FUNDAMENTAL STUDIES OF SAFETY ISSUES IN SMELT DISSOLVING TANK OPERATION IN KRAFT PULP MILLS

牛皮纸浆厂熔炼溶解罐运行安全问题的基础研究

• 批准号: RGPIN-2014-04387
• 负责人: Tran, Honghi
• 金额: $ 2.11万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=566489
• 关键词: FUNDAMENTAL; STUDIES; SAFETY; ISSUES; SMELT

The kraft process is the predominant method for making wood pulp. For a typical kraft mill in Canada, the process generates as much as 12,000 tonnes/day of dilute black liquor that contains water, dissolved wood components and spent pulping chemicals. This massive “waste” stream must be processed through the chemical recovery plant within the mill. The recovery process involves concentrating the black liquor and burning it in a recovery boiler to produce steam and power, and at the same time, converting the inorganic combustion residue back into pulping chemicals. The combustion results in the formation of molten smelt at the bottom of the recovery boiler. As it pours out of the boiler, molten smelt is shattered by a steam jet into small droplets before falling into the dissolving tank underneath where it interacts with water and dissolves. While shattering molten smelt with a high pressure steam jet, and dissolving the shattered smelt in the dissolving tank, are violent and often dangerous processes, they are necessary in order to process the large amount of molten smelt effectively, and to produce consistent green liquor. Dissolving tanks constantly rumble loudly, and at times, cause tremors of the ground and buildings nearby. In severe cases, explosions occur, causing substantial equipment damage and production loss associated with unscheduled boiler downtime. Personnel injuries and fatalities have also been reported to be caused by explosion or by being showered with hot/corrosive green liquor ejected from the dissolving tank. Over the past 30 years, there has been about one explosion incident a year reported in North America, although the actual number could be higher as many incidents go unreported. Needless to say, one explosion incident is too many when it comes to workplace safety. As regulations on occupational health and safety have become increasingly stringent in recent years, effective and safe dissolving tank operation has become a top priority for kraft pulp mills. The proposed research program consists of three main tasks: 1) investigation of the shattering behaviour of molten smelt by a steam jet, 2) investigation of molten smelt and water interaction and 3) development of an on-line noise monitoring system. The objectives are to obtain fundamental data on smelt shattering by a steam jet and smelt-water interaction in the dissolving tank, and to systematically examine the effects of key dissolving tank operating parameters on smelt shattering and explosion. The long-term goal is to help kraft pulp mills develop viable means/strategies to ensure safe and efficient dissolving tank operation. There are presently 28 kraft pulp mills in Canada. They will benefit greatly from the research program through a better understanding of how molten smelt and water interact, and the operating conditions under which an explosion can be completely controlled. This will allow mills to develop viable guidelines and strategies for increasing dissolving tank efficiency and safety, and provide mill personnel with a safer and quieter working environment. Successful completion of the research program will also help mills to devise ways to reduce shattering steam usage, reduce insurance premiums through safer and more predictable operation, and avoid a recovery boiler shutdown caused by dissolving tank explosion. The research program will help train 7 highly qualified personnel (1 PhD, 4 MASc and 2 undergraduate students). The research projects are intimately tied to industry applications, with great social, environmental and economical impacts, and thus will provide these HQP with many opportunities to prepare themselves for future careers.

牛皮纸工艺是制造木浆的主要方法，对于加拿大的一家典型牛皮纸工厂来说，该工艺每天会产生多达 12,000 吨的稀黑液，其中含有水、溶解的木材成分和废制浆化学品。 ” 流必须通过工厂内的化学回收装置进行处理。回收过程将黑液浓缩，并在回收锅炉中燃烧以产生蒸汽和电力，同时转化无机燃烧残留物。燃烧导致回收锅炉底部形成熔融熔体。当熔体从锅炉中流出时，熔融熔体被蒸汽喷射破碎成小液滴，然后落入下方的溶解罐中。与水相互作用并溶解，而用高压蒸汽喷射破碎熔融熔体，并在溶解罐中溶解破碎的熔体，是暴力且通常危险的过程，为了有效地处理大量熔融熔炼物并产生稳定的绿液，溶解罐不断发出巨大的隆隆声，有时会引起附近地面和建筑物的震动，严重时会发生爆炸，造成重大损失。过去也有报告称，因锅炉意外停机而造成的设备损坏和生产损失是由爆炸或溶解罐喷出的热/腐蚀性绿液造成的。 30年来，北美每年大约发生一起爆炸事件，尽管实际数字可能更高，因为许多事件没有报告，不用说，就工作场所安全而言，爆炸事件太多了。近年来，职业健康和安全日益严格，溶解罐的有效和安全运行已成为硫酸盐纸浆厂的首要任务。本研究计划包括三个主要任务：1）研究熔融熔体的破碎行为。蒸汽射流，2）研究熔融熔炼体与水的相互作用，3）开发在线噪声监测系统，目的是获得有关溶解槽中蒸汽喷射和熔炼体-水相互作用的熔体破碎的基本数据。彻底检查溶解罐关键操作参数对熔体破碎和爆炸的影响长期目标是帮助牛皮纸浆厂制定可行的手段/策略以确保溶解罐安全高效。目前，加拿大有 28 家硫酸盐纸浆厂将通过更好地了解熔融熔炼物与水的相互作用以及完全控制爆炸的操作条件而受益匪浅。制定可行的指导方针和策略，以提高溶解罐的效率和安全性，并为工厂人员提供更安全、更安静的工作环境。研究计划的成功完成还将帮助工厂找到减少破碎蒸汽使用、降低保险费的方法。通过更安全、更可预测的操作，并避免因溶解罐爆炸而导致回收锅炉停机。该研究项目将帮助培养 7 名高素质人才（1 名博士生、4 名硕士生和 2 名本科生）。该研究项目与行业应用密切相关。 ，具有巨大的社会、环境和经济影响，因此将为这些总部人员提供许多机会为未来的职业做好准备。