EA045892B1 - METHOD OF OPERATING A METALLURGICAL PLANT FOR THE PRODUCTION OF IRON PRODUCTS - Google Patents

Description

The invention generally relates to the field of iron metallurgy and, above all, to a metallurgical plant and method for the production of iron products. More particularly, the invention relates to iron metallurgy based on the direct reduction process of iron ore.

Manufacturing processes contribute significantly to overall CO2 emissions, and the modern iron and steel manufacturing process is very energy and carbon intensive.

With the Paris Agreement and near global agreement on the need for action on emissions, it is imperative that every industry looks at developing solutions to improve energy efficiency and reduce CO2 emissions. One technology developed to reduce the carbon footprint during steel production is the direct iron ore reduction process. Although the annual production of direct reduced iron remains small compared to blast furnace pig iron production, it is indeed very attractive due to its comparatively low CO2 emissions, which are 40-60% lower for the direct reduced electric arc furnace (EAF) process route. compared to the blast furnace, oxygen-converter route.

In a direct reduction shaft furnace, a charge of granular or lump iron ore is loaded into the top of the furnace and lowered by gravity through a reducing gas. Reducing gas consisting of hydrogen and carbon monoxide (syngas) flows upward through the ore layer. The reduction of iron oxides occurs at the top of the furnace, usually at temperatures up to 950°C or even higher. The solid product, called direct reduced iron (DRI), is typically hot charged into electric arc furnaces or hot briquetted to form hot briquetted iron (HBI).

In most existing DRI applications, the aforementioned syngas is produced by reforming natural gas. In some cases, suitable gas is already available, so natural gas is not required. As is known in the art, DRI and similar products are charged to a blast furnace or iron making plant or to a smelting furnace such as an EAF to produce pig iron or steel.

WO2017/046653 discloses a method and apparatus for the direct reduction of iron ores using coal-derived gas. The DRI production method uses syngas containing a relatively high proportion of CO with an H2/CO ratio of less than about 0.5 in a reduction system including a reduction reactor from which the hot reduction gas stream is removed as an overhead gas, a heat exchanger, in which heat is removed from the hot overhead gas and transferred to the liquid water stream, and a gas humidifier. The smelter-gasifier is used to produce slag and pig iron from iron ore, thereby producing CO and CO2-containing off-gas. The off-gas leaving the melter-gasifier is treated (cleaned, compressed...) before it is fed into two successive CO conversion units to increase the amount of H ₂ and CO ₂ in the gas stream. This stream is then fed to a CO2 removal unit, thereby forming a CO2-rich stream and a hydrogen-rich stream. The hydrogen-rich stream is fed into the reduction reactor. The CO2-rich stream is removed.

EP 0997 693 relates to a process for combining a blast furnace and a direct reduction reactor using cryogenic distillation. The purified blast furnace gas is supplied to the water-gas shift reactor. The resulting gas stream, containing mainly H ₂ and CO ₂ , is then supplied to an acid gas removal unit and to a methanization unit. A cryogenic unit is used to separate nitrogen from hydrogen. Carbon dioxide is removed from the system in a hot potassium carbonate system or pressure swing adsorption system.

The purpose of the present invention is to provide an improved approach for the production of direct reduced iron products, which is primarily more environmentally friendly.

Summary of the invention

This goal is achieved by the method according to claim 1 of the claims.

The present invention relates to a method for operating a metallurgical plant for producing iron products, comprising:

supplying an iron ore charge to a direct reduction plant to produce direct reduced iron products, operating an iron producing plant to produce pig iron, wherein biochar is introduced into the pig iron production plant as a reducing agent, and thereby the pig iron production plant generates an exhaust gas containing CO and CO ₂ , treating waste gas from an iron producing plant in a hydrogen enrichment plant to produce a hydrogen-rich stream and a CO2-rich stream, wherein at least a portion (i.e., a fraction or up to 100%) of the hydrogen-rich stream is supplied to a direct reduction unit and the CO2-rich stream at least partially converted for processing in a direct reduction unit, primarily converted to syngas or natural gas.

The present invention provides an optimal configuration for a direct recovery plant

- 1 045892 production and iron production plants, when they are located in one place and are based on green energy sources, especially biomass. Preferably, biochar is produced on site through a biomass pyrolysis plant from biomass material.

According to the invention, biochar is used as a reducing agent in an iron producing plant, and the off-gas from the iron producing plant (partially or completely) is then processed into a gas stream which is used in a direct reduction plant.

The iron producing plant receives a charge from the iron carrier material, which, as will be explained below, can have different origins and, above all, originate from the DR plant.

In various embodiments, a synergy of gases as well as solids is achieved: the direct reduction plant uses off-gases from the iron production plant, the iron production plant can benefit from the use of dust and residue from the DR plant. Thus, it is recognized that the waste from the DR plant can be reused in the iron producing plant, the iron producing plant can also/alternatively benefit from the use of DRI (directly reduced iron)/HDRI (hot straight reduced iron)/HBI (hot briquetted iron) obtained by installing direct recovery.

The advantage of the invention is the optimized and balanced connection between the direct reduction plant and the iron production plant, and the fact that they are both based on green energy/green fuel.

Accordingly, iron products produced by the direct reduction plant can be called green metal products.

In this text, DR means direct recovery or directly restored depending on the context.

