Methods and systems for increasing the carbon content of direct reduced iron in a reduction furnace

Abstract

A method for producing direct reduced iron having increased carbon content, comprises delivering each of the herein-described mixed carburizing gas streams, which are of different composition, to a transition zone of a direct reduction furnace, and exposing partially or completely reduced iron oxide to the mixed carburizing gas streams to increase the carbon content of resulting direct reduced iron to greater than 4.5 wt. %.

Claims

1. A direct reduced shaft furnace comprising: a reduction zone; a transition zone separate and after the reduction zone, wherein the transition zone has multiple vertically stacked tiers, and each tier is configured to receive a separate flow of a mixed carburized gas stream, wherein the mixed carburized gas stream comprises a mixture of a carbon monoxide-rich gas stream and a hydrocarbon-rich gas stream; and a cooling zone located below the transition zone, wherein the direct reduced shaft furnace is configured to expose reduced iron partially or completely to each of the mixed carburizing gas streams and increase the carbon content of resulting direct reduced iron of the direct reduced shaft furnace to greater than about 4.5 wt. %.

2. The direct reduced shaft furnace of claim 1, wherein the transition zone comprises a plurality of tiers of equal height within the transition zone and each tier comprises an arrangement of nozzles, and wherein the furnace is configured to receive each of the mixed carburizing gas streams in a separate tier of the transition zone via the arrangement of nozzles at each tier.

3. The direct reduced shaft furnace of claim 2, wherein the nozzles at each tier are configured in a circumferential ring of equal number of nozzles located at the bottom of each tier.

4. The direct reduced shaft furnace of claim 3, wherein the circumferential ring comprises between about 16 to 28 nozzles.

5. The direct reduced shaft furnace of claim 4, wherein the nozzles are individually-valved or header-valved with no more than 4 nozzles per header.

6. The direct reduced shaft furnace of claim 1, wherein the furnace is configured to receive each of the mixed carburizing gas streams introduced into a separate tier of the transition zone in varied in composition.

7. The direct reduced furnace of claim 1, wherein each tier comprises a different mixed carburized gas stream composition.

8. The direct reduced furnace of claim 6, wherein the transition zone is increased in total height by >0.5 m to a height between 1.5 m-3.5 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is illustrated and described herein with reference to the various drawings, in which like reference numbers are used to denote like system/assembly components/method steps, as appropriate, and in which:

(2) FIG. 1 is a schematic diagram illustrating one exemplary embodiment of the direct reduction (DR) process of the present invention for increasing the carbon content of the DRI, in which coordinated carburizing gas mixtures are introduced into the direct reduction shaft furnace in an extended transition zone region via a three mixer, three-tiered circumferential gas injection system;

(3) FIG. 2 is a schematic diagram illustrating another exemplary embodiment of the direct reduction (DR) process of the present invention for increasing the carbon content of the DRI, in which coordinated carburizing gas mixtures are introduced into the direct reduction shaft furnace in an extended transition zone region via a three mixer, three preheater, three-tiered circumferential gas injection system;

(4) FIG. 3 is a schematic diagram illustrating a further exemplary embodiment of the direct reduction (DR) process of the present invention for increasing the carbon content of the DRI, in which coordinated carburizing gas mixtures are introduced into the direct reduction shaft furnace in an extended transition zone region via a two mixer, two-tiered circumferential gas injection system; and

(5) FIG. 4 is a schematic diagram illustrating another exemplary embodiment of the direct reduction (DR) process of the present invention for increasing the carbon content of the DRI, in which coordinated carburizing gas mixtures are introduced into the direct reduction shaft furnace in an extended transition zone region via a two mixer, two preheater, two-tiered circumferential gas injection system.

