Heat Integrated Distillation Column Design And Economic Analysis

In previous studies, the vapor recompression distillation column(VRC) and the internally heat integrated distillation column(HIDiC) show better energy and economic performances than the conventional distillation column in close-boiling separation cases. In this work, we carry out some analysis and optimization researches by Aspen Plus about the conventional and various heat integrated distillation technologies based on multiple groups of binary-component mixtures with different relative volatility. What’s more, we also make elaborate design for the typical HIDiC configuration.In the case of propylene-propane splitter, we propose an intensified thermal coupling HIDiC configuration based on the concentric HIDiC column. In this intensified HIDiC, besides the internal heat integration way by the heat panels, an additional thermal coupling is introduced between the overhead vapor of the rectifying section and the bottom liquid of the stripping section. By this enhanced heat integration, the reboiler and the low pressure steam are no longer needed in the process. In addition, the effect of various heat distribution patterns and the corresponding operating conditions which mainly include the top pressure of the rectifying section and the compression ratio of the second compressor on total annual cost are investigated through vast simulations and computations. The results show that the total annual cost tends to decrease as more heat is transferred by the single external heat exchanger instead of multiple internal heat panels. Judging from the above investigations, we develop a HIDiC structure of two separated columns in which all the heat is transferred outside the column by the heat exchanger. It is notable that this HIDiC of two separated columns is superior to the VRC and all the other HIDiC schemes in this propylene-propane splitter.In the study of four groups of binary-component mixtures with the increasing relative volatility(benzene-fluorobenzene, benzene-n-heptane, benzene-toluene, benzene-chlorobenzene), the conventional distillation column and four heat integrated distillation column configurations(a vapor recompression distillation column, an ideal internally heat integrated distillation column, a simplified internally heat integrated distillation column, a pressure-swing distillation column)are optimized and compared for the total annual cost. The results illustrate that the heat integrated column schemes would show favorable energy and economic efficiency when separating mixtures that have close relative volatility. But the advantages of the heat integrated columns weaken continually as the temperature difference of the mixtures gradually increases. Moreover, the vapor recompression and pressure-swing distillation columns are the most promising two ones among all the heat integrated schemes. The configurations based on HIDiC present not to be as competitive as the former two due to its particular operating characteristics. In addition, the heat integration pattern and the heat transfer location in HIDiC have important effects on economic benefits.