Experimental Study Of Multi-Effect Evaporation System For The Purification Treatment Of The Oilfield Wastewater

Currently, many domestic 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 it in heat recovery boiler is one of the most effective means to solve these problems. This paper focuse on that oilfield wastewater has high salinity feature and relies on multi-effect evaporation machine. Through experiment and theoretical analysis to explore the efficiency and the actual results using the multi-effect evaporation technology in oilfield wastewater purification.The main works can be prerented as follows:We conduct automation design based on a set of automation devices in order to make the system run stable. Meanwhile the efficiency and operational stability of the system has greatly improved.A series of experiments have been conducted in order to discuss the effects of the operation parmeters (feed rate, concentration and temperature) on the system performances including water yield, GOR and water quality. It has been founded that the system can run stable and the basic design parameters and operating parameters are similar. When the feed flow ranges from 200 kg/h to 500kg/h, there is an optimal matching relation between the feed flow rate and the amount of steam. The GOR of system has a proportional relationship with the temperature of the feed. The concentration of feed flow has less impact on the system performance. The system’s maximum difference of GOR between fresh water and other different feed concentration is only 0.05. Product quality is good and stable. The total salinity is only 0.7667 mg/L and it meets the standards of boiler water.We establish the exergy balance equation of MEE systems using exergy analysis. Through the analysis and calculation we obtained the following conclusions:Exergy efficiency of the system is only 13.99% and the exergy loss accounted for 86.01% in the entire system input exergy. The temperature difference between the heat transfer is the main reason for the irreversible exergy loss. Evaporator systems, heat exchangers and final effect condenser system accounted for 58.10%,36.57% and 5.33% respectively in the total loss of exergy, wherein the evaporator and condenser of the final effect accounted for the most. There is a need to reduce the temperature of the heating steam, choose a higher heat transfer efficiency of the evaporator, increase the number of effect, rationaliy use secondary steam at the end of the effect and adopt other methods to reduce the irreversible exergy loss caused by temperature difference between the heat transfer and improve the economic benefits of system. Through experimental study and calculation we found that the temperature of the feed flow has a significant effect to the exergy efficiency of the system, the concentration of the feed flow has little effect on the exergy efficiency of the system.