At least a portion of the hydrogen enrichment plant's hydrogen-rich stream may be sent directly to a direct reduction plant where it may be used as a gas or fuel for metallurgical and/or heating purposes. Therefore, the hydrogen-rich stream may be part of a reducing gas stream and/or a gaseous fuel stream.

As noted above, preferably at least a portion (ie, a fraction or up to 100%) of the CO2-rich stream is converted for processing in a direct reduction unit. Depending on embodiments, the CO ₂ -rich stream may be primarily converted to form syngas or natural gas (a gas stream formed primarily from methane). This is particularly advantageous since the proposed metallurgical plant is thus able to recycle CO2 to the benefit of the direct reduction plant. Consequently, the CO2 is not emitted or recycled elsewhere, but is used directly on site.

In contrast, in the methods proposed by WO2017/046653 and EP 0997 693, carbon dioxide is removed from the system and is not converted for processing in a direct reduction plant.

Preferably, the CO ₂ -rich stream may be fed to a water electrolysis unit, preferably further fed with a steam stream to produce a syngas stream which is supplied to the direct reduction unit. This syngas stream typically contains primarily hydrogen and carbon monoxide, and therefore can be processed in a direct reduction plant as a reducing gas or gaseous fuel. The total H ₂ and CO content in the syngas stream may be at least 60 vol.%, preferably 70 or 80 vol.%.

In embodiments, at least a portion of the hydrogen-rich stream is routed indirectly to the direct reduction unit. The term here indirectly implies that the hydrogen-rich stream is converted/converted on its way to the direct reduction unit into a gas stream that can be processed in the direct reduction unit. For example, a hydrogen-rich stream and a CO2-rich stream may be sent from a hydrogen enrichment unit to a methanization unit to produce a methane stream. This stream is sent to a direct reduction unit for use as part of the reducing gas stream and/or as part of the gas fuel stream.

In embodiments, the hydrogen-rich gas is processed, directly or indirectly, in a direct reduction unit for use as a process gas. In this case, reducing gas is introduced into the DR unit to reduce the content of iron carriers in the pellets/agglomerates. In the context of the invention, the pellets/agglomerates typically include only iron carriers (eg iron ore particles/fines). Pellets/agglomerates generally do not contain added solid reducing material (charcoal/coal or carbon containing materials) except in trace or unavoidable quantities.

In embodiments, the DR plant may include a direct reduction furnace or reactor and additional equipment depending on the direct reduction technology that is being implemented. For example, a DR plant may include a reformer furnace and a heat recovery system in addition to the DR furnace. In this case, the methane stream can be used partially as

- 2 045892 gaseous fuel for heating the reforming furnace and/or partly as process gas by reforming and/or by direct injection into the DR furnace.

In embodiments, the water electrolysis unit is coupled to the methanization unit, whereby the steam stream exiting the methanization unit is supplied to the electrolysis unit to generate an auxiliary hydrogen stream, which is returned to the methanization unit. This provides a convenient way to recycle water vapor from the methanization process. Optionally, an additional steam stream, preferably from a green energy source, can be introduced into the water electrolysis unit.

When the waste gas stream from an iron production plant is to be processed as metallurgical gas (reducing gas) in a direct reduction shaft furnace, nitrogen removal is desirable. To this end, a portion of the off-gas stream from the iron production plant may be treated in a nitrogen separating plant before being sent to the hydrogen enrichment plant. In embodiments, the nitrogen removal unit may be located at the outlet stream of the hydrogen enrichment plant instead of the inlet stream thereof.

The present invention can be implemented with existing equipment well known in the metallurgical industry. For example, a direct reduction plant, an iron producing plant, a biomass pyrolysis plant can be based on suitable technology. The gas treatment systems used in the invention are also well known, as they are used in the metallurgical industry and more generally in the chemical industry.

For example, a hydrogen enrichment plant can be based on a variety of technologies. First of all, the hydrogen enrichment plant may include a water-gas shift reactor.

Biomass pyrolysis plants are used in many industries. When operated in what is known as slow pyrolysis, they produce biochar and biogas, which can be used as a carbonaceous material for heating and other purposes, primarily for metallurgical applications. In the context of the present invention, the term biochar is used to refer to solid pyrolysis products that can be used as a reducing agent in an iron production plant and which are commonly referred to as biochar or biocoke.

The iron production plant is fed with biochar as a reducing agent. In this context, biochar represents the main part of the reducing agent, namely at least 70%, 80%, 90% (by weight), and preferably up to 100%.

Nitrogen removal plants are commonly used in natural gas production.

Water electrolysis plants are also common and are used to convert water into hydrogen.

A DR installation can support the implementation of different technologies. In embodiments, it includes a shaft furnace, a reforming furnace, and a heat recovery system. In other embodiments, it includes a shaft furnace, a heater, and a CO2 removal unit (ie, without an additional reformer furnace). Such DR plants can be operated with natural gas and/or reduction streams. These are examples only and the specialist will know how to select the appropriate recovery processes.

Also, a cast iron production plant can support the implementation of different technologies.

