Analysis of flow field distribution and separation characteristics of degassing and oil-removal hydrocyclone system

doi:10.16085/j.issn.1000-6613.2021-0197

Abstract

Abstract:

At present, most of the oil fields in China have entered the stage of high water content, and there is often a lot of associated gas in the produced fluid, efficient separation of produced liquid by hydrocyclone separation is of great significance for simplifying surface treatment technology and developing the economy treatment technology of produced fluids for offshore platform. The degassing and oil-removal hydrocyclone system is composed of GLCC type gas liquid separator and oil-droplets size reconstruction hydrocyclone, and the purpose of the design is to ensure efficient degassing while further improving the removal effect of small oil droplets, so as to achieve high-efficiency three-phase separation. Based on the computational fluid dynamics (CFD) analysis, the population balance model (PBM) is used to simulate the coalescence and breakage of oil droplets, and the characteristics and particle size distribution of the internal flow field of the degassing and oil-removal hydrocyclone system were simulated and analyzed, and the effects of gas volume fraction and gas phase exit split ratio on the separation performance of the degassing and oil-removal hydrocyclone system were compared and analyzed by combining numerical simulation with the experiment. The results showed that the interaction between gas volume fraction and gas phase exit split ratio was significant. By considering degassing efficiency and oil removal efficiency, the best gas phase exit split ratios are 25%, 30% and 35% when the gas volume fractions are respectively 10%, 20% and 30%. The numerical simulation results were in agreement with the experimental results, which verified the reliability of the numerical simulation method. In addition, the larger the gas volume fraction, the more obvious the oil droplets reconstruction phenomenon of the oil-droplets size reconstruction hydrocyclone was. The oil-droplets size reconstruction hydrocyclone could improve the phenomenon of poor oil-water separation effect under gas-containing conditions to a certain extent, and the degassing and oil-removal hydrocyclone system had good applicability for the three-phase separation of oil, gas and water.

Key words: particle size distribution, three-phase separation, hydrocyclone, numerical simulation, population balance

摘要：

目前我国大部分油田已进入高含水阶段，且采出液中常带有大量伴生气，采用旋流分离法实现采出液高效分离对于简化陆上油田地面处理工艺及提升海上平台经济环保的采出液处理技术具有重要意义。脱气除油旋流系统由GLCC型气液分离器和油滴重构旋流器串联组成，设计的目的是在保证高效脱气的同时进一步改善对小油滴的去除效果，实现油气水三相高效分离。本文基于计算流体动力学（computational fluid dynamics，CFD）方法，利用种群平衡模型（population balance model，PBM）模拟油滴破碎与聚结，对脱气除油旋流系统内部流场特性及粒度分布进行模拟分析，并采用数值模拟与试验相结合的研究方法，对比分析不同含气体积分数和气相出口分流比对脱气除油旋流系统分离性能的影响规律。结果表明：含气体积分数与气相出口分流比对脱气除油旋流系统分离效率的交互作用较显著，在研究范围内综合脱气效率和除油效率可以得到，含气10%、20%、30%的最佳分流比分别为25%、30%、35%，数值模拟结果与试验结果吻合良好，验证了数值模拟方法的可靠性。另外，含气体积分数越大，油滴重构旋流器的油滴分层重构现象越明显，油滴重构旋流器可以在一定程度上改善含气情况下油水分离效果差的现象，脱气除油旋流系统对油气水三相分离的适用性较好。

关键词: 粒度分布, 三相分离, 旋流器, 数值模拟, 种群平衡

CLC Number:

TQ051.8

ZHANG Shuang, ZHAO Lixin, LIU Yang, SONG Minhang, LIU Lin. Analysis of flow field distribution and separation characteristics of degassing and oil-removal hydrocyclone system[J]. Chemical Industry and Engineering Progress, 2022, 41(1): 75-85.

张爽, 赵立新, 刘洋, 宋民航, 刘琳. 脱气除油旋流系统流场分布及分离特性[J]. 化工进展, 2022, 41(1): 75-85.

Figures/Tables 16

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结构参数	数值	结构参数	数值
气液分离器主直径D₁/mm	58	气液分离器高度H₁/mm	460
外层旋流器主直径D₂/mm	72	内锥高度H₂/mm	130
内层旋流器主直径D₃/mm	30	油滴重构旋流器高度H₃/mm	300
气相出口直径D₄/mm	15	内层旋流器旋流段高度H₄/mm	45
内层油相出口直径D₅/mm	5	内层旋流器锥段高度H₅/mm	110
内层旋流器底流段直径D₆/mm	15	内层旋流器底流段高度H₆/mm	75
外层旋流器底流段直径D₇/mm	32	外层旋流器旋流段高度H₇/mm	75
外层油相出口直径D₈/mm	23	外层旋流器锥段高度H₈/mm	125
水相出口直径D₉/mm	10	外层旋流器底流段高度H₉/mm	25
内锥底面直径D₁₀/mm	30	油滴重构旋流器入口高度H₁₀/mm	20
内层旋流器锥段锥度α₁/（°）	9	内层切向入口高度H₁₁/mm	7.4
外层旋流器锥段锥度α₂/（°）	19	外层切向入口高度H₁₂/mm	12.6

结构参数	数值	结构参数	数值
气液分离器主直径D₁/mm	58	气液分离器高度H₁/mm	460
外层旋流器主直径D₂/mm	72	内锥高度H₂/mm	130
内层旋流器主直径D₃/mm	30	油滴重构旋流器高度H₃/mm	300
气相出口直径D₄/mm	15	内层旋流器旋流段高度H₄/mm	45
内层油相出口直径D₅/mm	5	内层旋流器锥段高度H₅/mm	110
内层旋流器底流段直径D₆/mm	15	内层旋流器底流段高度H₆/mm	75
外层旋流器底流段直径D₇/mm	32	外层旋流器旋流段高度H₇/mm	75
外层油相出口直径D₈/mm	23	外层旋流器锥段高度H₈/mm	125
水相出口直径D₉/mm	10	外层旋流器底流段高度H₉/mm	25
内锥底面直径D₁₀/mm	30	油滴重构旋流器入口高度H₁₀/mm	20
内层旋流器锥段锥度α₁/（°）	9	内层切向入口高度H₁₁/mm	7.4
外层旋流器锥段锥度α₂/（°）	19	外层切向入口高度H₁₂/mm	12.6

含气体积分数/%	位置	d_0.1/mm	d_0.5/mm	d_0.9/mm
20	入口	0.003	0.024	0.072
	油相出口	0.004	0.175	0.325
	水相出口	0.003	0.029	0.264
30	入口	0.002	0.019	0.048
	油相出口	0.023	0.063	0.373
	水相出口	0.012	0.050	0.109

含气体积分数/%	位置	d_0.1/mm	d_0.5/mm	d_0.9/mm
20	入口	0.003	0.024	0.072
	油相出口	0.004	0.175	0.325
	水相出口	0.003	0.029	0.264
30	入口	0.002	0.019	0.048
	油相出口	0.023	0.063	0.373
	水相出口	0.012	0.050	0.109

含气体积分数/%	试验值/mg·L^-1	模拟值/mg·L^-1
10	947	1253
15	2083	1574
20	2661	1849
25	3026	2154
30	3521	2286