Direct reduced iron system and method using synthetic combustion air

A method of carbon dioxide emission reduction from a direct reduction of iron (DRI) process, the method comprising:

• reducing iron oxides present in a reduction unit to iron metal;
• producing a top gas stream in the reduction unit comprising process carbon dioxide, water, unreacted reducing gas, and unreacted hydrocarbon fuel;
• introducing the top gas stream to a top gas scrubber coupled to the reduction unit, wherein the top gas scrubber provides a scrubbed gas stream comprising the process carbon dioxide, the unreacted reducing gas, and the unreacted hydrocarbon fuel;
• introducing the scrubbed gas stream to a top gas separator coupled to the top gas scrubber, wherein the top gas separator provides:
• a first stream from at least two streams, the first stream comprising the unreacted reducing gas and the unreacted hydrocarbon fuel with essentially no process carbon dioxide;
• and a second stream from the at least two streams, the second stream comprising essentially the process carbon dioxide;
• providing the first gas stream directly or indirectly to a process gas heater, alone or in combination with additional hydrocarbon fuel and/or a portion of the scrubbed gas stream;
• providing synthetic combustion air to the process gas heater, the synthetic combustion air comprising a mixture of the second stream and a source of oxygen with essentially no nitrogen, the process gas heater producing a flue gas stream comprising flue gas carbon dioxide and the process carbon dioxide;
• introducing the flue gas stream to a flue gas scrubber and providing a carbon dioxide rich stream;
• sequestering the carbon dioxide rich stream and reducing carbon dioxide emission from the reduction unit.