Simulation And Thermodynamic Calculation Of Desalination Equipment With Low Temperature Multi-Effect Distillation

Because of the advantages such as the lower operating temperature which avoids or reduces the scaling and corrosion problems; the simpler pretreatment process; the larger scales of flexible manipulation; the smaller dynamical consumption; the higher thermal efficiency; the safer and credible working system; the possibility of utilizing low temperature waste heat sources, increasing the gained output ratio (GOR) and reducing water cost, low-temperature multi-effect distillation (LT-MED) configuration may become the main technology for future desalination plants.In the thesis, a mathematical simulation model is developed to describe the low-temperature multi-effect distillation (LT-MED) configuration, including the low temperature multi-effect distiller, the preheater, the condenser, the flashing box and the thermal vapor compress (TVC), which considers the boiling point elevation and the temperature losses in the demister and vapor transmission lines. Based on the mathematical simulation, the LT-MED calculation procedure is worked out by using the Visual Basic programming language, which can analyze not only the design calculation but also the checking calculation process in six different kinds of forward and parallel configurations. Through the dynamic data exchange between the Intouch and Visual Basic, the simulation of LT-MED is achieved.The procedure of forward feed water LT-MED configuration, based on the calculation data, analyzes the variation of thermodynamic performance with the number of effects,the temperature in the last effect,the temperature of heating steam in the first effect and concentration ratio; Compares the thermodynamic performance of four kinds of configuration which adopts different styles of preheater and is with thermal vapor compression or not, in conclusion, the configuration with thermal vapor compression that inlet seawater are preheated by the steam produced by the seawater in the front distiller is the best one; in allusion to the best configuration, the analysis of the variation of thermodynamic performance with pressure of primary liquid in TVC is discussed, which provides significant guidance in the appropriate pressure scale of primary liquid in TVC.Based on the calculation data of parallel feed water LT-MED configuration, the variation of thermodynamic performance with seawater temperature and heating steam temperature is investigated among four kinds of styles. Furthermore, the effects of the location of TVC,the quantity and location of preheater are shown.