Energy conservation is important in process design. In industrial experience, the
calculation of the minimum heating and cooling requirements reveal significant energy
savings. Specifically, Imperial Chemical Industries in the United Kingdom and Union
Carbide in the United States have both stated the results of numerous case studies that
indicate 30% to 50% energy savings compared to traditional practice. Therefore, energy
integration design procedure is a very beneficial tool and is an important phase in
determining the cost of preliminary design.
The first step in the energy integration analysis is the calculation of the minimum
heating and cooling requirements for a heat-exchanger network. In any process flow
sheet, there are several streams that need to be heated and there are some that need to be
cooled. In the acetic anhydride production, for example, the reaction stream in the second
reactor must be cooled, while the liquid product coming out of the same reactor must be
heated for distillation. For that reason, cooling water is needed to lower the temperature
of the reactor stream, and steam is needed for heating in the distillation column