What are the advantages and disadvantages of coal feeding from material-returning device of the CFB boiler?

　　Advantage

　　1.The coal is mixed with high-temperature circulating materials, and the process of water evaporation and volatilization can be carried out in the return leg, which prolongs the residence time of the fuel in the furnace and increases the combustion efficiency.

　　2.Coal enters the furnace together with a large amount of circulating materials and mixes with the bed material more evenly, which is conducive to the combustion of coal, and the temperature field in the furnace is more uniform.

　　Disadvantage

　　1.The coal feed line is longer and the coal feed system is more complicated.

　　2.The coal feed delay time is long, and the system reliability is slightly poor.