Pulp Bleaching Technology
Sulfate pulp bleaching operation conditions are usually maintained at high temperatures and under strong acid or alkaline conditions. Process temperature and pH are very high, the lowest temperature and pH are not drift tower, respectively, 75 ~ 85 ℃ and pH9.5 ~ 10.5. Therefore, the xylanase used in chemical wood pulp-assisted bleaching should have strong heat resistance and alkali stability, in which heat resistance is the first requirement. Most of the thermostable xylanase producing bacteria are bacteria, the optimum temperature for pulp bleaching is 55 ~ 80 ℃.
Alkaline pulping is the most important method of pulping, pulp by cooking after the alkalinity is high, pulp PH value of up to 11 or so, after dilution, washing pulp PH value is still higher than 10. Moreover, the boiled pulp is usually subjected to strong alkali extraction and oxygen delignification prior to bleaching, and the xylanase bleaching process is usually set before or after the oxygen delignification process, thereby achieving xylanase pulp bleaching Industrial applications, must be selected to be able to maintain high alkaline activity in the enzyme. The range of bleaching alkalinity stability test is mostly selected in PH8 ~ 10.
In the degradation of lignocellulose, low molecular weight enzymes easily penetrate the cell wall and promote fiber degradation. Low molecular weight xylanase may be more advantageous than high molecular weight xylanase in pulp bleaching because low molecular weight is advantageous for xylanase to enter the inner layer of pulp fiber cells, hydrolyze xylanase in the inner layer of the fiber, Releasing more lignin components.
Three Primary Colors