Abstract: Agglomeration in fluidized bed gasification system is considered as a primary operational problem, especially for catalytic coal gasification process because alkali catalyst worsens sintering and slagging. The optimal condition from the experiments will ensure the operation of coal gasification below sintering temperature and make the fluidized bed gasifier operate normally. In this paper a self-made pressurized pressure-drop measuring device combining analysis of X-ray diffractometer (XRD) analyzer were used to study the effects of alkali catalyst addition, operation pressure and reaction atmosphere on sintering temperature of Wangjiata bituminous coal from Inner Mongolia, China. Sintering temperatures declined markedly after adding potassium carbonate catalyst. Sintering temperatures decreased with increasing pressure in the range of 0.1—3.5 MPa, and a more obvious decrease could be observed in the interval of higher pressure. This effect could be related to coal ash composition and addition of alkali catalyst. Operation pressure influenced sintering temperatures by affecting reaction rate and mineral transformation in coal ash, as observed from XRD patterns. Sintering temperatures measured in the reducing reaction atmosphere were lower than those in inert and oxidizing atmospheres, which could be related to different existence forms of Fe ions and K. The addition of water vapor lowered sintering temperature significantly. The presence of water vapor led to formation of low melting point materials, such as KOH, and K-bearing materials were easier to react with minerals of coal ash to produce low temperature eutectics in water vapor atmosphere, thus lowering sintering temperature.

Key words: coal, gasification, catalyst, sintering temperature, pressure-drop technique, pressure, reaction atmosphere, water vapor

摘要： 煤催化气化工艺中碱金属催化剂的引入加剧了气化炉的结渣,直接影响了流化床气化炉结渣的正常操作。煤灰的烧结特性是流化床气化炉结渣的主要影响因素之一,通过摸索工艺条件使煤气化在烧结温度以下运行,可有效避免流化床气化炉内出现结渣问题。利用压差法测定烧结温度,结合灰渣的XRD分析结果系统研究了钾基碱金属催化剂的添加量、操作压力、反应气氛对王家塔烟煤低温灰化煤灰烧结温度的影响。结果表明,碳酸钾催化剂的添加明显降低了煤的灰熔点及烧结温度。0.1～3.5 MPa下,烧结温度随压力增大而降低,而且压力对烧结温度的影响在高压区更为明显,具体影响规律与煤种灰成分及钾基碱金属催化剂的添加有关。空气、CO₂氧化性气氛下的烧结温度较高,N₂惰性气氛下次之,还原性气氛下较低,而蒸汽的加入显著降低了烧结温度。烧结温度的变化与不同气氛下铁离子存在状态及钾的存在形态密切相关。蒸汽气氛下,钾更多以KOH等低熔点化合物形态存在,而且含钾物相在蒸汽气氛下更容易同煤灰中的硅铝、铁钙等矿物质反应,生成低共融点化合物,致使灰熔点及烧结温度大幅下降。

关键词: 煤, 气化, 催化剂, 烧结温度, 压差法测定技术, 压力, 反应气氛, 蒸汽