Development of sulfuric acid decomposer for thermo-chemical IS process

Noguchi, Hiroki  ; Ota, Hiroyuki; Terada, Atsuhiko  ; Kubo, Shinji  ; Onuki, Kaoru; Hino, Ryutaro

The Japan Atomic Energy Agency (JAEA) has been conducting R&D on thermo-chemical Iodine-Sulfur (IS) process, which is one of most attractive water-splitting hydrogen production methods using nuclear heat of a high-temperature gas-cooled reactor (HTGR). In the IS process, sulfuric acid is evaporated and decomposed into HO and SO in a sulfuric acid decomposer operated under high temperature condition up to 500C. Necessary heat is supplied by high temperature helium gas from the HTGR. Since the sulfuric acid decomposer will be exposed to severe corrosion condition, we have proposed a new decomposer concept of a block type heat exchanger made of SiC ceramic which has excellent corrosion and mechanical strength performance. To verify the concept, integrity of new type gaskets applied for boundary seal of the decomposer was examined as a first step. Pure gold gaskets coupled with absorption mechanism against thermal expansion showed good seal performance under 500C. Based on this result, a mock-up model for a IS pilot-plant with 30 m/h-hydrogen production rate was test-fabricated as the next step. Through the fabrication and gastight tests, fabricability and structural integrity were confirmed. Also, the decomposer showed good mechanical strength and seal performances against horizontal loading simulating earthquake motion.