PURPOSE: To enhance sintering efficiency in sintering of iron ore by using quick lime, as one of sintering raw materials, obtd. by using grate protecting bed ore covered with limestone to improve the gas permeability of the raw materials.

CONSTITUTION: Grate protecting bed ore is covered with limestone through the medium of water in pelletizer 22 and charged onto pallet 2. Sintering raw meterial consisting of fine iron ore and coke mixed is then fed onto the ore. The raw material is fired with firing furnace 6, sucked by the action of blower 11, and burned downward to be sintered. At this time, the limestone on the bed ore surface is calcined to quick lime, which is exfoliated from the sintered ore when passes through first and second crushers 13, 18. The quick lime is selected with screen 19, supplied to sintering raw material vessel 24 together with small lumpy or fine ore, mixed with iron ore and coke to form sintering raw material of superior pelletizability, and supplied onto grate protecting bed ore covered with limestone. The sintering raw material layer has superior gas permeability, and hence sintering efficiency is enhanced.