Operational and economic feasibility of different heat-pump systems with mechanical compression integrated to real batch distillation columns are investigated. This study is focused to the reduction of the external energy demand of the batch distillation. The separation of a low relative volatility mixture (nheptane-toluene) is studied by rigorous simulation performed with a professional dynamic flow-sheet simulator. The distillation column has AE-1000 reactor-reboiler of DIN standard type. The methods studied are vapour recompression, vapour compression and vapour recompression with the application of an external heat exchanger. Operational, heat transfer and economic issues are discussed. We stated that for the VRC in the minimal pay-pack period point the operation time of the batch process is significantly higher (the production capacity is much lower) than that of the conventional batch distillation. For boosting the overall performance of the VC system, we suggested to complete it with an external heat exchanger (VRCE) where the heat of the compressed top vapour is transferred to the usual heating medium (water). The original VRC system was not economical (payback period much above 10 y). However the payback period of the new VRC-E system was significantly shorter (less than 10 y). Distillation is one of the most widely used separation methods in the chemical industry in spite of its very high energy demand. The highest heat duties are required by creating the vapour flow in the reboiler (heating) and condensation of the top vapour in the condenser (cooling). The different methods of energy saving which is achieved by means of internal and external heat integrations were widely studied for the continuous distillation process and summarised by Bruinsma and Spoelstra (2010). Kiss et al. (2012) a practical selection scheme of energy efficient distillation technologies is proposed, with a special focus on heat pumps. The advantages of batch distillation (BD) over the continuous one are well-known. The energy saving methods for batch distillation have been much less studied than for the continuous one. Recently Jana and his co-workers (2011, 2012) investigated the feasibility and efficiency of the vapour recompression system for batch distillation. They proposed the application of variable compression ratio and pointed out the great economical potential of the vapour recompression systems for batch distillation. However they did not study in details the issues of the heat transfer in the reboiler. The goals of this paper -to study for batch distillation different heat pump (HP) systems with mechanical vapour compression (vapour recompression, vapour recompression with an external heat exchanger), -the rigorous simulation of the operation (including the heat transfer conditions) of these HP systems integrated to real batch distillation columns, -to estimate the costs and payback times of these systems and to compare them with those of the conventional batch distillation system. The calculations are performed with a professional dynamic flow-sheet simulator (CCDCOLUMN, Chemstation, 2007) for the separation of a low relative volatility (n-heptane-toluene) mixture. The reboiler of the systems is of DIN standard types (AE series). For the vapour compression system n-pentane was selected, as working fluid.
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