Method for operating a metallurgical plant for producing iron products

Abstract

The present invention relates to a method for producing pig iron from blast furnace charge materials, thereby producing metallurgical gases including blast furnace top gas (B1); The present invention relates to a method for producing an iron-containing product, comprising: operating a direct reduction plant for producing a directly reduced iron product from iron ore loaded at the top of a direct reduction furnace, wherein a reducing gas stream (D5) is introduced into the direct reduction furnace, the direct reduction plant comprising a reforming or heater device to which the reducing gas stream (D5) is discharged, whereby a top gas (D1) is produced by the direct reduction furnace, a first stream (D4) of the direct reduction plant top gas is treated in an enrichment stage arranged to enrich reducing species and is forwarded to the blast furnace plant for use therein as reducing gas; and a first stream of the metallurgical gases (B3 / B6) is forwarded to the reforming or heater device of the direct reduction plant for use therein as fuel gas. A corresponding metallurgical plant is also disclosed.

Description

[Technical field]

[0001] The present invention relates generally to the field of ferrous metallurgy, and in particular to metallurgical plants and methods for producing ferrous products. [Background technology]

[0002] Industrial processes account for 100% of global CO 2 Steel is a significant source of carbon dioxide emissions, and the current steelmaking process is highly energy and carbon intensive. With the existence of the Paris Agreement and a near-established global consensus on the need to address emissions, industrial sectors are focusing on improving energy efficiency and reducing CO 2 It is essential to research solutions to reduce CO emissions. 2 It is known for its emissions, but remains the most widely used process for steelmaking today, despite the existence of alternative methods (such as scrap melting and direct reduction in electric arc furnaces). In fact, the gas leaving the blast furnace, known as "top gas", typically contains high concentrations of CO, around 20 vol% to 30 vol%. 2 Contains:

[0003] Apart from this, blast furnace gas usually contains significant amounts of N 2 , CO, H 2 O and H 2 However, N 2 The content depends largely on whether hot air or (pure) oxygen is used in the blast furnace. In earlier times, this blast furnace top gas might simply have been allowed to be vented into the atmosphere, but this has long been considered a waste of resources and an undue burden on the environment.

[0004] Primarily to reduce coke usage, it has been proposed to capture blast furnace gas from the blast furnace, treat it to improve its reducibility, and reinject it into the blast furnace to assist the reduction process. One way to do this is to remove the CO in the blast furnace gas by Pressure Swing Adsorption (PSA) or Vacuum Pressure Swing Adsorption (VPSA). 2 The PSA / VPSA equipment reduces the amount of CO and H 2 a first stream of CO-rich gas; 2 and H 2 A second stream of gas that is rich in O is produced. The first stream of gas can be used as reducing gas and fed back to the blast furnace. One example of this is the Ultra Low CO2 Oxide (ULCOS) process. 2 Steelmaking; ultra-low CO 2 A top gas recycle OBF (oxygen blast furnace) process in which, apart from the first stream of recycled gas, pulverized coal and cold oxygen are fed to the blast furnace. This type of furnace is also called "top gas recycle OBF" (oxygen blast furnace). The second stream of gas is removed from the plant and can be disposed of after extraction of the residual calorific value. This disposal can be achieved by reducing CO 2 The PSA / VPSA system consists of pumping enriched gas into underground pockets for storage, which is controversial. 2 Although it is possible to significantly reduce the content from about 35 vol.% to about 5 vol.%, it is very expensive to acquire, maintain and operate, and requires a large amount of space.

[0005] Another technology developed to reduce carbon emissions during iron / steel production is the direct reduction process of iron ore. Although the annual production of direct reduced iron remains small compared to that of blast furnace pig iron, the CO 2 Emissions are significantly lower – 40-60% – for the direct reduction electric arc furnace (EAF) route compared to the blast furnace-basic oxygen route, making it very attractive.

[0006] In a direct reduction shaft furnace, the pelletized or lump iron ore charge is loaded into the top of the furnace and descends by gravity through the reducing gas. The reducing gas (syngas), consisting mainly of hydrogen and carbon monoxide, flows upward through the ore bed. Reduction of the iron oxide occurs in the upper part of the furnace, usually at temperatures up to 950 °C, but can be higher. The solid product, called direct reduced iron (DRI), is usually fed into an electric arc furnace at high temperature or is hot briquette (to form HBI).

[0007] As is known in the art, products such as DRI are fed into a blast furnace or steel plant, or a smelting furnace, such as an EAF, to produce pig iron or steel.

[0008] Blast furnace CO 2 Yet another approach aimed at reducing emissions involves the use of hot reducing gas, usually synthesis gas (CO and H), produced in a reformer from hydrocarbon gases. 2 It has been proposed to introduce hot reducing gas (synthesis gas) directly into the shaft of a blast furnace. Two possibilities have been proposed: injecting hot reducing gas directly into the shaft of the furnace through the tuyeres or above. This latter option is known as "shaft feeding" and involves introducing hot reducing gas (synthesis gas) into the outer wall of the furnace, above the tuyeres band, i.e. above the bosh, and preferably within the gas-solid reduction zone of ferrous oxide above the cohesive zone, typically in the stack area.

