Study On The Partial Diabatic Distillation With Side Stream Reflux

Partial diabatic distillation is an important method for energy saving,which is characterized by only selecting one or several trays for heat exchange.Compared to the complete diabatic distillation which requires heat exchangers on each tray,the partial diabatic distillation not only maintains high thermodynamic efficiency but also makes the devices easier to implement.The partial diabatic distillation has good operational prospects,and relevant studies have drawn more and more attention.The partial diabatic distillation with side stream reflux and the inter-reboiler was proposed.In this operation,some tray in the stripping section was surrounded by the jacketed inter-reboiler,the vapor stream in equilibrium was withdrawn from this tray and returned to its above appropriate position.The proposed operation could achieve a significant increase in the second thermodynamic efficiency while maintaining separation capacity.The mathematical model and exergy loss analysis method of the operation were constructed.The numerical simulation and analysis of the influence factors on the new operation mode were carried out.The comparison between the novel operation mode and the other distillation modes was carried out.The simulation results proved the energy saving superiority of the proposed mode.The experimental study of the partial diabatic distillation with side stream reflux and the inter-reboiler was carried out,and the 2-propanol and 1-propanol mixture was separated in the experiment.The experimental results were in line with theoretical expectations,and the feasibility and operability of the distillation method were verified.In order to enhance energy saving,a new method of combining the vapor recompression system and the partial diabatic distillation with side stream reflux and the inter-reboiler was proposed,which compressed the vapor withdrawn from the tower to provide heat of the bottom reboiler.The simulation results showed that the proposed operation could further reduce the operating energy consumption on the basis of improving the thermodynamic efficiency.The operation provided a feasible energy-saving method for the separation of the system with small temperature difference between the bottom of tower and the side stream.The partial diabatic distillation simultaneously performed in the rectifying section and the stripping section was further studied.First,the mathematical modeling and simulation of the partial diabatic distillation with side stream reflux and the inter-condensor was carried out,and the operating characteristics were analyzed.Then,in the partial diabatic distillation simultaneously performed in the rectifying section and the stripping section,the operating parameters were adjusted.Compared to the adiabatic distillation,the optimized partial diabatic distillation had the same separation properties but better thermodynamic properties.In the simulated separation of the 2-propanol and 1-propanol mixture with light component feed mole concentration of 0.2 and 0.8,the energy-saving efficiency of the operation was 26.3%and 31.7%,respectively.