Patent ID: 6126781
Filing Date: 2000-10-03
Classification: B01D,C01B,D21C,Y02C,Y02P

Abstract:
A method for conditioning an ozone gas recycle stream in an ozone pulp bleaching process, comprising:providing an oxygen containing feed gas to an ozone generator;generating ozone from said feed gas to produce an ozone rich oxygen gas;bleaching pulp with said ozone rich gas, thereby producing an exhaust gas containing contaminants including carbon dioxide;removing at least some of said contaminants to produce a recycle gas; anddirecting said recycle gas into the ozone generator to provide at least a portion of said oxygen containing feed gas;wherein said step of removing contaminants comprises removing entrained pulp fibers from said exhaust gas; removing ozone and a portion of the carbon monoxide by passing the gas through a thermal destruct unit; removing hydrocarbons and the remaining carbon monoxide from the gas which exits the thermal destruct unit; purging a portion of the exhaust gas; forming the recycle gas by cooling and drying the unpurged portion of said exhaust gas; and mixing said recycle gas with fresh oxygen containing gas to form the feed gas, thus maintaining the concentration of carbon dioxide in the feed gas at a level of about 6 wt. % to allow approximately full capacity operation of the ozone generator.