Typically, an iron-producing plant may include a blast furnace or a smelter, both fed with biochar as the reducing agent. The smelter and reduction reactor typically includes a countercurrent reactor fed with a mixture of iron carriers (iron-bearing materials) and solid reducing agents. Typically, iron carriers may often be present in the form of lumps, pellets or fines (small particles). Solid reducing agents typically include coal or carbon, however, in the context of the invention, biochar is used as the reducing agent. As is known, reduction smelting is used to produce liquid hot metal similar to a blast furnace, but without the dependence on coke. It requires little preparation of the feed material and uses coal (or carbon), oxygen and/or electrical energy.

In embodiments, the iron producing plant typically includes a low countercurrent reactor fed by a mixture of iron carriers (iron-bearing materials) and solid reducing agents. Iron carriers are typically agglomerated from fine-grained ores with a portion of reducing agents added thereto to facilitate iron production reactions. Materials are loaded into the reactor from above through special channels. Air, often enriched with oxygen, as well as gaseous reducing agents are blown in from the bottom of the reactor. Pig iron and slag are discharged from the bottom. This type of smelting reduction reactor with vertical stacks of materials is disclosed, for example, in WO 2019/110748 and is incorporated herein by reference. As one skilled in the art will appreciate, such a low reactor is based on low pressure moving bed reduction and is flexible in the iron-bearing and carbon-bearing feedstocks it can process. The ability of the process to melt either pellets or briquettes or even mixed loads of them provides a means

- 3 045892 for the use of a wide range of alternative feed materials.

It may be noted here that this kind of low smelting reduction reactor typically produces significant amounts of off-gas, comparatively more than other smelting-reduction technologies, making it particularly suitable for use in the context of the invention, that is, for using off-gas in a direct reduction plant. In other words, the smelter reduction reactor provides a feasible solution to the inventive concept where the off-gas from an iron producing plant must be capable of providing the main source of gas for operating the direct reduction plant. The blast furnace also produces a sufficient amount of gas.

In the context of the invention, it is desirable that the exhaust gas from an iron producing plant has a combined CO and CO2 content of at least 25% by volume, preferably more than 30, 35 or 40% by volume. Preferably, the CO content is at least 20, 25 or 30% by volume. %.

As one skilled in the art will appreciate, some smelter reduction furnaces (such as, for example, the aforementioned low counterflow reactor or a house furnace) can produce significant amounts of nitrogen. In this case, it is recommended to use a unit to remove nitrogen from the exhaust gas stream.

The present invention, in various possible embodiments, provides several advantages:

Biomass/green energy based production of pig iron, DRI (in various forms) and steel.

The synergy of two iron production technologies, where the direct reduction plant uses the exhaust gases of an iron production plant that is entirely biomass/green energy based, thereby becoming the most biomass/green energy based.

Operation of a direct reduction plant using the off-gases of an iron producing plant without the need for any steps to remove CO ₂ or N2 from such off-gases.

A combination of two iron production technologies, where the iron producing plant is suitable for using fines and residues from the direct reduction plant. First of all, the configuration according to the invention allows dust, fines and other residues from the DR plant to be charged as part of the charge to be melted. These materials, that is, dust, fines and other residues, can be, depending on the technology of the iron-producing plant, reused in bulk form (in the form of small particles) or in the form of agglomerates (of different sizes). This ability to easily reuse dust, fines and other residues from the direct reduction plant at the same location in the iron making plant is highly advantageous and particularly easy to use with the above-mentioned smelting reduction involving the use of a low countercurrent reactor.

A configuration of two iron-producing technologies where DRI production in a direct reduction plant can be a by-product of the iron-producing plant in any cases with the plants connected so that the direct reduction plant can also be operated when the iron-producing plant is not operating.

In further embodiments, at least a portion of the direct reduced product from the direct reduction plant is supplied to the iron producing plant as part of a charge to be smelted therein, wherein the direct reduced products include sponge iron and/or lump direct reduced products.

The operation of the iron producing plant can be controlled based on the amount of waste gas recirculated. Moreover, the operation of the iron-producing installation (14) is slowed down or stopped after reaching a steady state of operation in the direct reduction installation.

According to another aspect, the invention also relates to a metallurgical plant for producing iron products, including:

a direct reduction plant configured to produce directly reduced products from an iron ore charge, a biomass pyrolysis plant configured to produce biochar from the biomass material, an iron producing plant configured to produce pig iron, wherein the pig iron production plant uses biochar as a reduction material and generates waste gas , a hydrogen enrichment plant configured to receive exhaust gas from an iron producing plant and produce a hydrogen-rich stream and a CO2-rich stream, and means for converting the CO2 into a gas stream that is processed in a direct reduction plant, wherein the hydrogen-rich stream is directly or indirectly processed in the direct reduction plant. recovery.

In additional embodiments, the metallurgical plant includes a methanization unit configured to receive a hydrogen-rich stream and a CO ₂ rich stream from the plants.

- 4 045892 ki of enrichment with hydrogen and the production of a biogas stream from them, primarily a methane stream, which is sent to a direct reduction unit.

The metallurgical plant includes a water electrolysis unit coupled to a methanization unit, wherein a steam output stream from the methanization unit is supplied to the electrolysis unit to generate an auxiliary hydrogen stream that is returned to the methanization unit. In another embodiment, the metallurgical plant includes a water electrolysis plant coupled to a hydrogen enrichment plant, the water electrolysis plant configured to receive a CO2-rich stream as well as a steam stream and generate a syngas stream that is supplied to the direct reduction plant.

