Oxygen injection into reformer feed gas for direct reduction processes

Abstract

A direct reduction apparatus is disclosed. The direct reduction apparatus includes an oxygen injection system, a reformer, and a shaft furnace. The oxygen injection system includes an oxygen injection reactor and a main oxygen burner. The oxygen injection reactor is adapted to receive a gas mixture. The main oxygen burner is adapted to raise the temperature of the gas mixture by burning the fuel and oxygen mixture fed into the main oxygen burner. The reformer is adapted to reform the heated gas mixture. The shaft furnace is suitable for reducing iron ore using the reformed gas mixture.

Description

Technical Field

[0001] The present disclosure relates generally to direct reduction processes utilizing natural gas reformers. More specifically, the present disclosure relates to systems and methods for enhancing reformer performance by increasing the temperature of the reformer feed gas using oxygen. Background Art

[0002] Direct Reduced Iron (DRI) is a high-quality ore-based metal (OBM) raw material used in the manufacture of a wide variety of steel products. Figure 1 As shown, in the direct reduction process In the process, iron oxide is reduced to direct reduced iron with hot reducing gases such as H2 and CO in a shaft furnace 11 of a direct reduction unit 10. The top gas 1 (containing reduction products such as H2O and CO2, and reactants such as H2 and CO carried thereon) is treated by a top gas scrubber 12 to remove dust and reduce the temperature of the top gas 1, which can help control the H2O content of the top gas 1. About one-third of the scrubbed gas is discharged and directed to a reformer 17 to be used as fuel (top gas fuel) 3 for the reformer 17. The products of combustion are then sent out of the unit 10 through a flue gas chimney 14. The remainder of the scrubbed gas 2 is directed to one or more compressors 13. The compressed gas 4 is mixed with natural gas 5 before being directed to and recycled through the reformer 17.

[0003] Typically, the mixed gas 6 (mixed compressed gas 4 and natural gas 5) is preheated to about 560C using a tubular heat exchanger 15 before being directed to the reformer 17, which reduces the heat load of the reformer 17. Likewise, the combustion air supplied by the blower 16 will be preheated using the tubular heat exchanger 15.

[0004] The preheated gas mixture leaving the tubular heat exchanger 15 is referred to as feed gas 7. In the reformer 17, H2O and CO2 in the feed gas 7 will be reformed into H2 and CO using CH4 as shown in the following reaction equation, while the H2 and CO entrained in the top gas will be heated by passing through the reformer 17. The hot reformed gas 8 is directed to the shaft furnace 11, where it is used to reduce the iron oxide. Due to the volume expansion of the gas occurring during the reforming reaction, the top gas fuel 3 is discharged from the recycle gas loop 9 at the outlet of the top gas scrubber 12.

[0005] H2O+CH4→3H2+CO (endothermic reaction)

[0006] CO2+CH4→2H2+2CO (endothermic reaction)

[0007] The reformer 17, which is a tubular type reformer, comprises a catalyst packed bed inside reformer tubes through which the feed gas 7 passes, while the outside of the reformer tubes is externally heated by burners. The reformed gas 8 leaving the reformer 17 is close to equilibrium conditions and the performance of the reformer 17 is mainly limited by the heat of the feed gas 7 transferred to the reformer tubes.

[0008] The performance of the reformer 17 can be significantly enhanced by increasing the reformer box temperature or increasing the burner output. However, due to the limitations of the materials used in the construction of the reformer tubes, the box temperature has reached a limit, especially when considering the reasonable creep strength and service life of the reformer tubes. Although the performance of the reformer 17 can be enhanced by increasing the heat transfer area by increasing the number of reformer tubes and / or by increasing the diameter of the reformer tubes, such enhancement of the reformer 17 requires a large amount of capital expenditure.

