CN221166600U

CN221166600U - A direct reduction facility for producing direct reduced iron

Info

Publication number: CN221166600U
Application number: CN202190001036.5U
Authority: CN
Inventors: 乔治·茨维克; 德米特里·布拉诺夫; 洪·雷耶斯罗德里格斯; 奥迪勒·卡里埃; 萨拉·萨拉梅; 何塞·巴罗斯洛伦索; 马塞洛·安德雷德; 丹尼斯·卢
Original assignee: ArcelorMittal SA
Current assignee: ArcelorMittal SA
Priority date: 2021-05-31
Filing date: 2021-05-31
Publication date: 2024-06-18
Anticipated expiration: 2031-05-31
Also published as: WO2022254235A1; ZA202310476B; DE112021007754T5; UA130207C2

Abstract

A method for producing direct reduced iron, wherein iron ore is reduced in a direct reduction furnace by means of a reducing gas which is discharged from the furnace roof as a top reduction reaction gas through the furnace roof. The top reduction reaction gas is captured and at least partially subjected to a carbon dioxide recovery step during which it is separated into two streams, a carbon dioxide-rich stream and a carbon dioxide-poor stream. The carbon dioxide-rich stream is subjected to a hydrocarbon production step to produce a hydrocarbon product.

Description

Direct reduction facility for manufacturing direct reduced iron

The present invention relates to a direct reduction facility for manufacturing direct reduced iron.

Steel can currently be produced by two main manufacturing routes. The most common production route today is to reduce iron oxides in a blast furnace by using a reducing agent (mainly coke) to produce pig iron. In this process, about 450kg to 600kg of coke is consumed per metric ton of pig iron; this process releases significant amounts of CO ₂, both in the production of coke from coal in coking facilities and in the production of pig iron. The pig iron produced is then decarbonized, for example to produce steel in a reformer or Basic Oxygen Furnace (BOF), which is then refined to obtain the appropriate composition, which is known as the BF-BOF route.

The second major approach involves the so-called "direct reduction process". Included are the methods according to the brands MIDREX, FINMET, ENERGIRON/HYL, COREX, FINEX, etc., in which sponge iron in the form of HDRI (hot direct reduced iron), CDRI (cold direct reduced iron) or HBI (hot compacted iron) is produced by direct reduction of an iron oxide support. Sponge iron in the form of HDRI, CDRI and HBI is typically subjected to further processing in an electric arc furnace.

There are three zones in each direct reduction shaft furnace with cold DRI discharge: a reduction zone at the top, a transition zone at the middle, a cooling zone at the bottom of the cone. In hot discharge DRI, this bottom section is mainly used for product homogenization prior to discharge and subsequent control of the bulk solids.

The reduction of iron oxide occurs in the upper section of the furnace, with temperatures up to 950 ℃. Iron oxide ore and pellets containing about 30 wt% oxygen are charged to the top of the direct reduction shaft furnace and allowed to fall under gravity through the reducing gas. The reducing gas enters the furnace from the bottom of the reduction zone and flows counter-currently to the charged iron oxide. In the countercurrent reaction between gas and oxide, oxygen contained in the ore and pellets is removed in the progressive reduction of iron oxide. The oxidant content of the gas increases while the gas moves toward the top of the furnace.

The reducing gas typically comprises hydrogen and carbon monoxide (synthesis gas) and is obtained by catalytic reforming of natural gas. For example, in the so-called MIDREX process, methane is first converted in a reformer to produce synthesis gas or a reduction reaction gas according to the following reaction:

CH4+CO₂＝2CO+2H₂

And the iron oxide reacts with the reducing gas, for example, according to the following reaction:

3Fe₂O₃+CO/H₂->2Fe₃O₄+CO₂/H₂O

Fe₃O₄+CO/H₂->3FeO+CO₂/H₂O

FeO+CO/H₂->Fe+CO₂/H₂O

At the end of the reduction zone, the ore is metallized.

The transition section is positioned below the reduction section; the section is of sufficient length to separate the reduction section from the cooling section, allowing independent control of both sections. In this section carburization of the metallization product takes place. Carburization is a process of increasing the carbon content of a metallization product inside a reduction furnace by the following reaction:

3Fe+CH₄→Fe₃C+2H₂

3Fe+2CO→Fe₃C+CO₂

3Fe+CO+H₂→Fe₃C+H₂O

The injection of natural gas in the transition zone is to use the sensible heat of the metallization products in the transition zone to promote hydrocarbon cracking and carbon deposition. Because of the relatively low concentration of the oxidant, the transition zone natural gas is more likely to crack into H ₂ and carbon than reform into H ₂ and CO. Cracking of hydrocarbons to DRI carburization provides carbon and simultaneously adds a reducing agent (H ₂) to the gas, which increases the gas reduction potential.

Gas injection is also carried out in the cooling zone, typically consisting of recirculated cooling gas plus added natural gas. In addition to the cooling gas, natural Gas (NG) allows an operator to keep the recirculating cooling gas loop high in methane, otherwise the main component in the cooling gas will be nitrogen. The heat capacity of natural gas is far greater than N ₂, the recycle flow of cooling gas is 500-600 Nm3/t when natural gas is added, and 800Nm3/t when natural gas is not added. Although there is not much carbon deposition in the cooling zone, the upward flow of cooling gas to higher levels in the furnace will provide more hydrocarbons for cracking.

