2010 Volume 43 Issue 10 Pages 872-879
A thermal spraying technique was adopted to change the surface properties of heat exchanger tubes in pulverized coal fired boilers in order to reduce ash deposition. Initially, four types of coal ash with different melting points were tested as samples for ash deposition experiments. As a result, ash particles with higher fouling factor selectively adhered on the tube surface. Even for the ash particles with lower melting point, Ni alloy as a thermal spraying material played an effective role in reducing deposition. Ni alloy can reduce the ash deposition by limiting formation of molten slag at high temperature. In addition, long-term ash adhesion experiments were also carried out using a precise tension tester at high temperature. The effectiveness of the Ni alloy was also proved after long term contact between an ash pellet and a rod thermally sprayed Ni alloy at high temperature. This is because the Ni alloy can control the diffusion of Fe compounds from the tube rod to the ash deposition layer.
