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首页> 外文会议>Appita Annual Conference and Exhibition incorporating the ISWFPC(International Symposium on Wood, Fibre and Pulping Chemistry) vol.2: 13th ISWFPC Sessions - Oral Papers; 20050516-19; Auckland(NZ) >Desilication of wheat straw black liquor
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Desilication of wheat straw black liquor

机译：小麦秸秆黑液的脱硅

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摘要

Although wood is the most widely used raw material for pulp and paper industry, its availability is limited in many forest deficient countries. With the shortage of forest-based raw material and to preserve the depleting forest, the paper industry in Asia and other parts of the world is forced to use non-woody fibrous raw materials. India is also one of the leading countries using substantial proportion of non-wood raw materials such as bamboo, cereal straws, bagasse, etc., which constitute about 35% of the total raw material furnish used in Indian paper industry. Non-wood raw materials are characterized by high silica content which varies between 1.5 to 15%. Major portion of this silica gets dissolved in spent pulping liquor during alkaline pulping. Presence of this silica in black liquor creates innumerable problems in operating chemical recovery system. Evaporator, Recovery furnace, causticization and limekiln operations are adversely affected by the presence of silica in black liquor. Central Pulp & Paper Research Institute (CPPRI) is an apex R & D organization dedicated to applied research in the area of pulp and paper. The Institute has carried out extensive work on utilization of non-wood raw materials for pulp and papermaking and also to address the problems associated with these raw materials during processing in pulp & paper industry. Wheat straw and bagasse are the two main agro-residue raw material used in the Indian subcontinent. Silica content in bagasse black liquor is in the range of 0.4- 0.5% while in wheat straw it is 4.0 -5.0 % w/w. Due to the presence of this high amount of silica processing of wheat straw black liquor in chemical recovery is very difficult. Looking into this problem CPPRI initiated detailed studies on desilication of wheat straw black liquor. The objective of this study was to effectively remove silica from wheat straw black liquor. Black liquor was collected from an integrated wheat straw based mill. Silica content in the original black liquor was in the rage of 3.5 - 5.0 g/l. The black liquor was subjected to carbonation under controlled conditions using recovery boiler flue gas as source of carbon dioxide. Controlled pH reduction led to selective precipitation of silica without co-precipitation of lignin. Residual silica content in the black liquor after desilication was 0.4 g/l and nearly 90% desilication was achieved. Black liquor properties before and after desilication were evaluated. The results show improved black liquor properties after desilication. Viscosity was reduced to nearly 60% while swelling volume ratio increased by 1.5 times. The black liquor was colloidally stable up to 65% total solid concentration and no precipitation was observed. Improved black liquor properties of wheat straw black liquor after desilication makes it suitable for processing in conventional chemical recovery system.
机译：尽管木材是制浆和造纸工业中使用最广泛的原材料，但在许多森林资源匮乏的国家，木材的供应受到限制。由于缺乏以森林为基础的原料，并且为了保护正在枯竭的森林，亚洲和世界其他地区的造纸业被迫使用非木质纤维原料。印度还是使用大量非木材原料（例如竹，谷物秸秆，甘蔗渣等）的主要国家之一，约占印度造纸工业所用原料的35％。非木材原料的特点是二氧化硅含量高，介于1.5％至15％之间。在碱性制浆过程中，这种二氧化硅的大部分溶解在废制浆液中。黑液中这种二氧化硅的存在在操作化学回收系统中产生了无数问题。黑液中二氧化硅的存在会对蒸发器，回收炉，苛化和石灰窑操作产生不利影响。中央纸浆和造纸研究院（CPPRI）是一家致力于纸浆和造纸领域应用研究的顶尖研发组织。该研究所在利用非木材原料制浆和造纸方面开展了广泛的工作，并解决了制浆造纸行业加工过程中与这些原料相关的问题。小麦秸秆和甘蔗渣是印度次大陆使用的两种主要农残原料。蔗渣黑液中的二氧化硅含量在0.4-0.5％的范围内，而在麦草中为4.0 -5.0％w / w。由于存在大量的二氧化硅，因此麦秸黑液的化学回收非常困难。针对这一问题，CPPRI开始了对小麦秸秆黑液干燥的详细研究。这项研究的目的是有效地从小麦秸秆黑液中除去二氧化硅。黑液是从基于小麦秸秆的综合工厂收集的。原始黑液中的二氧化硅含量为3.5-5.0 g / l。使用回收锅炉烟道气作为二氧化碳源，在受控条件下对黑液进行碳化。 pH值的控制降低导致二氧化硅选择性沉淀，而木质素未发生共沉淀。脱硅后黑液中残留的二氧化硅含量为0.4 g / l，实现了近90％的脱硅。评估了脱硅前后的黑液性质。结果表明，脱硅后黑液性能得​​到改善。粘度降低到接近60％，而溶胀体积比增加了1.5倍。该黑液在高达65％的总固体浓度下是胶体稳定的，并且没有观察到沉淀。小麦秸秆黑液脱硅后黑液性质的改善使其适用于常规化学回收系统中的处理。

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