Synthetical Recovery of Oil Extraction Wastewater with Combined Membrane Distillation Crystallization Technology

Synthetical recovery of oil extraction wastewater with combined membrane distillation crystallization technology

Xiaobin Jiang*, Dapeng Lu, Gaohong He, Wu Xiao

State Key Laboratory of Fine Chemicals, Research and Development Center of Membrane Science and Technology, School of Chemical Engineering, Dalian University of Technology, Dalian, P. R. China

*Corresponding author: Email: xbjiang@dlut.edu.cn

Abstract

The regeneration of ethylene glycol (EG) aqueous solution used as an anti-freezer and hydration inhibitor from oil extraction wastewater is an important and challenging work due to the combining separation requirement of enrichment of EG and desalination[1]. Membrane distillation (MD) is a recently developed thermally or pressure-driven membrane process combined distillation and crystallization [2,3]. In recent decade, the combined membrane distillation crystallization (MDC) process had significant advantages on the brine treatment, crystals manufacture and crystallization control [4,5,6].

In this work, ethylene glycol (EG) aqueous solution of oil extraction wastewater was concentrated and desalinated by means of combined MDC technology using polypropylene (PP) hollow fiber membrane. The controlling strategy that inspired by the biomineralization control research on the porous membrane platform was developed [6]. Higher feed EG concentration could lead to a decline in the permeate flux and the best concentration was 60%, where the largest feed treatment equivalent could be obtained with NaCl rejection higher than 98.9 % and water content in the permeate higher than 99%.

The crystal size distributions were quite different. The crystal distribution of MDC method was more uniform than that of evaporation crystallization by introducing the synchronous concentration controlling approach. The average size of NaCl crystals from both methods were about 100 ¦Ìm, while the C.V. value of the crystals from membrane-crystallization was 33.76 lower than that from evaporation crystallization, 46.12. The secondary nucleation inhibited in MDC process led to the desire crystal size distribution. It is obvious that the uniform crystal size distribution is the prominent advantages of MDC, which could be benefit to solid-liquid separation process.

Fig.1 Comparison of crystal size distribution and crystal habit with evaporative crystallization (ED) and membrane distillation crystallizaiton (MDC).

Acknowledgment

This work is supported by National Natural Science Foundation of China (Grant No. 21306017, 21527812), Program for Changjiang Scholars and Support Project of the China Petroleum and Chemical Corporation (X514001).

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