[0009] In addition, CO 2 In order to reduce emissions, many EU steelmakers are considering integrating direct reduction plants into their existing metallurgical plants, i.e. those plants include blast furnaces and pig iron post-treatment facilities.

[0010] The strategy for such facilities is to operate both the direct reduction plant and the blast furnace in parallel for many years in order to transition from oxygen to electric steelmaking. The direct reduction plant will be powered by natural gas reforming and green electricity. 2 It can be operated with reducing gas obtained by electrolysis. DRI is fed into the EAF together with scrap. A blast furnace is operated in parallel with materials containing iron and coke, and conventionally produced pig iron is treated in a basic oxygen furnace. Both the blast furnace and the EAF produce liquid steel that can be combined for further processing in the steelworks.

[0011] US 2004 / 0226406 describes an integrated steel works including a coke oven, a blast furnace, an oxygen blown blast furnace BOF, and a direct reduction reactor for producing direct reduced iron. The top gas of the direct reduction reactor passes through a heat exchanger and is split into partial streams. A portion of the top gas is cooled, washed and dried. The resulting washed gas is then used to control the temperature of the direct reduction reactor. The resulting washed top gas is passed through a compressor and a CO 2 The gas is sent to an absorber to regenerate the reducing capacity of the gas to form a regeneration gas, which is further combined with a gas stream containing coke oven gas and BOF gas. The resulting reduction gas is heated in a heater and sent to a direct reduction reactor. A part of the top gas from the direct reduction plant is used as fuel gas in a coking plant. Another part of the top gas is used as fuel gas in a blast furnace stove, i.e. a part of the top gas from the direct reduction plant is burned in the stove to generate the heat required to heat the cold blast, which is then converted into hot blast. The blast furnace is operated in a conventional manner and is charged with a conventional heavy load (iron ore, coke, etc.). The hot blast is injected through the tuyere together with PCI. A part of the blast furnace top gas is sent to a heater upstream of the direct reduction reactor to be burned as fuel gas. Objectives of the invention

[0012] It is an object of the present invention to provide an improved process for the production of iron products, in particular a more environmentally friendly process. Summary of the Invention

[0013] This object is achieved by the method as claimed in claim 1. According to the present invention, a method for producing an iron-containing product comprises: operating a blast furnace plant for producing liquid pig iron from blast furnace charge material and thereby producing metallurgical gases, including blast furnace top gas; operating a direct reduction plant to produce a direct reduced iron product from iron ore loaded to the top of the direct reduction furnace; a reducing gas stream is introduced into said direct reduction furnace, the direct reduction plant including a reforming or heater unit into which the reducing gas stream is discharged; As a result, top gas (D1) is produced by the direct reduction furnace, a first stream of the direct reduction furnace top gas is treated in an enrichment stage configured to enrich said stream in gaseous reducing species and is forwarded to a blast furnace plant for use therein as a reducing gas; and A process, wherein a first stream of metallurgical gases originating from a blast furnace plant and comprising blast furnace top gas is diverted to a reformer or heater unit of a direct reduction plant and used therein for heating purposes.

[0014] The present invention relies on a synergistic inter-exchange of gases, where "valuable" gases are used for metallurgical purposes and lean gases are used as fuel.

[0015] For example, the useful top gas of a direct reduction plant generally contains primarily reductant species, typically at least 55 or 60 vol.% CO and H 2 However, it usually consists of 10v% or more CO2 Also included.

[0016] The typical composition of blast furnace gas is generally 20-30 vol% CO 2 , about 35 to 50 vol% N 2 and about 20-30 vol% CO, about 5% H 2 However, these percentages can vary significantly depending on process conditions.

[0017] Other gases commonly used and available in steel plants are: Converter gas: 60-70v% CO, 10-20v% CO 2 , 0-5v% H 2 , 5-15v% N 2 , Coke oven gas: 5-10v% CO, 50-55v% H 2 , 20v% CH 4 , less than 10v% other concentrated hydrocarbons and the balance N 2 (Very small amount of %CO 2 ),. These numbers can vary significantly depending on process conditions.

[0018] As will become apparent from this disclosure, the present invention proposes an approach that goes against the conventional wisdom in the art. Traditionally, direct reduction plants need to burn fuel to achieve their process scopes: MIDREX® plants operate the MIDREX® reformer in NG plants and gas heaters in MX-Col plants, while Energiron / HyL technology requires heating of the reducing gas. In particular, the reducing gas needs to be heated to a suitable temperature for the reduction process (usually above 800°C) before being introduced into the direct reduction furnace.

[0019] Instead, the blast furnace produces blast furnace top gas, which is a lean gas.When operating at the same location, the direct reduction plant uses rich gas for combustion purposes, but the blast furnace - or integrated BF-BOF-plant, according to the inventor's findings, produces a significant amount of lean gas that is suitable for the combustion purposes of the direct reduction plant.

