METHOD FOR OPERATING A METALLURGIC PLANT FOR PRODUCING IRON PRODUCTS

Abstract

A method of operating a metallurgic plant for producing iron products includes the following steps, wherein the metallurgic plant includes a direct reduction plant and an ironmaking plant, the metallurgic plant: feeding an iron ore charge into the direct reduction plant to produce direct reduced iron products, operating the ironmaking plant to produce pig iron, wherein biochar is introduced into the ironmaking plant as reducing agent, and whereby the ironmaking plant generates offgas containing CO and CO2, and treating offgas from the ironmaking plant in a hydrogen enrichment unit to form a hydrogen-rich stream and a CO2-rich stream. The hydrogen-rich stream is fed directly or indirectly to the direct reduction plant. The CO2-rich stream is converted to be valorized in the direct reduction plant.

A corresponding metallurgic plant is also related.

Claims

1. A method of operating a metallurgic plant for producing iron products, the metallurgic plant including a direct reduction plant and an ironmaking plant, said method including the following steps: feeding an iron ore charge into the direct reduction plant to produce direct reduced iron products, operating the ironmaking plant to produce pig iron, wherein biochar is introduced into the ironmaking plant as reducing agent, and whereby the ironmaking plant generates offgas containing CO and CO.sub.2, and treating offgas from the ironmaking plant in a hydrogen enrichment unit to form a hydrogen-rich stream and a CO.sub.2-rich stream, wherein the hydrogen-rich stream is fed directly or indirectly to the direct reduction plant.

2. The method according to claim 1, wherein the CO.sub.2-rich stream is converted, at least in part, to be valorized in the direct reduction plant, to syngas or natural gas.

3. The method according to claim 1, wherein dusts, fines, and other residues from the direct reduction plant are fed to the ironmaking plant as part of the charge to be melted therein.

4. The method according to claim 1, wherein at least part of the direct reduced products from the direct reduction implant are fed to the ironmaking plant and/or steelmaking plant as part of the charge to be melted therein, the direct reduced products including sponge iron and/or lumpy direct reduced products.

5. The method according to claim 1, wherein the hydrogen-rich stream is delivered to the direct reduction plant as part of a reducing gas stream.

6. The method according to claim 1, wherein the hydrogen-rich stream is delivered to the direct reduction plant as part of a fuel gas stream for heating purposes.

7. The method according to claim 5, wherein the CO.sub.2-rich stream is fed to a water electrolysis unit, further supplied with a steam stream, to form a syngas stream that is delivered to the direct reduction plant.

8. The method according to claim 1, wherein the hydrogen-rich stream and the CO.sub.2-rich stream are forwarded from the hydrogen enrichment unit to a methanation unit to form a methane stream that is forwarded to the direct reduction plant.

9. The method according to claim 8, wherein at least part of the methane stream is used in the direct reduction plant as part of a reducing gas stream.

10. The method according to claim 8, wherein the direct reduction plant comprises a shaft furnace and a reforming reactor, and wherein at least part of the methane stream is fed to the reforming reactor to generate a reducing gas, mainly hydrogen and carbon monoxide, forwarded to the shaft furnace to be used as part of a reducing gas stream.

11. The method according to claim 8, wherein at least part of the methane stream is used as part of a fuel gas stream.

12. The method according to claim 8, wherein a water electrolysis unit is associated with the methanation unit, a steam stream output from the methanation unit being fed to the electrolysis unit to form an auxiliary hydrogen stream that is fed back to the methanation unit.

13. The method according to claim 12, wherein a steam stream from a green energy is introduced into the water electrolysis unit; or wherein part of the offgas from the direct reduction plant is recycled towards the methanation unit, through a steam removal unit, the removed steam being fed to the water electrolysis unit.

14. (canceled)

15. The method according to claim 13, wherein the operation of the ironmaking plant is adjusted based on the amount of recycled offgas; or wherein the operation of the ironmaking plant is reduced or shut-off after reaching a steady state operation in the direct reduction plant.

