Abstract: Herein disclosed are both waste gas circulation method and system for effectively recovering waste heat from an on-strand type sintering apparatus which has its sintering and cooling zones extending continuously along a horizontal strand. The hottest waste gases coming from the final stage of the sintering zone and the front stage of the cooling zone, in which the sintering reaction of a charge mixture is completed, are subjected to heat recovery, and sulfur oxides in the hottest gases are prevented from condensing on the water pipe or pipes of a waste-heat boiler by preheating the water, which is supplied for the heat recovery, with the still hot waste gases coming from the downstream half of the cooling zone. The heat of the still hot waste gases are exchanged with cold water so that this water may be heated into hot water. On the other hand, the heat of the hottest gases is exchanged with steam so that this steam may be heated into superheated steam.

Abstract: A sintering plant of the type sintering raw materials, such as pulverized ores, while transporting them with a conveyor, in which quicklime is fed to the lower layer of the raw materials on the conveyor so that SO.sub.x produced during sintering process may be mainly contained in gases discharged to the downstream half of wind box array disposed below the conveyor and the gases only from the downstream half are fed through a heat exchanger to a desulfurization equipment having a relatively low capacity. The heat exchanger is arranged to heat water to be fed to a device, such as waste heat boiler, adapted to be operated with thermal energy recovered from a cooler for cooling the finished sinter discharged from the conveyor, whereby the thermal efficiency of the plant can be much improved.

Abstract: An improved apparatus for cooling hot pellets discharged from a kiln or the like with water is presented wherein the pellets are charged through a chute into a water cooling bath while avoiding oxidation thereof. The cooling bath is covered with a hood and the pressure difference between the chute and hood is controlled during the process.