Silicon distribution in straw black liquor recovery process of pyrolysis and combustion

doi:10.11949/j.issn.0438-1157.20171266

Abstract

Abstract:

Pyrolysis technology is a widely utilized process in biomass energy production, and has potential to serve as an alternative for recovery of straw black liquor. A 10 kg·h^-1 stirring type pyrolysis experimental apparatus was employed to prepare black liquor char (BLC) and fuel gas, aiming to analyze the differences of total alkali recovery and silicon distribution between BLC-leached and smelt-dissolved green liquor. The results showed that the total alkali in BLC-leached green liquor was equal to or a bit higher than that of smelt-dissolved green liquor. Around 30% to 40% of silicon retained in BLC-leached carbon powder as forms of insoluble silicates, which were mainly compound silicates of non-process elements such as Al, Ca, Fe and Mn. Because of the retention of a considerable part of silicon in leaching solid phase, the silicon concentration was lower in BLC-leached green liquor than that of smelt-dissolved green liquor, and the ratio of Na₂CO₃ to Na₂SiO₃ (or Na₄SiO₄) decreased to a large extent in the former green liquor compared to the latter. The findings indicate that chemical recovery using pyrolysis-leaching method is beneficial for decreasing the affects of silica problem especially improving the lime causticizing process.

Key words: black liquor, biomass, pyrolysis, gasification, chemical recovery, silica problem, char, leaching

摘要：

热解作为一种生物质能源利用技术，有望为草浆黑液的碱回收提供新途径。利用10 kg·h^-1搅拌热解实验装置对麦草浆黑液开展了研究，分析热解半焦浸取与燃烧熔融物溶解两种绿液制备方式在总碱回收及硅元素分布方面的差异。结果表明：热解浸取法所获得绿液中包括碳酸钠和硅酸钠在内的总碱量与燃烧溶解法相比基本相等或稍高；浸取完成后有30%～40%的硅元素未溶入绿液而留存于固相即炭粉之中，主要赋存形态为Al、Ca、Fe和Mn等非过程元素的复合硅酸盐；由于数量可观的硅元素留存于固相，因此热解浸取法相比燃烧溶解法绿液硅含量较低，也因此碳酸钠与硅酸钠之比较高。热解浸取法的硅元素分布特性有利于后续的石灰苛化操作。

关键词: 黑液, 生物质, 热解, 气化, 碱回收, 硅干扰, 半焦, 浸取

CLC Number:

TS79
TK6

YUAN Hongyou, WU Shubin, YIN Xiuli, HUANG Yanqin, LIU Huacai, WANG Guijin, ZHAN Hao, WU Chuangzhi. Silicon distribution in straw black liquor recovery process of pyrolysis and combustion[J]. CIESC Journal, 2018, 69(5): 2191-2198.

袁洪友, 武书彬, 阴秀丽, 黄艳琴, 刘华财, 王贵金, 詹昊, 吴创之. 草浆黑液热解和燃烧碱回收过程硅元素的分布[J]. 化工学报, 2018, 69(5): 2191-2198.

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