提升管反应器介尺度结构影响规律的数值模拟研究

doi:10.11949/0438-1157.20220399

摘要/Abstract

摘要：

提升管反应器存在典型的颗粒聚团介尺度结构，其分布特性对气固流动、反应有重要影响，对介尺度结构影响规律进行分析有助于为反应器的设计与优化操作提供基础信息。采用基于能量最小多尺度（EMMS）方法的曳力模型建立了提升管气固两相流动模型，考虑了颗粒聚团对气固相间动量传递的影响。此外，进一步通过考虑颗粒聚团的存在以及颗粒聚团的非均匀性对化学反应的影响，提出了描述介尺度结构对反应速率影响的修正因子，与气固流动模型进行耦合，建立了基于介尺度结构的流动-反应综合数学模型，并进行了模型验证。进一步应用该模型，对工业催化裂化提升管反应器的流动-反应特性进行了模拟分析。结果表明，该模型可以合理描述提升管气固相互作用，能够预测出壁面附近存在较多介尺度结构的分布特性，由于聚团的存在使得重油组分难以与催化剂充分接触，生成汽柴油的反应速率较低，转化较慢，聚团的分布特性导致靠近边壁处的重油组分浓度较高，汽柴油组分浓度较低；汽柴油在聚团内部的流动阻力较大，在聚团内发生过量的二次反应生成较多焦炭，导致壁面处焦炭浓度较高。与传统基于平均化而未考虑聚团影响的模型相比，基于介尺度结构的模型所预测的汽油收率最佳值与工业实际相接近。因此，基于介尺度结构的流动-反应综合数学模型可以合理描述提升管内进行的流动-反应耦合特性，并能揭示介尺度结构对催化裂化反应过程的影响，有望为工业提升管装置反应终止剂技术的开发提供重要的基础信息。

关键词: 颗粒聚团, 提升管, 介尺度模型, 流化催化裂化, 数值模拟

Abstract:

There exists typical mesoscale structure of particle clusters in riser reactor, and its distribution characteristics have important impacts on gas-solid flow and reaction characteristics. The analysis of the influence of mesoscale structure is helpful to provide basic information for reactor design and optimal operation. In this paper, the gas-solid flow model in the riser is established by using the drag model based on the energy-minimization multi-scale (EMMS) method, and the influence of particle cluster on the momentum transfer between gas and solid is therefore described. In addition, by considering the existence of particle clusters and the influence of the heterogeneity of particle clusters on the chemical reaction, a correction factor describing the influence of mesoscale structure on the reaction rate is proposed, which is coupled with the gas-solid flow model. A combined flow-reaction mathematical model based on mesoscale structure is therefore established. The model is validated against the experimental data. The model was further applied to simulate and analyze the flow-reaction characteristics of an industrial catalytic cracking riser reactor. The results show that the model can reasonably describe the gas-solid interaction in the riser and can predict the distribution characteristics of mesoscale structures near the wall. Due to the existence of clusters, it is difficult for the heavy oil components to fully contact with the catalyst. The distribution characteristics of clusters can lead to the high concentration of heavy oil and low concentration of gasoline and diesel near the wall. Due to the flow resistance in the cluster, excessive secondary reactions of gasoline and diesel occur in the cluster to produce more coke, resulting in higher coke concentration near the wall. Compared with the traditional model based on averaging method, the optimal value of gasoline yield predicted by the present model is closer to the industrial practice. Therefore, the present model can reasonably describe the coupled flow-reaction characteristics in the riser, reveal the influence of mesoscale structure, and is promising in providing important basic information for the development of reaction terminator technology in industrial risers.

Key words: particle cluster, riser, mesoscale model, fluid catalytic cracking, numerical simulation

中图分类号:

石孝刚, 王成秀, 高金森, 蓝兴英. 提升管反应器介尺度结构影响规律的数值模拟研究[J]. 化工学报, 2022, 73(6): 2708-2721.

Xiaogang SHI, Chengxiu WANG, Jinsen GAO, Xingying LAN. Numerical simulation study on influence of mesoscale structure in riser reactor[J]. CIESC Journal, 2022, 73(6): 2708-2721.

