Step air supply system for drum drying section of belt type roasting machine and control method

The invention relates to a belt type roasting machine blow-drying section cascade air supply system and a control method, and the belt type roasting machine blow-drying section cascade air supply system comprises a belt type roasting machine, an upper cover, an air bellow, a dust remover, a cooling exhaust fan, a blow-drying fan, an upper cover air taking opening and an air mixing device, an air outlet of the cooling exhaust fan is connected with an air inlet of a blow-drying fan I, and an air outlet of the blow-drying fan I is connected with a plurality of groups of air supply branch pipes I, an air supply adjusting valve I and an air mixing device through an air supply header pipe I; the upper cover air taking opening I is connected with an air taking header pipe through an air taking adjusting valve I, the upper cover air taking opening II is connected with the air taking header pipe through an air taking adjusting valve II, the air taking header pipe is connected with an air inlet of a blowing drying fan