Steady-state Simulation Of Agrawal Divided-Wall Column For Four-component Separation

As an effective process intensification approach,divided-wall column(DWC)has been applied to the separation process of ternary components.To further improve energy efficiency of the multiproduct system,four-product DWC has received attention in both industrial and academic research,and Agrawal DWC(ADWC)shows obvious advantages.However,the design and control of ADWC are more difficult due to the partitions.Therefore,studying the gas-liquid flow and solving the uncontrollable vapor splits have great theoretical significance for the industrial application of ADWC.Consequently,this thesis carried out the computational fluid dynamics(CFD)simulation study of ADWC,analyzed the gas-liquid two-phase flow,and compared the effect of different drag models on predicting the gas-liquid two-phase flow.And the optimization process of a new type of liquid-only configuration of ADWC(LTS-ADWC)was investigated.The contents are listed as follows(1)A four-component mixture of methanol,ethanol,n-propanol and n-butanol was selected to be investigated with conventional direct separation sequence,pre-fractionation process and ADWC.The results showed that ADWC had great advantages in energy efficiency Compared with conventional direct separation sequence,the reboiler duty and TAC of ADWC could be reduced by 40.6%and 35.1%.And compared with pre-fractionation process,the reboiler duty and TAC could be reduced by 20.0%and 29.0%respectively(2)A new type of liquid-only configuration of ADWC(LTS-ADWC)was investigated,and the results showed that the reboiler duty of LTS-ADWC could be reduced by 40.9%and 20.5%compared to direct separation sequence and pre-fractionation process,it had the same energy efficiency as ADWC.And the operational uncertainty associated with uncontrollable vapor splits could be eliminated,which provides multiple options for practitioners to implement(3)A CFD model based on Eulerian-Eulerian approach was used to simulate ADWC,the results showed that the model established in this paper was of good application.It was found that there was an obvious backflow near the partition wall.Compared with the simulation results under different drag models and liquid flow rates,it was shown that they had a certain impact on the prediction of the liquid volume fraction on the tray.