Abstract:

From the viewpoint of reaction engineering, this study compared the characteristics of existing coal pyrolysis technologies to tar and gas products, summarized the effect of heat and mass transfer in the key steps of coal pyrolysis process on volatiles, such as intra-particle generation and release, inter-particle diffusion and residence in the reactor, analyzed the effect of secondary reactions on products quality, and finally revealed the root of low yield, poor quality and high dust content in the target products of the existing coal pyrolysis technologies. On this basis, the effective measures of coal directional pyrolysis were proposed, including high temperature heating and fast heat transfer in the volatiles generation and char poly-condensation, tar reforming and dust filtering in the char bed during volatiles release, and directional overflow of volatiles by setting up gas channels in the reactor. Then, the technology of coal directional pyrolysis by a moving bed with internals developed by the research group was introduced. The adopted internals included heat transfer plate and gas collection cavity, by which the heat and mass transfer was intensified, the direction of gas flow in reactor was guided orderly and dust was filtered by the slowly moving char bed. With respect to this pyrolysis technology, the fundamental research in a pyrolysis equipment with a processing capacity (PC) of 1—5 kg/time, the model test on a pyrolysis equipment with a PC of 100 kg/time, and a pilot demonstration on a plant with a PC of 1000 t/a have been conducted. The results fully confirm the advantages of this pyrolysis technology in the simultaneous improvement of yield and quality for both of tar and pyrolysis gas, the reduction of dust content in oil, the good adaptability of crushed coal feedstock. Based on the above research, the internal component directional pyrolysis technology and the heat/electricity-oil-gas co-generation technology based on this technology have been formed.

Key words: coal, directional pyrolysis, reaction regulation, heat and mass transfer, moving bed

摘要：

对比了现有煤热解制油气技术的特点，从反应工程“三传一反”的角度系统分析和概括了煤热解过程中挥发分在颗粒内生成和释放、颗粒间扩散和反应器中停留等关键步骤中的热量、质量传递和挥发分二次反应对油气品质的影响，揭示了目前碎煤热解制油气技术普遍存在的目标产品产率低、品质差、含尘量高等技术难题的根源，并总结出煤定向热解调控的有效措施，即在挥发分生成和半焦缩聚段采用高温加热和快速传递的传热方式，在挥发分扩散过程中利用半焦床层重整焦油和过滤灰尘，在反应器中设置气体通道导流挥发分的定向溢出。针对研究团队前期开发的内构件移动床定向热解理念，介绍了导热板和集气腔等内构件的作用机制，即通过导热板和中心集气腔等内构件进行传热强化、热解气流动的有序引导，实现热量和挥发分的同向扩散和传递；通过移动床中颗粒的缓慢运动和床层的过滤作用除尘；概述了1~5 kg/次基础实验、反应器结构内传热和流动模拟，100 kg/次模试分析和1000 t/a中试验证的研究结果，充分证实了该技术在同步提高油气质量与品质、降低油中尘含量等方面的优势和对碎煤原料的适用性；基于上述研究形成了内构件定向热解技术及基于该技术的热/电-油-气联产技术。

关键词: 煤, 定向热解, 反应调控, 热质传递, 移动床