Numerical simulation and optimization of circulation cup in direct coal liquefaction reactor

doi:10.11949/j.issn.0438-1157.20170195

Abstract

Abstract:

To solve blockage caused by coking in direct coal liquefaction reactors, a multi-phase model was developed to simulate two-phase gas-slurry flows around the circulation cup, which spatial flow parameters such as gas holdup were obtained. The simulation results indicated that the main driver for deposition and coking was aggregation and break-up of foams as well as foam mist blending associated with gas-liquid separation process. The relationship between extent of blocking in the circulation cup and gas holdup in downcomer showed that gas holdup in the downcomer was increased from zero to 34% as the extent of blocking was increased, leading to pump depletion. The finding on the cause of coking allowed further optimization on circulation cup structure. Simulation results showed that optimized design of circulation cup could effectively enhance gas-liquid separation with 14% gas holdup in the downcomer at extreme conditions and thus maintained stable operation. This work provides a reference for modifications on industrial equipment.

Key words: coal liquefaction, slurry bed reactors with forced internal circulation, multi-phase flow, simulation

摘要：

针对煤直接液化反应器中的结焦问题，建立了多相流模型模拟了反应器内循环杯局部气-油煤浆两相的流动行为，得到了相含率等流体力学参数的空间分布情况。模拟结果表明，气液分离导致的泡沫聚并破碎以及雾沫夹带是形成结渣/结焦的主要原因。模拟研究了循环杯内堵塞程度与下降管中气含率的关系，表明随堵塞程度的提高，下降管中的气含率从0增加到34%，从而造成循环泵抽空。基于对结焦原因的分析，提出了优化的循环杯结构并进行了模拟分析。结果表明，改进后的循环杯结构可以有效强化气液分离，在极限条件下下降管中的气含率为14%，可以保证装置的稳定运行，为工业装置的改造提供了参考。

关键词: 煤直接液化, 强制循环悬浮床, 多相流, 模拟

CLC Number:

TQ021.1

ZHANG Chuanjiang, HAN Laixi, JIANG Xuedong, XU Ming, MEN Zhuowu. Numerical simulation and optimization of circulation cup in direct coal liquefaction reactor[J]. CIESC Journal, 2017, 68(7): 2703-2712.

张传江, 韩来喜, 蒋雪冬, 许明, 门卓武. 煤直接液化反应器循环杯的数值模拟及优化[J]. 化工学报, 2017, 68(7): 2703-2712.

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