DETAILED DESCRIPTION OF THE INVENTION

(6) Embodiments of the invention advantageously improve upon prior methods and systems for increasing the carbon content of direct reduced iron (DRI). For example, in some prior techniques, with a single circumferential injection system located at the bottom of a transition zone where all of the carburizing gas mixture is introduced, the carburizing gas passes rapidly from the outer walls of the reactor and combines to create a single column of upflowing gas in the center of the reactor. This geometry/process which is disclosed in the afore-referenced teaching of U.S. Pat. No. 10,508,314 and now also often referred to as Adjustable Carbon Technology, ACT, while beneficial may be improved upon, especially regarding the reaction system as the gas has limited heat transfer contact area and metallic carburizing surface area. A practice in transition zone injection is the introduction of hydrocarbon gas through a minimum number (?8) of nozzles grouped in pairs, located 90? apart. These nozzles supply gas that actually contacts a very small portion of the total area of the zone. This may result in some localized over cooling which may inhibit the kinetics of the carburizing reactions within this injection stream.

(7) It has been herein determined that it is not practical operationally to merely increase the number of nozzles on the periphery. The transition zone gases are introduced into the DR reactor through tuyeres penetrating the refractory wall of the reactor. These tuyeres are in contact with or exposed to thermal radiation from the burden itself which is about 700-860? C. The system is limited on how much total gas flow can be injected into the reactor by the requirement to maintain the majority of the thermal energy already present within the burden. Merely, increasing the number of nozzles on the periphery to increase contact area would necessitate one of two adjustments, neither of which is practical. The first is to increase the number of nozzles at the same size. This would create a significant drop in mass velocity within each nozzle thereby causing the nozzle to run hotter. Hotter nozzle tips result in premature activation of the carburizing reactions within the nozzle resulting in plugging of the nozzle. Secondly, increasing the number of nozzles and reducing their diameter to maintain adequate cooling velocity within the nozzle results in nozzle diameters that are too small and plug with metallized iron fines whenever the nozzles are not required to be in service and the reactor is in operation.

(8) Thus, embodiments of the present invention advantageously improve upon prior methods and practices of carburizing DRI, especially in HDRI or HBI plants. The challenges as put forth previously are focused on the adequate use of the heat available within the transition zone, which is a nearly adiabatic system. Only the heat losses through the walls of the shaft furnace keep it from being entirely adiabatic and these heat losses are relatively insignificant as they fall into the <1% range of the thermal energy in the transition zone.

(9) This previous practice, while beneficial, may only go so far in the optimization and utilization of the carburizing potential within the transition zone. Embodiments of the invention advantageously provide for even more carburizing potential by increasing the potential gas flows that can be handled within the transition zone, as well as increasing both gas-to-solid contact area at more elevated temperature and the gas chemistry profile for enhanced DRI carburization.

(10) For example, and as further explained below, embodiments of the invention advantageously provide a lengthened/extended transition zone >about 0.5 m longer length of furnace below bustle; the transition zone, which typically ranges from 1.0 m-3.0 m in height will be increased by more than 0.5 m in height to provide the additional volume needed to support the multi-tiered gas injection system to enhance carburization. The CO-rich gas from the ACT unit is routed to at least two or three tiers of gas mixers. Thus, the afore-referenced Adjustable Carbon Technology (ACT), a process that creates a CO-rich stream and mixes it with, e.g., natural gas, is improved in part to employ multiple injection points into the extended transition zone, according to embodiments. The afore-referenced mixers are ratio controlled to provide a coordinated mixing ratio of the CO-rich gas and a hydrocarbon gas. Each tier has an optimized gas mixture ratio. The upper tier is more hydrocarbon rich since the temperature profile is hotter there and hydrocarbon cracking is promoted more in the higher temperature regime, about 800-850? ? C. The lower tier is a much more CO-rich gas mixture as the exothermic nature of the CO carburizing reactions make them more favored at the lower temperature regime, about 700-750? C. The center tier is optimized to a ratio more balanced between CO reactions and cracking reactions as it operates in a temperature zone between the other two, about 750-800? C. The tiered gas injection system with independent mixers allows for the profiled application of the gas chemistry to match the temperature profile.

(11) Moreover, according to embodiments, each tier of gas injection is then made up of a full circumferential set of nozzles (optimally, 16-28 nozzles per tier) that penetrate through the shaft furnace wall to introduce the gas into the transition zone. Each ring of nozzles is located at the bottom of the segment of the transition zone that it serves. The countercurrent nature of the operation of the shaft furnace makes this the optimal location for each ring of nozzles for each tier of reactions. The nozzles on each ring are valved individually or via subheaders serving no more than 4 nozzles per header. This allows the gas injected at any level to be selectively introduced at a specified sector on the circumference of the transition zone or to the entire circumference if that is desired. Selectively adding the gases at specified sectors of the transition zone can provide additional temperature profile control for the reactions, as well as finer control of the discharge temperature from the transition zone to meet the operating target for the plant.

