Patent ID: 6511578
Filing Date: 2003-01-28
Classification: D21C

Abstract:
A method of bleaching and/or delignifying cellulosic pulp, comprising:(a) first producing a sodium hydroxide solution and a peroxydisulphate solution by electrolysis of a sulphate, (b) converting the peroxydisulphate solution by hydrolysis into Caro's acid/caroate solution, (c) cooling the Caro's acid/caroate solution, and (d) providing a bleaching vessel containing cellulose and immediately adding the Caro's acid/caroate solution from step c) and sodium hydroxide produced in step a) to the bleaching vessel to form a bleaching solution, where upon adding the sodium hydroxide solution, the Caro's acid/caroate solution is neutralized, (e) bleaching and/or delignifying the cellulose with the bleaching solution, (f) removing the bleaching solution and recovering the sulphate, (g) Kraft pulping lignocellulosic material to produce a cellulosic pulp; and (h) adding the sulphate of step (f) to step (a) and repeating steps (a)-(g) a plurality of times.