Simulation Study On The Separation Of Naphthalene And Its Hydrogenated Product Mixture By Divided-wall Colmun

The catalytic hydrogenation products of naphthalene are tetralin and decalin,both of which are high value products.It will consume a lot of energy to separate these products by traditional separation methods.As a chemical process strengthening equipment with great energy saving potential,the divided-wall colmun can achieve high purity separation of multi-component mixture with low energy consumption.In view of the difficulty in separation of mixtures of trans decalin and CIS decalin and tetrahydronaphthalene system,two kinds of divided-wall column were established to separate the mixtures of naphthalene and its hydrogenation products,namely KDWC and PDWC.First,simple calculation model of KDWC and PDWC were established based on minimum steam method,divided the KDWC and PDWC into different areas,than calculated the minimum steam required in each area and obtains the Vmin/F-D/F diagram.The analysis shows that the steam required in each area of KDWC is more than that in PDWC column.Then this paper makes a strict simulation of the two kinds of divided-wall column.Because the multi column model of the strict simulation of the divided-wall column is difficult to converge,the paper studies the establishment process of PDWC and KDWC and makes a detailed description.The four-column model of KDWC and eight-column model of PDWC can be successfully established by gradually establishing,gradually converging and finding the initial value of tearing stream from three-colmun or two-column model.the two-clomun model of KDWC and three-clomun model of PDWC were built by using the strategy of the extraction process and liquid feeding process at top of column is simulated as passing through a condenser,and the extraction process and vapor feeding at the bottom is simulated as passing through a reboiler.KDWC and PDWC are optimized with the annual total investment(TAC)as the goal and the optimal column structure and operation parameters are obtained.The separation state and process in the column was studied and it is found that there is backmixing between CIS decalin and tetrahydronaphthalene in the pre separation section of KDWC,and there is no backmixing between trans decalin and naphthalene in the whole column;In PDWC,there is backmixing of CIS decalin and tetrahydronaphthalene in pre separation section and middle section,and the analysis shows that the different energy-saving potential of KDWC and PDWC is related to the two separation methods:the "easy before hard" segmentation strategy of PDWC makes it more energy-saving potential.In addition,the liquid split and vapor split can greatly affect the energy consumption and separation process.The operating range of KDWC is different with different vapor split,and the liquid phase distributor in the main column of PDWC has the greatest impact on energy consumption.Finally,the traditional separation model is established and optimized.Comparing the traditional separation model with divided-wall column,it is found that divided-wall column can significantly reduce the energy consumption of condenser and energy consumption of reboiler and equipment investment;compared with the traditional separation method,KDWC saves TAC 32.3%,PDWC saves TAC 37.7%;PDWC saves TAC 8%compared with KDWC.