乙炔加氢制乙烯浆态床反应器的CFD模拟

doi:10.11949/j.issn.0438-1157.20181245

摘要/Abstract

摘要：

对浆态床反应器中乙炔加氢制乙烯过程进行了模拟研究，采用TFM-PBM耦合方法描述浆态床内气相与浆态相的流动，并耦合乙炔加氢反应动力学建立流动-反应综合模型。通过小试实验对该模型进行验证，并将验证后的模型应用于浆态床中试装置中内构件作用机制与操作条件影响的模拟分析。结果表明，在浆态床反应器放大时，可通过设置竖管内构件，以破碎气泡，抑制气相径向运动，使乙炔加氢过程均匀、充分地进行。乙炔加氢制乙烯过程与气相停留时间和反应温度密切相关，在反应器放大中需严格控制温度，并可通过改变反应器内液位高度实现对气相停留时间的调控，从而可在保证乙炔充分转化的同时获得更高的乙烯选择性。

关键词: 浆态床, 乙炔加氢, 计算流体力学, 多相流, 多相反应器

Abstract:

The simulation of hydrogenation of acetylene in slurry reactor was carried out. The TFM-PBM coupling method was used to describe the flow of gas phase and slurry phase in slurry bed, and the kinetics of acetylene hydrogenation reaction was coupled to establish flow-reaction synthesis. The model was validated in a lab-scale slurry bed reactor and was then applied to the simulation of a bench-scale slurry bed reactor with respect to the function mechanisms of internals and the effects of operating conditions. Simulation results showed that vertical tube in the bench-scale reactor can break up bubbles and suppress the radial flow of gas phase, which benefits the uniform and sufficient conversion of acetylene. The conversion of acetylene is closely related to the residence time of gas phase and the reaction temperature. In order to obtain complete conversion of acetylene and high selectivity of ethylene when the slurry bed reactor was scaled-up to an industrial scale, it is critical to control the reaction temperature and the residence time of gas phase which can be regulated by changing the height of the liquid phase.

Key words: slurry bed, hydrogenation of acetylene, CFD, multiphase flow, multiphase reactor

中图分类号:

TQ 021.1

苏武, 石孝刚, 吴迎亚, 高金森, 蓝兴英. 乙炔加氢制乙烯浆态床反应器的CFD模拟[J]. 化工学报, 2019, 70(5): 1858-1867.

Wu SU, Xiaogang SHI, Yingya WU, Jinsen GAO, Xingying LAN. CFD simulation on hydrogenation of acetylene to ethylene in slurry bed[J]. CIESC Journal, 2019, 70(5): 1858-1867.

图/表 18

图1 中试装置的几何模型

Fig.1 Geometric structure of bench-scale slurry bed reactor

表1 操作条件

Table 1 Equipment parameters and operating conditions

项目	催化剂量/kg	催化剂浓度/%(vol)	气体流量/(m³/h)	入口H₂:C₂H₂ (vol.)	压力/kPa	温度/℃
小试装置	0.002	2.4	0.09	4:01	101	150
中试装置	13	2	165, 300	4.45:1	450	123, 140

表2 网格无关性

Table 2 Mesh independency

项目	网格数/万	床层平均气含率	乙炔转化率/%	乙烯选择性/%
小试装置[border:border-top:solid;]	0.54	0.112	93.49	97.42
	1.15	0.118	93.08	95.13
	3.56	0.120	93.36	95.75
中试装置	4.5	0.211	97.84	91.42
	24	0.203	99.43	85.88
	34	0.207	99.65	89.60

表3 小试模拟结果与实验数据对比

Table 3 Comparisons between simulation results and experimental data in lab-scale equipment

项目	床层整体气含率	C₂H₂转化率/%	C₂H₄选择性/%
实验结果	0.125	100	95.51
模拟结果	0.118	93.08	95.13

图2 瞬时气含率等值面（α g=0.15）

Fig.2 Instantaneous iso-surface of gas hold-up (α g=0.15)

图3 不同高度处乙炔和乙烯浓度分布

Fig.3 C2H2 and C2H4 concentration at different heights

表4 中试模拟结果与实验数据对比

Table 4 Comparisons between simulation results and experimental data in bench-scale equipment

项目	工况1		工况2
项目	实验结果	模拟结果	实验结果	模拟结果
温度/℃	140		123
气体流量/(m³/h)	300		165
床层平均气含率	0.19	0.20	—	0.12
C₂H₂转化率/%	98.71	99.43	98.34	90.91
C₂H₄选择性/%	91.04	85.88	92.14	85.24

图4 瞬时气含率分布

Fig.4 Instantaneous distribution of gas hold-up

图5 瞬时气含率等值面（α g=0.15）

Fig.5 Instantaneous iso-surface of gas hold-up

图6 时均气含率的径向分布

Fig.6 Radial distribution of time-averaged gas hold-up

图7 时均气相轴向速度的径向分布

Fig.7 Radial distribution of time-averaged gas axial velocity

图8 时均液相轴向速度的径向分布

Fig.8 Radial distribution of time-averaged liquid axial velocity

图9 气泡平均尺寸径向分布

Fig.9 Radial distribution of mean bubble size at different heights

图10 C2H2转化率轴向分布

Fig.10 Axial distribution of C2H2 conversion

图11 C2H4摩尔分数轴向分布

Fig.11 Axial distribution of C2H4 mole fraction

图12 不同工况下C2H2摩尔分数轴向分布

Fig.12 Axial distribution of C2H2 mole fraction under different condition

表5 出口乙炔转化率及乙烯选择性

Table 5 Conversion of C2H2 and selectivity of C2H4 at outlet

项目	C₂H₂转化率/%	C₂H₄选择性/%
工况1	99.43	85.88
工况3	99.99	69.49

图13 乙炔和乙烯摩尔分数轴向分布

Fig.13 Axial distribution of C2H2 and C2H4 mole fraction

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