The classical blast furnace is still the principal means of hot metal production. In fact, over 95% of the total iron in the world today is produced using this process, as was the case a century ago. Figure 1.1 presents the percentage contribution of hot metal in steelmaking across the globe in 1990. 1 Such a long and sustained track record of blast furnaces arises out of the continuous developments in design, such as increases in capacity; alterations in profile; improved burden distribution systems like movable throat armor and Paul Wurth (PW) top; high top pressure operation, etc.. It also reflects upgrades of the process technology, such as the use of higher hot blast temperature, oxygen enrichment of the blast, auxiliary fuels including coal injection, prepared burdens, automatic measurement and control systems, and artificial intelligence systems, resulting in a significant increase in productivity, a decrease in coke rate, and an improvement in the quality of hot metal in classical blast furnaces. It is interesting to note that, in the year 1990, 527 million tons of hot metal were produced by 541 blast furnaces, which means an average production per furnace of almost 1 million tons of hot metal, 1 although many of the new furnaces constructed between 1986 and 1991 were either “very large” or “very small” — the latter comprising the so-called mini blast furnaces (Figure 1.2). 1 Percentage consumption of hot metal, scrap, and sponge iron in the world in 1990 at a charge of 1240 kg/t of crude steel https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9781315138220/6ba18297-7766-4c2a-9901-d50d96c5995a/content/fig1_1.tif"/> Blast furnaces newly built and shut down during the period 1986 to 1991 https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9781315138220/6ba18297-7766-4c2a-9901-d50d96c5995a/content/fig1_2.tif"/>