Abstract:

The migration and enrichment characteristics of elements have a significant impact on the long-term stable operation of coal gasification plants. The samples (the raw coal and the coarse and fine slag after gasification) collected from entrained-flow coal water slurry gasification plants were studied using X-ray diffraction (XRD) and X-ray fluorescence spectrometer (XRF). It is found that elements such as Na, P, V, and Ti were more easily enriched in the fine slag, while elements such as Fe, Ca, and Cr were more easily enriched in the coarse slag. The thermodynamic calculation results indicated that the V element mainly existed in the form of gaseous V₂O₃ or VO₂ during the gasification process; at high temperatures, the S element basically transformed into volatile forms such as gaseous COS and H₂S, with little residue in both coarse and fine slag. During the heating process, Cr element mainly combined with Mg and Fe to form solid phase MgCr₂O₄ and FeCr₂O₄. After reaching about 1100℃, it was more likely to exist in the form of CrO and Cr₂O₃ in the liquid slag. A weak reducing atmosphere was carried out in a tube furnace to explore the influence of temperature on the enrichment of elements in coal ash. The results showed that the higher the gasification temperature, the easier Na and S elements were enriched in the gas phase, while Ca, Fe, and Cr elements were enriched in the slag.

Key words: coal water slurry, coal gasification, migration, enrichment, thermodynamic

摘要：

元素的迁移与富集特性对煤气化装置的长周期稳定运行有重要影响。本文运用X射线衍射、X射线荧光光谱分析等手段，对气流床水煤浆气化装置使用的煤及气化后的粗细渣进行了研究，发现Na、P、V、Ti等元素较容易在细渣中富集，Fe、Ca、Cr元素则容易在粗渣中富集。热力学计算结果表明，气化过程中V元素主要是以气态V₂O₃或VO₂的形式存在；高温下S元素大部分以气态COS和H₂S等形式存在。在升温过程中Cr元素与Mg、Fe结合生成固相MgCr₂O₄、FeCr₂O₄，1100℃后Cr元素较容易以CrO及Cr₂O₃形式存在于液态熔渣中。在管式炉中开展了弱还原性气氛实验，探究了温度对煤灰中元素富集的影响特性。结果表明，气化温度越高，Na、S元素易向气相富集，Ca、Fe、Cr元素易在熔渣中富集。

关键词: 水煤浆, 煤气化, 迁移, 富集, 热力学