The direct recovery unit includes a shaft furnace, reformer and heat recovery system. In another embodiment, a direct reduction unit includes a shaft furnace, a heater, and a CO2 removal unit.

The hydrogen enrichment plant includes a water-gas shift reactor.

The nitrogen removal unit is located in the exhaust gas stream from the iron producing plant to the hydrogen enrichment plant or in the outlet stream from the hydrogen enrichment plant.

The hydrogen enrichment unit is connected directly to the direct reduction unit to supply at least a portion of the hydrogen-rich stream.

The metallurgical plant may also include means for transporting dust, fines and other residues from the direct reduction plant to the iron producing plant as part of the charge to be smelted therein.

The above and other embodiments are set forth in the appended claims.

Brief description of drawings

Other details and advantages of the present invention will become apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings, FIG. 1-4 are diagrams illustrating four different embodiments of a metallurgical plant implementing the present method. In the figures, unless otherwise indicated, the same or similar elements are designated by the same reference numerals.

Detailed Description of Preferred Embodiments

In fig. 1 shows a first diagram of an installation 10 for implementing the present method. The two main components of the plant 10 are a direct reduction plant 12 and an iron production plant 14. The plant 10 also includes a biomass pyrolysis plant 16 that produces biochar used in the iron production plant 14 as a reducing agent.

As will be seen in various embodiments, the proposed arrangements provide an optimal configuration for the combination of a direct reduction plant 12 and a green energy-based iron producing plant 14. In all embodiments, there is a synergy of gases (the direct reduction plant uses the off-gas from the iron production plant) as well as solid materials (the iron production plant can benefit from the use of dust and residues, as well as from the DRI/HDRI/HBI produced by the DR plant) .

The direct reduction unit 12 has a conventional design. In this embodiment, its main equipment includes (but is not limited to) a shaft furnace with an upper inlet and a lower outlet, a reforming furnace, and a heat recovery system (not shown). Iron ore charge 18 in lump and/or granular form is charged into the top of the furnace and allowed to fall by gravity through the reducing gas. Typically, additional mechanical equipment is installed to facilitate lowering of the solid material.

The charge remains in a solid state while moving from the inlet to the outlet. Reducing gas is introduced into the shaft furnace from the side at the base of the reduction zone, flowing upward through the ore layer. The reducing atmosphere consists mainly of H ₂ and CO. The reduction of iron oxides occurs in the upper part of the furnace at temperatures up to 950°C and above. Depending on the embodiment, the shaft furnace may include a transition zone below the reduction zone. This zone is of sufficient length to separate the recovery zone from the cooling zone, allowing independent control of both zones.

However, according to modern practice, a shaft furnace typically includes not a cooling zone, but a discharge zone (immediately below the reduction zone). Thus, the solid product of the shaft furnace is discharged hot. Then it could be:

1) loaded hot into downstream steelmaking equipment (electric arc furnace (EAF), submersible arc furnace (SAF)),

2) briquetted in a hot state to form HBI,

3) cooled in a separate tank in the form of cold direct reduced iron (Cold DRI),

4) a combination of the three previous products.

- 5 045892

The basis of the iron production plant 14 here is a conventional pig iron production plant with a relatively low counter-current reactor fed by a mixture of iron carriers (iron-bearing materials) and solid reducing agents. Iron carriers are usually agglomerated from fine-grained ores with a portion of reducing agents added to facilitate iron-producing reactions. Materials are loaded into the pig iron reactor from above through special channels. Air, often enriched with oxygen, as well as gaseous reducing agents are blown in from the bottom of the reactor. Pig iron and slag are discharged from the lower part (rectangle 24). The reactor may include a top stack for fill (iron carriers) on a bottom stack. Solid fuel feeders are located around the transition point between the upper and lower fuel fill stacks. Fuel is also introduced centrally through a nozzle located centrally on the top of the upper stack. In this way, different filler materials are loaded into vertical stacks.

This type of melting and reduction reactor with vertical stacks of materials is disclosed, for example, in WO 2019/110748 and is incorporated herein by reference. The use of this type of smelter and reduction reactor is intended for operation with coal/carbon reducing agents and is adapted for operation with biochar.

It also allows greater flexibility regarding the loading of iron carriers, also making it possible to reuse dust, fines and other residues from the DR plant, which can be introduced in lumps (particles) or in agglomerated form into the smelter reduction reactor.

Biomass pyrolysis unit 16 is also conventional. The principle of operation is pyrolysis: biomass is heated in the (almost complete) absence of oxygen, resulting in three different phases called respectively coal (solid), tar or bio-oil (liquid) and syngas (non-condensable gases). The distribution of the product among the three phases depends on the operating parameters, mainly sample size, residence time and temperature. In the context of the invention, particular consideration is the so-called slow pyrolysis (or charring), carried out at temperatures from 400 to 500° C. with a relatively long residence time, whereby the main product is coal. The pyrolysis unit 16 may typically include a reactor that is heated by electrical energy.

The raw biomass material 22 introduced into the pyrolysis unit 16 may vary. It is typically a material called biofuel and may include:

i) woody biomass and by-products of the forest industry: pieces of wood, wood chips and all other products of the forest industry (sawdust, sawmill waste...), ii) products of the agricultural sector: energy crops (brushwood, Chinese cane, grain... ), as well as crop residues (straw, bagasse, husks...), iii) organic industrial by-products: such as paper mill sludge or food processing waste (FPI), iv) organic waste: general waste, farm wastewater or other municipal waste (sewage sludge), and combinations of them.

