Direct reduced iron system and method using synthetic combustion air

Patent metadata

Field	Value
Publication number	US-2024218474-A1
Application number	US-202418610218-A
Country	US
Kind code	A1
Filing date	Mar 19, 2024
Priority date	May 24, 2021
Publication date	Jul 4, 2024
Grant date	—

Abstract

A system and method of direct reduction of iron (DRI) is disclosed, having a reduction unit configured to reduce iron oxides to metallic iron; a process gas heater coupled to the reduction unit, the process gas heater configured to supply the reduction unit directly with a source of heated reducing gas, where the process gas heater is further configured to receive a synthetic combustion air stream for heating the reducing gas, the synthetic combustion air stream comprising a source of oxygen with essentially no nitrogen. A method of carbon dioxide emission reduction from a direct reduction of iron (DRI) process is also disclosed.

First claim

We claim:

1 . A method of direct reduction of iron (DRI) in a reduction unit configured to reduce iron oxides to metalized iron, the method comprising:
providing to a reduction unit a source of heated reducing gas from a process gas heater; producing a top gas stream comprising process carbon dioxide, unreacted reducing gas, unreacted hydrocarbon fuel, and water; providing a synthetic combustion air stream to the process gas heater, the synthetic combustion air stream comprising a source of oxygen with essentially no nitrogen; and reducing iron oxides present in the reduction unit to iron metal.

2 . The method of claim 1 , wherein the reduction unit produces a top gas stream comprising process carbon dioxide, unreacted reducing gas, unreacted hydrocarbon fuel, and water and wherein the method further comprises:
introducing the top gas stream to a top gas separator configured to split the top gas into at least two streams: a first stream comprising the unreacted reducing gas, and the unreacted hydrocarbon fuel with essentially no process carbon dioxide; and a second stream comprising the process carbon dioxide; combining the first stream with fuel and sending to the process gas heater; and combining the second stream with the source of oxygen and sending to the process gas heater; wherein the process gas heater provides a flue gas stream, the flue gas stream comprising flue gas carbon dioxide and the process gas carbon dioxide.

3 . The method of claim 2 , wherein the top gas separator is a fractional distiller, a pressure swing absorption unit (PSA), or a vacuum pressure swing absorption unit (VPSA).

4 . The method of claim 1 , wherein the source of oxygen is provided by a cryogenic separator, a membrane separator, a pressure swing absorption unit (PSA), a vacuum pressure swing absorption unit (VPSA), a fractional distiller, or an air separation unit (ASU).

5 . The method of claim 1 , further comprising processing the flue gas stream with a flue gas scrubber, the flue gas scrubber providing a carbon dioxide rich stream.

6 . The method of claim 5 , further comprising receiving the carbon dioxide rich stream in a drying unit and/or further comprising compressing the carbon dioxide rich stream in a compressor.

7 . The method of claim 6 , wherein the compressor provides supercritical carbon dioxide to a geological sequestering pipeline.

8 . The method of claim 7 , wherein the geological sequestering pipeline is coupled to one or more subterranean oil reservoirs, natural gas deposits, un-mineable coal deposits, saline formations, shale, and basalt formations.

9 . The method of claim 1 , further comprising receiving the metalized iron in an electric arc furnace.

10 . The method of claim 9 , wherein the electric arc furnace is configured to receive the metalized iron continuously or semi-continuously.

11 . The method of claim 1 , wherein the method is absent a reformer.

12 . 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.

13 . The method of claim 12 , wherein the top gas separator is a pressure swing absorption unit (PSA), chemical absorption unit, or vacuum pressure swing absorption unit (VPSA).

14 . The method of claim 12 , wherein the source of oxygen is provided by a cryogenic separator, a membrane separator, a pressure swing absorption unit (PSA), a vacuum pressure swing absorption unit (VPSA), a fractional distiller, or air separation unit (ASU).

15 . The method of claim 12 , wherein prior to the sequestering, receiving the carbon dioxide rich stream in a drying unit and/or further comprising compressing the carbon dioxide rich stream in a compressor.

16 . The method of claim 15 , wherein the compressor provides supercritical carbon dioxide to a geological sequestering pipeline.

17 . The method of claim 16 , wherein the geological sequestering pipeline is coupled to one or more subterranean oil reservoirs, natural gas deposits, un-mineable coal deposits, saline formations, shale, and basalt formations.

Assignees

• Nucor Corp

Inventors

• Motamedhashemi Mirmohammadyousef

Classifications

• C21B2005/005

  Selection or treatment of the reducing gases · CPC title

• C21B5/001

  Injecting additional fuel or reducing agents · CPC title

• B01D2258/025

  from metallurgy plants · CPC title

• B01D2257/504

  Carbon dioxide · CPC title

• B01D53/78

  with gas-liquid contact · CPC title