Energy Saving for Batch Distillation with Mechanical Heat Pumps

• Main Authors: G. Modla, P. Lang
• Format: Article
• Language: English
• Published: AIDIC Servizi S.r.l. 2013-09-01
• Series: Chemical Engineering Transactions
• Online Access: https://www.cetjournal.it/index.php/cet/article/view/5999

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 (n-heptane-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 (VRC-E) 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).