SIMULATION OF COAL ASH DEPOSITION ON TO A SUPERHEATER TUBE

The deposition of coal ash particles on to a superheater tube under pu lverised coal combustion conditions was simulated using Soda Lime Sili ca Glass (SLSG) particles. For this purpose a small-scale furnace and an air-cooled probe representing a superheater tube was located in the duct section in the path of the flue gases. The deposition rate of pa rticles was determined for various parameters. Deposition was found to start when the particle viscosity was less than 6.7 x 10(9) Pa.s. The deposition rate increased with probe surface temperature, gas tempera ture and velocity; it also showed a complex dependence on particle siz e. For large particles (16, 29 and 35 mu m) deposition was controlled by stickiness of the probe surface (probe surface temperature) up to 7 00 degrees C; however, small particles did not show any dependence on stickiness. Addition of 1% NaCl to SLSG raised the rate of deposition to 100%. The formation of crystalline phases (Plagioclase and Melilite ) reduced the deposition rate of SLSG particles when NaCl and CaCO3 we re added to them.