Study On The Treatment Of High-salinity Gas Field Water By Membrane Aeration, Evaporation And Crystallization

With the development of China's industrial technology,the amount of industrial wastewater is increasing year by year.If not properly treated,it will not only aggravate the problem of water shortage,but also cause serious pollution to the environment.Produced water from gas field is the most produced wastewater in oil and gas industry,which contains a lot of organic and inorganic substances,and has a high salt content.At present,evaporation crystallization is widely used to treat the high salt gas field water at home and abroad,but the operation cost of the evaporation crystallizer is high,and the traditional metal crystallizer has many problems,such as easy corrosion,high equipment cost,large floor area,maintenance trouble,etc.,so it is necessary to develop new evaporation crystallization equipment to meet the needs of industrial production.In recent years,with the research of membrane materials and membrane separation process,it is gradually found that hydrophobic porous membrane materials have great potential in the high salinity wastewater treatment industry.However,in the conventional hydrophobic membrane separation process,membrane materials are faced with problems such as hydrophilic leakage and membrane pollution,which seriously hinders the application of hydrophobic membrane in industrial production.In view of the problems encountered in the treatment of gas field water and the problems encountered in the process of hydrophobic membrane separation,a new process,membrane aeration evaporation crystallization process,is proposed in this paper.In this process,PVDF hollow fiber hydrophobic membrane is used for high-density aeration treatment of high salt gas field water.The gas field water is concentrated and crystallized by the moisture absorption principle of air and the gas-liquid entrainment effect of bubbles.In the process of use,the bubbles produced by membrane materials disturb the water body,increase the gas-liquid contact area and improve the evaporation efficiency;meanwhile,the continuous purging effect of air in the process of membrane aeration can prevent pollutants from accumulating on the membrane surface contacting the material liquid,so as to avoid conventional deposition Cake layer contamination.First of all,we use the chlorinated polyvinyl chloride plastic with excellent temperature resistance to make the all plastic mold.There is no corrosion,infiltration or deformation of the mold during the use.Secondly,on the basis of single factor experiment,we optimize the experimental conditions such as the temperature of material liquid(°C),separation distance of gas and liquid(cm),membrane area(m2),and aeration intensity(Nm3 /(m2·h))by response surface method.The results show that at 90°C,separation distance 20 cm,membrane area 3.8×10-2m2,and aeration intensity 0.90Nm3 /(m2·h),the water quality of the produced water is 284.7?S/cm,and the water is evaporated At the same time,we tested the long-term stability of the membrane aeration evaporation crystallization process.The results showed that the membrane side pressure increased from 0.080 MPa to 0.110 MPa under the condition of keeping the aeration intensity of 0.90Nm3/(m2·h)during the 40 h continuous experiment,indicating that the surface of the hydrophobic membrane was lesspolluted Under the process conditions,after 30 hours of stable operation,72 L of gas field water is concentrated nearly 9 times to obtain crystal salt,which meets the needs of long-term experiments.At last,we made a preliminary study of the pilot test,in which PTFE membrane material with better ventilation performance was used.The results show that the self-made heat exchanger can achieve the purpose of heat exchange,and the performance of PTFE membrane material is stable in the operation process,which can meet the requirements of long-term test.