16. (canceled)

17. The method according to claim 1, wherein the offgas stream from the ironmaking plant is treated in a nitrogen rejection unit before being forwarded to the hydrogen enrichment unit.

18. The method according to claim 1, wherein the hydrogen enrichment unit comprises a water-gas shift reactor.

19. The method according to claim 1, wherein a charge of said ironmaking plant comprises iron ore fines; and/or wherein steam from a green energy is introduced into the hydrogen enrichment unit and/or wherein at least part of the offgas from the direct reduction plant is released to the atmosphere.

20. (canceled)

21. (canceled)

22. The method according to claim 1, wherein the biochar is produced in a biomass pyrolysis unit from biomass material.

23. The method according to claim 1, wherein a portion of CO.sub.2 removed in said direct reduction plant is forwarded to a water electrolysis unit, mixed with steam, to produce a syngas; and/or wherein the direct reduction plant is equipped with heat recovery systems generating steam.

24. (canceled)

25. A metallurgic plant for producing iron products, comprising: a direct reduction plant configured for producing direct reduced products from an iron ore charge; a biomass pyrolysis unit configured for generating biochar from biomass material; a ironmaking plant configured to produce pig iron, said ironmaking plant using said biochar as reducing material and generating offgas; and a hydrogen enrichment unit configured to receive the ironmaking plant offgas and form a hydrogen-rich stream and a CO2-rich stream; wherein the hydrogen-rich stream is valorized directly or indirectly in the direct reduction plant.

26. The metallurgic plant according to claim 25, comprising means to convert CO.sub.2 into a gas stream that is valorized in the direct reduction plant.

27. The metallurgic plant according to claim 26, comprising a methanation plant configured to receive the hydrogen-rich stream and a CO2-rich stream from the hydrogen enrichment unit and generate a biogas stream therefrom, a methane stream, that is forwarded to the direct reduction plant.

28. The metallurgic plant according to claim 27, comprising a water electrolysis unit associated with the methanation unit, a steam stream output from the methanation unit being fed to the electrolysis unit to form an auxiliary hydrogen stream that is fed back to the methanation unit.

29. The metallurgic plant according to claim 26, comprising a water electrolysis unit associated with the hydrogen enrichment unit, the water electrolysis unit being configured to receive the CO.sub.2-rich stream as well as a steam stream, and to form a syngas stream that is delivered to the direct reduction plant.

30. The metallurgic plant according to claim 25, wherein the direct reduction plant includes a shaft furnace, a reformer and heat recovery systems; and/or wherein the direct reduction plant includes a shaft furnace, a heater and a CO.sub.2 removal unit; and/or wherein the hydrogen enrichment unit comprises a water-gas shift reactor.

31. (canceled)

32. (canceled)

33. The metallurgic plant according to claim 25, wherein a nitrogen rejection unit is arranged on the flow of offgas from the ironmaking plant to hydrogen enrichment unit, or on the flow of the outlet of hydrogen enrichment plant.

34. The metallurgic plant according to claim 25, wherein the hydrogen enrichment unit is directly connected with the direct reduction plant to deliver at least part of the hydrogen-rich stream; and/or comprising means to forward dusts, fines, and other residues from the direct reduction plant to the ironmaking plant as part of the charge to be molten therein.

35. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Further details and advantages of the present disclosure will be apparent from the following detailed description of not limiting embodiments with reference to the attached drawings, wherein FIGS. 1 to 4 are diagrams illustrating four different embodiments of metallurgical plants implementing the present method.

[0060] In the Figures, unless otherwise indicated, same or similar elements are designated by same reference signs.

DETAILED DESCRIPTION OF THE DRAWINGS

[0061] FIG. 1 shows a first diagram of a plant 10 for implementing the present method. The two main components of the plant 10 are a direct reduction plant 12 and an ironmaking plant 14. Plant 10 further includes a biomass pyrolysis unit 16 that produces biochar used in the ironmaking plant 14 as reducing agent.