[0020] The term blast furnace plant, as used herein, includes not only blast furnaces but also integrated blast furnace plants that further include secondary metallurgical equipment such as blast oxygen furnaces, etc. In an embodiment, these other CO-containing export gases, e.g., converter gas, coke oven gas, and / or other CO-containing industrial gases, may be made valuable in the process.

[0021] Thus, the metallurgical gas stream originating from a blast furnace may be (only) blast furnace top gas or may contain a mixture of blast furnace top gas with amounts of gas from other facilities, e.g. gas from the BOF (usually less than 50%).

[0022] It should be noted that direct reduction plants, in standard operation, have a very good gas balance: export gas is usually not available. Every Nm of gas exported to other uses 3 must be replaced with suitable fuel.

[0023] The method of the present invention allows the parallel operation of a blast furnace plant and a direct reduction plant at the same site, with the benefit of mutual gas exchange and a reduction in coke consumption in the blast furnace. Initial evaluations suggest that a reduction in coke consumption of at least 15-20% (depending on the size of both the blast furnace and the DRI shaft furnace) is possible.

[0024] Depending on the embodiment, the blast furnace top gas and the direct reduction top gas can be split into several streams for use at different locations within the blast furnace or direct reduction plant. Conventionally, in a blast furnace plant, the blast furnace top gas leaving the blast furnace is preferably cleaned in a top gas cleaning unit before being exported to the direct reduction plant.

[0025] The enrichment stage is generally designed to condition / transform an inlet gas stream to obtain an outlet gas stream with a relatively increased content of gaseous reducing species. This usually involves mixing the enriched gas stream with an additional gas (to react with the enriched gas stream; mixing can occur upstream of the enrichment equipment or in the latter). The enrichment stage is preferably configured to carry out a reforming reaction, in particular dry or wet reforming.

[0026] The enrichment step preferably comprises the enrichment of gaseous reducing species, in particular H 2 and a reforming means (reforming plant) for producing an outlet syngas stream having an enriched content of CO. Such a reforming stage typically converts the CO present in the inlet gas mixture by a reforming reaction. 2 In other words, the enrichment stage allows the conversion of CO 2 CO and H 2 This allows the top gas from the direct reduction plant to be converted to CO 2 The content is significantly reduced (eg, below 5v%) upon passing through the enrichment stage.

[0027] In an embodiment, a second stream of blast furnace top gas (and / or converter gas, and / or coke oven gas, and / or another portion of another gas typically used in the industry) is used as fuel gas in the enrichment stage.

[0028] In the context of the present disclosure, the expression "used as fuel gas" means that the respective gas stream is combusted to generate heat. This is the gas at the heater that generates a flame that is used to heat the piping that contains the gas stream to be heated. Similarly, the expression "for heating purposes" means that the respective gas stream is used for its heating power, either by heat exchange or by combustion (i.e. as a fuel gas).

[0029] Furthermore, the expression "used as reducing gas" means that the respective gas stream is introduced into a furnace (blast furnace or DR plant furnace) to react with the input and operate the reduction of iron ore of iron oxide, respectively.

[0030] In an embodiment, a first stream of metallurgical gases (i.e., blast furnace top gas, possibly mixed with other portions of converter gas, and / or coke oven gas, and / or other gases typically used in the industry) is heated in a preheater upstream of a reforming or heater unit in a direct reduction plant, where a third stream of metallurgical gases can be combusted in the preheater.

[0031] As previously mentioned, the first, second or third stream of metallurgical gas may comprise only BF top gas or may comprise a mixture of blast furnace top gas (i.e. throat gas) and one or more other CO-containing gases, such as converter gas, coke oven gas, and / or other CO-containing industrial gases. Preferably, the metallurgical gas comprises at least 30% blast furnace top gas.

[0032] Conventionally, direct reduction plants recycle the top gas from the direct reduction reactor. A second stream of the direct reduction reactor top gas is injected into a reformer / heater unit, with the hydrocarbon gas forming / conditioning the reduction gas stream that is reintroduced into the direct reduction reactor. Also, a third stream of the direct reduction reactor top gas is used as fuel gas in the reformer-heater unit. The hydrocarbon gas used in the reformer-heater unit can be natural gas or CO 2 , H 2 O and CH 4 CO and H 2 may be any other suitable hydrocarbon gas suitable for conversion to

[0033] Advantageously, a portion of the first stream of direct reduction furnace top gas can be combined with a hydrocarbon gas (e.g., natural gas, coke oven gas, other suitable hydrocarbon) to form a synthesis gas which is treated in an enrichment stage (usually by a reforming reaction) before being introduced into the blast furnace.

[0034] A notable advantage of this technique is the reduction of CO from the gas stream. 2 Instead of removing CO from the synthesis gas, 2 (i.e., via a reforming-based enrichment step).

