Study on the Predicting Technique of Ash Deposition Tendency in the Entrained-Flow Coal Gasifier. 1st Report. Relationship between Ash Melting Characteristics and Deposition Characteristics.

Abstract

In an entrained flow coal gasifier, the gas temperature in the combustor or combustion region higher than the ash fluidizing point in order to discharge the mineral matter in the coal as molten slag. Following coal combustion, the gas temperature decreases as the gasification reactions proceed, eventually to below the ash softening point at the exit of the gasifier. This study focuses on the relationship between the ash melting characteristics and the ash deposition characteristics at temperatures below the ash softening point in the gasifier. Ash fusibility tests were conducted with DTA and ash liquid phase ratios were calculated as continuous ash fusibility index. The deposition tests were conducted using a drop-tube furnace for five types of coal. It was shown that the deposition characteristics have a close relationship with the ash liquid phase ratio and the difference of the ash deposition characteristics among coal types was explained by the ash liquid phase ratio. Furthermore, it was obvious that initial ash deposition phenomena at temperature below ash softening point are greatly influenced by Ca and Fe-aluminosilicate melts.