From the biomass 22, the pyrolysis unit 16 produces two streams:

biogas B2, which can be sent to the gas distribution network;

coal B3 (eg biochar or biocoke), which is sent to the iron producing plant 14.

Transport of the coal to the iron producing plant 14 is accomplished by any suitable means, for example, by means of conveyors, rails, boxes, or the like.

In the iron-producing installation 14, a charge is used that includes biochar B3 and iron ore fines T1 (rectangle 26). The fine iron ore T1 is optionally suitably agglomerated before loading into unit 14. This may involve several treatments of the fine iron ore, also using a portion of the biochar B3. In this embodiment, the stream D3 of dust, fines and other residues from the DR unit 12 is used to replace part T1 in the sintering process. Therefore, part of the charge from an iron-producing plant consists of waste from the 12 DR plant.

Biochar B3 acts as a reducing agent, thereby enabling the reactions necessary to remove oxygen from iron-bearing materials.

The exhaust gas stream of the iron producing plant 14 is designated T3 and contains mainly CO, CO ₂ , H ₂ , H 2 O and N 2 . Typically, the total content of CO and CO ₂ in the exhaust gas may be at least 25 vol.%, preferably more than 30, 35 or 40 vol.%.

Table 1 below provides an example of the composition of various gas streams for the embodiment of FIG. 1.

- 6 045892

Table 1

Configuration material flows with methanization for iron directly reduced by natural gas

Pig iron (T2) Flow 1 ton Steam from DR* unit (S4) Flow 558.8 nm ³ CO ₂ from WGS (C1) Flow 590.5 nm ³ Compound 94.64 Fe % ma. Steam to WGS** (S2) Flow 340 nm ³ Compound 95 CO ₂ % vol. 3.50 From % May. 5 N ₂ % vol. Iron Ore Powder (T1) Flow 1,440 tons Steam to SOEC*** (S3) Flow 1033 nm ³ H ₂ from WGS (HY1) Flux 624.2 nm ³ Compound 65 Fe % ma. Vapor from methanization (S5) Flow 1122 nm ³ Compound 83.31 H ₂ % vol. thirty About % May. 15.86 CO ₂ % vol. Powder from DR (D3) Flow 0.060 tons Exhaust gas (FG) Flow 2000 nm ³ 0.83 N ₂ % vol. H ₂ from SOEC (HY2) Flux 1930.6 nm Compound 95.5 Fe % ma. Compound 24 CO % vol. 3.5 From % May. 9 CO ₂ % vol. Compound 89.30 H ₂ % vol. 1 About % May. 2 H ₂ % vol. 10.70 H ₂ O % vol. Iron Ore (P1) Flow 2.525 tons 7 H ₂ O % vol. Natural gas NG1) Flow 694.7 nm ³ 58 n ₂ % vol. Compound 70 Fe % ma. Exhaust gas to WGS (T4) Flow 874.7 nm ³ Compound 80.75 CH ₄ % vol. thirty About % May. 14.25 CO ₂ % vol. ΗΒΙ**** (D4) Flow 1,870 tons Compound 54.87 CO % vol. 5.00 N ₂ % vol. 20.58 CO ₂ % vol. Flue gas (F1) Flow 3585.0 nm ³ Compound 95.5 Fe % ma. 4.57 H ₂ % vol. 3.5 From % May. 16.00 H ₂ O % vol. Compound 63 N ₂ % vol. 1 About % May. 3.97 n ₂ % vol. 22 H ₂ O % vol. Total steam demand (S1) Flow 1373 nm ³ Remote N2 (T5) Flux 1125.3 nm ³ 15 CO ₂ % vol. Compound 100 n ₂ % vol.

* Direct recovery.

** Water-gas shift.

*** Solid oxide electrolyzer cell.

**** Hot briquetted iron.

The off-gas stream passes through an optional cleaning unit 28, removing some N2 as well as dust and other components. The output stream T5 N ₂ is sent to storage 30 N2 for possible processing.

The residual exhaust gas stream T4 leaving the cleaning unit 28 contains mainly CO, CO2, H ₂ , H ₂ O and is sent to the converter 32. The amount of N2 removed depends on the N2 content in the T3 stream and the permissible maximum N2 in the DR unit 12. In the present embodiment, the technology selected for the iron producing plant 14 produces a significant amount of N ₂ . It may differ when using other technologies.

The converter 32 (also called a hydrogen enrichment unit) is configured to convert CO and H ₂ O into CO ₂ and H ₂ and to produce a CO ₂ -rich stream C1 and a separate H ₂ -rich stream HY1.

Stream HY1 typically consists of H ₂ , CO ₂ and N2 (the amount of N2 depends on the technology of the iron producing plant and the presence of a purification plant 28). Unlike _N2, the main component of the HY1 flow is _H2 .

Due to the design of plant 32, most of the N2 content of stream T4 will typically be directed into stream HY1. Accordingly, stream C1 contains substantially CO2, typically above 90%.

Since separating the two streams C1 and HY1 can be expensive, a single output stream composed of C1 and HY1 mixed together may be preferred. The converter 32 here is designed to carry out the water-gas shift reaction:

CO + H2O θ CO2 + H2

Water-gas shift converters are well known in the art and will not be described. To maximize the conversion of CO contained in the iron plant waste gas stream T4 (given that it already contains H2O), the converter 32 can be fed with a steam stream S2 originating from a green energy steam source 34.