[0062] As will be seen through the various embodiments, the proposed plant layouts provide an optimal configuration for the combination of direct reduction plant 12 and ironmaking plant 14, based on green energy sources. In all embodiments, there is a synergy of gases (direct reduction plant exploiting offgas from the ironmaking plant) as well as of solid materials (ironmaking plant can benefit from dust and residues as well as from DRI/HRDI/HBI produced by DR furnace).

[0063] Direct reduction plant 12 is of conventional design. In this embodiment, its core equipment includes (not limiting to) a vertical shaft with a top inlet and a bottom outlet, a reformer, and a heat recovery system (not shown). A charge of iron ore 18, in lump and/or pelletized form, is loaded into the top of the furnace and is allowed to descend, by gravity, through a reducing gas; typically, mechanical equipment is installed to facilitate solid descent. The charge remains in the solid state during travel from inlet to outlet. The reducing gas is introduced laterally in the shaft furnace, at the basis of a reduction section, flowing upwards, through the ore bed. The reducing atmosphere comprises mainly H.sub.2 and CO. Reduction of the iron oxides occurs in the upper section of the furnace, at temperatures up to 950° C. and higher. Depending on embodiments, the shaft furnace may comprise a transition section below the reduction section; this section is of sufficient length to separate the reduction section from the cooling section, allowing an independent control of both sections.

[0064] However, according to recent practice, the shaft furnace does typically not include a cooling section but an outlet section (directly below the reduction section). The solid product of the shaft furnace is thus typically discharged hot. It can then be: [0065] 1) charged hot into downstream steelmaking facility (EAF,SAF); [0066] 2) hot briquetted to form HBI; [0067] 3) cooled in a separate vessel as Cold DRI; [0068] 4) a combination of the three previous.

[0069] The core of ironmaking plant 14 is here a conventional pig iron production plant, with a relatively short-height counter-current reactor, fed with a mixture of iron bearings (iron bearing materials) and solid reducing agents. The iron bearings are typically agglomerated, starting from fine ores, adding a portion of reducing agents into them, to facilitate ironmaking reactions. The materials are charged into the pig iron reactor from its top, via dedicated channels. Air, eventually enriched with oxygen, as well as gaseous reducing agents are blown from the lower part of the reactor. Pig iron and slag are tapped from the bottom (box 24). The reactor may comprise an upper stack for the filler (iron bearings) on top of a lower stack. Solid fuel feeders are arranged around the junction between the upper and lower stacks, to supply fuel filler. Fuel is also introduced centrally via a hood positioned centrally on top of the upper stack. The various filler materials are thus charged in vertical stacks.

[0070] Such kind of smelt reduction reactor with vertical stacks of materials is e.g. disclosed in WO 2019/110748, incorporated herein by reference. The use of such kind of smelt reduction reactor is designed to operate with coal/carbon reductants, and is adapted to operate with biochar. It also allows great flexibility on the charging of iron bearings, also allowing recycling of dusts, fines, and other residues from the DR plant that may be introduced, in bulk (particles) or agglomerated form, into the smelt reduction reactor.

[0071] The biomass pyrolysis unit 16 is here also conventional. The operating principle is the pyrolysis: biomass is heated in (almost) absence of oxygen, which produces three distinct phases, respectively called char (solid), tar or bio-oil (liquid) and syngas (non-condensable gases). The product distribution among the three phases depends on the operating parameters, mainly sample size, residence time and temperature. In the context of the disclosure, a so-called slow pyrolysis (or carbonization) is particularly considered, operating at temperatures around 400 to 500° C. with relatively long residence time, whereby the main product is char. The pyrolysis unit 16 may generally include a reactor that is heated by means of electrical energy.

[0072] The raw biomass material 22 introduced into pyrolysis unit 16 can be diverse. It is typically a material qualifying as biomass fuel and may include: [0073] i) woody biomass and by-products of the wood industry: wood lumps, wood chips and all other products of the wood industries (sawdust, sawmill wastes . . . ); [0074] (ii) products of the farming sector: energy crops (willow, miscanthus, corn . . . ) as well as crop residues (straw, bagasse, hulls . . . ); [0075] (iii) organic by-products of the industry: such as papermilll sludge, or wastes from the food-processing industry (FPI), [0076] (iv) organic wastes: common wastes, farm effluents or other urban wastes (sewage sludges); [0077] and combinations thereof.