(12) Thus, according to embodiments, a method for producing direct reduced iron using a unique and coordinated arrangement of CO-rich and hydrocarbon-rich gas streams with specified gas compositions and temperature profiles to produce the direct reduced iron with a carbon content of >4.5% wt. is realized. For example, according to embodiments, using an extended transition zone and a multi-tiered, carburizing gas injection system, the reaction conditions along the length of the transition zone can be controlled to optimize the carburizing reactions desired. Each of the tiers can have a circumferential, independently or subheader-valved nozzle arrangement to further optimize the contact area and temperature profile of the transition zone. Such methods and systems provides a three dimensional control scheme designed to provide flexibility in operation and optimization, according to embodiments.

(13) Accordingly, an objective of embodiments of the invention to control the gas and temperature profile to enhance the carburization potential while not violating the minimum discharge temperature requirements inherent in the HDRI and HBI DR plants is advantageously achieved.

(14) Referring now specifically to FIG. 1, in one exemplary embodiment, the process 20 of the present invention includes the syngas or reformed gas stream 1 passing through an ACT unit C for the purpose of separating the CO from the rest of the syngas/reformed gas. It is noted that reformed gas stream 1 is derived from a reformer unit (not shown) of any design, such as a catalytic reformer (e.g., tubular reformer), a non-catalytic reformer (e.g., a partial oxidation reactor) or even a combination reformer (e.g., an auto-thermal reformer or a two-stage reformer), or any other reducing gas generating unit capable of producing a CO-containing gas with a relatively high CO/CO.sub.2 ratio) to close to ambient temperature. An optional cooler/chiller (not shown) may also be employed, as further described below. Preferably, the reformed gas stream 1 contains at least 20.0 mol % CO.

(15) As further shown in FIG. 1, the reformed gas stream 1 enters ACT unit C. As noted above, Adjustable Carbon Technology (ACT) geometry/processing is disclosed in afore-referenced U.S. Pat. No. 10,508,314, the contents of which are herein incorporated by reference, and embodiments of the invention improve upon this technology, as described herein. Accordingly, features of the ACT unit C will be briefly described below. In general, ACT unit C may employ the afore-referenced cooler/chiller. The cooler/chiller can utilize direct contact cooling, indirect contact cooling, refrigeration cooling, etc. During cooling, reformed gas can lose some of its water content, which in turn improves the carburization potential of the reformed gas. The cool/dry reformed gas optional flows through a compressor that can boost its pressure (to, e.g., 15 barg), as most separation/adsorption methods work best at higher pressures. During compression, the gas loses even more water, resulting in even further improved carburization potential. The compressed gas, after optional temperature adjustment, flows into a system of membrane modules for CO recovery. Any other kind of CO recovery unit/mechanism can also be employed, such as PSA/VPSA/TSA, refrigeration, etc.

(16) The H.sub.2-rich stream 13 (rejected gas from CO recovery unit of ACT unit C) can be sent back as, e.g., recycle to be used elsewhere in the process loop such as used in different portions of the DR plant as fuel, cooling gas, syngas, or process gas, or it can be exported to another facility.

(17) The CO-rich stream 2 exiting ACT unit C passes to a junction 15 that splits the flow into a first CO-rich stream 7, a second CO-rich stream 8 and a third CO-rich stream 9 and enters three separate gas mixers, a first gas mixer D, a second gas mixer E and a third gas mixer F, respectively, as shown in FIG. 1, and further described below.

(18) The high hydrocarbon gas (hydrocarbon-rich gas, e.g., natural gas) is introduced through hydrocarbon-rich gas stream 3 which is split into three independently controlled streams, a first hydrocarbon-rich gas stream 4, a second hydrocarbon-rich gas stream 5 and a third hydrocarbon-rich gas stream 6, going also into the gas mixers, D, E and F, respectively, as shown in FIG. 1.