It can be roughly assumed that the hydrogen-rich water-gas shift converter effluent stream is a product stream, while the CO ₂ -rich stream can be called a tail gas. The CO ₂ -rich stream is the tail gas of the converter 32. However, in the context of the invention, the CO ₂ -rich stream is not emitted, but is processed in plants, namely a direct reduction plant.

The two output streams of the converter 32, that is, the H ₂ -rich stream and the CO ₂ -rich stream, are supplied to the methanization unit 36 . The methanization unit is designed to produce a gas stream NG1 having a quality and methane content comparable to natural gas. The following reaction occurs in the methanization unit:

CO ₂ + 4 H ₂ O θ CH ₄ + H ₂ O

The produced gas stream NG1 has a quality and methane content that depends on the input stream. However, under some conditions it is similar to fossil natural gas and may therefore be called natural gas, biogas or renewable natural gas RNG. Preferably, the natural gas stream contains at least 65%, preferably more than 75, 80 or 85 vol.% CH ₄ .

Another output from unit 36 is stream S5, which is preferably supplied to solid oxide electrolyzer cell (SOEC) 38. The SOEC unit 38 is configured to convert H ₂ O to H ₂ , removing excess O ₂ (which can be used elsewhere).

Optionally, SOEC unit 38 may receive additional green steam stream S3 from source 34 to increase methane production.

As is known in the art, the SOEC has a solid oxide fuel cell structure consisting of a fuel electrode (cathode), an oxygen electrode (anode), and a solid oxide electrolyte. Steam is supplied along the cathode side of the electrolyser cell. When voltage is applied, steam is reduced at the catalyst-coated cathode-electrolyte interface and is reduced to form pure _H2 and oxygen ions. Hydrogen gas then remains on the cathode side and is collected at the outlet as hydrogen fuel, while oxygen ions are conducted through the solid and gas-tight electrolyte. At the electrolyte-anode interface, oxygen ions are oxidized to form pure oxygen gas, which collects on the anode surface. SOEC operates at high temperatures, typically between 500 and 850°C.

The H ₂ stream produced by the SOEC unit 38 is supplied to the methanization unit 36 .

The biogas stream NG1 produced by the methanization unit 36 is sent to the DR unit 12 for processing. The biogas stream NG1 can be used for heating purposes and/or for metallurgical purposes, ie as a reducing agent. Thus, the biogas stream NG1 can be part of the heating gas stream and/or part of the reducing gas stream, which means that it can be mixed with other gases for either of these purposes.

In the above case, where the unit 12 includes a shaft furnace, a reformer and a heat recovery system, then typically the majority of the NG1 stream is added to the gas recycled to the unit 12. This has a metallurgical purpose. Indeed, the NG1 stream is introduced into the recirculation line, which recirculates the furnace gas through the heat recovery system and the reformer. In the reformer, methane reacts with carbon dioxide and steam to produce carbon monoxide and hydrogen (dry and steam reforming processes are just an example). Other parts of NG1 are used as fuel (to support the reforming reactions required by the DR process) and also for direct injection into the unit 12 shaft to support carburization of product D4 and process optimization.

The exhaust gas (combustion flue gas produced from combustion to support the reforming process) of the 12 DR unit is sent to 40 for release to the atmosphere.

Considering the design of a real metallurgical plant with a biochar source and various gas treatments, the emissions of the waste gas stream F1 are classified as green or neutral.

Heat recovery systems in plant 12 make it possible to generate a green steam stream S4, which is sent to source 34 for further use.

In fig. 2 shows a second embodiment of the metallurgical plant 110, which differs from the previous embodiment in that the DR plant 12 is not operated on a biogas (CH ₄ ) stream, but is based on syngas. Its main equipment includes (but is not limited to) a vertical shaft (with an inlet at the top and an outlet at the bottom), a heater and a CO ₂ removal unit (not shown).

Similar to the first embodiment, biochar is produced in a pyrolysis unit 16 and is used to produce pig iron in an iron producing unit 14. The off-gas from the iron producing unit 14 is processed in an optional purification unit 28 and then in a hydrogen enrichment unit 32.

- 8 045892

However, here the methanization installation 36 is excluded.

The hydrogen enrichment unit 32 produces a hydrogen-rich stream HY1, which is sent directly to the direct reduction unit 12.

The CO ₂ -rich stream produced by the hydrogen enrichment unit 12 is sent to the SOEC unit 38 . In this case, the SOEC unit 38 is operated in a co-electrolysis mode in which CO ₂ and H ₂ O are converted to CO and H ₂ and oxygen is removed.

The output of SOEC unit 38 in this configuration is syngas, stream SG1, consisting primarily of CO and H ₂ . The ratio of H ₂ to CO in the syngas stream SG1 may be between 2 and 4, for example about 3. In embodiments (not shown), unit 12 may be equipped with a CO ₂ removal system and the CO ₂ thus removed may be sent to unit 38 SOEC to be used as an additional input stream.

The table presented below. 2 exemplifies the composition of different gas streams for the embodiment according to FIG. 2. It may be noted that this example corresponds to a situation where the purification unit 28 is inactive or excluded, that is, the nitrogen produced by the iron producing unit 14 remains in the exhaust gas of the hydrogen enrichment unit 32.

