing medium containing Ca(OH).sub.2 whereby sulfites are formed. The Ca(OH).sub.2 additive is at least partially the Ca(OH).sub.2 sludge produced in the manufacture of acetylene from CaC.sub.2. This sludge contains constituents which retard or inhibit the oxidation of sulfite to sulfate to thereby reduce the possibility of sulfate scaling in the system.

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Windsor Locks, CT, United States of America

Philip C Rader