生物质灰富含碱金属及碱土金属(AAEM),可作为天然催化剂应用于煤催化气化。生物质灰对煤焦气化反应促进作用也是生物质与煤共气化协同作用的本质原因。然而,生物质灰中AAEM在煤气化过程中会失活,失去部分催化作用。通过固定床热解及气化试验,结合XRD、Raman、XRF及BET等手段,分析了生物质灰种类、添加量、气化温度等因素对煤焦气化反应的影响。结果表明,生物质灰对煤焦气化反应催化作用与AAEM含量及存在形态相关。煤焦气化反应速率随小麦秸秆灰添加量增大而增大,小麦秸秆灰添加量达40%时,煤焦气化反应速率变化趋于平缓。气化反应前期,小麦秸秆灰对煤焦气化反应存在抑制作用;随转化率升高,在相同转化率下,温度越高,小麦秸秆灰催化作用越弱。为抑制小麦秸秆灰中K的失活,以蛋壳作为添加剂,探究了小麦秸秆灰与蛋壳的混灰对煤焦气化反应的影响。结果表明,25%小麦秸秆灰与5%蛋壳的混灰,可进一步增强小麦秸秆灰对煤焦气化反应催化作用。添加小麦秸秆灰使煤焦在气化过程中比表面积增大,孔隙结构丰富,石墨化程度减弱,无定形碳含量增加,气化反应活化能降低,气化反应速率增大。煤焦及添加小麦秸秆灰煤焦气化反应采用随机孔模型模拟效果最好。研究结果为生物质灰在煤催化气化中的应用提供参考。

Biomass ash, rich in alkali and alkaline earth metals (AAEM), can be served as a natural catalyst in coal catalytic gasification.The promoting effect of biomass ash on coal gasification is a fundamental reason for the synergistic effect during co-gasification of biomassand coal. However, the AAEM in biomass ash may undergo deactivation during gasification, leading to the loss of catalytic activity. Theeffects of factors such as biomass ash type, content and temperature on coal char gasification through fixed-bed pyrolysis and gasificationexperiments were analyzed, combined with the analysis of XRD, Raman, XRF, and BET. The results indicate that the catalytic effect ofbiomass ash is related to the content and existing form of AAEM. The gasification reactivity of coal char increases with the increasing addition of wheat straw ash. However, when the addition of wheat straw ash reaches 40%, the reactivity of the coal char tends to changesmoothly. Wheat straw ash has an inhibitory effect on the gasification of coal char in the early stage of gasification reaction. As the carbon conversion increases, the catalytic effect of wheat straw ash decreases with the increasing temperature at the same conversion level. Inorder to inhibit the deactivation of potassium in wheat straw ash, eggshell was used as an additive to investigate the effects of mixing wheatstraw ash with eggshell on the gasification of coal char. The results indicate that the catalytic effect of wheat straw ash on the gasificationof coal char can be further enhanced by adding 25% wheat straw ash and 5% eggshell. The addition of wheat straw ash results in a largespecific surface area, an enriched pore structure, a more disordered carbon structure, a decrease in the gasification reaction activation energy and an increase in the gasification rate of the coal char. Random pore model is the most appropriate model to simulate the gasificationbehavior of coal char and the coal char with wheat straw ash. The findings provide a reference for the application of biomass ash incatalytic coal gasification.

0 引言

1 试验

   1.1 试验原料

   1.2 样品制备

   1.3 样品分析测试方法

   1.4 气化反应性评价方法

   1.5 气化反应动力学

2 结果与讨论

   2.1 生物质灰对煤焦气化反应性的影响

   2.2 生物质灰对煤焦物理化学结构的影响

   2.3 煤焦气化反应动力学

3 结论