Depending on the _N2 content in the T3/T4 stream, the following actions can be taken:

1) accept a high _N2 content in stream T4 (and therefore in stream HY1) to make the primary use of HY1 for heating purposes in the 12 DR unit, or

2) remove the required amount of N ₂ from T3 and therefore make the combined use of HY1 and SG1 for both heating and reduction purposes in the 12 DR unit.

table 2

Material flow configurations with Synlink for DRI syngas

Pig iron (T2) Flow 1 ton Steam from unit DR* (S4) _h Flow 626.5 nm ³ CO ₂ from WGS (C1) Flow 590.5 nm ³ Compound 94.64 Fe % ma. Steam to WGS** (S2) Flow 340 nm ³ Compound 95 with ₂ % vol. 3.50 From % May. 5 n ₂ % vol. Iron Ore Powder (T1) Flow 1,433 tons Steam to SOEC*** (S3) Flow 1652.851 nm ³ H ₂ from WGS (HY1) Flux 1749.5 nm ³ Compound 65 Fe % ma. Compound 29.72 H ₂ % vol. thirty About % May. 5.66 with ₂ % vol. Powder from DR (D3) Flow 0.067 tons Exhaust gas (FG) Flow 2000 nm ³ 64.62 n ₂ % vol. Syngas from SOEC (SG1) Flow 2243.4 nm ³ Compound 95.5 Fe % ma. Compound 24 CO % vol. 3.5 From % May. 9 CO ₂ % vol. Compound 20.01 CO % vol. 1 About % May. 2 H ₂ % vol. 5.00 with ₂ % vol. Iron Ore (P1) Flow 2,830 tons Exhaust gas to WGS (T4) Flow 2000 nm ³ 58.94 H ₂ % vol. 2.95 H ₂ O% Compound 70 Fe % ma. 1.32 N ₂ % vol. thirty About % May. _N B!**** (D4) Flow 2,096 tons Compound 24.0 CO % vol. 9.0 CO ₂ % vol. Flue gas (F1) Flow 3486.3 nm ³ Compound 95.5 Fe % ma. 2.0 H ₂ % vol. 3.5 From % May. 7.0 H ₂ O % vol. Compound 63 n ₂ % vol. 1 About % May. 58.00 N ₂ % vol. 22 H ₂ O % vol. Total steam demand (S1) Flow 1992.851 nm ³ Remote N ₂ (T5) Flux 0 nm ³ 15 CO ₂ % vol. Compound 100 N ₂ % vol.

* Direct recovery.

**Water-gas shift.

*** Solid oxide electrolyzer cell.

**** Hot briquetted iron.

In the example according to table. The 2 N ₂ in stream T3 is not removed: the majority of stream HY1 (approximately 93%) is sent to DR unit 12 for heating purposes. Gas stream SG1 and the remainder of stream HY1

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Claims (26)

