Low Capital Bleaching of Chemical Pulp

Abstract

Bleaching methods and formulations for bleaching/delignification processes for chemical pulp are provided. The bleaching methods utilize peroxide and an organomanganese complex under aqueous caustic conditions, increasing bleaching efficiency of the overall bleaching/delignification process. Chemical pulp having increased brightness can be obtained at decreased temperatures and with reduced stage time, resulting in reduced chemical consumption and improved energy efficiency.

1 . A method of bleaching alkali oxidized chemical pulp comprising:
 treating alkali oxidized chemical pulp with peroxide and an organomanganese complex under aqueous caustic conditions subsequent to an acidic oxidative bleaching stage to form an enhanced chemical pulp.   
     
     
         2 . A method of enhancing chemical pulp comprising:
 treating chemical pulp under acidic oxidative conditions to form an acidic oxidized chemical pulp;   washing the acidic oxidized chemical pulp with aqueous caustic solution to form an alkali oxidized chemical pulp; and   treating the alkali oxidized chemical pulp with peroxide and an organomanganese complex to form an enhanced chemical pulp.   
     
     
         3 . The method of  claim 2 , wherein the aqueous caustic solution is at a temperature of from about 40° C. to about 90° C. 
     
     
         4 . The method of  claim 2 , wherein the washing step is an express alkali extraction. 
     
     
         5 . The method of  claim 2 , wherein the washing step is performed at atmospheric pressure. 
     
     
         6 . The method of  claim 2 , wherein the washing step is performed for about 10 minutes or less. 
     
     
         7 . The method of  claim 6 , wherein the washing step is performed for about 2 minutes or less. 
     
     
         8 . The method of  claim 7 , wherein the washing step is performed for about 1 minute or less. 
     
     
         9 . The method of  claim 2 , wherein the treating the alkali oxidized chemical pulp step is performed at a temperature of about 75° C. or less. 
     
     
         10 . The method of  claim 2 , wherein the treating the alkali oxidized chemical pulp step is performed at a temperature of about 55° C. or less. 
     
     
         11 . The method of  claim 2 , wherein the treating the alkali oxidized chemical pulp step is performed in a reaction tube. 
     
     
         12 . The method of  claim 1 , further comprising treating the enhanced chemical pulp under acidic oxidative conditions. 
     
     
         13 . The method of  claim 12 , wherein the acidic oxidative conditions of treating the enhanced chemical pulp result from treating the enhanced chemical pulp with chlorine dioxide. 
     
     
         14 . The method of  claim 1 , wherein the organomanganese complex is at a concentration of from about 0.0001 ppm to about 20 ppm, and the peroxide is at a concentration of from about 0.01% to about 5% by weight, relative to dry pulp in the chemical pulp. 
     
     
         15 . The method of  claim 1 , wherein the organomanganese complex is a manganese-triazacyclononane complex. 
     
     
         16 . The method of  claim 1 , wherein the organomanganese complex is Mn 2+  μ-(acetato-κO:κO′)][μ-[1,1′-(1,2-ethanediyl)bis[octahydro-4,7-dimethyl-1H-1,4,7-triazonine-κN1,κN4,κN7]]]di-μ-oxodi-X − . 
     
     
         17 . A thermally stable aqueous formulation for bleaching of a chemical pulp comprising an organomanganese complex and water, wherein the aqueous formulation has a pH of from about 3 to about 7 and the organomanganese complex is at a concentration of from about 0.0001% to about 3% by weight based on weight of the aqueous formulation. 
     
     
         18 . The formulation of  claim 17 , wherein the organomanganese complex is Mn 2+  μ-(acetato-κO:κO′)][μ-[1,1′-(1,2-ethanediyl)bis[octahydro-4,7-dimethyl-1H-1,4,7-triazonine-κN1,κN4,κN7]]]di-μ-oxodi-X − . 
     
     
         19 . The formulation of  claim 17 , wherein the organomanganese complex is at a concentration of from about 0.001% to about 2%, by weight based on the weight of aqueous solution and wherein the formulation has a pH of from about 4 to about 6. 
     
     
         20 . The formulation of  claim 17 , further comprising peroxide.