[0035] In an embodiment, the above-cited hydrocarbon is coke oven gas, in order to utilize the gas available in the background of steelmaking. Coke oven gas is usually H 2 and C.H. 4 When mixed with direct reduction top gas, the resulting synthesis gas stream contains 4 and CO along with H 2 It contains most of the reduced species such as H 2 , C.H. 4 and CO may represent 65, 70 or 75 vol.% or more.

[0036] When reformed in the reforming stage, this gas stream typically contains more than 80% reducing species, e.g., H 2 The content may exceed 55 vol.% and the CO content may exceed 25 vol.%.

[0037] The invention also relates to a metallurgical plant as defined in claim 17. These and further embodiments are defined in the accompanying dependent claims.

[0038] As is evident, the invention proposes the following advantageous approaches: 1) A solution to balance the gas exchange from the blast furnace plant to the direct reduction plant. 2) Solutions to optimize gas usage by promoting rich gas for metallurgical purposes and lean gas for combustion purposes. 3) CO from synthesis gas (before injection into the blast furnace) is enriched with reducing species (by reforming reactions) instead of using it to remove hydrocarbons. 2 A solution using. 4) A solution to export lean BF gas for use in the DR process without special treatment (except heating, mixing with gas, or combustion with added oxygen). [Brief description of the drawings]

[0039] [Figure 1] FIG. 1 is an applicable diagram showing a first embodiment of a metallurgical plant for carrying out the method. [Diagram 2] FIG. 2 is an applicable diagram showing a second embodiment of a metallurgical plant for carrying out the method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Further details and advantages of the present invention will become apparent from the following detailed description of non-limiting embodiments, with reference to the following drawings, in which Figures 1 and 2 are applicable diagrams showing two embodiments of a metallurgical plant 10 for carrying out the present method. The metallurgical plant 10 includes, but is not limited to, at least one blast furnace plant 12 and at least one direct reduction plant 14.

[0041] Conventionally, the metallurgical plant 10 further comprises: coke oven plants(s)24; A tuyere injection plant 26 (this plant produces the medium that is injected into the blast furnace through the tuyere. The most common medium is pulverized coal (PCI), but it could also be natural gas (NG)); Steelmaking facilities(38) Includes.

[0042] The blast furnace plant 12 conventionally includes a number of conventional elements (i.e. high-temperature stoves, storehouses, etc.) next to the blast furnace 16 itself, although only the furnace 16 is shown in the figures. As is known, the furnace 16 is fed with input materials (iron bearings, coke and flux) from the top. For this purpose, a top-feed installation (not shown), for example of the BELL LESS TOP® type, is arranged above the top of the furnace and serves to distribute the blast furnace materials in the furnace. A hot blast of air (or hot air) is introduced into the furnace 16 through tuyere tubes distributed circumferentially around the furnace 16 and connected to a peripheral / annular bustle tube 18.

[0043] The end products are hot metal and slag tapped from the bottom, and a waste gas leaving the top of the furnace 16 called top gas. A blast furnace is a countercurrent reactor: a downward flow of ore together with flux comes into contact with an upward flow of hot carbon monoxide-rich gas. The blast furnace top gas (exhausted through the blast furnace throat) produced by the operation of the blast furnace is denoted as B1. In a conventionally operated blast furnace, the top gas is generally 20-30 vol% CO 2 , about 35 to 50 vol% N 2 , about 20-30 vol% CO and about 5% H 2 It is a dilute gas containing

[0044] The top gas stream B1 leaving the blast furnace 16 is usually washed in a washing unit (not shown). In the process of its operation, the blast furnace plant 12 produces not only blast furnace top gas in the blast furnace 16 but also other CO-containing gases coming from other facilities, such as coke oven batteries and basic oxygen furnaces. The direct reduction plant 14 is of conventional design. It includes a vertical shaft furnace 20 with a top inlet and a bottom outlet. The charge of iron ore in lump and / or pellet form is loaded at the top of the furnace 20 and allowed to descend by gravity through the reducing gas. The charge remains in a solid state during the movement from the inlet to the outlet. The reducing gas, indicated as D5, is introduced laterally in the furnace 20 at the base of the reduction section and flows upwards through the ore bed. The reduction of the iron oxide takes place in the upper part of the furnace at temperatures up to 950° C. and higher.

[0045] The solid product - direct reduced iron (DRI) - is typically discharged from the furnace 20 at high temperature and can then be: charged hot to a downstream steelmaking facility (e.g., an electric arc furnace); formed into hot briquettes to form HBI; cooled in a separate vessel as cold DRI; or a combination of these options.

[0046] Regarding the direct reduction process, two processes, MIDREX (registered trademark) NG and HyL, are mainly used worldwide to produce the various forms of DRI described above.