[0078] From the biomass 22, the pyrolysis unit 16 generates two streams: [0079] Biogas B2, which may be conveyed to a gas distribution network [0080] Char B3 (e.g. biochar, biocoal or biocoke) that is routed to the ironmaking plant 14.

[0081] Conveying of the char to the ironmaking plant 14 is done in any appropriate way, e.g. by means of conveyors, rail, buckets, etc.

[0082] At the ironmaking plant 14, a charge comprising the biochar B3 and iron ore fines T1 (box 26) is used. Iron ore fines T1 are suitably agglomerated, if required, before being charged into plant 14; this can include several processing of iron ore fines, also with use of part of the biochar B3. In this embodiment, a flow D3 of dusts, fines, and other residues from DR plant 12, are used to replace a portion of T1 in the agglomeration process. Hence a portion of the charge of the ironmaking plant consists of waste materials of the DR plant 12.

[0083] The biochar B3 acts as reducing agent, thereby enabling reduction reactions required to remove oxygen from the iron bearing materials.

[0084] The offgas stream of ironmaking plant 14 is noted T3 and mainly contains CO, CO.sub.2, Hz, H.sub.2O and N.sub.2. In general, the combined CO and CO.sub.2 content in the offgas may represent at least 25% v, preferably more than 30, 35 or 40% v.

[0085] Table 1 below gives an exemplary composition of the various gas flows for the embodiment of FIG. 1.

TABLE-US-00001 TABLE 1 Material flows of the configuration with methanation for NG DRI. Pig Iron (T2) Steam from DR plant (S4) CO2 from WGS (C1) Flowrate 1 ton Flowrate 558.8 Nm3 Flowrate 590.5 Nm3 Composition 94.64 Fe % w Steam to WGS (S2) Composition 95 CO2% v 3.50 C % w Flowrate 340 Nm3 5 N2% v Iron Ore Fines (T1) Steam to SOEC (S3) H2 from WGS (HY1) Flowrate 1.440 ton Flowrate 1033 Nm3 Flowrate 624.2 Nm3 Composition 65 Fe % w Steam from Methanation (S5) 83.31 H2% v 30 O % w Flowrate 1122 Nm3 Composition 15.86 CO2% v Fines from DR (D3) Offgas (T3) 0.83 N2% v Flowrate 0.060 ton Flowrate 2000 Nm3 SOEC out H2 (HY2) 95.5 Fe % w 24 CO % v Flowrate 1930.6 Nm3 Composition 3.5 C % w 9 CO2% v Composition 89.30 H2% v 1 O % w Composition 2 H2% v 10.70 H2O % v Iron Ore (P1) 7 H2O % v Natural Gas (NG1) Flowrate 2.525 ton 58 N2% v Flowrate 694.7 Nm3 Composition 70 Fe % w Offgas to WGS (T4) 80.75 CH4% v 30 O % w Flowrate 874.7 Nm3 Composition 14.25 CO2% v HBI (D4) 54.87 CO % v 5.00 N2% v Flowrate 1.870 ton 20.58 CO2% v Flue Gas (F1) 95.5 Fe % w Composition 4.57 H2% v Flowrate 3585.0 Nm3 Composition 3.5 C % w 16.00 H2O % v 63 N2% v 1 O % w 3.97 N2% v Composition 22 H2O % v Total Steam Request (S1) N2 removed (T5) 15 CO2% v Flowrate 1373 Nm3 Flowrate 1125.3 Nm3 Composition 100 N2% v

[0086] Offgas stream T3 is here passed through an optional purifying unit 28, wherein a certain amount of N.sub.2 is removed as well as dust and other components. The output N.sub.2 stream T5 is sent to N.sub.2 stock 30 for possible valorization.

