ECONOMIC APPLICATIONS OF HEAT-PUMPS IN INTEGRATED DISTILLATION SYSTEMS

The influence of relevant parameters on the economics of distillation plants involving distinct heat pump cycles is scrutinised and the resu lts are compared to conventional and integrated schemes. On the basis of the COP, energy costs and efficiencies, simple expressions are prop osed for preliminary economic analysis and design of heat pump assiste d distillation. The influence of heat pump type, purity requirement, c olumn pressure drop, feed rate, energy cost, relative volatility etc. on the energetic aspects and economic range of application is presente d. Heat pumps can be economical substitutes for conventional distillat ion process design whenever direct refrigeration or chilled water are required for condensation and for separating close boiling mixtures in columns of small pressure drop. A design strategy for selecting the m ost economical distillation system, considering different types of hea t pump structures (vapour recompression, bottom flash, closed cycle, a bsorption cycle), is proposed, based on pinch technology, primary ener gy rate, energy cost factor and estimated payback time of excess capit al. The strategy is demonstrated by industrial case studies.