[0047] In the MIDREX process, the reducing gas stream D5 originates from the reformer 22 of the direct reduction plant 14, where a portion of the top gas leaving the furnace 20 is combined with a hydrocarbon gas (e.g., natural gas) to produce CO and H, as is known in the art. 2 The reformer 22 preferably implements a reforming process primarily by reaction, including but not limited to: CH 4 +CO 2 →2CO+H 2 (Formula.1) CH 4 +H2 O→CO+3H 2 (Formula.2) CO+H 2 O→CO2+H 2 (Formula.3)

[0048] In the MIDREX® NG process, the reformer 22 is typically equipped with an integrated heat recovery system, as known to those skilled in the art.

[0049] The reformer comprises a reactor in which the reforming reactions take place. As these reactions are endothermic, the reactor is heated in heat exchange relationship with combustion gases (produced by an integrated burner) and / or hot gases (external gases). An integrated heat recovery system typically comprises a heat exchange means arranged to heat one or more gas streams on their way to the reformer by hot gases from the DR plant, in particular flue gases from the reformer.

[0050] In the HyL process, there are instead two possibilities: 1) Hydrocarbons are reformed in a steam reformer into CO, H 2 , C.H. 4 The gas is then reformed into gases with different contents and then heated in a heater before being injected into the shaft furnace. 2) Hydrocarbons are added to a steam reforming (w / o reforming) process.

[0051] Thus, as will be appreciated by those skilled in the art, the reference number 22 in Figure 1 (and Figure 2) represents either a MIDREX reformer or a HyL steam reformer and / or heater, depending on the technology implemented, i.e., the reference number 22 can be a reformer (any suitable type, particularly MIDREX, HyL) or a heater (where reforming is not required prior to introduction into the furnace).

[0052] Reference numeral 24 denotes a coke oven plant, where reference numeral C1 denotes a coke oven gas (COG) stream and reference numeral C2 denotes the coke produced therein. The COG stream C1 contains, for example, at least 60 vol.% or 70 vol.% reducing species, mainly H2 (>50v%) and CH 4 The reducing gas includes

[0053] Reference numeral 38 represents a steelmaking facility which may include Basic Oxygen Furnaces (BOF), Electric Arc Furnaces (EAF) and / or other similar furnaces well known in the steelmaking industry. As shown, gases produced in one of these furnaces or facilities may be combined with blast furnace top gas for use in a direct reduction plant. Thus, as used herein, "metallurgical gases" refers to a gas stream originating from a blast furnace plant and including either only BF top gas or a mixture of BF top gas and other CO-containing gases from the BF plant, particularly from facility 38 and / or coke oven 24.

[0054] Reference 26 refers to the plant for final injection into the blast furnace. One of the most common systems is the Pulverized Coal Injection (PCI) system, which includes a conveying hopper and / or a distribution hopper for temporary storage of pulverized or granular coal or carbonaceous material connected via a dedicated pipe to the tuyere zone of the blast furnace. The pulverized coal stream is indicated by T1. Injecting pulverized coal is beneficial in terms of reducing the overall cost of the hot metal produced, not only by replacing the coke, but also by increasing the productivity and the possibility of rapid control of the blast furnace operation.

[0055] The coke oven plant 24 and system 26 may be of conventional design. The two plants operate in parallel to produce iron products, i.e., liquid pig iron and solid iron products. The DRI is melted in the EAF and mixed with the pig iron, and the mixture undergoes secondary metallurgy in the steel mill.

[0056] As mentioned above, the current CO 2In the framework of emissions reduction, many EU steelmakers are considering setting up direct reduction plants within existing integrated steelworks. The strategy for such installations is to operate both the direct reduction plant and the blast furnace for several years in order to transition from oxygen to electric steelmaking.

[0057] The present invention proposes a combined approach of a blast furnace plant and a direct reduction plant to reduce the coke consumption in the blast furnace. The present invention proposes a synergistic inter-exchange of gases where the "useful" gases are used for metallurgical purposes and the lean gases are used as fuel. When operating alone, the direct reduction plant needs to burn fuel (to generate heat) to achieve the working scope of its process (the MIDREX plant needs to run a reformer and the Energiron / HyL process needs to heat the reducing gas).

[0058] When operated in the same location, the direct reduction plant uses rich gas for combustion purposes, but the blast furnace plant - according to the inventors' knowledge - produces significant amounts of lean gas which is suitable for the combustion purposes of the direct reduction plant.

[0059] Furthermore, direct reduction plants, in standard operation, have a very good gas balance: there is usually no export gas available. For every Nm of gas exported for other uses, 3 must be replaced with a suitable fuel.

[0060] By operating a blast furnace plant and a direct reduction plant together at the same location according to the method of the present invention, it becomes possible to mutually exchange gases, and it is possible to reduce the amount of coke consumed in the blast furnace, as will be described below.

[0061] EMBODIMENT 1 In the embodiment of FIG. 1 , a top gas stream, designated D1, exits the furnace 20 of the direct reduction plant 14 and is split into several streams: a first stream D2 which, after being treated in a reformer / heater unit 22, is recycled to the direct reduction reactor 20 as reducing gas, which may also be supplied with a hydrocarbon gas, such as natural gas; A second stream D3 sent to a reformer / heater for use as fuel gas to process and heat the D2 / D5 streams. This stream D3 may be combusted to provide heat to enable the reforming reactions of D2 / D5, which can be easily extracted by heat exchange to heat D2 / D5; A third stream D4 forms the export gas stream which is valued at the blast furnace plant.

