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US-12618120-B2 - Direct reduction of iron by hydrogen plasma in a rotary kiln reactor

US12618120B2US 12618120 B2US12618120 B2US 12618120B2US-12618120-B2

Abstract

A hydrogen-plasma rotary kiln furnace reactor and a method of reducing iron ore to iron using the same are disclosed. The hydrogen-plasma rotary kiln furnace includes a rotary kiln furnace and a hydrogen-plasma generator.

Inventors

  • Zuotao Zeng
  • John P. Kopasz
  • Theodore R. Krause
  • Angel YANGUAS-GIL
  • Meimei LI

Assignees

  • UCHICAGO ARGONNE, LLC

Dates

Publication Date
20260505
Application Date
20220930

Claims (20)

  1. 1 . A method of reducing iron with zero-CO 2 emission, the method comprising: reducing iron ore or iron ore concentrate to iron at a pressure in a range of 0.9 atm to 1.1 atm in a hydrogen-plasma rotary kiln furnace reactor, wherein the reactor comprises: a rotary kiln furnace including a hollow and cylindrical furnace body elongated along a first axis, the furnace body comprising: a first zone, a second zone, and third zone, the second zone located between the first zone and the third zone; and a liner forming an innermost layer of the furnace body; a hydrogen-plasma generator, wherein heat dissipated by the hydrogen-plasma generator is reused for further reduction of the iron ore or iron ore concentrate; wherein the hydrogen-plasma generator is disposed in the second zone and the liner is disposed around the hydrogen-plasma generator, the hydrogen-plasma generator configured to generate hydrogen plasma, the hydrogen plasma configured to flow towards the third zone; and wherein the iron ore or iron ore concentrate is configured to move down an incline from the third zone to the first zone, and reduction of the iron ore or iron ore concentrate to iron occurs in the second zone.
  2. 2 . The method of claim 1 , wherein the hydrogen-plasma generator is disposed substantially coaxially inside the furnace body.
  3. 3 . The method of claim 1 , wherein the rotary kiln furnace comprises: a shell; and a thermal insulator.
  4. 4 . The method of claim 1 , wherein the rotary kiln furnace is inclined at an angle of 1° to 15° with respect to a horizontal axis.
  5. 5 . The method of claim 1 , wherein the rotary kiln furnace rotates at a rate of 3 rpm to 15 rpm.
  6. 6 . The method of claim 1 , wherein the iron ore or iron ore concentrate is reduced to iron at a temperature lower than 1550° C. at approximately 1 atm.
  7. 7 . A method of claim 1 , wherein the iron ore or iron ore concentrate is reduced at a temperature lower than or equal to 1000° C. at approximately 1 atm.
  8. 8 . The method of claim 1 , wherein the hydrogen-plasma generator comprises a plurality of jet nozzles disposed along the first axis, the plurality of jet nozzles configured to discharge the hydrogen plasma.
  9. 9 . The method of claim 1 , wherein the iron ore or iron ore concentrate is reduced to iron at a temperature less than or equal to 800° C. at approximately 1 atm.
  10. 10 . The method of claim 1 , wherein the rotary kiln furnace rotates at a rate of 3 rpm to 25 rpm.
  11. 11 . The method of claim 1 , further comprising continuously producing the iron by reducing the iron ore or iron ore concentrate.
  12. 12 . The method of claim 1 , wherein the reactor does not emit CO 2 .
  13. 13 . The method of claim 1 , wherein the reactor comprises: an end cap connected to a first end of the furnace body; and a kiln hood connected to a second end of the furnace body and configured to receive the hydrogen-plasma generator such that the hydrogen-plasma generator is disposed inside the furnace body, wherein the second end is opposite to the first end, and wherein both the end cap and the kiln hood are fixedly configured such that they do not rotate while allowing rotation of the furnace body.
  14. 14 . The method of claim 1 , wherein the reactor comprises: a feeder connected to an end cap and configured to feed iron ores or iron ore concentrate into the furnace body; an exhaust gas outlet connected to the end cap; a water-hydrogen separator connected to the exhaust gas outlet; and a sponge iron cooler connected to kiln hood, wherein the water-hydrogen separator is configured to transfer recycled hydrogen to the sponge iron cooler.
  15. 15 . The method of claim 1 , wherein the iron ore or iron ore concentrate is reduced to iron at a temperature less than or equal to 600° C.
  16. 16 . The method of claim 1 , wherein the iron ore or iron ore concentrate is reduced to iron at a temperature less than 570° C.
  17. 17 . The method of claim 1 , wherein flowing the hydrogen plasma from the second zone to the third zone and moving the iron or iron ore concentrate from the third zone to the first zone allows for utilization of the heat to initiate hydrogen reduction of the iron or iron ore concentrate.
  18. 18 . A method of reducing iron with zero-CO 2 emission, the method comprising: reducing iron ore or iron ore concentrate to iron at a pressure in a range of 0.9 atm to 1.1 atm in a hydrogen-plasma rotary kiln furnace reactor, wherein the reactor comprises: a rotary kiln furnace including a hollow and cylindrical furnace body elongated along a first axis; a hydrogen-plasma generator, wherein heat dissipated by the hydrogen-plasma generator is reused for further reduction of the iron ore or iron ore concentrate; a feeder connected to an end cap and configured to feed the iron ore or iron ore concentrate into the furnace body; an exhaust gas outlet connected to the end cap; a water-hydrogen separator connected to the exhaust gas outlet; and a sponge iron cooler connected to a kiln hood, wherein the water-hydrogen separator is configured to transfer recycled hydrogen to the sponge iron cooler.
  19. 19 . The method of claim 18 , further comprising continuously producing the iron by reducing the iron ore or iron ore concentrate.
  20. 20 . A method of reducing iron with zero-CO 2 emission, the method comprising: reducing iron ore or iron ore concentrate to iron at a pressure in a range of 0.9 atm to 1.1 atm in a hydrogen-plasma rotary kiln furnace reactor, wherein the reactor comprises: a rotary kiln furnace including a hollow and cylindrical furnace body elongated along a first axis; a hydrogen-plasma generator, wherein heat dissipated by the hydrogen-plasma generator is reused for further reduction of the iron ore or iron ore concentrate; an end cap connected to a first end of the furnace body; and a kiln hood connected to a second end of the furnace body and configured to receive the hydrogen-plasma generator such that the hydrogen-plasma generator is disposed inside the furnace body, wherein the second end is opposite to the first end, and wherein both the end cap and the kiln hood are fixedly configured such that the end cap and the kiln hood do not rotate while allowing rotation of the furnace body.

