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在纸浆漂白过程中,即使存在极少量的残余发色基团,纸浆也很难达到最终目标白度,这是因为一些包含某种化学结构的模型化合物在不同的二氧化氯和臭氧用量下,仍然存在于半漂浆中。通过研究这些模型(醌类或木素结构单元)与不同化学试剂的反应,得到了不同的实验结果。二氧化氯与木素结构单元进行反应,产生了新的发色基团,这些发色基团在后续的降解过程中会产生抗药性而难以除去。同样,对于臭氧漂白,也会产生新的发色基团,而这些发色基团在多加化学试剂的情况下能够完全降解。而且,在二氧化氯漂白过程中,醌类的化合物模型很难降解。相反,在臭氧漂白时,这些醌类化合物就很容易降解。这些结果表明了,在漂白末段时,浆料会对二氧化氯产生抗性,更有效的末段漂白工艺是臭氧漂白。在一个纸浆漂白顺序的最后一段采用臭氧进行漂白,其操作工艺并不像在脱木素阶段那样严格。最后一段的臭氧漂白也能在高温(80℃)下进行。
Pulp can hardly reach the final target whiteness even in the presence of a very small amount of residual chromophore during pulp bleaching because some of the model compounds containing a chemical structure differ in chlorine dioxide and ozone levels, Still present in half-bleached pulp. Different experimental results were obtained by studying the reaction of these models (quinones or lignin building blocks) with different chemical reagents. Chlorine dioxide reacts with lignin building blocks to create new chromophore groups that are resistant to removal during subsequent degradation. Likewise, for ozone bleaching, new chromophore groups are also created, which are completely degraded with more chemicals. Moreover, the quinone compound model is difficult to degrade during the chlorine dioxide bleaching process. Conversely, these quinones are easily degraded during ozone bleaching. These results show that the slurry is resistant to chlorine dioxide at the end of the bleaching stage and the more efficient stage bleaching process is ozone bleaching. Bleaching with ozone in the last paragraph of a pulp bleaching sequence is not as critical as the delignification stage. The last paragraph of ozone bleaching can also be carried out at high temperature (80 ℃).