The invention discloses a gradient
waste heat recovery and direct reduction
system and method for iron-containing
metallurgical slag particles. The
system comprises a
waste heat recovery system, a material mixing system and a direct reduction system which are sequentially connected, wherein the
waste heat recovery system comprises a calcining furnace, a separator and a pyrolyzing furnace; when a mode A is adopted, the calcining furnace, the separator and the pyrolyzing furnace are sequentially connected; and when a mode B is adopted, the calcining furnace, the pyrolyzing furnace and the separator are sequentially connected. The method comprises the following steps that the iron-containing
metallurgical slag particles and a
calcium carbonate precursor are calcined in proportion to obtain cooled particles and CaO, the CaO is separated or is added into carbon-containing
solid waste together with the particles for
pyrolysis to obtain
solid semi-
coke and cooled particles, the
solid semi-
coke and the cooled particles enter a stock bin together with the CaO, and after
pelletizing is carried out according to needs,
direct reduced iron is obtained through reduction. According to the systemand the method, the waste heat of the iron-containing
metallurgical slag particles can be efficiently recovered, and the waste heat recovery efficiency, the efficiency and the iron recovery rate are greatly improved; and the particle waste heat is converted into the CaO and the solid semi-
coke which are used as a
slag forming agent and a
reducing agent in the reduction process correspondingly, sothat in-situ consumption of materials is realized, and the system and the method have extremely high social value and economic value.