(19) It is further noted that, optionally, if the hydrocarbon-rich gas stream 3 is wet, one or more dehumidification units (not shown) can be used to make the gas dry for suppressing decarburization reactions. Optionally, if the hydrocarbon-rich stream 3 includes a significant amount of sulfur compounds, a desulfurization unit (not shown) can be used to decrease and control the amount of total sulfur to, e.g., below 100 ppm.

(20) The first hydrocarbon-rich gas stream 4, second hydrocarbon-rich gas stream 5 and third hydrocarbon-rich gas stream 6 are blended with the first CO-rich stream 7, the second CO-rich stream 8 and the third CO-rich stream 9, respectively, before being introduced to the DR furnace A.

(21) The resultant mixed carburizing gas streams, each with a coordinated composition based on the ratio control of the gas mixer steps, exit gas mixers D, E, and F as a first mixed carburizing gas stream 12, a second mixed carburizing gas stream 11 and a third mixed carburizing gas stream 10, respectively.

(22) As further shown in FIG. 1, the first mixed carburizing gas stream 12, second mixed carburizing gas stream 11 and third mixed carburizing gas stream 10 are then introduced into transition zone B of furnace A through a circumferential set of nozzles located at the bottom of each tier of the transition zone B comprising, a first tier, a second tier and a third tier, tiers B-1, B-2 and B-3, respectively, as shown in FIG. 1. The nozzles are each individually valved or valved in a subheader arrangement grouping preferably no more than 4 nozzles on each subheader. This provides the chemistry and thermal profile control that enables the carburizing potential of the transition zone B to be increased from maximum of 3.5 wt % carbon in the DRI with conventional ACT teachings to >4.5 wt. % carbon in the DRI. More particularly, according to embodiments, each tier of gas injection is made up of a full circumferential set (ring) of nozzles 30, 32, 34, respectively (optimally, 16-28 nozzles per tier) that penetrate through the shaft furnace wall to introduce the gas into the transition zone B. Each ring of nozzles 30, 32, 34 is located at the bottom of the segment of the transition zone B that it serves. The countercurrent nature of the operation of the shaft furnace A makes this the optimal location for each ring of nozzles 30, 32, 34 for each tier of reactions. The nozzles on each ring are valved individually or via subheaders serving no more than 4 nozzles per header. This allows the gas injected at any level to be selectively introduced at a specified sector on the circumference of the transition zone B or to the entire circumference if that is desired. Selectively adding the gases at specified sectors of the transition zone B can provide additional temperature profile control for the reactions, as well as finer control of the discharge temperature from the transition zone B to meet the operating target for the plant.

(23) Referring now to FIG. 2, in another exemplary embodiment the process 22 of the present invention includes the syngas or reformed gas stream 1 passing through an ACT unit C for the purpose of separating the CO from the rest of the syngas/reformed gas. It is noted that reformed gas stream 1 is derived from a reformer unit (not shown) of any design, such as a catalytic reformer (e.g., tubular reformer), a non-catalytic reformer (e.g., a partial oxidation reactor) or even a combination reformer (e.g., an auto-thermal reformer or a two-stage reformer), or any other reducing gas generating unit capable of producing a CO-containing gas with a relatively high CO/CO.sub.2 ratio) to close to ambient temperature. An optional cooler/chiller (not shown) may also be employed, as further described below. Preferably, the reformed gas stream 1 contains at least 20.0 mol % CO.

(24) As further shown in FIG. 2, the reformed gas stream 1 enters ACT unit C. As noted above, Adjustable Carbon Technology (ACT) geometry/processing is disclosed in afore-referenced U.S. Pat. No. 10,508,314, and embodiments of the invention improve upon this technology, as described herein. Accordingly, features of the ACT unit C will be briefly described below. In general, ACT unit C may employ the afore-referenced cooler/chiller. The cooler/chiller can utilize direct contact cooling, indirect contact cooling, refrigeration cooling, etc. During cooling, reformed gas can lose some of its water content, which in turn improves the carburization potential of the reformed gas. The cool/dry reformed gas optional flows through a compressor that can boost its pressure (to, e.g., 15 barg), as most separation/adsorption methods work best at higher pressures. During compression, the gas loses even more water, resulting in even further improved carburization potential. The compressed gas, after optional temperature adjustment, flows into a system of membrane modules for CO recovery. Any other kind of CO recovery unit/mechanism can also be employed, such as PSA/VPSA/TSA, refrigeration, etc.

