There is described a mill for the production of steel from liquid and solid charging substances. It includes a coking plant, a blast furnace plant, a converter steelworks, and a plant for the direct reduction of iron ore. The converter steelworks is charged with molten pig iron from the blast furnace and with scrap as well as with sponge iron from the direct reduction plant. The reduction gas is composed of converter offgas, top gas and blast furnace gas. In order to avoid coal deposits in the direct reduction plant and to improve the composition of the reduction gas, the coke oven gas component is subjected to fractionation by alternating pressure adsorption so as to increase its portion of hydrogen and to lower its portion of hydrocarbons.