Abstract To reduce the tar yield, a horizontal fixed bed is proposed to replace a conventional fluidized bed in the pyrolysis stage of two-stage gasification. Effects of alkali and alkaline-earth metals on the generation of tar are studied. Roles of the interparticle and inner-furnace retention time are also investigated. Ultraviolet–visible spectrophotometry was used to determine the aromatic compounds in tars. The results showed that absorbance intensity of the tar solution increased linearly with its concentration within the examined concentration range. The removal of alkali and alkaline-earth metals increased the tar yield of coal. Increase in the absorbance intensity of tar is attributed to the increase in aromatic ring systems. Ion-exchangeable Na plays a dominant role in the retention of tar precursors, mainly polycondensed aromatic rings, by connecting them with the char matrix. Increasing the retention time in interparticle diffusion decreased the yield of tar, especially for polycondensed aromatic rings. Increasing the retention time in inner-furnace diffusion slightly decreased the tar yield. Introduction of a fixed bed could effectively solve the problems of high tar yield from coal and low catalyst contents in char.

中文翻译：

---

碱金属和碱土金属及停留时间对卧式固定床反应器煤热解焦油生成的影响

摘要 为降低焦油产率，在两段气化热解阶段提出用水平固定床代替常规流化床。研究了碱金属和碱土金属对焦油生成的影响。还研究了颗粒间和炉内保留时间的作用。紫外-可见分光光度法用于测定焦油中的芳香族化合物。结果表明，在检测浓度范围内，焦油溶液的吸光度强度随其浓度呈线性增加。碱金属和碱土金属的去除提高了煤的焦油产率。焦油吸收强度的增加归因于芳环系统的增加。离子交换钠在焦油前体的保留中起主导作用，主要是缩聚芳环，通过将它们与字符矩阵连接起来。增加颗粒间扩散的停留时间会降低焦油的产率，特别是对于缩聚芳环。增加炉内扩散的保留时间会略微降低焦油产率。固定床的引入可以有效解决煤焦油收率高和焦炭催化剂含量低的问题。