(25) The H.sub.2-rich stream 13 (rejected gas from CO recovery unit of ACT unit C) can be sent back as, e.g., recycle to be used elsewhere in the process loop such as used in different portions of the DR plant as fuel, cooling gas, syngas, or process gas, or it can be exported to another facility.

(26) The CO-rich stream 2 exiting ACT unit C passes to a junction 15 that splits the flow into a first CO-rich stream 7, a second CO-rich stream 8 and a third CO-rich stream 9 and enters three separate gas mixers, a first gas mixer D, a second gas mixer E and a third gas mixer F, respectively, as shown in FIG. 2, and further described below.

(27) The high hydrocarbon gas (hydrocarbon-rich gas, e.g., natural gas) is introduced through hydrocarbon-rich gas stream 3 which is split into three independently controlled streams, a first hydrocarbon-rich gas stream 4, a second hydrocarbon-rich gas stream 5 and a third hydrocarbon-rich gas stream 6, going also into the gas mixers, D, E and F, respectively, as shown in FIG. 2.

(28) It is further noted that, optionally, if the hydrocarbon-rich gas stream 3 is wet, one or more dehumidification units (not shown) can be used to make the gas dry for suppressing decarburization reactions. Optionally, if the hydrocarbon-rich stream 3 includes a significant amount of sulfur compounds, a desulfurization unit (not shown) can be used to decrease and control the amount of total sulfur to, e.g., below 100 ppm.

(29) The first hydrocarbon-rich gas stream 4, second hydrocarbon-rich gas stream 5 and third hydrocarbon-rich gas stream 6 are blended with the first CO-rich stream 7, the second CO-rich stream 8 and the third CO-rich stream 9, respectively, before being introduced to the DR furnace A.

(30) The resultant mixed carburizing gas streams, each with a coordinated composition based on the ratio control of the gas mixer steps, exit gas mixers D, E, and F as a first mixed carburizing gas stream 12, a second mixed carburizing gas stream 11 and a third mixed carburizing gas stream 10, respectively.

(31) As further shown in FIG. 2, the first mixed carburizing gas stream 12, second mixed carburizing gas stream 11 and third mixed carburizing gas stream 10 are then introduced into transition zone B of furnace A through a circumferential set of nozzles located at the bottom of each tier of the transition zone B comprising, a first tier, a second tier and a third tier, tiers B-1, B-2 and B-3, respectively, as shown in FIG. 2. The nozzles are each individually valved or valved in a subheader arrangement grouping preferably no more than 4 nozzles on each subheader. This provides the chemistry and thermal profile control that enables the carburizing potential of the transition zone B to be increased from maximum of 3.5 wt % carbon in the DRI with conventional ACT teachings to >4.5 wt. % carbon in the DRI. More particularly, according to embodiments, each tier of gas injection is made up of a full circumferential set (ring) of nozzles 30, 32, 34, respectively (optimally, 16-28 nozzles per tier) that penetrate through the shaft furnace wall to introduce the gas into the transition zone B. Each ring of nozzles 30, 32, 34 is located at the bottom of the segment of the transition zone B that it serves. The countercurrent nature of the operation of the shaft furnace A makes this the optimal location for each ring of nozzles 30, 32, 34 for each tier of reactions. The nozzles on each ring are valved individually or via subheaders serving no more than 4 nozzles per header. This allows the gas injected at any level to be selectively introduced at a specified sector on the circumference of the transition zone B or to the entire circumference if that is desired. Selectively adding the gases at specified sectors of the transition zone B can provide additional temperature profile control for the reactions, as well as finer control of the discharge temperature from the transition zone B to meet the operating target for the plant.

(32) Advantageously, in this exemplary embodiment and as further shown in FIG. 2, the temperature profile control for the transition zone B is enhanced further by passing each of the carburizing gas mixtures, i.e., the first mixed carburizing gas stream 12, second mixed carburizing gas stream 11 and third mixed carburizing gas stream 10 through independently controlled preheaters, e.g., a first preheater G, a second preheater H and a third preheater I, respectively, as shown in FIG. 2 to preheat to suitable and desired temperatures as needed. This provides the flexibility of adding the suitable temperature gas to the appropriate tier within the carburizing gas injection system.

