In chemical industries, physical conditions of process streams must be adjusted to satisfy the condition of the following processes such as separation and reaction processes. This required physical condition change can be explained by Helmholtz and Gibbs free energies with the second law of thermodynamics. However, many energy saving technologies recently developed are only considered on the basis of the first law of thermodynamics, energy conservation. Simultaneously, some researchers have been paid attention to the analysis of process exergy and irreversibility of the process under the consideration of the second law of thermodynamics. However, many of these investigations only show the calculation results of exergy analysis and the possibility of energy saving of the processes.
Recently, Kuchonthara and Tsutsumi have proposed the energy recuperative integrated gasification power generation system and developed the design way of the system in their papers. Based on exergy recuperation, Kansha et al. have developed the self-heat recuperation technology, applied it to several chemical processes and showed the energy saving possibility as compared with the conventional counterparts.
In this research, the minimum energy required for the thermal processes was derived theoretically according to the irreversibility point of view. This minimum energy required was compared with the energy required for the self-heat recuperative thermal processes and conventional processes by using process simulator. From these results, we show the direction of energy saving process designs from irreversibility point view with fundamental developments.