[0087] The residual offgas stream T4 exiting the purifying unit 28 mainly contains CO, CO.sub.2, Hz, H.sub.2O and is routed to a converter 32. The N.sub.2 rejection quantity depends on the N.sub.2 content in stream T3, and N.sub.2 maximum acceptance in DR Plant 12. In the present embodiment the technology selected for the ironmaking plant 14 generates a significant amount of N.sub.2. This may differ with other technologies.

[0088] Converter 32 (also referred to as hydrogen enrichment unit) is configured to convert CO and H.sub.2O into CO.sub.2 and H.sub.2; and to output a CO.sub.2-rich stream C1 and a separate Hz-rich stream HY1.

[0089] The stream HY1 typically consists of H.sub.2, CO.sub.2 and N.sub.2 (amount of N.sub.2 depends on ironmaking plant technology and presence of purifying unit 28). Apart from N.sub.2, the main component of stream HY1 is H.sub.2.

[0090] Due to the design of unit 32, typically most of the N.sub.2 content of stream T4 will be directed in stream HY1. Accordingly, the stream C1 contains essentially CO.sub.2, typically above 90%.

[0091] Since the separation of the two flows C1 and HY1 can be costly, one can opt for a unique output, composed by C1 and HY1 mixed together. Converter 32 is here configured to implement the water-gas shift reaction:

CO+H.sub.2OCO.sub.2+H.sub.2

[0092] Water-gas shift converters are well known in the art and will not be described. In order to maximize conversion of the CO present in the ironmaking plant offgas stream T4 (considering that it already contains H.sub.2O), converter 32 can be fed with a steam stream S2 originating from a source 34 of steam produced from green energy.

[0093] It may be noted that, conventionally, the hydrogen-rich output stream of WGS converter is ‘product’ stream, whereas the CO.sub.2-rich stream may be referred to as ‘tail gas’. The CO.sub.2-rich stream is the tail gas of the converter 32; however in the context of the disclosure the CO.sub.2-rich stream is not discarded, but valorized within the plant arrangement, namely into the direct reduction plant.

[0094] The two output streams of converter 32, i.e. the Hz-rich stream and CO.sub.2-rich stream are fed to a methanation plant 36. The methanation plant 36 is configured to produce a gas stream NG1 having a quality and methane content comparable to natural gas. In the methanation plant the following reaction takes place:

CO.sub.2+4H.sub.2CH.sub.4+H.sub.2O

[0095] The produced gas stream NG1 has a quality and methane content that depends from the input streams; however, under certain conditions, it is similar to fossil natural gas, and may thus be referred to as natural gas, biogas or renewable natural gas, RNG. The natural gas stream NG1 preferably contains at least 65% v, preferably above 75, 80 or 85% v of CH.sub.4.

[0096] Another output of plant 36 is steam S5, which is advantageously fed to a Solid Oxide Ectrolyzer Cell (SOEC) unit 38. SOEC Unit 38, is configured to transform H.sub.2O into H.sub.2, while removing excess 02 (which can be used elsewhere).

[0097] SOEC Unit 38 may optionally receive an additional green steam stream S3 from source 34, in order to increase the methane production.

[0098] As it is known in the art, a SOEC follows the same construction of a solid-oxide fuel cell, consisting of a fuel electrode (cathode), an oxygen electrode (anode) and a solid-oxide electrolyte. Steam is fed along the cathode side of the electrolyser cell. When a voltage is applied, the steam is reduced at the catalyst coated cathode-electrolyte interface and is reduced to form pure H.sub.2 and oxygen ions. The hydrogen gas then remains on the cathode side and is collected at the exit as hydrogen fuel, while the oxygen ions are conducted through the solid and gas-thight electrolyte. At the electrolyte-anode interface, the oxygen ions are oxidized to form pure oxygen gas, which is collected at the surface of the anode. The SOEC operates at high temperature, generally 500 to 850° C.

[0099] The H.sub.2 stream produced by SOEC unit 38 is fed to the methanation unit 36.