are thus supplied directly to the 12 DR installation and used there as reducing gases. No reformer required. It may be noted that alternative heat (electricity) sources may be used in unit 12, which may change the gas balance shown in the examples. In fig. 3 shows another exemplary embodiment of the metallurgical plant 210, which is a variant of the exemplary embodiment of FIG. 1. Compared to FIG. 1 installation 210 includes several options that can be implemented alone or in combination: Option A). A portion of the DRI/HBI/HDRI (D5 stream) generated in the direct reduction plant can be sent to the iron producing plant as input raw material. Option B). A portion of the DRI/HBI/HDRI (D5 stream) generated in the direct reduction plant can be sent as input to a green energy steelmaking plant (e.g. BOF, EAF, SAF, others) . Option B). A portion of the flue gas leaving the DR unit F1 and/or a portion of the recycle gas to the DR unit 12, designated F2, may be directed to the H2O/CO2/N2 separation unit, and the resulting stream, stream S6, is directed to the SOEC unit 38, while as CO ₂ - designated by F3 - is sent to the methanization unit 36. If N2 is also separated, then it can be recycled. In this way, the DR plant 12 can also be operated if the iron producing plant 14 is not running (requiring only minimal external fuel/charges). Depending on the overall demand, the fuel/gas unit 12 can adjust the corresponding percentages of the recirculated flow F2 and the flow T3. In fig. 4 shows another exemplary embodiment of the metallurgical plant 310, which is a variant of the exemplary embodiment of FIG. 2. Compared to FIG. 2 The 310 installation includes several options that can be implemented alone or in combination: Option A). A portion of the DRI/HBI/HDRI (stream D5) from the DR unit 12 is sent to the iron producing unit 14 as an input raw material. Option B). A portion of the DRI/HBI/HDRI (stream D5) from the DR unit 12 is sent to the green energy-based steel production unit 44 as feedstock. Option B). The portion leaving the DR unit 12 of the flue gas and/or the portion of the gas recycled to the unit 12, designated stream F2, is sent to the SOEC unit 38 for its co-electrolysis (an N ₂ separation step may be required). Thus, the DR plant 12 can also be operated if the iron producing plant 14 is not running (requiring only minimized external fuel/charges). Depending on the overall demand, the fuel/gas unit 12 can adjust the corresponding percentages of the recirculated flow F2 and the flow T3. CLAIM 1. A method of operating a metallurgical plant for the production of iron products, including a direct reduction plant (12) and an iron producing plant (14), in which: supplying an iron ore charge to a direct reduction plant for producing direct reduced iron products, operating a pig iron production plant to produce pig iron, wherein biochar is introduced into the pig iron production plant as a reducing agent, and thereby the pig iron production plant produces an exhaust gas containing CO and CO2, treating the exhaust gas from the iron producing plant in a hydrogen enrichment unit (32) to form a hydrogen-rich stream and a CO ₂ -rich stream, wherein the hydrogen-rich stream is directly or indirectly supplied to a direct reduction unit and the CO ₂ -rich stream is at least partially converted for processing in a direct reduction unit, it is primarily converted to syngas or natural gas. 2. The method according to claim 1, wherein dust, fines and other residues from the direct reduction plant are supplied to the iron producing plant as part of the charge to be melted therein. 3. The method according to claim 1 or 2, wherein at least a portion of the directly reduced product from the direct reduction plant is supplied to the iron producing plant as part of the charge to be smelted therein, wherein the directly reduced products include sponge iron and/or lump direct reduced products. 4. A method according to one of the preceding claims, wherein the hydrogen-rich stream is sent to the direct reduction unit as part of the reducing gas stream. 5. A method according to one of the preceding claims, wherein the hydrogen-rich stream is sent to a direct reduction unit as part of the gaseous fuel stream for heating purposes. 6. The method according to claim 4 or 5, wherein the CO _2- rich stream is supplied to a water electrolysis unit, supplemented - 10 045892 specifically provided by a steam stream to form a syngas stream, which is supplied to the direct reduction unit. 7. A method according to one of claims 1 to 3, wherein the hydrogen-rich stream and the CO2-rich stream are directed from the hydrogen enrichment unit to the methanization unit (36) to form a methane stream, which is sent to the direct reduction unit. 8. The method of claim 7, wherein at least a portion of the methane stream is used in the direct reduction unit as part of the reducing gas stream. 9. Method according to claim 7 or 8, wherein the direct reduction unit (12) includes a shaft furnace and a reformer reactor, and wherein at least a portion of the methane stream is supplied to the reformer reactor to produce reducing gas, preferably mainly hydrogen and monoxide carbon sent to the shaft furnace for use as part of the reducing gas stream. 10. The method according to claim 7, 8 or 9, wherein at least a portion of the methane stream is used as a portion of the gaseous fuel stream. 11. Method according to one of claims 7 to 10, wherein the water electrolysis unit (38) is connected to the methanization unit, wherein the steam output stream from the methanization unit is supplied to the electrolysis unit to form an auxiliary hydrogen stream, which is returned to the methanization unit. 12. The method according to claim 11, wherein a stream of steam from green energy is introduced into the water electrolysis installation. 13. The method according to claim 11 or 12, wherein a portion of the off-gas from the direct reduction unit is recycled to the methanization unit through a steam removal unit, wherein the removed steam is supplied to a water electrolysis unit. 14. The method according to claim 13, wherein the operation of the iron producing plant is controlled based on the amount of recycled exhaust gas. 15. The method according to claim 14, wherein the operation of the iron producing plant (14) is slowed down or stopped after reaching a steady state of operation in the direct reduction plant. 16. The method according to one of the preceding claims, wherein the off-gas stream from the iron producing plant is treated in a nitrogen removal unit (28) before being sent to a hydrogen enrichment unit. 17. Method according to one of the preceding paragraphs, wherein the hydrogen enrichment unit (32) includes a water-gas shift reactor. 18. A method according to one of the preceding claims, wherein the batch from the iron producing plant comprises substantially iron ore fines. 19. The method according to one of the preceding claims, wherein steam from green energy is introduced into the hydrogen enrichment plant. 20. The method according to one of the preceding claims, wherein at least a portion of the waste gas from the direct reduction plant is released into the atmosphere. 21. Method according to one of the preceding claims, wherein the biochar is produced in a biomass pyrolysis unit (16) from the biomass material. 22. The method according to one of the previous paragraphs, wherein part of the CO ₂ removed in the direct reduction unit is sent to a water electrolysis unit and mixed with steam to produce syngas. 23. The method according to one of the preceding claims, wherein the direct reduction unit is equipped with a steam-generating heat recovery system. 24. A metallurgical plant for the production of iron products for carrying out the method according to any of the preceding paragraphs, including: a direct reduction plant (12) configured to produce directly reduced products from an iron ore charge, a biomass pyrolysis plant (16) configured to produce biochar from the biomass material, an iron producing plant (14) configured to produce pig iron, wherein the pig iron production plant uses biochar as a reduction material and waste gas generation, a hydrogen enrichment unit (32) configured to receive the waste gas of an iron producing unit and produce a hydrogen-rich stream and a CO2-rich stream, and means for converting CO ₂ into a gas stream that is processed in a direct reduction, wherein the hydrogen-rich stream is directly or indirectly processed in a direct reduction unit. 25. The metallurgical plant of claim 24, including a methanization plant configured to receive a hydrogen-rich stream and a CO2-rich stream from the hydrogen enrichment plant and produce therefrom a biogas stream, primarily a methane stream, which is sent to a direct reduction plant. 26. Metallurgical plant according to claim 24 or 25, including a water electrolysis plant, -