SynopsisFor a stable operation of blast furnace and a decrease in fuel rate, the improvement of the qualities of sinter which is the principal charging material is very important. At Wakamatsu Sinter Plant of Nippon Steel Corporation which is equipped with a double-layer charging system, the plant experiment has been made to improve the reducibility of sinter by making uniform and ideal heat pattern in the sintering bed. In this experiment, sinter with excellent properties, 3.7 % FeO, 70 % JIS RI, good hightemperature properties has been manufactured. Findings obtained are summarized as follows:(1) An effective means o f improving the sinter reducibility is to cause porous ore to remain as unmelted ore by lowering the sintering temperature at about 1 250 to 1 300 °C and by increasing the temperature-rise rate in the high-temperature zone.(2) Compact ore should have fine grains to improve the sinter reducibility.(3) The reduction degradation index (RDI) of sinter can be improved by reducing the ratio of A1203JSiO2 in fine raw mix and by lowering the sintering temperature.

The mineral structure of sinter is strongly affected by the heat pattern in the sintering process. For this reason, the control of heat pattern in sintering bed is an important operating factor in the sintering process of iron ore. In the theoretical investigation of sintering process, a simulation model which is considering the coke breeze size distribution, the moisture condensation reaction, the Fe0 formation/reoxidation reaction and other reactions are considered was developed. Many useful findings on an actual sintering operation were obtained from the study of the effects of various operating factors on the heat pattern with the aid of this simulation model.

No abstract

The wide use of ox)'gen converter steel-making, coll/)Ied with the much illl/Hoved blast furnace process, and recent abundance of rich iron ore supplies have altered the whole steelmaking situation. Progress in the chemical indust./y did, for a time, spur the develo/)lI1ent of , direct reduction' processes, as the various methods of making iron withollt a blast furnace were called. However, blast furnace has become so e.Dicient that direct redllctioll processes are now aimed less at replacing the conventional /JI'ocess than at supplementing it. This sllp/Jlemenlmy /JI'ocess has come to be kllown as , pre-reduction,' since its product is to be subsequently treated by the conventional /Jrocess. Yawata Iron & Steel Co., Ltd. carried out a series of tests on olle /y/Je of IHe-reduced material, slJonge iron, and /Ha ctically confirmed that its lise reduced coke rate and increased iron output. Pre-reduction at mines ""D' be economical. BlIt , for the /Hesen t, although technically feasible , (He-redllction at j a/Janese steelworks has not yet /) roved economical.