High-gravity MVR Heat Pump Distillation System Simulation And Optimization

The high-gravity MVR heat pump distillation technology,as a new type of distillation technology,has huge energy-saving potential and can bring good economic benefits.However,the current high-gravity MVR heat pump distillation is mainly based on experimental research.Limited by the experimental conditions,it is impossible to comprehensively and accurately analyze the thermal characteristics in the distillation process.In response to this situation,a rate-based simulation model suitable for high-gravity MVR heat pump distillation system is developed.Using the developed simulation model,the thermal characteristics of the high-gravity MVR heat pump distillation process are analyzed,and the system operating parameters under given conditions are optimized.Based on the strong non-ideal phase equilibrium characteristics of ethanol-water mixture,the NRTL-RK combined thermodynamic model is selected.In order to develop a rate-based simulation model suitable for the high-gravity MVR heat pump distillation system,the Fortran subroutine of the parameters of mass and phase boundary area constructs the mathematical model of the supergravity distillation column.Taking the rectification column top product concentration(x_D),heat pump coefficient of performance(COP)and evaporation per unit energy consumption(SMER)as the evaluation parameters,the reflux ratio and feed position of the high-gravity MVR heat pump rectification system are changed.In this case,the influence on system performance is simulated separately.The simulation results are compared with the experimental results in the literature,and the average errors are 0.74%,9.52%and13.26%,respectively,and the maximum error is 15.45%,which verifies the accuracy of the developed simulation model.It shows that the simulation model can be used for the thermal characteristics analysis and optimization research of the high-gravity MVR heat pump distillation system.Using the developed high-gravity MVR heat pump distillation system simulation model,the thermal characteristics of conventional distillation system and the high-gravity MVR heat pump distillation system are analyzed under the same operating conditions.which are from gas and liquid phase concentration distribution,molar flow distribution and temperature distribution.The single variable method is used to analyze the influence of the six operating parameters of the feed flow rate,the rectification column speed,the reflux ratio,the feed position,the product recovery rate and the feed concentration on the performance of the system.The results show that the heat and mass transfer rate of the high-gravity MVR heat pump distillation system is faster.Under given conditions,only 7 trays can achieve the set separation effect.Compared with the conventional distillation system,it can save 10 trays space.The concentration of ethanol at the top of the distillation column increases as the feed flow rate increases,the feed concentration increases,the feed position moves down,the distillation column speed increases,the reflux ratio increases,or the product recovery rate increases.Increasing the feed flow rate or the product recovery rate can increase the product recovery.Increasing the feed concentration,increasing the product recovery rate or moving the feed position down can reduce the overall energy consumption of the system.Take the high-gravity MVR heat pump distillation system with a processing capacity of 0.3m~3/h as an example.While ensuring the purity and output of ethanol products,the energy consumption of the system is minimized.The operating parameters of the high-gravity MVR heat pump distillation system are optimized.The hydraulic performance,comprehensive energy consumption and economy of the optimized system are analyzed.The corresponding optimal operating parameters are:the feed flow rate is 0.3 m~3/h,the speed is 3000 rpm,the reflux ratio is6.8,the feed position is the 15th tray,the product recovery rate is 0.37,and the feed concentration is 54%.The actual flow rates of the gas and liquid phases of the optimized system are between the maximum allowable flow and the minimum ideal flow,and are closer to the minimum ideal gas-liquid flow curve,making the system more feasible.Compared with the traditional distillation system,the optimized high-gravity MVR heat pump distillation system can reduce carbon emissions by 79.59%,save 74.43% of energy consumption,and save41.8%of operating costs.Calculated based on 8000 hours of work per year,￥170,400 can be saved.The optimized high-gravity MVR heat pump distillation system provides a reference scheme for the research and extension of high gravity MVR heat pump distillation technology.