[0062] The top gas of a direct reduction furnace is rich, primarily reducing gas, typically containing at least 55 or 60 vol.% of reducing species, i.e., CO and H. 2 This is the case for flows D1, D2, D3, and D4. H 2 The content may be between about 40 and 50 vol%.

[0063] The two first streams D2 and D3 are conventional. It is indeed common in direct reduction plants to recycle a portion of the top gas of the direct reduction furnace as process gas to be combined with hydrocarbon gases (e.g. methane) to produce synthesis gas in unit 22, while another portion of the top gas is used in the heating section to produce, by combustion, heat to heat unit 22. Indeed, in the MIDREX configuration, the direct reduction top gas is recycled to form synthesis gas in the reformer, but is also directed to the heater side of the reformer and burned there.

[0064] However, in the present process, a portion of the direct reduction furnace top gas, i.e., stream D4, is branched off and mixed with coke oven gas C1 (or other hydrocarbon gas source) to produce synthesis gas S1. Stream S1 is rich in reducing species, but contains a non-negligible proportion of CO 2 originating from the direct reduction furnace 20. 2 Stream S1 is fed to an enrichment unit 30 that includes a reforming facility, where the reforming reaction occurs with the hydrocarbon gases (e.g., natural gas, coke oven gas) contained in S1 to produce CO 2 , H 2O and CH 4 CO and H 2 (similar to Equations 1, 2, and 3). At the outlet of the reformer 30, the output stream S2 is converted into reduced species, i.e., H 2 and CO, resulting in a suitable (strongly reducing) chemical composition for injection into the blast furnace 12. Preferably, a heat exchanger 32 is used to heat stream S1 in heat exchange with stream S2 before entering the dry reforming plant 30. After the heat exchanger, stream S2 still has a suitable temperature for injection in the blast furnace. The heat exchanger S2 simply releases heat and does not change its chemical composition.

[0065] In this case, due to the nature of the dry reforming process, the flue gas leaves unit 30 at a high temperature (i.e. around 700°C) and such heat can be utilized to heat stream B4 (by heat exchange - thus saving the consumption of B5).

[0066] Flow S1 includes CH 4 and CO, mainly H 2 It contains most of the reduced species such as H 2 , C.H. 4 and CO may have values ​​greater than 65, 70 or 75 vol.%.

[0067] Stream S2 has a further reducing strength, with the total reduced species exceeding 80%. For example, H 2 The content may exceed 55 vol.% and the CO content may exceed 25 vol.%.

[0068] As mentioned before, the conventionally operated direct reduction plant is balanced and has no export gas. However, in order to divert a part of the direct reduction furnace top gas via stream D4 used to generate synthesis gas S1 / S2 for the blast furnace plant 12, it is necessary to replace the heat content of D4 in the direct reduction plant 14. This is achieved by replacement with blast furnace gas, i.e. by stream B6. B6 is thus a metallurgical gas stream that is used as fuel gas in the DR plant, i.e. combusted to generate heat for the DR process.

[0069] Because stream B6 may have an inherently lower heating value than stream D4, it may be necessary to combust B6 using an air / oxygen mixture (stream O1 from oxygen source 34) or by using additional fuel.

[0070] In addition, it may be necessary to preheat stream B6 prior to use in unit 22. The blast furnace top gas stream exiting the top of blast furnace 16 is split into several streams: a first stream B2 which is sent to the reforming unit 30 and used therein as fuel (i.e. combusted in a burner) to enable / sustain the reforming reaction; A second stream B3 is sent to the direct reduction plant 14 to replace the stream D4 exported to the blast furnace. B3 is split into: Stream B5, which may be combusted in preheater 36 to provide suitable heating for stream B4 (if necessary); Stream B4 / B6, optionally heated in preheater 36 and then combusted in the heater section of unit 22; The B7 is exported to a variety of users.

[0071] Note that in standard blast furnace operation, streams B2, B3, B4, B5, and B6 do not exist.

[0072] EMBODIMENT 2 2, a second embodiment is shown which differs from the first embodiment in the way in which the synthesis gas stream S1 is treated: the reforming stage 30 and heat exchanger 32 are replaced by a separate reformer 42 and heater 40.

[0073] As will be appreciated by those skilled in the art, device 40 is the same type of heater as device 36 of the first embodiment.

[0074] The reformer 42 is similar to the MIDREX® reformer in that it has a heat recovery system integrated with the reformer. The synthesis gas S2 in this embodiment is produced simply by mixing stream D4 with an appropriate amount of hydrocarbon (i.e., natural gas).

[0075] Fuel for the burners of unit 42 (i.e. stream B3.1) is produced using blast furnace top gas, similar to stream B3 of embodiment 1. It may be necessary to preheat stream B3.1 (into B6.1) by burning a portion (B5.1) in unit 40. This is in fact the same idea as described for unit 36 ​​of embodiment 1.

