At present, the domestic circulating fluidized bed boiler wear-resistant refractories can generally be divided into the following three categories according to their role:
(1) wear-resistant refractory bricks, castables, plastics and mortar.
(2) Refractory bricks, castables and mortar.
(3) Refractory insulation materials of bricks, castables and mortar.
Commonly used varieties of wear-resistant refractory materials are phosphate brick and castable, sillimanite brick and castable, silicon carbide brick and castable, corundum brick and castable, wear-resistant refractory brick and castable, as well as silicon nitride bonded silicon carbide products and other varieties.
1. Phosphate bricks
Phosphate bricks are usually used in the range of 1200 ~ 1600 ° C and are non-fired bricks that are heat treated at low temperature (500 ° C). Most of the design materials of early circulating fluidized bed boilers are phosphate bricks and phosphate castables. Because there is no high temperature sintering process, and because the circulating fluidized bed boiler is operating in the range of 850 ~ 900℃, at this temperature, the physical properties of the refractory are unstable, and the wear resistance can not be fully played. Although phosphate material has its shortcomings in the use of circulating fluidized bed boilers, its price can be accepted by various manufacturers.
2 Sillimanite
Sillimanite added to the refractory can increase the load softening temperature by 100 ~ 150℃, is a kind of refractory raw material. The temperature of the change of the refractory is 1450 ~ 1600℃, and the sintering temperature of the sillimanite brick reaches this temperature, so the sillimanite brick is an ideal wear-resistant refractory material on CFB.
3. Silicon carbide products
Silicon carbide products have high wear resistance and good thermal shock stability when used in high temperature oxygen free atmosphere, and can form a glazed protective layer on the surface after sintering at a certain temperature. There is a small amount of oxidizing atmosphere in the combustion of CFB boiler, so the use effect is not good.