[0009] Another option to increase the available heat for the reforming reaction is to further increase the temperature of the feed gas 7. However, due to the risk of coking in the use of tubular heat exchangers 15, the current temperature of 560°C of the feed gas 7 cannot be further increased much using tubular heat exchangers 15. In particular, the cracking of heavy hydrocarbons contained in the natural gas of the mixed gas 6 will cause carbon to be deposited on the alloy surface of the tubes of the tubular heat exchanger 15 at elevated temperatures. Carbon deposition or fouling has a negative impact on the heat transfer efficiency of the tubular heat exchanger 15, which may lead to excessive temperatures in the tubes. Over an extended period of time, the result of excessive temperatures may be tube failure and shortened working life of the tubular heat exchanger 15. Although heavy hydrocarbons can be removed from natural gas using a pretreatment system, the pretreatment system requires a large capital investment and will increase operating costs, such as increasing the natural gas consumption of the direct reduction unit 10.

[0010] Even if the heavy hydrocarbons are removed from the mixed gas 6 before directing the mixed gas 6 to the tubular heat exchanger 15, conventional alloy materials used for the tubes in the tubular heat exchanger 15 will only be able to withstand an increase of approximately 100° C. Due to this limitation on the amount of temperature increase of the feed gas 7 and the large capital investment required for a pretreatment system for removing heavy hydrocarbons from the natural gas in the mixed gas 6, it is difficult to justify the additional investment.

[0011] When the feed gas 7 enters the reforming tube, contacts the catalyst and is heated by the burner, the feed gas 7 is exposed to a temperature range that is favorable for the deposition of Boudouard carbon on the catalyst in the lower part of the reformer tube. This feed gas temperature range at the tube inlet is 500-700°C and is a kinetically favorable region for Boudouard carbon formation. This is an important issue because Boudouard carbon quickly causes the catalyst to be broken into fine fragments, which requires the replacement of the catalyst. In order to minimize the risk of Boudouard carbon deposition on the catalyst, an inert catalyst or a catalyst with lower reactivity is loaded at the lower region of the reformer tube to quickly raise the temperature of the feed gas 7 to a temperature range above the Boudouard reaction. However, loading an inert or less reactive catalyst reduces the reforming capacity of the reformer 17 compared to the capacity of the reformer 17 fully loaded with a high-activity catalyst. Therefore, it is desirable to raise the temperature of the feed gas 7 to a temperature range above the Boudouard reaction, such as above 700°C, to mitigate the risk of Boudouard carbon deposition and catalyst destruction. Summary of the invention

[0012] The present disclosure generally provides a direct reduction apparatus having an oxygen injection system. In particular, the oxygen injection system burns a mixture of oxygen and fuel to increase the temperature of the gas mixture before feeding the gas mixture to a reformer. The reformer reforms the gas mixture to prepare for use of the reformed gas mixture in an iron ore direct reduction process.

[0013] Typically, the oxygen injection system receives the gas mixture from a heat exchanger that preheats the gas mixture, such as by capturing heat from the flue gas. By using the oxygen injection system to further increase the temperature of the gas mixture before feeding it to the reformer, the capacity of the reformer is increased without the need to expend capital to increase the size of the reformer (such as by increasing the size and number of reformer tubes). Increasing the capacity of the reformer results in an increase in the capacity of the direct reduction unit.

[0014] In addition, the oxygen injection system can raise the temperature of the gas mixture above the Boudouard reaction temperature range, which reduces the likelihood of Boudouard carbon deposition on the catalyst in the lower portion of the reformer tubes. As a result, a more active catalyst can be used in all areas of the reformer tubes because the risk of Boudouard carbon deposits damaging the catalyst is reduced, further improving the efficiency of the reformer.

[0015] In an exemplary embodiment, the present disclosure provides a direct reduction device. The direct reduction device includes a reformer, an oxygen injection system, and a shaft furnace. The reformer is adapted to reform a gas mixture with an increased temperature. The oxygen injection system is adapted to increase the temperature of the gas mixture by burning the gas mixture with oxygen, and is adapted to discharge the gas mixture with an increased temperature to the reformer. The shaft furnace is adapted to reduce iron ore using the reformed gas mixture.

