Development of SO3 decomposer for thermochemical hydrogen production by IS process. Basic of SiC plate-type SO3 decomposer and catalyst test results

Thermo-chemical Iodine-Sulfur (IS) process has a potential to produce large amount of hydrogen without carbon dioxide emission using thermal energy of a high temperature gas-cooled reactor (HTGR). Sulfur-trioxide (SO3) decomposer is one of the key components of the IS process, in which SO3 gas is catalytically decomposed into oxygen (O2) and sulfur dioxide (SO2) under high temperature condition up to 850degC using the sensible heat of helium gas. The decomposer is exposed to the severe corrosive condition, where SiC ceramics shows good corrosion resistance. However, it is very difficult to manufacture large-size SiC ceramics structure required in the commercial plant. We have proposed a new concept of the decomposer, which featured a plate-type heat exchanger made of SiC ceramics. The concept ensures the scale-up by connecting the heat exchanger units in series. To examine the fabricability of the proposed concept, a mock-up model was test-fabricated. Through the test-fabrication, issues on the fabricability of large-sized heat-exchanger-type SO3 decomposer using SiC ceramics were clarified. Also, preliminary catalyst tests were carried out to clarify catalyst bed specification of the SO3 decomposer. This report describes the proposed structure, results of thermal-hydraulic and mechanical strength analysis, the mock-up model test-fabrication, and the catalyst tests. (author)