Problems with the refractory material in the water wall
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Why are silicon carbide refractory materials used in all water-cooled wall gasifiers? Silicon carbide has good thermal conductivity, while corundum refractory materials have a relatively low thermal conductivity. From the perspective of protecting the water-cooled walls, shouldn’t materials with lower thermal conductivity be more suitable as the refractory layer for these walls? . The slag accumulation on the water wall of our plant’s gasification furnace has been a persistent problem; the thermal load on this water wall is quite high. I was wondering whether it would be possible to apply another layer of corundum refractory material on the surface of the silicon carbide refractory material used on the water wall, or to use corundum refractory material directly, in order to replace part of the solid slag layer
The purpose of installing water wall instead of refractory bricks is to provide an additional factor for determining the operating temperature of the furnace; it is not intended to generate steam using the water wall drum. The advantage of water walls is that they can quickly and accurately reflect the degree of slag accumulation on the furnace walls as well as the furnace temperature
During normal operation of a water-cooled wall gasifier, there is a solid slag layer and a liquid slag layer behind the refractory material. The thermal resistance of the solid slag layer is similar to that of the refractory material itself, but it is much lower than that of the liquid slag layer (by an order of magnitude). It is crucial that the refractory material used in the water-cooled wall be able to withstand the erosion caused by the slag layers.
1. The primary function of refractory materials is to protect the furnace structure behind them. 2. As for thermal conductivity, among refractory materials, silicon carbide and alumina both have relatively high thermal conductivity; however, compared to metals, their values are still low. Therefore, the impact of thermal conduction can be considered negligible. 3. In the gasification furnace, a reducing atmosphere exists; under such conditions, silicon carbide has a much better resistance to erosion than alumina, which is why silicon carbide is used. The advantage of alumina over silicon nitride is that it is a neutral material that can be used in both oxidizing and reducing atmospheres, offering wide adaptability.