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首页> 外文期刊>Paperi ja Puu >Lignin precipitation from kraft black liquors: kinetics and carbon dioxide absorption
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Lignin precipitation from kraft black liquors: kinetics and carbon dioxide absorption

机译：牛皮纸黑液中木质素的沉淀：动力学和二氧化碳吸收

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摘要

Lignin extraction from black liquor is today an interesting option for pulp mills since it makes it possible to increase the production capacity of pulp without increasing the load in the recovery boiler. Extracted lignin can be used either as a solid biofuel or as a feed stock producing various chemicals after it has been separated from the liquor and properly washed. The lignin must first, however, be precipitated from the black liquor. Although this can be performed in several ways, this investigation deals only with precipitation using CO_2 as the acidifying agent. In this study, the gas absorption process and the kinetics of the chemical reactions have been evaluated. Several precipitation experiments were carried out on five kraft black liquors from different mills. A theoretical model, based on the film theory, was developed and fitted to experimental data. The film thickness obtained varied between 0.1-10~(-9) and 0.3-10~(-9)m, which showed that the mass transport of CO_2 through the film to the reaction zone is fast. This may indicate that the course of events is dominated by the chemical composition of the black liquor rather than the parameters that influence absorption, e.g. mixing conditions.
机译：如今，从黑液中提取木质素是制浆厂的一个​​有趣的选择，因为它可以提高纸浆的生产能力而又不增加回收锅炉的负荷。从液体中分离出木质素并适当洗涤后，提取的木质素可用作固体生物燃料或产生多种化学物质的原料。但是，首先必须从黑液中沉淀出木质素。尽管这可以通过多种方式进行，但本研究仅涉及使用CO_2作为酸化剂的沉淀。在这项研究中，已经评估了气体吸收过程和化学反应的动力学。在来自不同工厂的五种牛皮纸黑液上进行了几次沉淀实验。建立了基于电影理论的理论模型，并将其拟合到实验数据中。得到的膜厚在0.1-10〜（-9）〜0.3-10〜（-9）m之间变化，表明CO_2通过膜到反应区的传质速度很快。这可能表明事件的进程是由黑液的化学组成而不是影响吸收的参数决定的，例如混合条件。

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