| Nowadays the thermal recovery technology has been adopted by the majority of oil production industries. But it leads to the production of many undesirable byproducts as well, in which wastewater accounts for the largest share. It is usually of high salinity for its containing of many complex components.There is no doubt that it will lead to the waste of many fresh water resources and the pollution of the environment if the wastewater is not treated very well. So it will bring a lot of benefits economically and environmentally to carry out a new technology for the purification of the oilfield wastewater.In this paper, the a new treatment process-- Multi-Effect Evaporation system (MEE)--has been introduced for the purification of the oilfield wastewater, and the feasibility research of the process has been carried out theoretically and experimentally, which will provide a guideline for the application of multi-effect evaporation technology in the oilfield wastewater treatment field.The main works and some bright spots can be presented as follows:The multi-effect evaporation process of different flowsheets has been simulated with the process simulation software of Aspen Plus, and the thermal performance of different feed-pattern systems with and without thermo vapor compressor (TVC) has been analyzed. It is indicated that the coupling of MEE and TVC can improve the performance of the system drastically.Different feed-pattern MEE systems have their own advantages corresponding to different application conditions and capacities,and a proper design of feed pattern for MEE system according to the capacity output gain ratio and effect numbers can save a lot of capital investment and operation cost. as for the MEE-TVC system, there is an optimal suction position for maximizing the performance so it is recommendable to select the rational suction position for the TVC.Besides the operation pressure of TVC has influence on the performance of the system.it has been found that the improvement of motive steam pressure will improve the performance of MEE-TVC system while the effect will decline with the increase of the pressure. On the other hand the pressure of entrained pressure play a great role in the performance of system,which will improve greatly with the decrease of the entrained pressure.The steady-state mathematical model of MEE-TVC based on LINGO algorithm has been developed and examined against commercial desalination plants. The model can be adapted to conventional equal temperature difference design method and equal heat transfer area design method as well because of the generality of the model and the maintainability of the programs By introducing suction position variable the influence of parameters of TVC including suction position, suction pressure, motive vapor pressure, top brine temperature etc. on the operation of MEE-TVC system has been investigated. It is found that the improvement of performance ratio and decreasing energy consumption can be achieved by optimization of integrating TVC suction position with operations of each effect. The end effect is almost the optimal position for TVC expect for some cases in equal temperature difference design situation with the gain output ratio as objective.A series of experiments have been conducted in order to discuss the effects of the operation parameters (mainly input feed flow rate and the concentration) on the system performance. It has been found that the flow rate of feed water has a great effect on the performance of MEE system. The pressure of each effect will change with the input flow rate, and it must be exist a optimal operation status when the flow rate of the feed water matches with the flow rate the steam. At the same time, the MEE system can get its optimal performance. then the quality of product water has been analyzed. The results verify the feasibility of the multi-effect evaporation technology for sewage purification. At last, a predict model has been established for the reformed MEE system in order to predict the operation conditions of each effects and give a guide for the operation of it. The predict results has compared with the experiment data, which proves the reliability of the mathematical model. |
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