Thermal Performance Analysis And Experiment Research Of Multi-effect Desalination Concentrating The Saline Wastewater From Petrochemical Enterprises

Petrochemical enterprises have become the important economy pillar in China,but more and more water are consumed and then the wastewater discharge at the same time.In order to alleviate the current situation that water resources is increasingly nervous,achieving energy conservation and emission reduction of petrochemical enterprises is imperative.High costs and heat consumption of salinity wastewater treatment also block off the achievement of "zero discharge" in petrochemical enterprises.Mathematical models for MED were established based on the investigation of saline wastewater treatment from petrochemical enterprises at home and abroad,and analyzed the thermal performance of MED concentrating the saline wastewater from petrochemical enterprises.And on this basis,the effect of four operation schemes treating simulate saline wastewater were investigated,to use the lab-scale vertical tube MED system.Through thermodynamic calculation,the heating steam utilization(HSU)from different systems were obtained and the optimum operation scheme(three falling-falling-climbing system)was determined.In order to optimize the key parameters three falling-falling-climbing system was taken as the research objects,such as feed water salinity and feed water flow rate.Finally,multi-effect evaporation(MED-TVC)was studied and the installation position of TVC was optimized in order to improve the performance of the MED system.The main conclusions in this paper are as follows:(1)through the thermodynamic calculation of the forward feed MED concentrated saline wastewater,The results show that performance of MED is influenced significantly by effect number.CR has slightly influences on gained output ratio(GOR)and total heat transfer areas.Although evaporation temperature in last effect has slightly influences on GOR,which influences the total heat transfer areas remarkable when effect number is bigger.In addition,water capacity and economic performance of MED with the feed preheater are enhanced strikingly.(2)The results showed that climbing film system performance was better than falling film by gas-water ratio(GWR)and concentration ratio(CR)were taken as evaluating indicators.The performance of MED raised with the increase of effect numbers,and GWR and CR of three falling-climbing-climbing(FCC)system were 0.50:1 and 3.57 respectively.In addition,FCC had the maximum heating steam utilization efficiency,which was 80.32%.Ultimately,FCC was considered as optimal operation scheme.(3)Experimental results demonstrated CR and GOR raised with the increase of the effect numbers,the fresh steam flow rate and the feed water temperature,while decreased with the increase of the feed water salinity and flow rate.It was found that the optimal operation parameters consisted of the feed water with salinity(0.6 %),flow rate(75 kg/h)and temperature(45 °C),and the fresh steam with flow rate(17 m3/h).The maximum CR and GOR were 4.50 and 2.99,respectively.(4)PP MED-TVC system had the better performance due to higher gained output ratio(GOR)and lower total heat transfer areas in comparison with others.If the installation position of TVC was used suitably by GOR and total heat transfer areas,the energy efficiency of MED-TVC could be enhanced greatly.Through the exploration of these basic data,operation law and investment cost,we lay the foundation for the technology of multi-effect evaporation used to treat with saline wastewater of petrochemical enterprises in China to realize industrialization.