A system for energy optimization in a plant (3) for producing direct-reduced metal ores (3). The plant (3) has at least one reduction unit (12), a device for separating gas mixtures (7, 7a, 7b) having an associated compressing device (4, 4a, 4b), and a gas-heating device (10) upstream of the reduction unit (12). Part of the process gases (2, 2a, 2b) is fed by a feed line from a smelting reduction plant to the plant for producing direct-reduced metal ores (3). A turbine (8, 8a, 8b) is fit between the device for separating gas mixtures (7, 7a, 7b) and the gas-heating device (10) upstream of the reduction unit (12) such that a pressure drop between the device for separating gas mixtures (7, 7a, 7b) and the reduction unit (12) is converted into forms of energy that can be used to operate additional components (4, 4a, 4b, 15, 15a, 15b) of the plant (3), in particular electrical energy and/or mechanical energy. Energy consumption of the plant (3) is reduced.

In a process of reducing iron ore powder by fluidized bed reduction furnaces and a smelting reduction furnace, CO.sub.2 emissions are significantly reduced and stable operation is possible regardless of fluctuations in various conditions. A method of reducing iron ore powder, the method including: a fluidized bed reduction process of fluidizing and reducing iron ore powder in a fluidized bed reduction furnace using a first reducing gas to produce partially reduced iron; and a smelting reduction process of reducing the partially reduced iron in a smelting reduction furnace using a second reducing gas. Fluidized bed reduction furnace top gas discharged from the top of the fluidized bed reduction furnace is used for synthesis of methane and reforming of methane-containing gas.

Disclosed are improved processes and systems to produce metals, carbon, CO, or H.sub.2, starting with a metal ore and biomass. Raw biomass can be co-fed with a metal ore into a chemical reactor for simultaneous biomass pyrolysis along with metal oxide reduction using intermediates generated during the biomass pyrolysis. The carbon made by pyrolysis is directly utilized in situ to reduce a metal oxide to a metal. Some variations provide a process for reducing a metal oxide with biomass, comprising: feeding a biomass feedstock and a starting metal oxide into a chemical reactor to pyrolyze the biomass feedstock and to reduce the starting metal oxide, thereby generating (i) a carbon product, (ii) a metal product comprising a metal or a metal oxide having a lower oxidation state than the starting oxidation state, (iii) and a reaction off-gas; and recovering the carbon product and the metal product, individually or in combination.

A method for producing reduced iron that produces reduced iron by reducing iron oxide charged in a shaft furnace, in which a gas mixture which contains a reducing gas and a nitrogen gas, and has a predetermined temperature, is blown into the shaft furnace. The reducing gas contains 90 volume % or more of a hydrogen gas.

System and method for producing steel is provided that efficiently reduce carbon dioxide emissions. A steel production system includes: a first gas generating section configured to obtain a first gas by converting carbon monoxide, to carbon dioxide, in a gas containing the carbon dioxide and carbon monoxide; a reducing gas supply section 3 configured to supply a reducing gas containing a reducing substance to reduce a reducing agent, the reducing agent containing metal oxide to reduce carbon dioxide and being oxidized by contact with the carbon dioxide; and a reaction section 4 including a plurality of reactors 4a and 4b, respectively connected to at least one of the first gas generating section and the reducing gas supply section 3, and the reducing agent arranged in the reactors 4a and 4b, the reaction section being capable of switching between the first gas and the reducing gas to be supplied to each of the reactors 4a and 4b, wherein a second gas is configured to be supplied to a blast furnace, the second gas being obtained by contacting the first gas supplied to the reactors 4a and 4b with the reducing agent to convert the carbon dioxide to carbon monoxide and the second gas having the carbon monoxide as a main component.

A method for operating a smelting furnace installation, in particular a blast furnace installation, the method including the following steps: feeding coke, iron oxide containing material and if required fluxing agents to the top of the smelting furnace; injecting a first reducing gas containing hydrogen at a tuyere level of the smelting furnace at a temperature above 1600 C.; and injecting a second reducing gas at a lower shaft level of the smelting furnace.

The coke is fed at a lump coke rate below 220 kg/t HM, and the density of the first reducing gas is below 0.80 kg/Nm.sup.3.

A method for producing molten iron. The reduction of iron oxide-containing material to form a metallized product is performed using a reduction gas consisting at least largely of hydrogen H2. Top gas is accumulated during the reduction process. First sub-quantity of top gas is combined with reducing reduction gas components to provide reduction gas, and second sub-quantity of the top gas, as a discharged gas, is subjected to a gas separation process into a hydrogen-enriched gas flow and a hydrogen-depleted tail gas flow. Metallized product of the reduction process is combined with carbon carriers to be melted in a melting device to form a molten iron, and a smelting exhaust gas is accumulated. Sub-quantity of the tail gas flow is combined with at least a sub-quantity of the smelting exhaust gas, and a tail gas mixture is produced. Sub-quantity of the tail gas mixture is supplied to a thermal use.