[0076] Example 1 Because stream B6.1 may have an inherently low heating value, it may be necessary to combust B6.1 using an air / oxygen mixture (stream O1.1 from oxygen source 34) or by using additional fuel.

[0077] As mentioned above, streams B3, B3.1, B4, B4.1, B5, B5.1, B6 and B6.1 may be referred to as metallurgical gases and, depending on the embodiment, may refer to the initial 100% BF top gas stream B3 or may refer to a mixture of the BF top gas stream, additional gases such as CO-containing gases from the steelmaking facility 38 and / or the coke ovens 24.

[0078] It should be noted that the reforming stage in the blast furnace plant (using reformer 42 and heater 40) and the reformer 22 with heater 36 in the direct reduction plant are functionally equivalent. Therefore, in some embodiments (not shown), the two pieces of equipment can be merged, so to speak. In other words, a larger reformer and heater system can be designed that can handle the DR top gas sent to the DR furnace and blast furnace.

[0079] Calculation example The following data refers to a specific case study analyzed using the configuration of embodiment 1. For illustrative purposes, exemplary compositions of the various streams are shown in Table 1.

[0080] [Table 1]

[0081] Example 1 A simulation was performed using an example in which a blast furnace produces approximately 8 MTPY and a direct reduction plant produces approximately 3.7 MTPY, and the following approximate values ​​were obtained. B1=1500Nm 3 / tHM (Nm per ton of hot metal 3 ) B2=350Nm 3 / tHM B3=560Nm 3 / tHM B7=640Nm 3 / tHM D4=142Nm 3 / tHM (DRI or HBI 300Nm 3 / t) C1=75Nm 3 / tHM O1=35Nm 3 / tHM (DRI or HBI 75Nm 3 / t) S2=250Nm 3 / tHM,BF injection 950℃ C2=228kg / tHM T1=198kg / tHM

[0082] When comparing the blast furnace and direct reduction furnace operated independently without gas exchange and at the same processing capacity (8MTPY BF plant, 3.7DR plant), the following changes are observed. T1 - No change C2-Consumption of Example 1 reduced by 47kg / tHM (0.37MTPY) C1 - consumption 75Nm 3 / tHM increase B7 - Export volume 730Nm 3 / tHM reduction O1 - consumption 35Nm 3 / tHM increase As can be seen, the process of the present invention can reduce the coke consumption by about 16%.

[0083] Use of enriched top gas In the present process, the blast furnace gas stream B3 can be mixed with other gases, such as, for example, converter gas, coke oven gas, and / or other CO-containing industrial gases. That is, the blast furnace top gas (i.e., throat gas) can be mixed with other gases from the steel plant. The use of mixed blast furnace gas may require adaptation of other process parameters, such as injection of oxygen. However, as shown in Table 2, mixing the blast furnace top gas with other gases in various ratios can make these alternative gas sources valuable while maintaining a proper heat balance in the reformer.

[0084] [Table 2]

[0085] In Table 2, BFG stands for blast furnace top gas (throat gas), COG stands for coke oven gas, BOF stands for basic smelter gas, and TGF stands for direct reduction top gas fuel. For all compositions in Table 2, the same flame temperature, i.e., heat balance in the reformed state, is achieved. As is evident, if the blast furnace top gas is mixed with other gases, the BFG portion can be reduced to 20% and still achieve the desired heat balance.

[0086] Example 2 Example 2 relates to the second embodiment described with reference to FIG. In the following Table 3, the inventive approach of embodiment 2, the described invention, is compared with a counter example. The counter example represents a conventional example in which a blast furnace plant and a direct reduction plant are operated in parallel and independently.

[0087] [Table 3]

[0088] As can be seen, the process of the present invention, with synergistic gas exchange between the blast furnace plant and the direct reduction plant, requires less coal consumption per tonne of hot metal (compensated by electricity input) and less CO 2Emissions can be reduced by approximately 11%.

Claims

1. Operating a blast furnace plant (12) to produce pig iron from blast furnace feed materials and thereby generate a metallurgical gas comprising blast furnace top gas (B1); Operating a direct reduction plant (14) to produce a direct reduced iron product from iron ore charged to the top of a direct reduction furnace (20), A reducing gas stream (D5) is introduced into the direct reduction furnace, and the direct reduction plant includes a reforming or heater device (22) from which the reducing gas stream (D5) is discharged, whereby top gas (D1) is generated by the direct reduction furnace, A first stream (D4) of direct reduction plant top gas is treated in an enrichment stage (30; 42, 40) configured to enrich gaseous reducing species and transferred to the blast furnace plant where it is used as a reducing gas; And A first stream of the metallurgical gas (B3 / B6) is transferred to the reforming or heater device of the direct reduction plant and used therein as fuel gas, A method for producing an iron-containing product.

