Direct-reduced iron (denoted DRI hereinafter) is obtained when fine ore and lump ore are reduced in a solid state at the relatively low temperature of about 1,273K (1,000) using reformed natural gas. The methods now used include the FIOR, FINMET and CIRCORED processes and IRON CARBIDE process, all of which reduce fine ore in a fluidized bed; the HYL-I process, and HYL-II process, which use a retort bed, and the Midrex process and the HYL-III process, which use a countercurrent shaft furnace to reduce pellets and lump ore, and others. Of these, the Midrex, HYL-I and HYL-III processes have been successfully industrialized in large scale production. The Midrex and HYL-III processes are now most commonly used for direct reduction, the former having the largest manufacturing share. Production of DRI totaled 31 million tons in 1995. The Midrex process is shown in the figure. Reforming natural gas has a H2/CO ratio of 1.6, the temperature is 1,173K (900), the in-furnace pressure of the countercurrent shaft furnace is 100 kilopascals, and the energy necessary for reduction is 10.5 gigaJoules/ton-DRI. Part of the exhaust gas is mixed with natural gas and reformed, and the remainder is used as the fuel for the reformer furnace. In the HYL-III process, the H2/CO of the reformed gas is 3, the temperature is 1,203K (930), the in-furnace pressure of the countercurrent shaft furnace is 450 kilopascals, and the energy necessary for reduction is basically the same as in the Midrex process. In both processes, higher furnace temperatures result in higher productivity, because the metal is reduced by an endothermic reaction. However, an excessive furnace temperature will cause the pellets and lump ore to melt during reduction and agglomeration. The maximum reduction rate is about 95%, and the carbon content is limited to about 2.5%. Plant locations have been confined to places where natural gas is available, although the demand for steel in such places was not necessarily great. Furthermore, the large specific area of the active surface of spongy DRI makes it sensitive to reoxidation and ignition when it comes into contact with air and water, especially sea water. Handling and transportation were therefore difficult and potentially hazardous, making large-volume export unprofitable. As a result, the production of DRI has failed to reach expectations. To overcome this difficulty, a hot-briquetting facility to minimize the specific area by compaction was developed and industrialized, and has been installed in the lower part of the countercurrent shaft furnaces since 1984. This had two repercussions. Hot briquetted iron (HBI) has minimized the risk of ignition and substantially reduced reoxidation, making handling and transportation of DRI much easier, and enabled DRI to be used as a substitute for scrap in steelmaking by the electric furnace. Subsequently, as minimills began to produce steel sheet, DRI was no longer a mere substitute for scrap, and began to be used as a material for high-grade steel with deep drawing quality, because of its low contents of residuals such as Cu, Sn, As, Sb, Bi, Zn, and Pb which all deteriorate the quality of steel products. According to the statistics of the International Iron and Steel Institute (IISI), the world's DRI production more than tripled from 9.1millon tons in 1984 to 31millon tons in 1995. During this period, the world's hot metal production leveled off at approximately 500 million tons. Consequently, the ratio of DRI production to world hot metal production has increased from 2% to 6%. Additional attempts are underway to remove geographic restriction of the reductant by replacing natural gas by coal. The SL/RN process, which utilizes rotary kiln to reduce lump ore, pellets and sand iron with coal, is in commercial production. This process suffers, however, from relatively big heat loss and facility size, and hence finds limited acceptance of 2 million tons/year. A new attempt, called FASTMET process, mixes fine coal powder in green pellets, reduces the pellets by firing in rotating hearth furnace in a very short period of time, aiming at commercialization in the near future. In 1997, the world's DRI production is estimated to reach a high 4.4 million tons.