石炭灰の付着挙動に及ぼす液相成分の影響

Abstract

In order to prevent adhesion of molten ash particles on the surface of heat exchanger tubes in coal combustion boilers, surface treatment of the tubes, using a thermal spray coating technique, is conducted in this study. As one of the important mechanisms of ash adhesion relates to liquid-bridge force between the tube surface and the molten ash particles, contact angle of the liquid-phase on the surface for the simulated molten ash particles was measured, varying types of coating metal species. The ash deposition experiments on the coated tubes were also conducted, using a vertical furnace under the high-temperature condition. The result showed that the two values of the wettability and the slagging factor of the ash particles deposited could evaluate the ash adhesion characteristics. The wettablity could be controlled by changing types of the coating metal species. The amount of ash deposition increased with an increase of the slagging factor. Especially, sodium and potassium compounds were concentrated in the position apart from 60 degrees from the stagnation point. These results suggest that the surface treatment of the tubes, using a thermal spray coating technique, can control the ash deposition behaviors.