TBCFB system simulation and optimization for pyrolysis-gasification-combustion of low rank coal

doi:10.11949/j.issn.0438-1157.20180280

Abstract

Abstract:

The quality-based utilization technology of low rank coal has attracted much attention due to its advantages in energy saving and emission reduction. A novel triple-bed combined circulating fluidized bed (TBCFB) system, which includes a pyrolyzer, a gasifier and a combustor, is developed to minimize energy loss. A new process was proposed to used char coal particles instead of sand particles as heat-carried circulating medium and an Aspen Plus process simulation was established to obtain optimum operating conditions for material conversion and energy utilization between three bed reactors. The results showed that 40% char coal combustion could provide enough energy for both low rank coal pyrolysis at 600℃ and gasification of water over 60% residual char coal at 800.9℃. High heat capacity char coal particles significantly reduced amount of heat-carried particles needed to circulate in the system. To meet the requirements of heat transportation, mass ratio of char coal to low rank coal was 5.5, whereas mass ratio of quartz and ash to low rank coal were 11 and 12, respectively. Comprehensive analysis of syngas composition, cold gasification efficiency (CGE) and lower heating value (LHV) indicated optimal ratio of steam to char coal (St/C) was 1.5 in gasification. The simulation results would provide some guidance on industrial application of TBCFB system with char coal as heat-carried particles.

Key words: quality-based utilization, circulating fluidized bed, simulation, gasification, optimization

摘要：

三塔式循环流化床（TBCFB）是基于低阶煤分质转化利用理念开发的新型工艺系统，包含热解、气化及燃烧三个主反应器。提出了采用半焦颗粒代替石英砂作为循环热载体的新工艺，并使用Aspen Plus建立了基于半焦颗粒的TBCFB系统模拟流程，寻求系统内物料转化和能量利用的适宜操作条件。结果表明，只需燃烧40%的热解半焦，即可满足低阶煤在600℃热解和60%的热解半焦在800.9℃进行水蒸气气化所需热量；与石英砂或高温灰相比，利用热容较高的半焦颗粒作为循环介质可以显著降低热载体循环量，与原煤质量比仅为5.5。综合气化产物组成、低热值和冷煤气效率等指标，适宜的水蒸气与反应半焦质量比为1.5。上述模拟结果对半焦循环TBCFB新技术的工业应用具有一定指导意义。

关键词: 分质利用, 循环流化床, 模拟, 气化, 优化

CLC Number:

TQ015.1

WANG Yaxiong, YANG Jingxuan, ZHANG Zhonglin, MA Xuli, LI Peng, HAO Xiaogang, GUAN Guoqing. TBCFB system simulation and optimization for pyrolysis-gasification-combustion of low rank coal[J]. CIESC Journal, 2018, 69(8): 3596-3604.

王亚雄, 杨景轩, 张忠林, 马旭莉, 李鹏, 郝晓刚, 官国清. 低阶煤热解-气化-燃烧TBCFB系统模拟及优化[J]. 化工学报, 2018, 69(8): 3596-3604.

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