[0016] In one embodiment of the direct reduction unit, the oxygen injection system includes an oxygen injection reactor adapted to receive the gas mixture, and a main oxygen burner adapted to increase the temperature of the gas mixture by burning a mixture of fuel and oxygen fed into the main oxygen burner. Optionally, the oxygen injection system is adapted to stoichiometrically burn the oxygen and fuel to prevent unreacted oxygen from being carried into the reformer.

[0017] In another embodiment of the direct reduction device, the direct reduction device further comprises a nitrogen purge system adapted to purge oxygen remaining in the oxygen injection system during a shutdown process of the direct reduction device.

[0018] In another embodiment of the direct reduction unit, the oxygen injection system is adapted to raise the temperature of the gas mixture to at least 700°C to mitigate the risk of Boudouard carbon deposition at the reformer.

[0019] In yet another embodiment of the direct reduction plant, the direct reduction plant further comprises a flame detection system adapted to monitor a flame of the oxygen injection system.

[0020] In yet another embodiment of the direct reduction device, the direct reduction device further comprises an oxygen sensor adapted to monitor the oxygen concentration of the gas mixture after the temperature of the gas mixture is increased by the oxygen injection system.

[0021] In yet another embodiment of the direct reduction apparatus, the direct reduction apparatus further comprises a heat exchanger adapted to receive the gas mixture, heat the gas mixture, and discharge the gas mixture to the oxygen injection system.

[0022] In another exemplary embodiment, the present disclosure provides a method for a direct reduction process for direct reduction of iron. The method includes feeding a gas mixture into an oxygen injection system. The method also includes increasing the temperature of the gas mixture in the oxygen injection system by burning a mixture of fuel and oxygen. The method also includes reforming the gas mixture with increased temperature in a reformer. The method further includes using the reformed gas mixture to reduce iron ore.

[0023] In one embodiment of the method, increasing the temperature of the gas mixture in the oxygen injection system by burning a mixture of fuel and oxygen includes: receiving the gas mixture in an oxygen reactor including a main oxygen burner, and burning the mixture of fuel and oxygen fed to the main oxygen burner. Optionally, the method further includes stoichiometrically burning the oxygen and fuel to prevent unreacted oxygen from being carried into the reformer.

[0024] In another embodiment, the method further comprises: purging remaining oxygen in the oxygen injection system with nitrogen during a shutdown of the direct reduction unit.

[0025] In another embodiment of the method, increasing the temperature of the gas mixture in the oxygen injection system includes passing the gas mixture to at least 700° C. to mitigate the risk of Boudouard carbon deposition at the reformer.

[0026] In yet another embodiment, the method further comprises: monitoring a flame of the oxygen injection system.

[0027] In yet another embodiment, the method further comprises monitoring the oxygen concentration of the gas mixture after the temperature of the gas mixture is increased by the oxygen injection system.

[0028] In yet another embodiment, the method further comprises heating the gas mixture in a heat exchanger prior to feeding the gas mixture to the oxygen injection system.

[0029] In another exemplary embodiment, the present disclosure provides a direct reduction device. The direct reduction device includes a heat exchanger, a reformer, and an oxygen injection system. The heat exchanger is suitable for preheating the gas mixture. The reformer is downstream of the heat exchanger. The reformer is suitable for reforming the gas mixture in preparation for the iron ore reduction process. The oxygen injection system is located between the heat exchanger and the reformer. The oxygen injection system is suitable for receiving the gas mixture preheated by the heat exchanger and increasing the temperature of the gas mixture by burning the gas mixture with oxygen. The oxygen injection system is suitable for discharging the gas mixture with increased temperature to the reformer.

[0030] In one embodiment of the direct reduction unit, the oxygen injection system includes an oxygen injection reactor adapted to receive the gas mixture, and a main oxygen burner adapted to increase the temperature of the gas mixture by combusting a mixture of fuel and oxygen fed into the main oxygen burner.

[0031] In another embodiment of the direct reduction unit, the oxygen injection system is adapted to raise the temperature of the gas mixture to at least 700° C. by stoichiometrically combusting oxygen and fuel.