图/表 19

表1 EMMS曳力模型表达式

Table 1 EMMS model equations

项目	方程表达式
曳力模型系数β	$β = 34 C d ε s ε g ρ g u g - u s d p ε g - 2.65 H D ???????????? ε g ≥ 0.4 150 ε s 2 μ g ε g d p 2 + 1.75 ε s ρ g u g - u s d p ???????? ε g < 0.4$
曳力系数修正因子	$H D = A e R e + B e C e$
ε_g>0.997	$A e = 1 B e = 1 C e = 0$
0.997>ε_g>0.99	$A e = 0.4243 + 0.88 1 - 1 1 + e x p 0.9989 - ε g 3 × 10 - 5 1 + e x p 0.9942 - ε g 2.18 × 10 - 3 B e = 1.661 × 10 - 3 + 0.2436 e x p - 0.5 0.9985 - ε g 1.91 × 10 - 3 2 C e = 8.25 × 10 - 2 - 0.0574 e x p - 0.5 0.9979 - ε g 7.03 × 10 - 3 2$
0.99>ε_g>0.545	$A e = 49.1698 - 49.5722 ε g - 0.4896 B e = 137.6308 - 21.6308 ε g 13.031 C e = ε g - 1.0013 - 6.633 × 10 - 2 + 9.1391 ε g - 1.0013 + 6.9231 ε g - 1.0013 2$
0.545>ε_g>0.4	$A e = 0.8526 - 0.5846 1 + ε g 0.4325 22.6279 B e = 1 C e = 0$

表1 EMMS曳力模型表达式

Table 1 EMMS model equations

项目	方程表达式
曳力模型系数β	$β = 34 C d ε s ε g ρ g u g - u s d p ε g - 2.65 H D ???????????? ε g ≥ 0.4 150 ε s 2 μ g ε g d p 2 + 1.75 ε s ρ g u g - u s d p ???????? ε g < 0.4$
曳力系数修正因子	$H D = A e R e + B e C e$
ε_g>0.997	$A e = 1 B e = 1 C e = 0$
0.997>ε_g>0.99	$A e = 0.4243 + 0.88 1 - 1 1 + e x p 0.9989 - ε g 3 × 10 - 5 1 + e x p 0.9942 - ε g 2.18 × 10 - 3 B e = 1.661 × 10 - 3 + 0.2436 e x p - 0.5 0.9985 - ε g 1.91 × 10 - 3 2 C e = 8.25 × 10 - 2 - 0.0574 e x p - 0.5 0.9979 - ε g 7.03 × 10 - 3 2$
0.99>ε_g>0.545	$A e = 49.1698 - 49.5722 ε g - 0.4896 B e = 137.6308 - 21.6308 ε g 13.031 C e = ε g - 1.0013 - 6.633 × 10 - 2 + 9.1391 ε g - 1.0013 + 6.9231 ε g - 1.0013 2$
0.545>ε_g>0.4	$A e = 0.8526 - 0.5846 1 + ε g 0.4325 22.6279 B e = 1 C e = 0$

表2 颗粒聚团上的平均反应速率和单颗粒上的反应速率的比值

Table 2 Ratio of reaction rate on cluster to that on single particle

空隙率	气速/(m/s)	短轴	长短轴比	倾角/(°)	$H c$
空隙率	气速/(m/s)	短轴	长短轴比	倾角/(°)	一次反应H_c,1	二次反应H_c,2
0.83	0.1	0.67	1	0	0.1560	0.8900
0.83	0.5	0.67	1	0	0.1930	0.9589
0.83	1	0.67	1	0	0.2107	0.9937
0.83	1.5	0.67	1	0	0.2228	1.0165
0.83	2	0.67	1	0	0.2325	1.0339
0.83	2.5	0.67	1	0	0.2409	1.0484
0.83	3	0.67	1	0	0.2485	1.0609
0.90	5	0.5	1	0	0.4511	1.1105
0.90	7.5	0.5	1	0	0.5242	1.1119
0.90	10	0.5	1	0	0.5828	1.1073
0.96	0.5	0.5	1	0	0.5638	1.0498
0.96	1	0.5	1	0	0.6299	1.0522
…	…	…	…	…	…	…

表2 颗粒聚团上的平均反应速率和单颗粒上的反应速率的比值

Table 2 Ratio of reaction rate on cluster to that on single particle

空隙率	气速/(m/s)	短轴	长短轴比	倾角/(°)	$H c$
空隙率	气速/(m/s)	短轴	长短轴比	倾角/(°)	一次反应H_c,1	二次反应H_c,2
0.83	0.1	0.67	1	0	0.1560	0.8900
0.83	0.5	0.67	1	0	0.1930	0.9589
0.83	1	0.67	1	0	0.2107	0.9937
0.83	1.5	0.67	1	0	0.2228	1.0165
0.83	2	0.67	1	0	0.2325	1.0339
0.83	2.5	0.67	1	0	0.2409	1.0484
0.83	3	0.67	1	0	0.2485	1.0609
0.90	5	0.5	1	0	0.4511	1.1105
0.90	7.5	0.5	1	0	0.5242	1.1119
0.90	10	0.5	1	0	0.5828	1.1073
0.96	0.5	0.5	1	0	0.5638	1.0498
0.96	1	0.5	1	0	0.6299	1.0522
…	…	…	…	…	…	…

