The main function is to make full use of the thermal enthalpy of raw materials in the hot gas flow discharged from the rotary kiln and the rotary kiln, to preheat and decompose part of the carbonates, and then enter the rotary kiln and continue to heat and decompose to complete the calcining of clinker. Therefore, it must have the following three functions: sufficient dispersion and uniform distribution of gas-solid phase, rapid heat exchange, and efficient separation