Processes and systems for bleaching lignocellulosic pulps after cooking with soda and anthraquinone

摘要

Process for bleaching a lignocellulosic pulp comprising the steps of: cooking a lignocellulosic material with sodium anthraquinone carbonate in the absence of sulfur to form a lignocellulosic pulp, wherein the sodium carbonate comprises sodium hydroxide, sodium carbonate, or sodium hydroxide and sodium carbonate; feeding the lignocellulosic pulp to a first stage in which the lignocellulosic pulp contacts a first alkali containing oxygen that; removing the lignocellulosic pulp from the first stage and place it in a second stage in which the lignocellulosic pulp contacts an acid; removing the lignocellulosic pulp from the second stage and introducing a third stage in which the lignocellulosic pulp contacts a first chlorine dioxide or a first chlorine dioxide and ozone; removing the lignocellulosic pulp from the third stage and enter it in a fourth stage in which the lignocellulosic pulp contacts a second alkali and a hydrogen peroxide; removing the lignocellulosic pulp from the fourth stage and place in a fifth step or further bleaching in which the lignocellulosic pulp contacts a second chlorine dioxide and / or other chemicals in one or more steps to obtain a shine above 89% (% ISO) end; and removing the lignocellulosic pulp from the fifth stage.