Abstract
We have developed a heat-transfer tube for use as a heat exchanger in waste gasification and melting systems. This heat-transfer tube, which is made of a pressureless-sintered silicon carbide material, is a single end-type with cantilever support. Ceramic heat-transfer tubes fixed both ends to a metallic heat exchanger body are easily broken, due to differences in thermal expansion at high temperatures, but silicon carbide tubes on a cantilever support do not have this problem. We measure basic properties of the heat-transfer tube such as the coefficient of heat transfer and corrosion resistance, and discuss ash removal. We conduct a low-temperature heat transfer experiment, using saturated steam at 0.4 MPa pressure as a heating medium, and actual exhaust gas from a waste gasification and melting system at about 1150 K as a high-temperature range. Air of 290 K, 79.2 m3[normal]/h reaches 820 K after two heat exchanger passes. Near the dew point, silicon carbide shows high corrosion resistance to the exhaust gas. Regarding ash removal, sandblasting effectively cleans the tube surface, because of hardness of a pressureless-sintered silicon carbide material. We simulate application of a large heat transfer tube, about φ200 × φ179 × 1800 mm, in a furnace. Results indicate that a heat transfer tube made of pressureless-sintered silicon carbide is suited to waste gasification and melting systems.