[0032] In another embodiment of the direct reduction device, the direct reduction device further comprises a monitoring system adapted to monitor at least one of a flame of the oxygen injection system and an oxygen concentration of the gas mixture after the temperature of the gas mixture is increased by the oxygen injection system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present disclosure is illustrated and described with reference to the following drawings, in which:

[0034] Figure 1 is a schematic diagram of a direct reduction unit;

[0035] Figure 2 is a schematic diagram of a direct reduction unit including an oxygen injection system;

[0036] Figure 3 yes Figure 2 a schematic diagram of an exemplary embodiment of an oxygen injection system; and

[0037] Figure 4 is a flow chart of a method for a direct reduction process of direct reduced iron. DETAILED DESCRIPTION

[0038] In various embodiments, the present disclosure relates to a direct reduction apparatus for directly reducing iron ore into direct reduced iron and a method for directly reducing iron. Furthermore, the direct reduction apparatus includes an oxygen injection system that burns a mixture of oxygen and fuel to increase the temperature of a gas mixture, which is then fed to a reformer. The reformer reforms the gas mixture at the increased temperature, which is then used in the iron ore direct reduction process.

[0039] Moreover, the oxygen injection system typically receives a gas mixture from a heat exchanger that preheats the gas mixture. The temperature of the gas mixture that is increased due to further heating improves the performance of the reformer. In particular, the thermal load of the reformer is reduced, and the reforming capacity of the reformer is increased. Increasing the capacity of the reformer results in an increased capacity of the direct reduction unit. In addition, this increase in capacity can be achieved without increasing the size of the reformer, such as by increasing the size of the reformer tubes and increasing the number of reformer tubes in the reformer, which requires a large amount of capital investment.

[0040] As noted above, the oxygen injection system can raise the temperature of the gas mixture to a temperature above the boudouard reaction temperature range fed to the reformer, which reduces the likelihood of boudouard carbon deposition on the catalyst at the lower portion of the reformer tube. This allows for further increased reformer capacity, since highly active catalysts can be used in all regions of the reformer tube. It is no longer necessary to load an inert or less reactive catalyst at the lower region of the reformer tube to quickly raise the gas temperature in the reformer tube.

[0041] The oxygen injection system further ensures that the mixed gas delivered to the reformer is not contaminated with oxygen by stoichiometrically combusting the mixture of oxygen and fuel (ie, by maintaining a stoichiometrically balanced fuel to oxygen ratio).

[0042] Figure 2 is a schematic diagram of a direct reduction unit 110 including an oxygen injection system 120. Figure 2 , the direct reduction unit 110 includes a vertical furnace 111, a gas scrubber 112, one or more gas compressors 113, a flue gas chimney 114, a heat exchanger 115, an oxygen injection system 120, and a reformer 117. In the direct reduction unit 110, the top gas 101 containing the reduction products is recycled from the vertical furnace 111 to the top gas scrubber 112. The top gas fuel 103 is delivered to the reformer 117 burner system as a fuel source. The remaining scrubbed gas 102, which is dedusted and has its temperature reduced, is directed to one or more compressors 113. The compressed gas 104 is mixed with the natural gas 105 and then directed to the heat exchanger 115, which is arranged to capture heat from the flue gas 98, which is directed from the reformer 117 to the flue gas chimney 114. In an embodiment, the heat exchanger 115 is a tubular heat exchanger.

[0043] The preheated gas mixture 107 is directed to an oxygen injection system 120 which uses oxygen to further heat the preheated gas mixture 107. The feed gas 100 exits the oxygen injection system 120 at an elevated temperature which is fed to a reformer 117. The hot reformed gas 108 is directed to a shaft furnace 111 where the hot reformed gas 108 reduces iron oxide of a feed (such as by gravity feed) passing through the shaft furnace containing the hot reformed gas 108.

[0044] The oxygen injection system 120 injects oxygen 99 into the preheated gas mixture 107 to increase its temperature, which causes the feed gas 100 to have an increased temperature compared to the preheated gas mixture 107 leaving the heat exchanger 115. Preferably, the preheated gas mixture 107 leaves the heat exchanger at a maximum of 560° C., and the oxygen injection system 120 further increases the temperature of the feed gas 100 while injecting a minimum amount of oxygen 99.

