Method for recycling spent reduction gas in a direct reduction of iron ore system utilizing an electric gas heater

A process for producing direct reduced iron with a hydrogen rich reducing gas, utilizing a non-fired reducing gas heater to heat the hydrogen rich reducing gas to a temperature sufficient for iron reduction, comprising:

• providing a reduction shaft furnace of a direct reduction plant to reduce iron oxide to metallic iron with the hydrogen rich reducing gas;
• providing a reduction shaft furnace top gas stream comprising spent reducing gas to a scrubber for removing steam and particulates from the spent reducing gas with the scrubber to process the shaft furnace top gas and produce a scrubbed top gas;
• processing all or a portion of the scrubbed top gas in a pressure swing adsorption gas separation unit to create a dry hydrogen/nitrogen rich stream with its fraction of non-hydrogen or non-nitrogen compounds reduced, and a methane/oxidant rich stream comprising CH4, CO2, CO, H2O, CH4, H2 and N2;
• further processing the dry hydrogen/nitrogen rich stream in a membrane gas separation unit to recover a hydrogen rich stream;
• and
• recycling the hydrogen rich stream from the membrane gas separation unit and at least a portion of the scrubbed top gas with hydrogen from another hydrogen rich stream to create the hydrogen rich reducing gas introduced to the shaft furnace, wherein prior to introduction into the shaft furnace, the created hydrogen rich reducing gas is heated in the non-fired reducing gas heater to heat the hydrogen rich reducing gas to 800˜1100° C.

A process for producing direct reduced iron with a hydrogen rich reducing gas, utilizing a non-fired reducing gas heater to heat the hydrogen rich reducing gas to a temperature sufficient for iron reduction, comprising:

• providing a reduction shaft furnace of a direct reduction plant to reduce iron oxide to metallic iron with the hydrogen rich reducing gas;
• providing a reduction shaft furnace top gas stream comprising spent reducing gas to a scrubber for removing steam and particulates from the spent reducing gas with the scrubber to process the shaft furnace top gas and produce a scrubbed top gas;
• processing all or a portion of the scrubbed top gas in a pressure swing adsorption gas separation unit to create a dry hydrogen/nitrogen rich stream with its fraction of non-hydrogen or non-nitrogen compounds reduced, and a methane/oxidant rich stream comprising CH4, CO2, CO, H2O, CH4, H2 and N2;
• further processing the methane/oxidant rich stream in a membrane gas separation unit to create a methane rich stream;
• and
• injecting the methane/oxidant rich stream from the membrane gas separation unit into a transition zone of the shaft furnace to carburize the direct reduced iron, after being blended with a hydrocarbon bearing gas.

A system for producing direct reduced iron with a hydrogen rich reducing gas, utilizing a non-fired reducing gas heater to heat the hydrogen rich reducing gas to a temperature sufficient for iron reduction, comprising:

• a reduction shaft furnace of a direct reduction plant configured to reduce iron oxide to metallic iron with the hydrogen rich reducing gas;
• a scrubber configured to receive a reduction shaft furnace top gas stream comprising spent reducing gas and remove steam and particulates from the spent reducing gas with the scrubber to process the shaft furnace top gas and produce a scrubbed top gas;
• a gas separation unit configured to process all or a portion of the scrubbed top gas to create a hydrogen rich stream with its fraction of non-hydrogen compounds reduced, and an inert/oxidant rich stream comprising CO2, CO, CH4, H2 and N2;
• and
• a recycle line configured to recycle the hydrogen rich stream from the gas separation unit and at least a portion of the scrubbed top gas with hydrogen from another hydrogen rich stream to create the hydrogen rich reducing gas introduced to the shaft furnace, wherein prior to introduction into the shaft furnace, the hydrogen rich reducing gas is configured to be heated in the non-fired reducing gas heater to heat the hydrogen rich reducing gas to 800˜1100° C.

A system for producing direct reduced iron with a hydrogen rich reducing gas, utilizing a non-fired reducing gas heater to heat the hydrogen rich reducing gas to a temperature sufficient for iron reduction, comprising:

• a reduction shaft furnace of a direct reduction plant configured to reduce iron oxide to metallic iron with the hydrogen rich reducing gas;
• a scrubber configured to receive a reduction shaft furnace top gas stream comprising spent reducing gas and remove steam and particulates from the spent reducing gas with the scrubber to process the shaft furnace top gas and produce a scrubbed top gas;
• a pressure swing adsorption gas separation unit configured to process all or a portion of the scrubbed top gas to create a dry hydrogen/nitrogen rich stream with its fraction of non-hydrogen or non-nitrogen compounds reduced, and a methane/oxidant rich stream comprising CH4, CO2, CO, H2O, CH4, H2 and N2;
• a secondary membrane gas separation unit configured to process the dry hydrogen/nitrogen rich stream and create hydrogen rich stream;
• and
• a recycle line configured to recycle the hydrogen rich stream from the secondary membrane gas separation unit and at least a portion of the scrubbed top gas with hydrogen from another hydrogen rich stream to create the hydrogen rich reducing gas introduced to the shaft furnace, wherein prior to introduction into the shaft furnace, the hydrogen rich reducing gas is configured to be heated in the non-fired reducing gas heater to heat the hydrogen rich reducing gas to 800˜1100° C.

A system for producing direct reduced iron with a hydrogen rich reducing gas, utilizing a non-fired reducing gas heater to heat the hydrogen rich reducing gas to a temperature sufficient for iron reduction, comprising:

• a reduction shaft furnace of a direct reduction plant configured to reduce iron oxide to metallic iron with the hydrogen rich reducing gas;
• a scrubber configured to receive a reduction shaft furnace top gas stream comprising spent reducing gas and remove steam and particulates from the spent reducing gas with the scrubber to process the shaft furnace top gas and produce a scrubbed top gas;
• a pressure swing adsorption gas separation unit configured to process all or a portion of the scrubbed top gas to create a dry hydrogen/nitrogen rich stream with its fraction of non-hydrogen or non-nitrogen compounds reduced, and a methane/oxidant rich stream comprising CH4, CO2, CO, H2O, CH4, H2 and N2;
• a secondary membrane gas separation unit configured to process the methane/oxidant rich stream to create a methane rich stream;
• and
• an injection line configured to inject the methane/oxidant rich stream from the membrane gas separation unit into a transition zone of the shaft furnace to carburize the direct reduced iron, after being blended with a hydrocarbon bearing gas.