(33) Referring now to FIG. 3, in a further exemplary embodiment, the process 24 of the present invention includes the syngas or reformed gas stream 1 passing through an ACT unit C for the purpose of separating the CO from the rest of the syngas/reformed gas. It is noted that reformed gas stream 1 is derived from a reformer unit (not shown) of any design, such as a catalytic reformer (e.g., tubular reformer), a non-catalytic reformer (e.g., a partial oxidation reactor) or even a combination reformer (e.g., an auto-thermal reformer or a two-stage reformer), or any other reducing gas generating unit capable of producing a CO-containing gas with a relatively high CO/CO.sub.2 ratio) to close to ambient temperature. An optional cooler/chiller (not shown) may also be employed, as further described below. Preferably, the reformed gas stream 1 contains at least 20.0 mol % CO.

(34) As further shown in FIG. 3, the reformed gas stream 1 enters ACT unit C. As noted above, Adjustable Carbon Technology (ACT) geometry/processing is disclosed in afore-referenced U.S. Pat. No. 10,508,314, and embodiments of the invention improve upon this technology, as described herein. Accordingly, features of the ACT unit C will be briefly described below. In general, ACT unit C may employ the afore-referenced cooler/chiller. The cooler/chiller can utilize direct contact cooling, indirect contact cooling, refrigeration cooling, etc. During cooling, reformed gas can lose some of its water content, which in turn improves the carburization potential of the reformed gas. The cool/dry reformed gas optional flows through a compressor that can boost its pressure (to, e.g., 15 barg), as most separation/adsorption methods work best at higher pressures. During compression, the gas loses even more water, resulting in even further improved carburization potential. The compressed gas, after optional temperature adjustment, flows into a system of membrane modules for CO recovery. Any other kind of CO recovery unit/mechanism can also be employed, such as PSA/VPSA/TSA, refrigeration, etc.

(35) The H.sub.2-rich stream 13 (rejected gas from CO recovery unit of ACT unit C) can be sent back as, e.g., recycle to be used elsewhere in the process loop such as used in different portions of the DR plant as fuel, cooling gas, syngas, or process gas, or it can be exported to another facility.

(36) The CO-rich stream 2 exiting ACT unit C passes to a junction 15 that splits the flow into first CO-rich stream 7 and third CO-rich stream 9 and enters two separate gas mixers, first gas mixer D and third gas mixer F, respectively, as shown in FIG. 3, and further described below.

(37) The high hydrocarbon gas (hydrocarbon-rich gas, e.g., natural gas) is introduced through hydrocarbon-rich gas stream 3 which is split into two independently controlled streams, first hydrocarbon-rich gas stream 4 and third hydrocarbon-rich gas stream 6, going also into the gas mixers, D and F, respectively, as shown in FIG. 3.

(38) It is further noted that, optionally, if the hydrocarbon-rich gas stream 3 is wet, one or more dehumidification units (not shown) can be used to make the gas dry for suppressing decarburization reactions. Optionally, if the hydrocarbon-rich stream 3 includes a significant amount of sulfur compounds, a desulfurization unit (not shown) can be used to decrease and control the amount of total sulfur to, e.g., below 100 ppm.

(39) The first hydrocarbon-rich gas stream 4 and third hydrocarbon-rich gas stream 6 are blended with the first CO-rich stream 7 and third CO-rich stream 9, respectively, before being introduced to the DR furnace A.

(40) The resultant mixed carburizing gas streams, each with a coordinated composition based on the ratio control of the gas mixer steps, exit gas mixers D and F as a first mixed carburizing gas stream 12 and third mixed carburizing gas stream 10, respectively.