[0045] In an embodiment, the oxygen injection system 120 is adapted to inject oxygen 99 to raise the temperature of the feed gas 100 to above the temperature range of the Boudouard reaction, and in particular, above 700° C. With the temperature of the feed gas 100 raised to above the Boudouard reaction temperature range, the reformer 117 can be fully loaded with a high activity catalyst without the problem of catalyst destruction in the reformer 117 due to Boudouard carbon deposition.

[0046] In the oxygen injection system 120, the oxygen 99 injected into the preheated gas mixture 107 reacts with H2, CO and CH4 to produce combustion products such as H2O and CO2 in the resulting feed gas 100. These heated combustion products will ultimately be regulated by the outlet temperature of the top gas scrubber 112 or by the moisture content in the recycled scrubbed gas 102 and therefore do not affect the gas quality.

[0047] Due to the increase in the temperature of the feed gas 100, the capacity of the reformer 117 is increased, which allows the flow rate of the iron oxide fed through the shaft furnace 111 to be increased. The increase in the flow rate of the iron oxide through the shaft furnace 111 results in an increase in the capacity of the direct reduction unit for producing direct reduced iron. In an embodiment, the flow rate of the recycle gas with the natural gas 105, the flow rate of the feed gas 100, and the flow rate of the reformed gas 108 are all increased. Therefore, operating a 2.5MTPY direct reduction unit 110 with an oxygen injection system 120, such as a Midrex 2.5MTPY HDRI unit, increases in capacity for producing direct reduced iron by 13% when the temperature of the feed gas 100 is increased by 200°C using the oxygen injection system 120, while maintaining the heat load of the reformer 117 relative to the direct reduction unit 10 without the oxygen injection system 120. Increasing the capacity of the reformer 117 without changing the size of the reformer 117 using the oxygen injection system 120 results in reduced capital costs compared to increasing the capacity of the reformer 117 by increasing the number of reformer tubes in the reformer 117 or the diameter of the reformer tubes.

[0048] Figure 3 yes Figure 2 Schematic diagram of an exemplary embodiment of an oxygen injection system 120 of the present invention. The oxygen injection system 120 includes an oxygen injection reactor 121, a main oxygen burner 122, a mixed gas inlet 123 and a feed gas outlet 124. The main oxygen burner 122 is independent and is suitable for heating the preheated mixed gas 107 fed into the oxygen injection reactor 121 through the mixed gas inlet 123. After being heated, the feed gas 100 is led out of the oxygen injection reactor 121 through the feed gas outlet 124.

[0049] The oxygen injection system 120 also includes an oxygen feed 125 and a fuel feed 126. The oxygen feed 125 supplies oxygen 99 to the main oxygen burner 122, and the fuel feed 126 supplies fuel to the main oxygen burner 122. In some embodiments, the fuel is a mixture of natural gas and the top gas fuel 103 exhausted from the recirculating gas loop 109. In other embodiments, the fuel is natural gas. In an embodiment, the main oxygen burner 122, the oxygen feed 125, and the fuel feed 126 are adapted to stoichiometrically maintain a fuel to oxygen ratio such that all of the oxygen 99 fed to the main oxygen burner 122 is combusted in the burner flame.

[0050] By maintaining the fuel to oxygen ratio stoichiometrically, oxygen 99 is prevented from mixing into the feed gas 100, so that no unreacted oxygen is carried into the reformer 117. By ensuring that no unreacted oxygen is carried into the reformer 117, the temperature of the feed gas 100 is prevented from rapidly increasing or fluctuating due to unreacted oxygen entering the reformer tubes and reacting with the catalyst of the reformer 117. In addition, any negative effects of unreacted oxygen on the catalyst or on reforming performance are avoided.

