College of Chemical Engineering and Technology, Taiyuan University of Technology
Yingkou Qingying Petroleum Chemical Equipment Company Limited
School of Chemistry and Chemical Engineering, North University of China

离心双涡流(CDV)反应器是内置离心力场与双涡流气旋的新型下行床反应器,契合低阶煤快速热解反应特性,但仍需理解其关键传热机制为传热速率调控提供参考。基于大涡模拟和MP-PIC(multiphaseparticle-in-cell)模型,研究载热颗粒为热源的CDV低阶煤热解器中气固相温度的时空分布特性。结果表明:煤颗粒升温速率可达700K/s,满足快速热解需要,相比传统下行床,由离心力场在近壁区产生的局部高固含率可在较低的载热颗粒流量下将煤颗粒下行过程中的升温梯度提高到300K/m以上;除了固含率,气旋长度对传热效果影响显著,相比顶部排气结构,底部排气结构的气旋长度更大,煤颗粒终温更高;底部排气结构的另一个优势在于中心区域气流温度显著低于边壁气流温度,在近壁高温区释放的初级热解产物受向心气流裹挟汇入中心低温区,由于初级热解产物二次反应的程度与其升温速率相关,中心区域的低温环境有利于抑制初级热解产物的二次反应,从而获得更高的焦油收率,且焦油含尘量也较低。

The centrifugal and double vortex (CDV) reactor is a novel downer reactor that harnesses centrifugal force and a double vortex, and it enables rapid pyrolysis of low-rank coal. However, further research is necessary to fully understand the heat transfer mechanisms to provide theoretical guidance for optimization. In this study, the flow and temperature distribu-tions of gas and solid in a CDV pyrolyzer was investigated, where heat-carrying particles serve as the heat source by the large eddy simulations and the MP-PIC (multiphase particle-in-cell) model. The results show that coal particles can be heated at a rate of 700 K/s , leading to rapid pyrolysis. Due to the centrifugal force, the solid hold-up near the reactor wall is much higher than that in the conventional donwer, resulting in an over 300 K/m of temperature rise gradient even in a small mass flow rate of heat-carrying particles. In addition, the cyclone length also has a signifi-cant effect on the heat transfer. The cyclone length within the base bleed reactor is much longer than that within the top bleed reactor, resulting in a much higher final temperature of coal parti-cles. Another advantage of the base bleed reactor is that the airflow temperature in the central re-gion is significantly lower than that near the wall. The primary pyrolysates are primarily genera-ted in the region with high temperature near the wall, then they are carried by the gas flowing in-to the central region with low temperature. Because the secondary reaction of the primary pyroly-sates is enhanced by the high temperature, the gas flowing into the central region helps to sup-press secondary reactions of the primary pyrolysates, resulting in higher tar yields and lower dust content.

国家自然基金青年项目(22108262)、山西省基础研究计划自然科学研究面上项目(202203021211164)和山西科化技术服务有限公司项目(20210507).

韩碧龙,付晓庆,杨景轩,等.低阶煤在离心双涡流反应器中的流动与传热过程[J].煤炭转化,2023,46(6):23-32

HAN Bilong,FU Xiaoqing,YANG Jingxuan,et al.Flow and heat transfer process of low rank coal in centrifugal and double vortex reac-tors[J].Coal Conversion,2023,46(6):23-32