Study on the effects of structural parameters of bubble-cap distributor with Venturi downcomer on the liquid distribution performance

doi:10.11949/0438-1157.20210871

Abstract

Abstract:

In order to improve the liquid center aggregation of bubble-cap typed gas-liquid distributor in trickle bed reactor and investigate the relationship between structural parameters and performance of liquid distribution, a new gas-liquid distributor with the Venturi downcomer was designed while the effect of its structure parameters on the distribution quality was explored. A cold experimental bench was established, and the performance of the new gas-liquid distributor was verified. Euler-Euler-PBE mathematical model was built up and validated to simulate the gas-liquid flow in the new gas-liquid distributor. Combining the experimental and numerical data, the effect of the structure parameters on pressure drop, liquid distribution, and spray area was analyzed systematically. The results show that the use of a Venturi with a shrink-and-expansion structure as a downcomer can effectively improve the distribution uniformity and spray radius of the entrainment type distributor, and significantly reduce the pressure drop. Based on the orthogonal cases numerically, the significance of main structure parameters was clarified, and empirical correlations of the distribution performance with structural parameters were obtained. The expansion section of the downcomer is a key structure to improve the liquid distribution performance, and the liquid distribution performance is the best when the expansion angle is 30°.

Key words: gas-liquid distributor, trickle-bed reactor, two-phase flow, computational fluid dynamics, numerical simulation

摘要：

为了改善滴流床用的内卷吸型气液分配器的液体分散差的现象，提出了一种文丘里卷吸型气液分配器，并对其结构参数进行了参数化研究，定量认识卷吸型分配器的结构参数对其气液分配性能的影响。在冷态实验装置上进行了文丘里卷吸型气液分配器性能实验，建立了耦合群体平衡模型的欧拉-欧拉两相流模型，数值模拟了文丘里卷吸型气液分配器气液两相分配流动过程。冷模实验结合数值模拟，系统性考察了各结构参数对卷吸型气液分配器的液体分布均匀性、喷淋半径以及压降的影响。结果表明，采用具备缩-扩结构的文丘里管作为降液管能够有效提升卷吸型分配器的分布均匀度和喷淋半径，并显著降低压降。通过正交试验，获得了主要结构参数与分配性能的相关性，给出了结构参数与性能指标的经验关联式。降液管的扩张段是改善液体分配性能的关键结构，其扩张角为30°时液体分配性能最好。

关键词: 气液分配器, 滴流床反应器, 两相流, 计算流体力学, 数值模拟

CLC Number:

TQ 028.8

Hanyang MO, Yumei YONG, Guangji ZHANG, Kang YU, Wenqiang CHEN, Chao YANG. Study on the effects of structural parameters of bubble-cap distributor with Venturi downcomer on the liquid distribution performance[J]. CIESC Journal, 2021, 72(12): 6241-6253.

莫晗旸, 雍玉梅, 张广积, 于康, 陈文强, 杨超. 文丘里卷吸型气液分配器液体分配性能的结构参数研究[J]. 化工学报, 2021, 72(12): 6241-6253.

Figures/Tables 17

Fig.1 Schematic diagram of cold-flow experiment of performance test on gas-liquid distributor

Fig.2 Schematic of three types of G-L distributor

Table 1 Standard structural and operation parameters of G-L distributor

φ₁/mm	φ₂/mm	φ₃/mm	φ₄/mm	h₁/mm	h₂/mm	h₃/mm	h₄/mm	n_s	w	h₅/mm	h₆/mm	Deg1/(°)	Deg2/(°)	U_g/(m³/h)	U_l/(m³/h)
30	50	27	53	20	29	29	66	6	3	16	65	10	45	18.0000	0.1522

Fig.3 Validation on repeatability of cold-flow model experiment (new G-L distributor, φ1=30 mm,Ug=18 m3/h, Ul=0.1522 m3/h)

Fig.4 Mesh configuration of G-L distributor in simulations

Fig.5 Mesh independence test on Euler-PBE model with experimental data (new G-L distributor, φ1=30 mm, Ug=18 m3/h, Ul=0.1522 m3/h)

Fig.6 Contours of liquid velocity distribution at flow distance of 0.135 m of different types of G-L distributor (φ1=30 mm)

Fig.7 ?P, CoV and Rc of different G-L distributor (φ1=30 mm) at flow distance of 0.135 m

Fig.8 ?P, CoV and Rc under different Ug/Ul at flow distance of 0.135 m (Ug=14.4 ~ 21.6 m3/h, Ul=0.1522 m3/h)

Fig.9 ?P, CoV and Rc of different Deg2 at flow distance of 0.135 m

Fig.10 Comparison of Ul profiles based on numerical simulation and experimental data at flow distance of 0.135 m

Fig.11 Distribution of droplet size in bubble cap distributor

Table 2 Orthogonal experiments of numerical simulation on G-L distributor（L27（3，9））

实验序号	φ₂/mm	(h₂+h₃)/mm	α/(°)	n_s	h₅/mm	w	(h₄-h₆)/mm	Deg2/(°)	φ₃/mm
1	50	21+29	7.5	4	13	2.5	9	15	23
2	50	21+29	7.5	6	16	3	17	45	31
3	50	21+29	7.5	8	19	3.5	13	30	27
4	50	28+29	15.12	4	16	3.5	9	30	31
5	50	28+29	15.12	6	19	2.5	17	15	27
6	50	28+29	15.12	8	13	3	13	45	23
7	50	35+29	10.12	4	19	3	9	45	27
8	50	35+29	10.12	6	13	3.5	17	30	23
9	50	35+29	10.12	8	16	2.5	13	15	31
10	53	21+29	15.12	4	19	3	17	30	23
11	53	21+29	15.12	6	13	3.5	13	15	31
12	53	21+29	15.12	8	16	2.5	9	45	27
13	53	28+29	10.12	4	13	2.5	17	45	31
14	53	28+29	10.12	6	16	3	13	30	27
15	53	28+29	10.12	8	19	3.5	9	15	23
16	53	35+29	7.5	4	16	3.5	17	15	27
17	53	35+29	7.5	6	19	2.5	13	45	23
18	53	35+29	7.5	8	13	3	9	30	31
19	56	21+29	10.12	4	16	3.5	13	45	23
20	56	21+29	10.12	6	19	2.5	9	30	31
21	56	21+29	10.12	8	13	3	17	15	27
22	56	28+29	7.5	4	19	3	13	15	31
23	56	28+29	7.5	6	13	3.5	9	45	27
24	56	28+29	7.5	8	16	2.5	17	30	23
25	56	35+29	15.12	4	13	2.5	13	30	27
26	56	35+29	15.12	6	16	3	9	15	23
27	56	35+29	15.12	8	19	3.5	17	45	31

Fig.12 Best and worst profiles of Rc and CoV in orthogonal experiments

Fig.13 Main effect plots response for CoV, Rc, and ?P

Fig.14 Vector of gas phase velocity in expanding part with different Deg2

Fig.15 Comparison of empirical and experimental data on CoV and ?P

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