[0051] In some embodiments, the oxygen injection system 120 includes a pilot burner (pilot burner) 127, a pilot oxygen feed 128, and a pilot fuel feed 129. In the illustrated embodiment, some of the oxygen 99 from the oxygen feed 125 and the fuel from the fuel feed 126 are transferred to the pilot burner 127, as shown by the pilot oxygen feed 128 and the pilot fuel feed 129. The temperature of the preheated gas mixture 107 after leaving the heat exchanger 115 (approximately 560° C.) may not be high enough to ensure automatic ignition of the feed gas components (such as H2, CO, and CH4) with oxygen. In order to ensure ignition of the fuel gas with oxygen 99, the pilot burner 127 is adapted to remain in operation during idle conditions of the direct reduction unit 110. With the pilot combustion maintained in operation during idle conditions of the direct reduction unit 110, the main oxygen burner 122 can be quickly and safely restarted in the feed gas atmosphere.

[0052] Furthermore, to ensure safe shutdown of the oxygen injection system 120 (including the main oxygen burner 122 and the pilot burner 127 ), the oxygen injection system 120 is adapted to introduce nitrogen to purge any oxygen remaining in the oxygen feed 125 and the oxygen injection reactor 121 .

[0053] In some embodiments, the oxygen injection system 120 further includes a monitoring system 130 to monitor any of the oxygen levels within the pilot burner 127, the main oxygen burner 122, the oxygen injection reactor 121 (e.g., at the inlet to the feed gas outlet 124), etc. In an embodiment, the monitoring system 130 is adapted to trigger an alarm upon detecting a problem with the oxygen level within the pilot burner 127, the main oxygen burner 122, the oxygen injection reactor 121, etc.

[0054] In the illustrated embodiment, the monitoring system 130 includes an oxygen sensor 131 and a flame detection system 132. The oxygen sensor 131 is adapted to monitor the oxygen concentration of the gas mixture after the temperature of the mixed gas is raised by the oxygen injection system 120. This monitoring is performed at one of the oxygen injection reactor 121 and the feed gas outlet 124. The flame detection system 132 is adapted to monitor the flames of the oxygen injection system 120, including the flames of the main oxygen injection burner 122 and the pilot burner 127.

[0055] In an embodiment, the direct reduction unit 110 includes a nitrogen injection system 140. The nitrogen injection system 140 may be a stand-alone system or integrated into the oxygen injection system 120. The nitrogen injection system 140 is adapted to purge oxygen remaining in the oxygen injection system 120 during a shutdown process of the direct reduction unit 110.

[0056] Figure 4 4 is a flow chart of a method 400 for a direct reduction process of direct reduced iron. The method 400 includes feeding a gas mixture into an oxygen injection system 120 at step 402. In an embodiment, the gas mixture includes at least one of natural gas and top gas 101. In an embodiment, the top gas 101 is washed before mixing with the natural gas. In some embodiments, the gas mixture is preheated in a heat exchanger 115. In some embodiments, the temperature of the gas mixture fed into the oxygen injection system 120 is less than 560°C.

[0057] The method also includes increasing the temperature of the gas mixture in the oxygen injection system 120 by burning a mixture of fuel and oxygen at step 404. In embodiments, the ratio of dye to oxygen is such that all of the oxygen fed to the main oxygen burner 122 is burned in the burner flame. In some embodiments, increasing the temperature of the gas mixture in the oxygen injection system 120 by burning a mixture of fuel and oxygen includes: receiving the gas mixture in an oxygen reactor 121 including the main oxygen burner 122, and burning the mixture of fuel and oxygen fed to the main oxygen burner 122. In some embodiments, the temperature is increased to a temperature above the temperature range of the Boudouard reaction. In some embodiments, the temperature is increased to a temperature above 700°C. In embodiments, the temperature is increased by at least 200C.

[0058] The method further includes reforming the gas mixture at an elevated temperature in a reformer at step 406. The method still further includes using the reformed gas mixture to reduce iron ore at step 408.

[0059] In some embodiments, the method further comprises: stoichiometrically combusting the oxygen and the fuel to prevent unreacted oxygen from being carried into the reformer. In some embodiments, the method further comprises:

[0060] In embodiments, at least some of the fuel combusted with the oxygen is exhausted from a recycle gas loop that draws top gas from the shaft furnace 111. In some embodiments, the method further comprises maintaining a pilot flame in the oxygen injection system 120 during an idle process of the direct reduction unit 110. In some embodiments, the method further comprises purging remaining oxygen in the oxygen injection system 120 with nitrogen during a shutdown process of the direct reduction unit 110.

