Process for operating a blast furnace installation with top gas recycling

A process for the operation of a blast furnace plant, comprising:

• an air plant comprising, a compression unit and an air separation unit, a blast furnace, and a gas treatment plant,
• the process comprising:
• generating compressed air in the compression,
• introducing the compressed air into the air separation unit thereby generating at least an oxygen-rich air gas and a nitrogen-rich air gas,
• injecting a blast comprising an oxidizing gas into the blast furnace, said oxidizing gas having an oxygen concentration Cvox 21.0 vol % and a flow rate Dvox,
• generating a top gas in the blast furnace,
• introducing the top gas into the gas treatment unit generating at least a top gas enriched in CO2 and a top gas enriched in CO, recovering at least a portion of the top gas enriched in CO injecting the top gas enriched in CO into the blast furnace as reducing gas with a flow rate Drco, wherein the oxidizing gas is chosen from:
• (a) compressed air generated by the air compression unit,
• (b) oxygen-rich air gas,
• (c) a mixture of said compressed air with said oxygen-rich air gas,
• (d) a mixture of said oxygen-rich air gas with the nitrogen-rich air gas, or
• (e) a mixture of said compressed air with said oxygen-rich air gas and with said nitrogen-rich air gas, and
• wherein the concentration Cvox of the oxidizing gas is regulated as a function of the flow rate Drco of the recovered top gas enriched in CO.

A blast furnace plant, comprising:

• an air plant comprising:
• 1. an air compression unit,
• 2. an air separation unit,
• a blast furnace, and
• a gas treatment plant,
• in which blast furnace plant:
• the air compression unit exhibits an atmospheric air inlet and a compressed air outlet,
• the air separation unit exhibits (a) a compressed air inlet connected to the compressed air outlet of the air compression unit and (b) an outlet for oxygen-rich air gas and an outlet for nitrogen-rich air gas,
• the blast furnace (a) comprises a top and (b) is equipped with tuyeres for the injection of blast into the blast furnace, said tuyeres being connected to the air plant via an air gas feed network,
• the gas treatment plant (a) is connected to the top of the blast furnace and (b) exhibits an outlet for top gas enriched in CO2 and an outlet for top gas enriched in CO,
• the outlet for top gas enriched in CO being connected by a recovery loop to injectors for the injection into the blast furnace of a flow rate Drco of top gas enriched in CO,
• wherein:
• the air gas feed network makes it possible to connect the tuyeres to one or more of the following outlets:
• the compressed air outlet of the air compression unit,
• the outlet for oxygen-rich air gas of the air separation unit,
• and the outlet for nitrogen-rich air gas of the air separation unit,
• and in that the blast furnace plant also comprises a control unit for regulating the flow rate and the oxygen concentration Cvox of the air gas supplied to the tuyeres by means of the air gas feed network, said control unit being connected to the gas treatment plant and/or to the recovery loop and controls the oxygen concentration Cvox of the air gas thus supplied as a function of the flow rate Drco of the recovered top gas enriched in CO.