Numerical simulation of oil-water separation in sedimentation tank based on CFD-PBM model

ABSTRACT

A significant amount of wastewater has been produced from the oilfield extractive fluid with the development of oilfields in recent decades. Settling is the first process in the treatment of oilfield wastewater. As one of the most crucial devices in oilfield wastewater treatment, the vertical sedimentation tank has been widely utilized in the precipitation process. This work aims to explore the properties of vertical sedimentation tanks for oil-water separation and analyze related variables in the separation. First, we utilize the for-profit software Fluent for computational fluid dynamics, in which the RNG k-ε model, the multiphase flow mixing model, and the PBM model are used to simulate the internal flow field distribution in the vertical sedimentation tank under various boundary conditions. Then, the implication of changing the boundary conditions on the vertical sedimentation tanks is analyzed. It is demonstrated that by replacing the PBM model for the homogeneous particle size, the simulation of oil-water two-phase flow in sedimentation tanks is more correctly measured. The findings demonstrate that raising the operating temperature increases the oil content at the output and dewatering rate of the sedimentation tanks by 73.1%; however, above 44°C, the effect of oil removal gradually tends to deteriorate; the longer hydraulic retention time within the 8-h range, the better the effect of oil-water separation, with the best effect occurring at 8 h; and the more viscous the oil phase, the more resistance of the oil droplets to float, increasing the water phase oil-carrying capacity, resulting in a 36.5% reduction in oil content at the outlet and dewatering rate of the settling tanks. The simulation in this paper can provide theoretical direction and conference for the design of vertical sedimentation tanks, as well as improve the performance of oily wastewater treatment facilities.

KEYWORDS:

• CFD-PBM coupling model
• dehydration rate
• numerical simulation
• oil-water separation
• sedimentation tank

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Hanbing Qi

Hanbing Qi received the Ph.D. degree in Oil and gas storage and transportation engineering from Northeast Petroleum University, Daqing, China, in 2009. He is currently a Full Professor and the Vice Dean of the School of Architecture and Civil Engineering, Northeast Petroleum University, Daqing, China. His current research interests is oilfield wastewater treatment and optical detection of its pollutants.

Xiao Shang

Xiao Shang received the B.S. degree in water supply and drainage engineering from Taiyuan College, Taiyuan, China, in 2020. He is currently working toward the M.S. degree in municipal engineering with the School of Architecture and Civil Engineering, Northeast Petroleum University, Daqing, China. His research interests include study of oily wastewater treatment technology.

Xiaoxue Zhang

Xiaoxue Zhang received the M.S. degree in municipal engineering from Northeast Petroleum University, Daqing, China, in 2017. She is currently a teacher of the School of Architecture and Civil Engineering, Northeast Petroleum University, Daqing, China. Her research interests include study of oilfield pollutant management and online detection.

Qiushi Wang

Qiushi Wang received the M.S. degree in municipal engineering from Northeast Petroleum University, Daqing, China, in 2013. He is currently a teacher of the School of Architecture and Civil Engineering, Northeast Petroleum University, Daqing, China. His research interests include study of pollutant control and detection methods.

Fanbin Meng

Fanbin Meng received the M.S. degree in thermal power Engineering from Harbin Engineering University, Harbin, China, in 2014. He is currently a teacher of the School of Architecture and Civil Engineering, Northeast Petroleum University, Daqing, China. His research interests include study of oilfield new energy utilization technology.

Zhilong Liang

Zhilong Liang received the B.S. degree in water supply and drainage engineering from Northeast Petroleum University, Daqing, China, in 2022. He is currently working toward the M.S. degree in municipal engineering with the School of Architecture and Civil Engineering, Northeast Petroleum University, Daqing, China. His research interests include study of oily wastewater treatment technology.

Shujuan Liang

Shujuan Liang received the B.S. degree in water engineering from Hebei University of Engineering, Handan, China, in 2022. She is currently working toward the M.S. degree in municipal engineering with the School of Architecture and Civil Engineering, Northeast Petroleum University, Daqing, China. Her research interests include study of oily wastewater treatment technology.