[0061] In an embodiment, the method further comprises monitoring the oxygen injection system 120. The monitoring comprises monitoring at least one of: a flame of the oxygen injection system 120; and an oxygen concentration of the gas mixture after the temperature of the gas mixture is increased by the oxygen injection system.

[0062] Although the present disclosure has been illustrated and described herein with reference to preferred embodiments and specific examples thereof, it will be apparent to one of ordinary skill in the art that other embodiments and examples may perform similar functions and / or achieve similar results. All such equivalent embodiments and examples are within the spirit and scope of the present disclosure, are contemplated, and are intended to be covered by the appended claims.

Claims

1. A direct reduction device, comprising: a reformer adapted to reform the gas mixture at an elevated temperature; an oxygen injection system adapted to increase the temperature of the gas mixture by combusting the gas mixture with oxygen and to discharge the gas mixture at the increased temperature into the reformer, wherein the oxygen injection system is adapted to increase the temperature of the gas mixture to at least 700° C. to mitigate the risk of Boudouard carbon deposition at the reformer; a heat exchanger adapted to receive the gas mixture, heat the gas mixture, and discharge the gas mixture into the oxygen injection system, wherein the gas mixture exits the heat exchanger at a maximum of 560° C.; and A shaft furnace suitable for reducing iron ore using a reformed gas mixture.

2. The direct reduction device according to claim 1, wherein the oxygen injection system includes an oxygen injection reactor and a main oxygen burner, wherein the oxygen injection reactor is suitable for receiving the gas mixture, and the main oxygen burner is suitable for increasing the temperature of the gas mixture by burning a mixture of fuel and oxygen fed into the main oxygen burner.

3. The direct reduction device according to claim 2, wherein the oxygen injection system is adapted to cause the oxygen and the fuel to combust stoichiometrically to prevent unreacted oxygen from being carried into the reformer.

4. The direct reduction device according to claim 1, further comprising: A nitrogen purge system is adapted to purge residual oxygen in the oxygen injection system during a shutdown process of the direct reduction unit.

5. The direct reduction device according to claim 1, further comprising: A flame detection system is adapted to monitor a flame in the oxygen injection system.

6. The direct reduction device according to claim 1, further comprising: An oxygen sensor is adapted to monitor the oxygen concentration of the gas mixture after the temperature of the gas mixture is increased by the oxygen injection system.

7. A method for a direct reduction process for direct reduced iron, the method comprising: The gas mixture is heated in a heat exchanger, wherein the gas mixture leaves the heat exchanger at a maximum temperature of 560° C., and then feeding the gas mixture from the heat exchanger into an oxygen injection system; raising the temperature of the gas mixture in the oxygen injection system by combusting a mixture of fuel and oxygen, wherein raising the temperature of the gas mixture in the oxygen injection system comprises: raising the gas mixture to at least 700° C. to mitigate the risk of Boudouard carbon deposition at the reformer; reforming the gas mixture at an elevated temperature in a reformer; and The reformed gas mixture is used to reduce iron ore.

8. The method of claim 7, wherein increasing the temperature of the gas mixture in the oxygen injection system by combusting a mixture of fuel and oxygen comprises: The gas mixture is received in an oxygen reactor including a main oxygen burner therein and a mixture of fuel and oxygen fed into the main oxygen burner is combusted.

9. The method according to claim 8, further comprising: The oxygen and the fuel are combusted stoichiometrically to prevent unreacted oxygen from being carried into the reformer.

10. The method according to claim 7, further comprising: During the shutdown process of the direct reduction unit, nitrogen is used to purge the remaining oxygen in the oxygen injection system.

11. The method according to claim 7, further comprising: Monitor the flame of the oxygen injection system.

12. The method according to claim 7, further comprising: The oxygen concentration of the gas mixture is monitored after the temperature of the gas mixture is increased by the oxygen injection system.

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