Detection of gas-liquid dispersion in jet bubbling reactor

doi:10.11949/0438-1157.20190460

Abstract

Abstract:

In the jet bubbling reactor, as the liquid jet velocity increases, the gas-liquid dispersion shows three states including the flooding, loading, and complete dispersion. In this work, the liquid velocity near the wall above the gas distributor of the jet bubbling reactor was measured by the Pavlov tube to identify the aforementioned three dispersion states. It was found that the standard deviation of liquid velocity and the average liquid velocity both appeared four stages with the increase of jet velocity, which included the first plateau, the ascending stage, descending stage and second plateau. Wherein, the first plateau corresponded to the flooding state, the ascending and descending stages corresponded to the loading state, and the second plateau corresponded to the complete dispersion state. Therefore, the criterion for the critical jet velocity was proposed. The jet velocity at the intersection of the first plateau and the ascending stage was the flooding velocity u _jf, and the jet velocity at the intersection of the descending stage and the second plateau was the complete dispersion velocity u _jcd. Compared with the visual observation method, the average relative deviation of u _jf obtained by liquid velocity standard deviation analysis was 5.82%, the average relative deviation of u _jcd was 18.2%; the average relative deviation of u _jf obtained by time-averaged liquid velocity analysis was 5.86%, and the average relative deviation of u _jcd was 12.1%. The study also found that the blunt jet velocity increases as the superficial gas velocity increases.

Key words: jet bubbling reactor, gas-liquid dispersion, gas-liquid flow, liquid velocity, critical jet Reynolds number, turbulence, bubble

摘要：

射流鼓泡反应器内随着射流速度的增大，先后经历气泛、载气和完全分散三种气液分散状态。本文在射流鼓泡反应器实验装置中，利用Pavlov管测量气体分布器上方壁面附近的液速波动信号，发现液速标准差和时均液速随射流速度的增大均依次出现第一平稳段、上升段、下降段和第二平稳段，其中，第一平稳段对应气泛状态，上升和下降段对应载气状态，第二平稳段对应完全分散状态。据此提出了临界射流速度的判断准则：第一平稳段与快速上升段的交点对应的射流速度为泛点射流速度u _jf，下降段与第二平稳段的交点对应的射流速度为完全分散射流速度u _jcd。与目测法相比，液速标准差分析得到的u _jf的平均相对偏差为5.82%，u _jcd的平均相对偏差为18.2%；时均液速分析得到的u _jf的平均相对偏差为5.86%，u _jcd的平均相对偏差为12.1%。研究还发现泛点射流速度随表观气速的增大而增大。

关键词: 射流鼓泡反应器, 气液分散状态, 气液两相流, 液速, 临界射流速度, 湍动, 气泡

CLC Number:

TQ 021.9

Zhengliang HUANG, Xiaoyun GUO, Yun SHUAI, Yao YANG, Jingyuan SUN, Binbo JIANG, Jingdai WANG, Yongrong YANG. Detection of gas-liquid dispersion in jet bubbling reactor[J]. CIESC Journal, 2019, 70(10): 3906-3913.

黄正梁, 郭晓云, 帅云, 杨遥, 孙婧元, 蒋斌波, 王靖岱, 阳永荣. 射流鼓泡反应器内气液分散状态检测[J]. 化工学报, 2019, 70(10): 3906-3913.

Figures/Tables 6

Fig.1 Schematic diagram of experimental setup

Fig.2 Gas-liquid dispersion in a jet bubbling reactor

Fig.3 Variation of StduL with liquid jet velocity under different superficial gas velocities

Table 1 Comparison of critical liquid jet velocity obtained by StduL analysis and visual observation

u _g/(m/s)	u _jf /(m/s)			u _jcd/(m/s)
u _g/(m/s)	Std_u _L analysis	Visual observation	Relative error/%	Std_u _L analysis	Visual observation	Relative error/%
0.00245	3.589	3.275	9.59	7.640	7.641	0.01
0.0049	3.781	3.820	1.03	8.746	7.641	14.5
0.0098	4.499	4.366	3.05	10.021	7.641	31.1
0.0147	4.284	4.912	12.8	10.075	7.641	31.8
0.0196	5.313	5.458	2.66	8.689	7.641	13.7
average	—	—	5.82	—	—	18.2

Fig.4 Variation of time-average water velocity with liquid jet velocity under different superficial gas velocities

Table 2 Comparison of critical liquid jet velocity obtained by time-average water velocity analysis and visual observation

u _g/(m/s)	u _jf /(m/s)			u _jcd /(m/s)
u _g/(m/s)	$u ˉ L$ analysis	Visual observation	Relative error/%	$u ˉ L$ analysis	Visual observation	Relative error/%
0.00245	3.689	3.275	12.6	7.562	7.641	1.03
0.0049	3.998	3.820	4.66	8.544	7.641	11.8
0.0098	4.611	4.366	5.61	8.914	7.641	16.7
0.0147	5.076	4.912	3.34	9.149	7.641	19.7
0.0196	5.290	5.458	3.08	8.500	7.641	11.2
average	—	—	5.86	—	—	12.1

Table 2 Comparison of critical liquid jet velocity obtained by time-average water velocity analysis and visual observation

u _g/(m/s)	u _jf /(m/s)			u _jcd /(m/s)
u _g/(m/s)	$u ˉ L$ analysis	Visual observation	Relative error/%	$u ˉ L$ analysis	Visual observation	Relative error/%
0.00245	3.689	3.275	12.6	7.562	7.641	1.03
0.0049	3.998	3.820	4.66	8.544	7.641	11.8
0.0098	4.611	4.366	5.61	8.914	7.641	16.7
0.0147	5.076	4.912	3.34	9.149	7.641	19.7
0.0196	5.290	5.458	3.08	8.500	7.641	11.2
average	—	—	5.86	—	—	12.1

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