Method for carburization of HDRI produced in H2 based direct reduction process

A method for producing carburized directly reduced iron from iron oxide material, comprising:

• directly reducing the iron oxide material in a reduction zone by a reduction gas having a hydrogen content of at least 80% by volume;
• taking off a used reduction gas as a topgas;
• increasing, after the reducing operation, a carbon content in the directly reduced iron in a carburization zone by feeding in a carburizing gas;
• and
• taking off, after the increasing of the carbon content operation, at least some of the carburizing gas, while avoiding substantial mixing of the carburizing gas with the reduction gas, resulting in a proportion of carbon-containing gases in the topgas being less than 20% by volume;
• wherein the reduction gas is heated before it comes into contact with the iron oxide material;
• wherein a first partial amount of the topgas is fed to utilization as fuel gas for heating at least one of the reduction gas and the carburizing gas, and a size of the first partial amount of the topgas is regulated as a function of at least one of nitrogen N2, carbon dioxide CO2, carbon monoxide CO, and methane CH4 content in the topgas;
• and
• wherein a second partial amount of the used carburizing gas is fed to utilization as fuel gas for heating the reduction gas, and a size of the second partial amount of the used carburizing gas is regulated as a function of at least one of carbon dioxide CO2, carbon monoxide CO, and methane CH4 content in the topgas.