Improving performance of dividing wall column using multistage vapor recompression with intermediate reboiler

Abstract

Conventional vapor recompression assisted dividing wall column has limited energy-saving efficiency because of large temperature difference between two ends of column. Meanwhile, the side vapor recompression assisted dividing wall column has limited heat integration because the side vapor or liquid withdrawn flow rate is always small. To improve the energy performance of dividing wall column, this paper proposes the multistage vapor recompression assisted dividing wall column with intermediate reboiler arrangements. In these arrangements, the overhead vapor is compressed by the first compressor, part of compressed vapor is to vaporize the side liquid in the intermediate reboiler, and the rest compressed vapor is further compressed by the second compressor to be at higher temperature and vaporize the bottom liquid in the bottom reboiler. Then heat integration can be performed between two VRC cycles under enough driving force of heat transfer. The simulation results in two separation cases show that the proposed configurations can largely improve the energy-saving performance of dividing wall column especially when the compression ratio of the first compressor is low and enough amount of liquid can be withdrawn from the side stage.