[0100] The biogas stream NG1 generated by the methanation unit 36 is sent to the DR plant 12 to be valorized. The biogas stream NG1 can be used for heating purposes and/or for metallurgical purposes, i.e. as reducing agent. The biogas stream NG1 can thus be part of a heating gas stream and/or part of a reducing gas stream, meaning that it can be mixed with other gases for either of these purposes.

[0101] In the above-mentioned case of where plant 12 comprises a shaft furnace, a reformer and a heat recovery system, then typically, most of the NG1 stream is added to the gas recirculating into plant 12; this has a metallurgical purpose. Indeed, the NG1 flow is introduced into the recirculation piping that recycles furnace gas via the heat recovery system and reformer. In the reformer, methane reacts with carbon dioxide and water vapour to form carbon monoxide and hydrogen (dry & steam reforming process are only an example). Other portions of NG1 are used as fuel (to sustain the reforming reactions required by the DR process), as well as direct injection into the shaft of plant 12, to boost carburization of the product D4, and to optimize the process.

[0102] The offgas (combustion flues—deriving from the combustion to sustain the reforming process) of the DR Plant 12 is routed to a stack 40 to be released to atmosphere.

[0103] Considering the layout of the present metallurgic plant, with biochar source and various gas treatments, the emissions of offgas stream F1 qualify as green or neutral.

[0104] Heat recovery systems in plant 12 allow producing a green steam stream S4 that is sent to source 34 for further use.

[0105] FIG. 2 illustrates a second embodiment of metallurgical plant 110, which mainly differs from the previous embodiment in that the DR plant 12 does not operate on the biogas stream (CH.sub.4), but based on syngas. Its core equipment includes (not limiting to) a vertical shaft (with a top inlet and a bottom outlet), a heater and a CO.sub.2 removal unit (not shown).

[0106] Similar to the first embodiment, biochar is produced in pyrolysis unit 16 and used for the production of pig iron in the ironmaking plant 14. Offgas from the ironmaking plant 14 is treated in optional purifying unit 28 and then in the hydrogen enrichment unit 32.

[0107] Here however the methanation unit 36 is omitted.

[0108] Hydrogen enrichment unit 32 produces the hydrogen-rich stream HY1, sent directly to the direct reduction plant 12. The CO.sub.2 rich stream C1 output by hydrogen enrichment unit 32 is forwarded to the SOEC unit 38. In this case, SOEC unit 38 is operating in co-electrolysis mode, where both CO.sub.2 and H.sub.2O are transformed into CO and H.sub.2, and oxygen is removed.

[0109] The outlet of SOEC unit 38 in this configuration is a syngas, stream SG1, composed mainly of CO and H.sub.2. The ratio H.sub.2 to CO in syngas stream SG1 may be between 2 and 4, e.g. of about 3. In embodiments (not shown), plant 12 may be equipped with a CO.sub.2 removal system, and the CO.sub.2 thus removed can be sent to SOEC unit 38, to be used as additional input flow.

[0110] Table 2 below gives an exemplary composition of the various gas flows for the embodiment of FIG. 2. It may be noted that this example corresponds to a situation where purifying unit 28 is inactive or omitted, i.e. nitrogen generated by the ironmaking plant 14 remains in the offgas to the hydrogen enrichment unit 32.

[0111] Depending on the N.sub.2 content in stream T3/T4, one can implement one of the following actions: [0112] 1) accept a high N.sub.2 content in stream T4 (and therefore in stream HY1), to make primarily use of HY1 for heating purposes in DR plant 12; or [0113] 2) remove the required quantity of N.sub.2 from T3, and hence make joint use of HY1 and SG1 for both heating and reducing purposes in DR plant 12.

