Application of SO₂/SO₃ Reversible Thermochemical Reaction to High-Temperature Heat Transport

Abstract

As a stage of the study for a high-efficiency, high-temperature thermal energy transport, experiments were carried out on the heat transport by SO₂/SO₃ reversible thermochemical reaction in a labscale hermetic gas-circulating reaction system. In this system, the thermal energy is converted into the chemical energy in the form of SO₂ and O₂ by absorbing the reaction heat through the deoxidization process of SO₃ in the higher temperature side. The produced SO₂ and O₂ are transported to the lower temperature side by a gas-circulating pump. Then, the thermal energy is recovered by the exothermic oxidation of SO₂ with O₂. Subsequently, the produced SO₃ is fed back to the higher temperature side. In this study, the feasibility of this heat transport characteristics were investigated fundamentally in terms of both the change in reactant gas composition and the temperature change in a Pt-catalyst particle bed during SO₂-oxidiation and SO₃-deoxidization.
Under the conditions employed in the present experiments, SO₂ and SO₃ of nearly equilibrium concentration were found to be attained in both the oxidation and deoxidization reactors. It was verified that the thermal energy transport could be achieved continuously. Further, it was recognized that the catalyst-bed temperatures showed the maximum and the minimum in the vicinity of the bed inlet in the process of SO₂-oxidation and SO₃-deoxidization, respectively. These maximum and minimum temperatures became higher with increases in both the molar ratio of SO₂ to O₂ and the circulating rate of the reactant gas.