What are fluidized bed boilers and circulating fluidized bed boilers?

　　A fluidized bed boiler is a device that uses gas-solid fluidized combustion to produce steam. Fluidization is the mixing and interaction of particulate solid fuel and ash with air under the drag force of the rising gas after the solid particle bed is filled with gas, thereby forming a state that resembles a liquid state.

　　Studies have confirmed that different fluidization states can be formed due to differences in particle size and properties, gas velocity and physical properties. Broadly speaking, fluidization includes the fluidization state, which is arranged from small to large gas velocity, respectively, fixed bed, dispersive fluidization, bubbling bed, turbulence, turbulent bed, rapid bed, and pneumatic conveying. Fluidized bed boilers can be divided into two types according to the fluidization state applied:

　　The first type of combustion is carried out in a bubbling fluidized state, which is called a bubbling bed boiler, which is also called a fluidized combustion boiler in my country. The second type of combustion chamber has a fast bed at the upper part and a bubbling bed at the lower part, which is called circulating fluidization. Bed boiler. According to the flue gas pressure in the furnace, fluidized bed boilers can also be divided into atmospheric fluidized bed boilers and pressurized fluidized bed boilers. The main structure of the circulating fluidized bed boiler is the combustion chamber (including the dense phase zone and the dilute phase zone), the circulation loop (including the gas-solid separator and the return material system) and the tail flue. Compared with bubbling fluidized bed boilers, circulating fluidized bed boilers have higher operating fluidization wind speeds and better performance parameters. Especially its boiler structure is easy to be large-scaled, so it has become the most industrialized clean coal combustion technology in the world. The maximum capacity has reached the supercritical parameter level of 600MW, which has played an important role in the combustion and utilization of refractory coal types, low-calorific value coal types and special fuels.