表3 非均匀的颗粒聚团对化学反应速率的影响因子表达式［19］

Table 3 Correlation for influence factor of heterogeneous cluster on reaction rate［19］

H_r表达式	ε_g范围
$H r = 4.5484 - 8.8775 ε g$	[0.4,0.4162]
$H r = - 42.3887 + 203.6538 ε g - 239.6766 ε g 2$	[0.4162,0.4257]
$H r = - 34.6239 + 219.6173 ε g - 446.5862 ε g 2 + ?????? 297.1701 ε g 3$	[0.4257,0.5457]
$H r = 0.3667 - 0.04321 ε g + 0.6543 ε g 2$	[0.5457,1.0]

表3 非均匀的颗粒聚团对化学反应速率的影响因子表达式［19］

Table 3 Correlation for influence factor of heterogeneous cluster on reaction rate［19］

H_r表达式	ε_g范围
$H r = 4.5484 - 8.8775 ε g$	[0.4,0.4162]
$H r = - 42.3887 + 203.6538 ε g - 239.6766 ε g 2$	[0.4162,0.4257]
$H r = - 34.6239 + 219.6173 ε g - 446.5862 ε g 2 + ?????? 297.1701 ε g 3$	[0.4257,0.5457]
$H r = 0.3667 - 0.04321 ε g + 0.6543 ε g 2$	[0.5457,1.0]

图1 模拟对象的装置示意图（a）[26]及其几何结构和网格划分（b）

Fig.1 Schematic diagram (a) and geometry and mesh (b) of simulation set-up

表4 模拟对象尺寸和物性

Table 4 Size of simulation set-up and properties of materials

参数	数值
提升管直径D/m	0.076
提升管高度h/m	10
颗粒粒径d_p/μm	76
颗粒密度ρ_p/(kg/m³)	1780
气体密度ρ_g/(kg/m³)	1.1795

图2 提升管内臭氧浓度的轴向分布（Ug=9 m/s，虚线代表基于平均化的模型，实线代表基于介尺度结构的模型）

Fig.2 Axial distribution of ozone concentration in riser (Ug=9 m/s, dash line is for homogeneous model while solid line for mesoscale model)

图3 提升管内臭氧浓度的径向分布（Ug=9 m/s，虚线代表基于平均化的模型，实线代表基于介尺度结构的模型）

Fig.3 Radial distribution of ozone concentration in riser(Ug=9 m/s, dash line is for homogeneous model while solid line for mesoscale model)

图4 工业催化裂化提升管反应器示意图

Fig.4 Industrial FCC riser and its geometry

表5 工业提升管反应器工艺参数

Table 5 Simulation parameter for industrial FCC riser

参数	数值
原料油质量流率/(t/h)	152
雾化蒸汽质量流率/(t/h)	9.6
预提升蒸汽质量流率/(kg/h)	4070
催化剂循环量/(t/h)	1156
剂油比	7
物料混合温度/℃	550

图5 催化裂化反应十四集总动力学模型反应网络

Fig.5 14-lump kinetic network for FCC reactions

图6 提升管高度方向催化剂颗粒浓度分布

Fig.6 Axial distribution of catalyst particle in the riser

图7 催化裂化提升管反应器内的瞬时催化剂颗粒浓度分布

Fig.7 Instantaneous distribution of particle concentration in FCC riser

图8 催化裂化提升管反应器内的油气和催化剂颗粒瞬时温度分布

Fig.8 Average temperature of oil gas and instantaneous distribution of particle temperature in FCC riser

图9 提升管高度方向转化率变化

Fig.9 Conversion along the height in riser

图10 重油组分浓度分布

Fig.10 Distribution of heavy oil concentration

图11 汽油组分浓度分布

Fig.11 Distribution of gasoline concentration

图12 柴油组分浓度分布

Fig.12 Distribution of diesel concentration

图13 焦炭组分浓度分布

Fig.13 Distribution of coke concentration

图14 提升管高度方向上各产物产率变化（实线为基于介尺度结构的模型，虚线为基于平均化的模型）

Fig.14 Yield of different components along riser height (solid line for mesoscale model, and dash line for homogeneous model)

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