Large integrated steelworks

From the late 19th century through the mid-20th century, virtually all global steel production took place in so-called integrated steel mills, which grew both in number and in per-unit production capacity. These steel mills are almost always based on the production of pig iron in blast furnaces from iron ore and, for the past sixty years or so, the oxygen conversion of this pig iron into steel.

Today, we are witnessing competition from another steel production process based on melting scrap metal in electric arc furnaces –, occasionally using pig iron and, increasingly, directly reduced iron ores, such as DRI (Direct Reduction Iron) or HBI (Hot Briquetted Iron). This forms the basis of what are known as mini-mills (see [M 7 110] and [M 7 130]).

Integrated mills, which are the subject of this article, accounted for 70.4% of global steel production in 2024, or 1,345 Mt. After a trend toward ever-larger facilities and the construction of plants producing 15 or even 20 Mt of steel per year (a trend that continued in Asia until 2020), these mills in the pioneering countries (Europe, the U.S., and Japan) are now tending to restructure into more compact facilities in the range of 2 to 10 Mt per year.

Current global steel production, at 1,885 Mt in 2024, is ten times that of 1950 (189 Mt). More than half is produced in China (53% in 2024), despite stagnation in Chinese production following the peak in 2021.

Alongside this race toward ever-greater scale, energy requirements have fallen sharply over the past thirty years and now stand at around 18 to 20 GJ·t ^{– 1} of hot-rolled steel strip. These requirements are primarily met by coal.

Alongside the significant efforts made over the past fifty years to increase reactor productivity and reduce their energy consumption, it has been possible to reduce their environmental impacts.

Among these, notable progress has been made regarding byproducts (dust, sludge, slag), the quantities of which have been reduced, partially recycled internally, and for which external recovery solutions have been strengthened.

Furthermore, growing environmental pressure for a drastic reduction in greenhouse...