Patent ID: 6294139
Filing Date: 2001-09-25
Classification: B01D

Abstract:
A method for purifying fumes containing gaseous pollutants including mercury and nitrogen monoxide, by a wet method in a scrubber having an entrance through which the fumes are introduced into the scrubber and wherein at least one dispersing device is disposed in the scrubber, the method comprising:a) introducing the fumes through the entrance and into the scrubber;b) dispersing, at a point of dispersion through the at least one dispersing device, a scrubbing liquid into the fumes within the scrubber;c) collecting the scrubbing liquid from the scrubber and maintaining the scrubbing liquid at a substantially constant acidic pH;d) bleeding a first portion of the collected scrubbing liquid and separating solids therefrom;e) recycling a second portion of the collected scrubbing liquid to the at least one dispersing device;f) injecting into said second portion of the collected scrubbing liquid a compound including an oxidizing agent which will oxidize the pollutants in the fumes including mercury and nitrogen monoxide, said injecting being at a point during recycling of the second portion of the scrubbing liquid such that a time of flow of the second portion of the scrubbing liquid from the point of injection of said compound to the at least one dispersing device allows the oxidizing agent to be released from the compound by reaction of the compound with a releasing agent maintained in the second portion of the scrubbing liquid and such that the release of the oxidizing agent is achieved substantially as the second portion of the scrubbing liquid is dispersed into the scrubber so that consumption of the released oxidizing agent with pollutants other than mercury and nitrogen monoxide present in the second portion of the scrubbing liquid is minimized and such that the oxidizing agent oxidizes the pollutants in the fumes to thereby obtain oxidized pollutants which are soluble in the scrubbing liquid;g) thereafter, neutralizing the oxidized pollutants in the scrubbing liquid by a physico-chemical reaction downstream of the point of dispersion of the second portion of the scrubbing liquid, said physico-chemical reaction being achieved by introducing a bleed of the second portion of the scrubbing liquid into the scrubber at a point downstream of the at least one dispersing device relative to the entrance into the scrubber, said bleed being obtained upstream of the point of injection of the compound; andh) removing purified fumes from the scrubber.