Optimal design and performance analysis of multi-stage spiral separator

doi:10.11949/0438-1157.20230993

Abstract

Abstract:

In order to solve the problem of the complicated process of downhole oil-water separation hydrocyclones connection in parallel, a new structure of multi-stage spiral separator is proposed based on the principle of tandem hydrocyclone separation. Response surface method combined with computational fluid dynamics is used to build a mathematical relationship model between the structural parameters and the separation efficiency of a multi-stage spiral separator, resulting in an optimal structural parameter, and systematically explored the optimal structural model within a certain range. The separation performance changes corresponding to different inlet flow rates, oil phase volume fractions and split ratios. Indoor separation performance experiments are conducted to verify the accuracy of numerical simulation results and the efficiency of optimization results. The results showed that the optimized structure could increase the separation efficiency from 91.0% to 96.2%. Comparison of separation performance at different inlet flow rates, the optimal inlet flow rate of 2.5 m³/h was obtained; within a certain range, with the increase of oil phase volume fraction and overflow split ratio, the separation efficiency showed a tendency of increasing and then decreasing, of which the simulated efficiency could reach up to 99.72%, and the experimental efficiency could reach up to 97.70%, which further verified the reliability of the simulation results and the efficiency of optimization results.

Key words: hydrocyclone separation, oil-water separation, numerical simulation, optimal design, separation performance, computational fluid dynamics

摘要：

为解决井下油水分离水力旋流器串接工艺较为复杂的问题，基于串联旋流分离原理提出一种新型多级螺旋分离器结构。利用响应曲面设计结合计算流体动力学方法，构建多级螺旋分离器参数与分离效率间的数学关系模型，得出最佳结构参数匹配方案，并针对最优结构模型系统地探究在一定范围内不同入口流量、油相体积分数及分流比对应的分离性能变化规律。开展室内分离性能实验，对数值模拟结果的准确性及优化结果的高效性进行验证。结果表明，优化后的结构可使分离效率由91.0%提高至96.2%。对比不同入口流量条件下的分离性能，得出最佳入口流量为2.5 m³/h；在一定范围内，随着油相体积分数及溢流分流比的增加，分离效率均呈先增大后减小趋势，其中模拟效率最高可达99.72%，实验效率可达97.70%，进一步验证了模拟结果的可靠性及优化结果的高效性。

关键词: 旋流分离, 油水分离, 数值模拟, 优化设计, 分离性能, 计算流体力学

CLC Number:

TQ 051.8

Lei XING, Chunyu MIAO, Minghu JIANG, Lixin ZHAO, Xinya LI. Optimal design and performance analysis of multi-stage spiral separator[J]. CIESC Journal, 2023, 74(11): 4587-4599.

邢雷, 苗春雨, 蒋明虎, 赵立新, 李新亚. 多级螺旋分离器结构优化设计与性能分析[J]. 化工学报, 2023, 74(11): 4587-4599.

Figures/Tables 21

Fig.1 Working principle of multi-stage spiral separator

Fig.2 Structure of multi-stage spiral separator

Table 1 Structural parameters of multi-stage spiral separator

结构参数	数值	结构参数	数值
D₁/mm	6	L₁/mm	8
D₂/mm	8	L₂/mm	30
D₃/mm	12	L₃/mm	8
D₄/mm	22	L₄/mm	25
D₅/mm	10	L₅/mm	25
D₆/mm	6	L₆/mm	50
D₇/mm	8	L₇/mm	200
D₈/mm	22	L₈/mm	200
D₉/mm	25	L₉/mm	100
R₁/mm	10

Fig.3 Result of grid independence tests

Fig.4 Experimental facilities and process

Table 2 Factors and levels design

因素	水平
因素	高（+1）	低（-1）	中心点（0）
油相体积分数x₁/%	9	1	5
一二级间距x₂/mm	300	100	200
二三级间距x₃/mm	300	100	200

Table 3 Design and results of box-Behnken design

实验序号	x₁/%	x₂/mm	x₃/mm	E/%
1	5	200	200	91.0
2	9	100	200	81.1
3	5	300	300	90.9
4	1	100	200	97.1
5	9	200	300	81.1
6	1	300	200	97.9
7	5	300	100	90.1
8	5	100	100	90.2
9	5	200	200	91.0
10	5	100	300	90.5
11	9	300	200	80.8
12	1	200	300	97.9
13	5	200	200	91.0
14	9	200	100	81.3
15	1	200	100	96.9
16	5	200	200	91.0
17	5	200	200	91.0

Table 4 The model results of variance analysis

类型	离差平方和	自由度	均方	F值	P
模型	547.58	9	60.84	5495.48	<0.0001
x₁	536.28	1	536.28	48438.31	<0.0001
x₂	0.0800	1	0.0800	7.23	0.0312
x₃	0.4512	1	0.4512	40.76	0.0004
x₁x₂	0.3025	1	0.3025	27.32	0.0012
x₁x₃	0.3600	1	0.3600	32.52	0.0007
x₂x₃	0.0625	1	0.0625	5.65	0.0492
x₁²	8.85	1	8.85	799.59	<0.0001
x₂²	0.4447	1	0.4447	40.17	0.0004
x₃²	0.2632	1	0.2632	23.77	0.0018
残差	0.0775	7	0.0111	—	—
失拟项	0.0775	3	0.0258	—	—
纯误差	0	4	0	—	—

Table 5 The model results of statistic analysis

统计项目	数值	统计项目	数值
标准偏差	0.1052	R²	0.999
均值	90.05	adjusted R²	0.999
C.V.	9.69%	predicted R²	0.997
		adeq precision	212.66

Fig.5 Comparison of structure and oil phase volume fraction between before and after optimization

Fig.6 Change of velocity at the outlet of the flow channel in different flow rate conditions

Fig.7 Axial velocity distribution at center axis in different flow rate conditions

Fig.8 Oil phase volume fraction distribution at the center axis in different flow rate conditions

Fig.9 Pressure distribution at center axis in different flow rate conditions

Fig.10 Separation efficiency and bottom flow pressure drop in different flow rate conditions

Fig.11 Change of velocity at the outlet of the flow channel in different oil volume fraction conditions

Fig.12 Oil phase volume fraction distribution at the center axis in different oil volume fraction conditions

Fig.13 Change of oil volume fraction at the outlet of the flow channel in different oil volume fraction conditions

Fig.14 Pressure distribution at center axis in different oil volume fraction conditions

Fig.15 Separation efficiency in different oil volume fraction conditions

Fig.16 Separation efficiency in different split ratio conditions

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