Method and system for operating a blast furnace with top-gas recycle and a fired tubular heater

A blast furnace system for producing molten iron in a blast furnace to which iron ore, metallurgical coke and fluxes are charged at its upper part and molten iron and slag are tapped from its lower part, said blast furnace having a plurality of tuyeres in its lower part for introducing an oxygen-containing gas for generating heat and reducing gases by combustion of the coke within said furnace, resulting in a top gas stream comprising CO, CO2, and H2 from said upper part of said blast furnace;

• having:
• first cooling means for washing and cooling said top gas stream and removing dust and water therefrom being connected to receive a hot top gas stream from the upper part of said blast furnace;
• pump means for increasing the pressure of the resulting cooled top gas stream to enable recycling of said top gas to the blast furnace;
• means for removing CO2 from at least a portion of said cooled top gas stream forming a CO2-lean reducing gas stream,
• a tubular gas heater for heating said CO2-lean reducing gas stream to a temperature above 850° C., and
• first piping means connecting the first cooling means, the pump means, the means for removing CO2, and the heater, to the blast furnace to form a first gas circulation gas path through said gas heater to recycle the heated CO2-lean reducing gas stream to said blast furnace during normal operation of the blast furnace system;
• characterized by comprising;
• second cooling means for cooling hot gas effluent diverted thereto from said heater;
• second piping means connecting said second cooling means with said gas heater and said pump means defining a second path for gas circulation through said gas heater;
• first valve means for selectively diverting the flow of gas effluent from said heater to said second cooling means and to flow through said second gas path;
• and
• second valve means for blocking the flow of gas effluent from said heater to said blast furnace when the gas effluent from said reactor is flowing through said second gas path;
• whereby in case that the operation of the blast furnace system is interrupted, the gas that was circulating through the heater is capable of being diverted to flow through said second gas path and to continue flowing through said heater to prevent damage of said heater from sudden thermal changes caused by said blast furnace system operation interruption.