TABLE-US-00002 TABLE 2 Material flows of the configuration with Synlink for syngas DRI. Pig Iron (T2) Steam from DR plant (S4) CO2 from WGS (C1) Flowrate 1 ton Flowrate 626.5 Nm3 Flowrate 590.5 Nm3 Composition 94.64 Fe % w Steam to WGS (S2) Composition 95 CO2% v 3.5 C % w Flowrate 340 Nm3 5 N2% v Iron Ore Fines (T1) Steam to SOEC (S3) H2 from WGS (HY1) Flowrate 1.433 ton Flowrate 1652.851 Nm3 Flowrate 1749.5 Nm3 Composition 65 Fe % w Offgas (T3) 29.72 H2% v 30 O % w Flowrate 2000 Nm3 Composition 5.66 CO2% v Fines from DR (D3) 24 CO % v 64.62 N2% v Flowrate 0.067 ton 9 CO2% v SOEC out syngas (SG1) 95.5 Fe % w Composition 2 H2% v Flowrate 2243.4 Nm3 Composition 3.5 C % w 7 H2O % v 20.01 CO % v 1 O % w 58 N2% v 5.00 CO2% v Iron Ore (P1) Offgas to WGS (T4) Composition 58.94 H2% v Flowrate 2.830 ton Flowrate 2000.0 Nm3 2.95 H2O % v Composition 70 Fe % w 24.00 CO % v 1.32 N2% v 30 O % w 9.00 CO2% v Flue Gas (F1) HBI (D4) Composition 2.00 H2% v Flowrate 3486.3 Nm3 Flowrate 2.096 ton 7.00 H2O % v 63 N2% v 95.5 Fe % w 58.00 N2% v Composition 22 H2O % v Composition 3.5 C % w N2 removed (T5) 15 CO2% v 1 O % w Flowrate 0 Nm3 Total Steam Request (S1) Composition 100 N2% v Flowrate 1992.851 Nm3

[0114] In the example of Table 2, N.sub.2 in stream T3 is not removed: most of the stream HY1 (approx. 93%) is sent to DR plant 12 for heating purposes. The gas stream SG1 and the remaining part of the stream HY1 are thus directly fed to the DR plant 12 and are used therein as reducing gases.

[0115] No reformer is required.

[0116] It may be noted that alternative sources of heat (electricity) can be used in plant 12, that may change the gas balance indicated in the examples.

[0117] FIG. 3 shows a further embodiment of a metallurgical plant 210, which is a variant of the embodiment of FIG. 1. Compared to FIG. 1, plant 210 includes several options that can be implemented alone or in combination: [0118] Option a). Part of the DRI/HBI/HDRI (stream D5) produced in the direct reduction plant may be sent to the ironmaking plant, as input raw material. [0119] Option b). Part of the DRI/HBI/HDRI (stream D5) produced in the direct reduction plant may be sent to a green steelmaking plant (eg. BOF, EAF, SAF, others), as input raw material. [0120] Option c). Part of the flue gas F1 leaving the DR plant, and/or part of the gas recirculating in DR plant 12, noted stream F2, may be sent to a H.sub.2O/CO.sub.2/N.sub.2 separation plant, and the resulting steam—stream S6—is sent to SOEC unit 38, while the CO.sub.2—noted F3—is sent to the methanation plant 36. If also N.sub.2 is separated, it can be valorized. In such a way DR plant 12 can also be operated when the ironmaking plant 14 is not working (requiring only minimized external fuels/inputs). Depending on the total fuel/gas request of plant 12, the respective percentages of recycled stream F2 and of stream T3 can be regulated.

[0121] FIG. 4 shows a further embodiment of a metallurgical plant 310, which is a variant of the embodiment of FIG. 2. Compared to FIG. 2, plant 310 includes several options that can be implemented alone or in combination: [0122] Option a). Part of the DRI/HBI/HDRI (stream D5) from the DR plant 12 is sent to the iron ore ironmaking plant 14, as input raw material. [0123] Option b). Part of the DRI/HBI/HDRI (stream D5) DR plant 12 is sent to a green steelmaking plant 44, as input raw material. [0124] Option c). Part of the flue gas leaving the DR plant 12 and/or part of the gas recirculating in plant 12, noted as stream F2, is sent to SOEC cells 38 for its co-electrolysis (a N.sub.2 separation stage may be required). In such a way plant 12 can also be operated when ironmaking plant 14 is not working (requiring only minimized external fuels/inputs). Depending on the total fuel/gas request of plant 12, the respective percentages of recycled stream F2 and of stream T3 can be regulated.