禾草类氧系高效节能清洁化纸浆制备体系的研究

The cereal straws are abundant in natural resources. It seems, however, that the application of them in paper industry is conditioned by their well-known handicaps such as high silica content and more non-fibrous cells, so as not to reach the level of high efficiency, energy-saving, and clean production of wood pulp. It is also true that making full use of the straw's characteristics superior to wood is a prerequisite to high-efficient, energy-saving and clean production of straw pulp. This study is to aim at establishing the total oxygen pulping system for straws. Rice straw and wheat straw as straw representatives are pulped with alkali-oxygen at low-temperature, then highly selectively bleached with ozone. Firstly, it is hoped that the two-stage pulping give rise to high quality of straw pulps with brightness of ca. 80% ISO, where the lost of the pulps in viscosity is within 10% during ozonation. An additional bleaching with hydrogen peroxide would brighten the pulps up to 84% ISO or more, becoming genuine total oxygen pulps. Secondly, the organic substances such as acids, phenolic compounds etc. will be screened out from the ozone bleaching waste liquors as ozonation additives and carbohydrates protectors, to try to meet the need of self-sufficient additives and carbohydrate protectors in ozone bleaching. Thirdly, the black liquors from low-temperature alkali-oxygen pulping, the waste liquors from ozone bleaching as well as hydrogen peroxide bleaching will be recycled to a great extent in order to eliminate the effluent ultimately. Finally, through revealing the reaction mechanisms during the pulping, it will help to establish a truly total oxygen pulping system with high-efficient, energy-saving and clean, for rice straw and wheat straw, and advance the straw pulping technology, also accelerate the utilization of straw pulps in paper industry.

禾草类植物纤维原料资源量巨大，却碍于其先天的不足而难以具备与木材纸浆所具有的高效、节能、清洁制备的优势，使其在造纸工业中的应用受到了极大的限制。要提升禾草类纸浆的竞争优势，充分利用好禾草类纤维原料的特点是实现高效、节能、清洁纸浆制备的前提条件。氧系制浆以稻草和麦草作为禾草类原料的代表，对它们分别进行低温氧碱蒸煮和高效臭氧漂白，两步制浆直接获取白度达80%ISO，臭氧化黏度损失低于10%的高品质稻、麦草浆；之后加一步过氧化氢漂白将获取84%ISO以上的高品质高白度稻、麦草氧系浆；活用臭氧漂白废液中有机组分作为臭氧化反应助剂和碳水化合物保护剂，力求由臭氧漂白废液提取分离的有机酸、酚类等供给臭氧漂白；对氧碱蒸煮黑液、臭氧漂白废液及至过氧化氢漂白废液高度循环利用；揭示整个制浆体系的反应机理与特征，建立稻、麦草真正意义上的高效、节能、清洁的氧系浆制备体系，将禾草类制浆提升至一个更高的发展平台。

禾草类氧系高效节能清洁化纸浆制备体系的研究是在克服及规避禾草制浆饱受诟病问题，以禾草类特性通过氧系制浆以期扬长避短，建立能与木材制浆水平相当的新型制浆体系以为重振草类制浆工业夯实基础的大背景下提出来的。通过对稻、麦草各自的氧系制浆体系的系统研究，最终达成了纸浆制备蒸煮的高效节能清洁化目标。.对稻草先碱预蒸后于105℃低温氧碱蒸煮，可得到得率52%、卡伯值9.6、白度51.6%ISO、黏度848mL/g的稻草氧碱浆。将其在草酸保护作用下进行臭氧漂白两步法可漂白至80%ISO，且得到废液循环漂白纸浆质量稳定的效果。进一步优化稻草氧碱蒸煮还获得了得率54.4%、卡伯值6.7、白度58%ISO、黏度858mL/g的低卡伯值稻草氧碱浆，对其一步臭氧漂白得到80%ISO白度、选择性接近20的漂白浆。与此同时，与稻草传统碱法蒸煮相比，稻草氧碱蒸煮黑液的含硅量降低约85%，黏度临界点的固形物浓度可达近60%、热膨胀系数成倍增加，热解温度降低25-30℃，非常利于碱回收。.对麦草先预蒸煮，置换部分黑液，再于110℃低温氧碱蒸煮，可得到得率近46%、卡伯值8.6、白度近60%ISO、黏度682mL/g的麦草氧碱浆。其在草酸保护作用下的臭氧漂白轻松达到80%ISO的白度，而漂白选择性可上100。该结果的意义在于一步臭氧漂白可冲击高白度漂白浆，即氧碱蒸煮加臭氧漂白两步过程就能获得高质量的麦草氧系漂白浆。.对稻、麦草氧系制浆反应的机制、机理的基础性研究，得到了大量的科学数据，揭示了许多内在的规律，让氧系制浆体系变得更为清晰，充实了氧系制浆的理论。它不仅为草类氧系制浆技术的发展提供理论依据，也为在工程化推广与应用提供重要的科学依据。经过稻草氧碱制浆在工程化应用中的成功运行试验，禾草类氧系制浆体系的应用前景就更为值得期待。