2. The method according to claim 1, wherein a second stream (B2) of the metallurgical gas is used as fuel gas in the enrichment stage.

3. The method according to claim 1 or 2, wherein the first stream (B3) of the metallurgical gas is heated in a preheater (36) upstream of the reforming or heater device (22).

4. The method according to claim 3, wherein a third stream (B5) of the metallurgical gas is burned in the preheater.

5. A second stream (D2) of top gas of the direct reduction furnace is supplied to the reforming or heater device (22) together with a hydrocarbon gas to form the reducing gas stream (D5) introduced into the direct reduction furnace, the method according to claim 1 or 2.

6. The method according to claim 1 or 2, wherein a third stream (D3) of top gas of the direct reduction furnace is used as fuel gas in the reforming or heater device.

7. The first stream (D4) of direct reduction furnace top gas is combined with a hydrocarbon gas upstream of the enrichment stage to form a synthesis gas stream (S1) supplied to the enrichment stage, and the synthesis gas stream (S2) at its outlet is introduced into the blast furnace, the enrichment stage preferably including reforming means, the method according to claim 1 or 2.

8. The method according to claim 7, wherein the hydrocarbon stream combined with the direct reduction top gas stream (D4) comprises coke oven gas.

9. The synthesis gas stream (S1) contains 45 to 55 vol.% H2, 15 to 25 vol.% CO and 7 to 15 vol.% CH4; and the outlet stream (S2) contains more than 55 vol.% H2 and more than about 25 vol.% CO, the method according to claim 8.

10. The preheating of the synthesis gas stream (S1) is achieved by heat exchange with the synthesis gas stream at the outlet downstream of the enrichment stage, the method according to claim 1 or 2.

11. The enrichment stage includes a reformer with an integrated heat recovery system, and the fourth stream of the metallurgical gas is possibly fed to the heat recovery system directly with the top gas stream of the direct reduction plant and optionally with an additional hydrogen stream, the method according to claim 1 or 2.

12. A heater is associated with the reforming stage; the fourth stream of the metallurgical gas is preheated in the heater and part of it is optionally burned in the heater, the method according to claim 11.

13. An oxygen-enriched stream is supplied to the reforming or heater device for combustion, the method according to claim 1 or 2.

14. The reforming device (22) includes an integrated heat recovery system to which blast furnace gas is supplied, the method according to claim 1 or 2.

15. The metallurgical gas consists of blast furnace top gas; or blast furnace top gas mixed with other CO-containing gases from a blast furnace plant, in particular coke oven gas or basic refining furnace gas, the method according to claim 1 or 2.

16. The flue gas of the enrichment stage is transferred to a preheater (36) for heating purposes, the method according to claim 1 or 2.

17. A blast furnace (16) plant for producing pig iron, the blast furnace plant generating a metallurgical gas containing blast furnace top gas (B1), A direct reduction plant (14) including a direct reduction furnace (20) configured to produce direct reduced iron products from iron ore, and a reforming or heater device (22) for generating a reducing gas introduced into the direct reduction furnace, the direct reduction furnace generating a top gas (D1), A first pipe for carrying a first stream (B3) of the metallurgical gas to the direct reduction plant for use as fuel gas for the reforming or heater device therein. A second pipe for conveying a first stream (D4) of top gas from the direct reduction furnace to an enrichment stage configured to enrich the reducing species, and a third pipe for conveying the resulting enriched stream (S2) from the enrichment stage to the blast furnace plant for use as a process gas. A metallurgical plant including the above. **Claim 18** The metallurgical plant according to claim 17, comprising means for injecting the enriched stream (S2) into the blast furnace for direct injection via tuyeres or into the stack region. **Claim 19** The metallurgical plant according to claim 17 or 18, wherein the first stream (D4) of top gas from the direct reduction furnace is mixed with a hydrocarbon gas upstream of the enrichment stage to form a synthesis gas stream (S1). **Claim 20** The metallurgical plant according to claim 19, wherein the synthesis gas stream passes through a heat exchanger heated by the enriched stream (S2) exiting the enrichment stage. **Claim 21** The metallurgical plant according to claim 17 or 18, wherein the first stream (B3) of the metallurgical gas is heated by a preheater (36) before being burned in the reforming or heater device. **Claim 22** The metallurgical plant according to claim 17 or 18, wherein in the enrichment stage, a second stream (B2) of the metallurgical gas is used as fuel gas. **Claim 23** The metallurgical plant according to claim 17 or 18, wherein the third stream (B5) of the metallurgical gas is burned in the preheater (36). **Claim 24** The direct reduction plant is configured such that a second stream of the top gas is treated in the reforming or heater device before being recycled in the furnace, and a third stream of the top gas is burned in the reforming or heater device. The metallurgical plant according to claim 17 or 18. **Claim 25** The enrichment stage includes reforming means and is specifically configured to enrich the first stream (D4) with reducing species by a reforming reaction with hydrocarbons, i.e., by increasing the H2 and CO content. The metallurgical plant according to claim 17 or 18.

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