To save energy in a distillation column, engineers have discussed the application of side-boilers and side-coolers and heat pumps to a distillation column. But no quantitative method which represents the relationship between temperature level and the minimum exchanging heat load of heat source and/or coolant at any plate has been developed. It is very difficult to design a distillation column with such equipment.
This paper represents the energy-saving effects of a side-boiler and a side-cooler on a distillation column on the basis of exergy concepts, and then proposes a quantitative method to determine the feasible domains for the use of a side-boiler and a side-cooler, and to clarify the important relationship mentioned above. This method can be used to design a distillation column with a heat pump and a multi-effective distillation system.