Energy-saving Study Of The Concentric Internal Heat Integrated Distillation Column Based On Heat Transfer Model

Distillation process is widely used in chemical separation.However,this process has high energy consumption and low thermodynamics efficiency.Nowadays,with the increasing energy consumption trend in the global wide,it is of great significance for building a resource-conserving and low-carbon oriented society to investigate energy saving principle and technology of distillation process.The internal heat integrated distillation column（HIDiC）enhances the reversibility of distillation operation,and improves the thermodynamic efficiency of the process,thereby reduces the energy consumption.Hence,the study of HIDiC attracts the attention of many researchers.A pilot-scale concentric internal heat integrated distillation column is designed,manufactured and installed by our team.In the case of ethanol-water system,the systematic experimental research of performance and energy saving effect for this column is carried out.This paper analyzed the effect of pressure ratio and reflux ratio on temperature distribution,concentration distribution,pressure distribution,reboiler heat duty and condenser energy,and this analysis provides basic data for the rigorous simulation and optimization of HIDiC.The heat transfer model of concentric internal heat integrated distillation column is presented.The phase transformation heat transfer coefficient and the overall heat transfer coefficient are calculated by physical property data and measuring temperature.Then the amount of heat transfer between rectifying section and stripping section can be obtained.The heat transfer model is applied to two-column distillation model,the rigorous calculation mathematic model of HIDiC is gained.The calculated value of the overall heat transfer coefficient decreases with the increase of the pressure ratio and is shown to be between 300 and 800 W·m^-2·K^-1.Under the condition of operating conditions and product purity consists with the experimental value,the temperature distribution simulated is correlated with the experimental temperature,which indicates the proposed mathematic model is reliable.Based on the simulation and optimization of HIDiC,energy saving effect and economic feasibility are analyzed.This study compares the value of heat transfer between the two column-sections under different pressure ratios on the basis of the first law of thermodynamics.As a result,the heat duty saving of HIDiC is 32.23%and the decreased condenser duty is 66.61%relative to the conventional distillation column（CDC）.Also,in foundation of the second law of thermodynamics,the available energy of HIDiC is analyzed and the thermodynamic efficiency is computed.The conclusion shows that HIDiC has a higher thermodynamic efficiency than CDC by about 162.6%at 2.2 pressure ratio.Furthermore,this study also conducts the economic feasibility analysis of HIDiC based on total annual cost（TAC）,and proves that under the condition of same packing type and product purity,the TAC value of HIDiC decreases by 30.81%compared to CDC.