Studies On Mechanism And Control Technique Of Metal Membrane Filtration For Oilfield Waste Water Treatment

Shengli Oil Field has entered the middle-final phase of petroleum exploitation. As a result, water content rate of produced fluid has been increasing with the augmentation of injection water year after year. Using the injection scheme to exploit oil field with qualified effluent, it can protect the environment of oil field,make sustainable development for petroleum exploitation, and enhance the economic benefit. To reduce membrane fouling and promote permeation flux during the treatment of oilfield waste water with metal porous membrane (hereinafter referred to as metal membrane), factors influencing permeation flux, pollution mechanism and cleaning methods were systematically studied in this thesis.The influence of different membrane pore size on permeation flux was compared, and the influences of TMP (trans-membrane pressure), CVF (cross velocity of feed) , feed temperature , filtration period and the feature of the slurry concentration of wastewater were investigated by experiments at the same time. Some conclusions from the Ti membrane experiment are as follows: that the permeate flow can meet the A2 reinjection standard, the optimum operating conditions are a trans-membrane pressures between 0.10⁰.15MPa, a crossflow velocities between 2.5³.5 m·s^-1and a feed temperature between 40⁵0°C, under which the perfect permeate flux and operation effect can be gained .And also, the bacterial concentration and Fe³⁺ concentration has an important effect on the filtration.The proportion of different resistances in the process was calculated with the resistance model. It was shown that the key factor leading to the decrease of permeation flux was the resistance of filter cake,and the proportion is about 60 percent of total resistances. The effects of membrane pore size, trans-membrane pressure, CVF and the filtration period on the fouling mechanism were also investigated.The main elements causing membrane fouling have been analyzed by the methods of ICP, SEM, EDX , GC-MS and LRS. The results show that most of ingredients leading to membrane fouling were the suspended solid and crude oil deposited on the membrane surface in waste water filtration.According to the analysis of the pollutant component on the metal membrane, a short-time chemical cleaning technology combined with the acid- ultrasonic joint cleaning is proposed in this paper. The experiment shows that this kind of the cleaning technology can remove the fouling ingredients on the membrane surface and even in the membrane pore, and restore the membrane flux.