Abstract:

Considering the difficulty in treating high-ash coking coal by the existing fluidized bed gasification technology, Institute of Process Engineering, Chinese Academy of Sciences has developed a jetting pre-oxidation fluidized bed gasification (JPFBG) technology for gasifying washing middlings and other caking coals. The coal is jetted into the pre-oxidation zone of a fluidized bed gasifier using an O₂-containing gas stream to quickly disperse the particles and oxidize the viscous and plastic matter formed during heating. The char falls into the gasification zone to react with gasification agent as in other fluidized beds. This study was devoted to investigating the product distribution of pre-oxidation and the structure as well as reactivity of the formed char with respect to gasification condition parameters like temperature, air equivalence ratio (ER) and steam/coal ratio. The suitable conditions for pre-oxidation were temperature about 950℃ and ER₁ about 0.13. The produced char had relatively larger specific surface area and higher gasification reactivity. The suitable gasification conditions were 1000℃, ER₂ about 0.17 and mass ratio for steam/coal about 0.09. Then, the produced fuel gas had relatively higher quality and its tar contained more light species that were easier to be eliminated downstream. Obviously, all these results would support the design and scale-up of the JPFBG technology.

Key words: fluidized-bed, pyrolysis, gasification, caking coal, pre-oxidation, destruction of caking property

摘要：

针对现有流化床气化技术难以处理黏结性、高含灰洗中煤的问题, 中国科学院过程工程研究所开发了可处理黏结性碎煤的射流预氧化流化床气化技术, 该技术利用含氧气体将煤颗粒快速喷射送入预氧化区内破除其黏结性, 形成的半焦进入气化区内发生气化反应, 进而实现对黏结性煤的利用。本工作采用小型流化床射流预氧化反应装置研究较强黏结性煤预氧化破黏后的产物分布、半焦结构与活性变化, 并考察气化操作条件(温度、当量空气系数、水煤比等)对半焦气化行为的影响。结果表明:当预氧化区温度为950℃、当量空气系数为0.13时, 黏结性煤生成半焦的孔结构和气化活性较好;当半焦气化区温度为1000℃、当量空气系数为0.17、水蒸气与煤质量比为0.09时, 生成燃气的品质较好, 而且生成焦油中的轻质组分最多, 有利于焦油被进一步脱除。研究结果可为射流预氧化气化技术的设计放大提供基础数据。

关键词: 流化床, 热解, 气化, 黏结性煤, 预氧化, 破黏