(418bd) Development of Chemical Heat Transformer for High Temperature Systems

Recently, an energy saving has caught a great attention in chemical industries due to the fuel price rapid increase and green house effect. In fact exothermic reaction is usually carried at low temperatures with cooling and endothermic reaction is carried at high temperatures supplying heat from fuel combustion in many conventional chemical processes. As a result, large exergy destruction is taken places in this process. To provide further energy saving in these processes, we should pay more attention to minimization of this exergy destruction.

One of the ideas to solve this problem is to develop a heat transport system, called heat transformer, which receives heat by an endothermic reaction and releases heat by exothermic reaction. To use this system, the process does not require the fuel combustion and coolers which mainly causes large exergy destruction in the process. However, in many conventional heat transport systems, the unique system for each chemical process has to be designed because all of processes have their own process conditions, leading to increase of investment cost.

To overcome this problem, authors proposed a chemical heat transformer system using a reversible reaction for high temperature range. This chemical heat transformer system transports the heat using chemical reaction. Thus, it can adjust the heat transport condition and amount by controlling conversion ratio and reaction conditions such as reactant composition, temperature and total pressure by following the Le Chatelier’s principle.

For this reasons, the chemical heat transformer has been investigated in this research. The target reversible reaction for the representative chemical heat transformer was selected as methane reforming reaction and methanation reaction for this chemical heat transformer because these reactions occur at high temperature range (about 600-800 degree C). The methane reforming reaction and the reverse reaction was examined as the specific chemical heat transformer. At this point, conversion ratio near the turning temperature of the methane steam reforming reaction which is an endothermic reaction of chemical heat transformer was measured by this experiment. Also, it is drawn the optimum reaction conditions by considering efficiency of chemical heat transformer including the reverse reaction from the point of exergy. From these experiment and calculation results, this system has a great potential to contribute the industrial energy saving and to realize the coproduction in chemical industry.