Study of container using hybrid technique for sulfuric acid decomposition of thermochemical water-splitting iodine-sulfur process

Abstract

A thermochemical water-splitting iodine-sulfur process (IS process) is one of the candidates for the large-scale production of hydrogen using heat from solar power or nuclear energy. Severe corrosive environment which is thermal decomposition of sulfuric acid exists in the IS process. To achieve the IS process, one of the key factors is the development of structural materials against the severe corrosive environment. A hybrid material with the corrosion-resistance and the ductility was made by a silicon powder plasma spraying and laser treatment. The hybrid materials had excellent corrosion resistance in the condition of 95 mass% boiling sulfuric acid. This was attributed to the formation of SiO2 on the surface. To confirm the manufacturability of a container using the hybrid technique, the production of container with a welded part, a chamfer and a curved surface was experimentally tried. A configuration of the container is 150mm inside diameter, 120mm in height and 6mm in thickness. In the production process of the container, the treatment of the welded part is very important. The preliminary examination of the welded part was carried out using Hastelloy C276 plates. The distance between fusion line and the plasma spraying and laser treatment area was decided to 15 mm from the results of the preliminary examination. The container firstly divided into the upper and the lower part, the inside of them was conducted the plasma spraying and laser treatment and then they were welded by a tungsten inert gas. Finally, the surface of the welded part was covered by plasma spraying and laser treatment. There was no detachment in the plasma spraying and laser treated layer of the container after the laser treatment. We succeeded in the production of the container using the hybrid technique.