相思木自水解过程产酸对后续硫酸盐法制浆的影响

Effect of Acid Generated During Autohydrolysis of Acacia Wood on the Subsequent Kraft Pulping

为研究相思木自水解过程产酸行为及其对水解后木片硫酸盐法制浆的影响,在水热预处理强度指标P因子93~1 008的范围内进行木片自水解预处理,然后将一部分预抽提后木片通过超声波洗涤去除残留酸,将除酸处理后的预浸渍木片和对照样(即未进行超声波洗涤)以相同的条件进行硫酸盐法制浆。研究结果表明:自水解液(AHL)中产生的酸含量随预处理强度的增强而增大,导致AHL的pH值呈下降趋势;其中乙酸是主要酸成分,P因子606时乙酸质量浓度达到4.21 g/L,之后随自水解过程缓慢增加到P因子1 008时的4.41 g/L;P因子1 008时还检测到少量甲酸。超声波洗涤去除残留酸后木片蒸煮细浆得率比自水解木片提高了10.1%,同时纸浆Kappa值由31.24下降至19.69(P因子1 008),纸浆黏度没有明显变化,但纤维长度由0.76 mm下降至0.64 mm(P因子1 008),可能是导致超声波洗涤后木片纸浆手抄片的抗张和耐破强度轻微降低的原因。

In order to study the acid generation of Acacia wood during autohydrolysis and its influence on the chemical properties of sulfate pulping of hydrolyzed wood chips,the wood chips autohydrolysis was pretreated in the P severity range of 93-1 008.Then,a part of the pretreated wood chips were washed by ultrasonic wave to remove the residual acid.The pre-impregnated wood chips treated with acid removal and the control sample(i.e.without ultrasonic treatment) were sulfate pulped under the same conditions.The results showed that the content of acid in autohydrolysate(AHL) increased with the increase of pretreatment intensity,resulting in the pH value of AHL decreased.Among them,acetic acid was the main acid component.The concentration of acetic acid reached 4.21 g/L at P factor of 606,which slowly increased to 4.41 g/L at 1 008,and a small amount of formic acid was also detected.The results showed that the pulp yield of wood chips increased by 10.1% after ultrasonic washing,and the Kappa value of pulp decreased from 31.2 to 19.7 when the P factor was 1 008.The pulp viscosity did not change significantly,while the fiber length decreased from 0.76 mm to 0.64 mm at the P factor of 1 008,which may be the reason of the slight decrease in the tensile and breaking strength of wood chips after ultrasonic washing.