Upgrading Paper-grade Softwood Kraft Pulp to Dissolving Pulp by Cold Caustic Extraction

Cold caustic extraction has potential applications in the production of dissolving-grade pulps due to its ability to selectively remove hemicellulose from lignocellulosic materials. In this study,we demonstrate the conversion of paper-grade kraft pulp into dissolving pulp by a single-stage cold caustic extraction. Under the extraction conditions of 12 wt% NaOH lye,11% pulp consistency,a temperature of 35℃,and 2 h,a paper-grade softwood kraft pulp was purified to high-grade dissolving pulp with 97. 1% α-cellulose content,1. 2% pentosane content,and narrowed molecular weight distribution. The resulting extraction filtrate was concentrated by nano-filtration to obtain the hemicellulose content of 59. 0 g / L,while the permeate was a clear Na OH solution with 10. 9 wt% concentration. A process configuration was also proposed,integrating this cold caustic extraction process with existing pulp and paper production and multi-purpose utilization of the extraction filtrate.

纸浆纯化处理工艺对超高压绝缘纸性能的影响

本研究以硫酸盐云杉浆为原料,探讨了碳酸氢镁和醋酸镁对纸浆纯化处理效果的差异。采用冷碱抽提、过氧化氢漂白工艺对纸浆进行纯化,并对纸浆的化学组分和纸张电气性能进行分析。结果表明,相比醋酸镁,碳酸氢镁对Na+的置换作用更强,对纸浆化学性能的提升更为显著。碳酸氢镁处理能够使纸浆水抽提液pH值和电导率满足500 kV超高压变压器匝间绝缘纸的指标要求。冷碱抽提和过氧化氢漂白均可有效去除木质素,提高纸浆α-纤维素含量,有效降低纸张的介质损耗。其中,冷碱抽提对纸张电气性能的提升效果更显著,可降低纸张在全频段的相对介电常数,并使浸油后的绝缘纸在工频下的tanδ值降低61.6%。

采用冷碱抽提工艺改善溶解浆纤维素纯度的研究

纤维素纯度是溶解浆质量的首要要求。本研究采用冷碱抽提工艺,对溶解浆进行纯化处理,探讨了冷碱抽提主要工艺条件对抽提效果的影响;并与聚木糖酶处理工艺进行对比。结果表明,碱浓是影响抽提效果的最主要因素,在碱浓22%、浆浓20%、温度35℃、时间1 h抽提条件下,某预水解硫酸盐阔叶木溶解浆的α-纤维素含量由94.84%提高至98.51%;冷碱抽提对聚木糖类半纤维素具有很高的选择性,聚葡萄糖甘露糖类半纤维素需要冷碱抽提碱浓达到10%以上开始溶出;冷碱抽提在提高溶解浆纤维素纯度方面的作用明显优于聚木糖酶处理。

提高竹纤维化学纯度的研究

以漂白硫酸盐竹浆为原料,用保尔筛分仪进行筛分去除细小组分,然后再通过水解处理、冷碱精制进一步提高其纯度。实验结果表明:漂白竹浆用250目筛板筛分,去除15%细小组分后,浆料的纤维素含量由83.97%提高至87.41%;经水解处理后浆料的ɑ-纤维素可增至93.76%,再经冷碱精制后ɑ-纤维素达到95.91%,能够满足高纯度溶解浆的要求。

竹浆冷碱精制的研究

以漂白硫酸盐竹浆为原料,用保尔筛分仪筛分去除细小组分,取200目截留长纤维进行水解处理,然后再进行冷碱精制。实验结果表明:冷碱精制能明显提高竹浆α-纤维素含量,碱浓越高浆料α-纤维素含量越高,当碱液浓度为12.5%时α-纤维素含量可达到98.13%;另外,聚木糖酶预处理、超声波预处理和机械磨解协同处理,对竹浆的冷碱精制有明显的促进作用。