(41) As further shown in FIG. 3, the first mixed carburizing gas stream 12 and third mixed carburizing gas stream 10 are then introduced into transition zone B of furnace A through a circumferential set of nozzles located at the bottom of each tier of the transition zone B comprising two tiers, tiers B-1 and B-2, respectively, as shown in FIG. 3. The nozzles are each individually valved or valved in a subheader arrangement grouping preferably no more than 4 nozzles on each subheader. This provides the chemistry and thermal profile control that enables the carburizing potential of the transition zone B to be increased from maximum of 3.5 wt % carbon in the DRI with conventional ACT teachings to >4.5 wt. % carbon in the DRI. More particularly, according to embodiments, each tier of gas injection is made up of a full circumferential set (ring) of nozzles 30, 34, respectively (optimally, 16-28 nozzles per tier) that penetrate through the shaft furnace wall to introduce the gas into the transition zone B. Each ring of nozzles 30, 34 is located at the bottom of the segment of the transition zone B that it serves. The countercurrent nature of the operation of the shaft furnace A makes this the optimal location for each ring of nozzles 30, 34 for each tier of reactions. The nozzles on each ring are valved individually or via subheaders serving no more than 4 nozzles per header. This allows the gas injected at any level to be selectively introduced at a specified sector on the circumference of the transition zone B or to the entire circumference if that is desired. Selectively adding the gases at specified sectors of the transition zone B can provide additional temperature profile control for the reactions, as well as finer control of the discharge temperature from the transition zone B to meet the operating target for the plant.

(42) Referring now to FIG. 4, in a still further exemplary embodiment, the process 26 of the present invention includes the syngas or reformed gas stream 1 passing through an ACT unit C for the purpose of separating the CO from the rest of the syngas/reformed gas. It is noted that reformed gas stream 1 is derived from a reformer unit (not shown) of any design, such as a catalytic reformer (e.g., tubular reformer), a non-catalytic reformer (e.g., a partial oxidation reactor) or even a combination reformer (e.g., an auto-thermal reformer or a two-stage reformer), or any other reducing gas generating unit capable of producing a CO-containing gas with a relatively high CO/CO.sub.2 ratio) to close to ambient temperature. An optional cooler/chiller (not shown) may also be employed, as further described below. Preferably, the reformed gas stream 1 contains at least 20.0 mol % CO.

(43) As further shown in FIG. 4, the reformed gas stream 1 enters ACT unit C. As noted above, Adjustable Carbon Technology (ACT) geometry/processing is disclosed in afore-referenced U.S. Pat. No. 10,508,314, and embodiments of the invention improve upon this technology, as described herein. Accordingly, features of the ACT unit C will be briefly described below. In general, ACT unit C may employ the afore-referenced cooler/chiller. The cooler/chiller can utilize direct contact cooling, indirect contact cooling, refrigeration cooling, etc. During cooling, reformed gas can lose some of its water content, which in turn improves the carburization potential of the reformed gas. The cool/dry reformed gas optional flows through a compressor that can boost its pressure (to, e.g., 15 barg), as most separation/adsorption methods work best at higher pressures. During compression, the gas loses even more water, resulting in even further improved carburization potential. The compressed gas, after optional temperature adjustment, flows into a system of membrane modules for CO recovery. Any other kind of CO recovery unit/mechanism can also be employed, such as PSA/VPSA/TSA, refrigeration, etc.

(44) The H.sub.2-rich stream 13 (rejected gas from CO recovery unit of ACT unit C) can be sent back as, e.g., recycle to be used elsewhere in the process loop such as used in different portions of the DR plant as fuel, cooling gas, syngas, or process gas, or it can be exported to another facility.

(45) The CO-rich stream 2 exiting ACT unit C passes to a junction 15 that splits the flow into first CO-rich stream 7 and third CO-rich stream 9 and enters two separate gas mixers, first gas mixer D and third gas mixer F, respectively, as shown in FIG. 4, and further described below.

(46) The high hydrocarbon gas (hydrocarbon-rich gas, e.g., natural gas) is introduced through hydrocarbon-rich gas stream 3 which is split into two independently controlled streams, first hydrocarbon-rich gas stream 4 and third hydrocarbon-rich gas stream 6, going also into the gas mixers, D and F, respectively, as shown in FIG. 4.

