Production of prehydrolyzed pulp
AssigneeSunds Defibrator Pori Oy
InventorsPanu Tikka, Kari Kovasin
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Abstract
Processes for preparing pulp from lignin-containing cellulosic material are disclosed including a prehydrolysis step followed by neutralizing hydrolysate and the prehydrolyzed cellulosic material in the reactor with alkaline neutralizing liquor, removing the neutralized hydrolysate from the reactor and delignifying the neutralized prehydrolyzed cellulosic material with alkaline cooking liquor containing sodium sulfide and sodium hydroxide.
Claims28
A batch process for the preparation of pulp from lignin-containing cellulosic material comprising prehydrolyzing said cellulosic material in a reactor so as to produce prehydrolyzed cellulosic material and hydrolysate, neutralizing said hydrolysate and said prehydrolyzed cellulosic material in said reactor with alkaline neutralizing liquor containing sodium hydroxide and sodium sulfide so as to produce neutralized hydrolysate and neutralized prehydrolyzed cellulosic material and so as to dissolve hemicellulose contained in said cellulosic material, removing said neutralized hydrolysate from said reactor as a separate stream essentially comprising only said neutralized hydrolysate, and delignifying said neutralized prehydrolyzed cellulosic material with alkaline cooking liquor containing sodium sulfide and sodium hydroxide.
A batch process for the preparation of pulp from lignin-containing cellulosic material comprising prehydrolyzing said cellulosic material in a reactor so as to produce prehydrolyzed cellulosic material and hydrolysate, neutralizing said hydrolysate and said prehydrolyzed cellulosic material in said reactor with alkaline neutralizing liquor so as to produce neutralized hydrolysate and neutralized prehydrolyzed cellulosic material, removing said neutralized hydrolysate from said reactor as a separate stream essentially comprising only said neutralized hydrolysate by displacement with spent cooking liquor, and delignifying said neutralized prehydrolyzed cellulosic material with alkaline cooking liquor containing sodium sulfide and sodium hydroxide.
A process for the preparation of pulp from lignin-containing cellulosic material comprising prehydrolyzing said cellulosic material in a batch digester so as to produce prehydrolyzed cellulosic material and hydrolysate, neutralizing said hydrolysate and said prehydrolyzed cellulosic material in said batch digester with alkaline neutralizing liquor comprising from about 5 to 25% active alkali calculated as Na.sub.2 O equivalents on dry wood so as to produce neutralized hydrolysate and neutralized prehydrolyzed cellulosic material, removing said neutralized hydrolysate from said batch digester, and delignifying said neutralized prehydrolyzed cellulosic material with alkaline cooking liquor containing sodium sulfide and sodium hydroxide.
Dependencies are inferred from the claim text.