Migration characteristics of organic potassium during the thermal conversion process of cellulose char under different atmospheres

doi:10.16085/j.issn.1000-6613.2020-1916

Abstract

Abstract:

The release of potassium (K) in biomass thermal utilization can cause severe technical problems with deposition, slagging and corrosion on heat transfer surfaces. Char-associated organic K (char-K) is an important occurrence form of K in biomass char. In this study, the migration behavior of char-K during pyrolysis and oxidization of cellulose char was investigated. Under Ar pyrolysis atmosphere, obvious release of char-K can be observed at 800—1000℃. The release rate of char-K increased significantly with temperature. In the end, part of char-K stably remained in the cellulose char. Under reaction atmosphere, only a small amount of K was released at 800℃, and the release ratio of K increased significantly with temperature. The K release ratio first increased slowly and then rapidly with time. After the cellulose char was completely oxidized, there was still obvious K released from ash. Combined with the XRD analysis of ash residues, it was found that with the consumption of cellulose char matrix, char-K was first converted into K₂CO₃, and then was released to the gas phase at temperatures above 900℃.

Key words: biomass, organic K, cellulose char, reaction atmosphere, migration

摘要：

生物质热转化过程中钾（K）的释放会造成换热面积灰、结渣、腐蚀等技术问题。有机钾是生物质焦中K的重要赋存形式。本文研究了在Ar热解气氛和O₂反应气氛下纤维素焦中有机K的迁移行为。Ar热解气氛下，在800～1000℃都有明显的有机K释放，释放速率随温度增加明显增加，但最终都有部分有机K稳定地留在固相中。O₂反应气氛下，800℃时纤维素焦中只有少量K发生释放；随着温度的增加，K的释放比例明显增加。在900℃和1000℃ K的释放比例随时间先缓慢增加后快速增加，当纤维素焦完全氧化后，灰分中仍有明显的K释放。结合对灰分的XRD分析发现，随着纤维素焦的消耗，其中稳定存在的有机K主要转化为K₂CO₃，然后在900℃以上发生明显的气相释放。

关键词: 生物质, 有机钾, 纤维素焦, 反应气氛, 迁移

CLC Number:

ZHAO Haibo, XU Wenting, SONG Qiang. Migration characteristics of organic potassium during the thermal conversion process of cellulose char under different atmospheres[J]. Chemical Industry and Engineering Progress, 2021, 40(8): 4631-4637.

赵海波, 徐文婷, 宋蔷. 不同热转化气氛下纤维素焦中有机钾的迁移特性[J]. 化工进展, 2021, 40(8): 4631-4637.

Figures/Tables 6

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