(47) It is further noted that, optionally, if the hydrocarbon-rich gas stream 3 is wet, one or more dehumidification units (not shown) can be used to make the gas dry for suppressing decarburization reactions. Optionally, if the hydrocarbon-rich stream 3 includes a significant amount of sulfur compounds, a desulfurization unit (not shown) can be used to decrease and control the amount of total sulfur to, e.g., below 100 ppm.

(48) The first hydrocarbon-rich gas stream 4 and third hydrocarbon-rich gas stream 6 are blended with the first CO-rich stream 7 and third CO-rich stream 9, respectively, before being introduced to the DR furnace A.

(49) The resultant mixed carburizing gas streams, each with a coordinated composition based on the ratio control of the gas mixer steps, exit gas mixers D and F as a first mixed carburizing gas stream 12 and third mixed carburizing gas stream 10, respectively.

(50) As further shown in FIG. 4, the first mixed carburizing gas stream 12 and third mixed carburizing gas stream 10 are then introduced into transition zone B of furnace A through a circumferential set (ring) of nozzles located at the bottom of each tier of the transition zone B comprising two tiers, tiers B-1 and B-2, respectively, as shown in FIG. 4. The nozzles are each individually valved or valved in a subheader arrangement grouping preferably no more than 4 nozzles on each subheader. This provides the chemistry and thermal profile control that enables the carburizing potential of the transition zone B to be increased from maximum of 3.5 wt % carbon in the DRI with conventional ACT teachings to >4.5 wt. % carbon in the DRI. More particularly, according to embodiments, each tier of gas injection is made up of a full circumferential set of nozzles 30, 34, respectively (optimally, 16-28 nozzles per tier) that penetrate through the shaft furnace wall to introduce the gas into the transition zone B. Each ring of nozzles 30, 34 is located at the bottom of the segment of the transition zone B that it serves. The countercurrent nature of the operation of the shaft furnace A makes this the optimal location for each ring of nozzles 30, 34 for each tier of reactions. The nozzles on each ring are valved individually or via subheaders serving no more than 4 nozzles per header. This allows the gas injected at any level to be selectively introduced at a specified sector on the circumference of the transition zone B or to the entire circumference if that is desired. Selectively adding the gases at specified sectors of the transition zone B can provide additional temperature profile control for the reactions, as well as finer control of the discharge temperature from the transition zone B to meet the operating target for the plant.

(51) Advantageously, in this exemplary embodiment and as further shown in FIG. 4, the temperature profile control for the transition zone B is enhanced further by passing each of the carburizing gas mixtures, i.e., the first mixed carburizing gas stream 12 and the third mixed carburizing gas stream 10 through independently controlled preheaters, e.g., first preheater G and third preheater I, respectively, as shown in FIG. 4 to preheat to suitable and desired temperatures as needed. This provides the flexibility of adding the suitable temperature gas to the appropriate tier within the carburizing gas injection system.

(52) Advantageously, as shown in each of FIGS. 1-4, iron oxide enters the top of furnace A. Partially or completed reduced iron oxide may thus be exposed to the afore-described CO-rich and hydrocarbon-rich streams, according to embodiments.

(53) As further advantageously shown in each of FIGS. 1-4, primary reduction zone/bustle area 36, where most reduction takes place, is shown in furnace A above transition zone B. Transition zone B extends from the bottom of the primary reduction zone/bustle area 36 to the top of the cooling zone 38 including tiers stacked vertically, as further shown in FIGS. 1-4, and is where the mixed gases and received and further reduction takes place. Transition zone B advantageously forms an extended transition zone (extended length below the bustle area) in the furnace, as further explained above. It is noted that no mixed gases are received in cooling zone 38, according to embodiments. It is further noted that, in general, the partially or completely reduced iron oxide in the transition zone B and/or the cooling zone 38 contains 0.0 wt. % to 3.0 wt. % combined carbon before, however, employing the afore-described vertically stacked, multiple tiered transition zone B, as shown in FIGS. 1-4, carbon content in the resultant DRI of greater than about 4.5 wt. % can advantageously achieved.

(54) Although the present invention is illustrated and described herein with reference to particular and preferred embodiments, and specific examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples may perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the present invention, are contemplated thereby, and are intended to be covered by the following non-limiting claims. Moreover, all features, elements and embodiments described herein may be used in any combinations.