Low Temperature Multi-effect Desalination For Low Salinity Waste Water Discharged From Petrochemical Plant And Numerical Simulation Of Ejector

Petrochemical industry is known as high energy consumption, high discharge and high pollution with numerous waste water being discharged during its production. It is the major fields for cleaner production and the development of recycling economy. Comprehensive utilization of energy, optimized distribution of water resources and recycling is the main part of<Nation Long-term Scientific and Technological Development Plan of2006-2020>.In order to make full recycling use of waste water with low salinity discharged by the petrochemical industry every year, first, this thesis summarized and analysis the development of salinity desalination technologies, and then chose low temperature multi-effect to recycle the salinity waste water according to the characteristics of the petrochemical industry that it has low temperature exhaust heat. Forward feed multiple effects was used and theoretically analysised, on this basis, in order to use evaporation steam in the last effect. Ejector is considered to bring thermal efficiency for this system.A low-temperature multi-effect process compiled through VC++was used. Analysis for the various parameters such as spray density, evaporation temperature in the first effect (or Top-brine temperature, TBT), evaporation temperature in the last effect, concentration factor and ejector has been conducted. The results show that for the forward feed multiple effects the high evaporation temperature in the first effect, the low evaporation temperature in the last effect not only can make a high performance ratio, but also can reduce the mean heat transfer areas. The use of ejector showed a good thermal efficiency for this system.On the basis of the above analysis, analyses of ejector based on the kinetic theory of gases have been completed. For the low temperature multi-effect, an ejector was designed by MATLAB. As the flow inside the ejector is complex, by the flexibility of numerical simulation, take FLUENT as the platform, under FLUENT simulation, the entrainment ratio and the distribution of flow filed will be acquired. Analysis for the various structure parameters such as the length of mixing-chamber converging segment, the length of mixing-chamber constant segment, the length of diffuser has been conducted. At the optimum structure of the ejector, the pressure of the motive fluid, the pressure of the suction fluid and the pressure of the discharging pressure have also been analyzed. Effecting mechanisms of parameters on the ejector performance is inquired after comparing the simulation results at different conditions.