Experimental Study Of Multi-Effect Evaporation With Thermal Vapor Compressor System For The Purification Treatment Of Oilfield Wastewater

Currently,many oilfields have entered into the third stage of exploration.The increase of the water content in crude oil not only results in the waste of water resources,but also a huge pollution to environment.The oilfield wastewater desalination treatment and reuse in heat recovery boiler is the most effective means to solve these problems admittedly.In this paper the oilfield wastewater is desalinated in a 500kg/h Low Temperature Multi-effect Evaporation system(LT-MEE).A thermal vapor compressor(TVC)is coupled with MEE system for a higher efficiency and lower energy-consumption.Experiments and analysis are conducted to study the practical application of MEE-TVC in the deep purification of oilfield wastewater.The formation,stability and economy of the application of MEE-TVC in deep purification and reuse of oil field wastewater are studied as well.A steady state mathematical model of MEE/MEE-TVC is developed and optimization calculation is achieved.Meanwhile,it is of practical significance to research the influence of some factors on the performance.The main works can be conducted as followings:Firstly,experiments are carried out to research performance and operating parameters of MEE system,which were necessary data for the design of TVC coupled with MEE system.Secondly,a series of experiments are carried out to study the desalination of different materials by MEE-TVC system.The influence of operation parameters on performance is observed.The results indicate that the GOR of MEE-TVC increases firstly and then decreases with the backward movement of entrainment location.The actual maximum GOR and capacity of MEE-TVC are 23.41% and 28.57% higher than that of MEE.For both MEE and MEE-TVC,the GOR increases then decreases with the increasing of feed rate.The increasement of feed temperature has positive effect of GOR.The system is insensitive to the variation of feed salinity which means that MEE-TVC system has a good adaptability to high salinity oilfield wastewater.The results of chemical analysis show that product water meet the standards of boiler water after decreasing hardness,which proves the application of MEE-TVC in deep purification of oilfield wastewater has a good prospect.Finally,a mathematical model of MEE with different numbers of evaporator and MEE-TVC with different entrained location are developed.It is convenient to switch between MEE and MEE-TVC,as well as MEE-TVC systems with different entrained location by LINGO programs.The optimal design is launched by using the LINGO solver with the objective function of GOR.Then the influence of many factors(evaporator number,entrained location,feed parameters et.al)are study by optimizing method.The results show that:The GOR of optimal design is 23.67% higher than routine design while the specific heat transfer areas are equal.With the number of effects increased,the GOR increase linearly and the specific heat transfer area increase but its increment is reducing.The theoretical maximum GOR of MEE-TVC is 13.65% higher than that of MEE.The GOR and Concentration Ratio of MEE-TVC increase then decrease with the backwards movement of TVC.The GOR increases linearly with the increase of feed temperature.The increasing pressure of primary steam leads the increasing GOR,while its increment is reducing.