Description

This invention was made with government support under Contract No. DE-AC02-06CH11357 awarded by the United States Department of Energy to UChicago Argonne, LLC, operator of Argonne National Laboratory. The government has certain rights in the invention. TECHNICAL FIELD The present disclosure relates generally to an eco-friendly method for producing iron with zero-CO2 emission. More specifically, the present disclosure describes methods for producing iron with zero CO2 emission using hydrogen plasma and/or hydrogen with rotary kiln furnace, and a hydrogen-plasma rotary kiln furnace used therein. BACKGROUND Conventional steel manufacturing is not an environmentally friendly process. Globally, the steel industry emits more than 3.3 billion tons of carbon dioxide (“CO2”) annually, which accounts for 30% of the global industrial and 8% of the global total CO2 emissions. Of various steps in the steel manufacturing process, the blast furnace process for reducing iron ore to metallic iron accounts for about one-third of the total CO2 emissions. Specifically, during the blast furnace process, iron ore is reduced using coke and limestone at temperatures above 2,000° C. to create molten pig iron. Pig iron has a high carbon content, approximately 4-5%, which makes it brittle. To reduce the carbon content, pig iron is processed in the basic oxygen furnace by treating it with pure oxygen using a water-cooled lance, which then removes the carbon as CO2, yielding a crude steel product. Additional processing may further be utilized to produce a high-grade steel product. However, conventional steel manufacturing processes operate close to their thermodynamics limit, making it difficult to meet the goals set in the Paris Agreement adopted on Dec. 12, 2015. Furthermore, conventional steel manufacturing process requires high energy consumption. Conventional blast furnace process requires operation of the furnace at a temperature above 1550° C. A substantial amount of energy is lost in the sensible heat of the high temperature iron and slag. Many have attempted to solve the issues addressed above with new processes, including direct reduced iron (“DRI”) processes, which offer the advantages of lower capital cost, complexity in design, operation compared to conventional blast furnace processes. Currently, about 100 million tons of steel are produced annually by various DRI processes. As an example, the MIDREX DRI process uses a shaft furnace as the reactor and pellets or lump ore as the raw material. The DRI shaft furnace requires that the iron ore be fed into the reactor in pellet form. While the MIDREX DRI process allows a lower carbon footprint compared to the traditional blast furnace process, further reductions in the required energy and resulting carbon footprint are desired. In addition, the MIDREX DRI has disadvantages in that pelletizing the iron ore adds additional cost and produces about 200 kg of CO2 per ton of steel. Furthermore, shaft furnaces cannot match the production rate of blast furnaces due to sticking, fusion of particles, and pellet disintegration. Another DRI process studied is directed to producing sponge iron using a rotary kiln furnace. However, the DRI-rotary kiln furnace process uses coal as the reducing agent. The process burns coal with air to obtain heat for the iron ore reduction, and because of the high nitrogen content in air, the flue gas contains a substantial amount of nitrogen that carries a lot of heat out of the reactor. That is, the DRI-rotary kiln furnace process does not provide efficiency advantages compared to the blast furnace technology. Iron reduction by hydrogen plasma has also been studied. Hydrogen plasma provides advantages thermodynamically and kinetically for reducing iron oxide compared to thermal processes utilizing hydrogen, because the plasma can generate monoatomic (H·), ionic (H+) species, and energetic rotationally- and vibrationally-excited molecular hydrogen states (H2*). The energy carried by these species is released at the reduction interface leading to localized heating. Thus, a hydrogen plasma does not require volumetric heating as is required with thermal processes, which reduces heat loss from the reactor and subsequently reduces cost. The reduction of Fe2O3 to Fe3O4 and Fe3O4 to FeO by molecular H2 are thermodynamically favorable at temperatures above 900 K (627° C.). However, the reduction of FeO to Fe with molecular H2 is thermodynamically unfavorable. All three reduction processes become favorable in a hydrogen plasma due to the presence of plasma-generated monoatomic (H·) and ionic (H+) hydrogen that can be generated at relatively low temperatures. The above described iron reduction by hydrogen plasma is not free of disadvantages. For example, ionizing hydrogen to plasma requires a lot of energy, and after the hydrogen plasma reduces iron ore, a lot of heat is released. Previous studies have not considered recovering the heat after the hydrogen plasma rea