Effect of tall oil soap on sodium salt scaling in kraft black liquor evaporators

2016年，加拿大生产了165亿吨木浆，主要是通过硫酸盐制浆，出口额约为72亿美元。化学回收循环使硫酸盐制浆过程在环境和经济上都是可行的，这也是它在世界范围内使用的主要制浆过程的原因。化学回收循环的第一步是黑液蒸发。黑液是溶解的有机物和废制浆化学品的混合物，主要是溶解的钠盐。在蒸发过程中，这些钠盐结晶，导致黑液蒸发器中的钠盐结垢。最近的工厂经验表明，添加脂肪酸和树脂酸溶液（塔尔油皂和类似的）可以显著减少甚至消除钠盐结垢。限制其广泛应用的是缺乏对高油皂如何减少结垢的了解。本文建议研究树脂和脂肪酸对钠盐结晶的单独和联合作用，以阐明其潜在的机理。本研究旨在通过添加含有树脂和脂肪酸的纸浆厂液，广泛减少纸浆厂的钠盐结垢。由于洗涤循环次数的减少，这将导致蒸发器中蒸汽使用量的减少。这反过来又会减少工厂的二氧化碳排放量。拟议工作的一个重要部分是调查可以应用这项工作的其他盐系统，以便我们可以最大限度地提高加拿大和环境的总体效益。

Canada produced 16.5 billion tonnes of wood pulp in 2016, primary through kraft pulping, accounting for about $7.2 billion in exports. The chemical recovery cycle makes the kraft pulping process both environmentally and economically viable and is the reason it is the dominant pulping process used worldwide. The first step in the chemical recovery cycle is black liquor evaporation. Black liquor is a mixture of the dissolved organics and spend pulping chemicals which are predominantly dissolved sodium salts. During evaporation, these sodium salts crystallize, leading to sodium salt scaling in the black liquor evaporators. Recent mill experience has shown that the addition of a solution of fatty and resin acids (tall oil soap and similar) can significantly reduce or even eliminate sodium salt scaling. What is limiting its widespread application is a lack of knowledge about how the tall oil soap reduces scaling. This is a proposal to study the effects of resin and fatty acids, individually and in combination, on sodium salt crystallization to clarify the underlying mechanism.This research is intended to lead to a widespread reduction in sodium salt scaling in pulp mills through the addition of pulp mill streams containing resin and fatty acids. This would lead to a reduction in steam usage in evaporators due to a reduction in the number of wash cycles. This in turn will result in a smaller CO2 footprint of the mills. An important part of the proposed work is to investigate other salt systems to which this work can be applied so that we can maximize the overall benefit to Canada and the environment.