A new Kraft white liquor oxidation process has been demonstrated. The process using a novel catalyst can effectivily produce a polysulfide cooking liquor. The selected catalyst is a granulated activated carbon, characterized by a large pore volume occupied with pores more than 10 nm diameter. This catalyst has high oxidation activity and selectivity of polysulfied formation. The polysulfide yield in higher than the reported value. One year pilot plant test exibited steady performance using mill

more »

... white liquor. The long life of the catalyst was attained by installing a special designed filter to remove suspended solids which would accummlate on the catalyst. The filter, up-flow type, contained sand bed which removed 95% of incoming solids. The pilot plant data were correlated as an empirical equation for polysulfide production rate with temperature, liquid hourly space velocity, air/liquid ratio, and the catalyst activity . The first commercial plant was in operation from July '87 at Shirakawa Mill of the Mitsubishi Paper Mills Ltd., without any trouble. The pulp yield is up at least 1% with same or better quality.