From the above reaction, it can be seen that even though the CO ₂ footprint of the direct reduction pathway is lower than the BF-BOF pathway, the direct reduction process remains the producer of CO ₂.

There is a need for a method that allows for further reduction of carbon emissions.

There is also a need for a process that allows for an increase in the carbon content of the DRI product without the need for an external carbon source. The carbon content of the DRI product is a critical parameter which plays an important role in the subsequent steps and also helps to improve the transportability of the DRI product.

This problem is solved by the process according to the invention, wherein the iron ore is reduced in a direct reduction furnace by a reducing gas, which leaves the top of the furnace as a top reducing reaction gas, which is captured and at least partially subjected to a carbon dioxide recovery step, in which it is split into two streams, a carbon dioxide rich stream and a carbon dioxide deficient stream; the carbon dioxide rich stream is subjected to a hydrocarbon production step to produce a hydrocarbon product.

The method of the invention may also comprise the following optional features considered alone or in combination according to all possible techniques:

-hydrocarbon product is at least partially injected into the direct reduction furnace;

-the lack of a carbon dioxide stream as reducing gas to be re-injected into the furnace;

The carbon dioxide-rich stream comprises 80% to 100% by volume of carbon dioxide,

-1% To 20% by volume of the top reduction reaction gas is subjected to a hydrocarbon production step;

-providing a hydrogen stream to the hydrocarbon production step, reacting with a carbon dioxide rich stream;

The hydrocarbon product produced is a gas which is mixed with the reduction reaction gas before injection into the furnace;

the hydrocarbon produced is a liquid,

The hydrocarbons produced are injected separately from the reducing gas into the transition zone of the furnace,

The hydrocarbons produced are injected into the cooling zone of the furnace together with the cooling gas,

The hydrocarbon chain comprises 1 to 5 carbons,

The hydrocarbon production step is a methanation step,

The methanation step is a cold plasma reaction,

-Heating the reducing gas in a reducing gas preparation step, which releases the preparation off-gas, at least partly fed to the hydrocarbon production step, before it is injected into the direct reduction furnace.

The invention also relates to a direct reduction plant for performing the method according to the invention comprising a hydrocarbon production unit.

Other features and advantages of the invention will appear clearly from the description of the invention given below by way of indication and in no way limiting, with reference to the accompanying drawings, in which:

Fig. 1 shows that the elements in the layout diagram of a direct reduction device allowing to perform the method according to the invention are illustrative and may not be drawn to scale.

Fig. 1 shows a layout of a direct reduction facility allowing to perform the method according to the invention. The direct reduction furnace (or shaft) 1 is charged at its top with iron oxide 10 in the form of ore or pellets. The iron oxide 10 is reduced in the furnace 1 by a reducing gas 11 injected into the furnace and flowing counter-currently to the iron oxide. The reduced iron 12 leaves the bottom of the furnace 1 for further processing, such as briquetting, before use in a subsequent steelmaking step. After reducing the iron, the reducing gas 11 exits at the top of the furnace as top reducing reaction gas 20 (TRG).

The top reduction reaction gas 20 typically includes 15% to 25% by volume CO,12% to 20% by volume CO ₂, 35% to 55% by volume H ₂, 15% to 25% by volume H ₂ O,1% to 4% by volume N2. Its temperature is 250 to 500 ℃.

The cooling gas 13 is captured from the cooling zone of the furnace, passed through a cleaning step into a cleaning device 30, such as a scrubber, compressed in a compressor 31 and then returned to the cooling zone of the shaft 1.

According to the invention, the top reduction reaction gas 20, after a dust and mist removal step, preferably in a cleaning device 5 such as a scrubber and mist eliminator, is sent to a CO ₂ recovery device 8, where in the device 8 the CO ₂ from the top reduction reaction gas is concentrated and split into a CO 2-lean stream 21 and a CO 2-rich stream 22. The first stream 21, due to the lack of carbon dioxide content, is sent to a production unit 7 to be mixed with other gases, optionally reformed and heated, to produce the reducing gas 11. In a preferred embodiment, the preparation device 7 is a reformer. The preparation device 7 discharges a preparation exhaust gas 27, also called flue gas.

The CO2 recovery unit may be an absorption unit, an adsorption unit, a cryogenic distillation unit or a membrane. It is also possible that a combination of these different devices is possible.

The second stream 22, which is enriched in CO ₂ and preferably 1-20% by volume of the top reduction reaction gas 20, is sent to the hydrocarbon production unit 6 for the hydrocarbon production step. The second stream may comprise 80% to 100% by volume of carbon dioxide. In the hydrocarbon production plant 6, CO2 is first converted into carbon monoxide CO. This can be achieved by a hydrogenation step, when the amount of hydrogen is sufficient, to produce CO according to the following reaction:

CO₂+H₂->CO+H₂O

This reaction is the so-called reverse water gas shift Reaction (RGWS). The reaction is carried out in the presence of a catalyst such as ZnAl ₂O₄ or Fe ₂O₃/Cr₂O₃.

It may also be accomplished by thermochemical conversion, such as the Boudouard reaction or methane reforming, by electrochemical conversion or plasma technology.

According to the fischer-tropsch reaction, the CO thus produced is converted into hydrocarbons:

(2n+1)H₂+nCO->C_nH_2n+2+nH₂O

Where n is an integer greater than or equal to 1 and n takes precedence over 1 to 5.

The person skilled in the art knows how to select the correct catalyst and process conditions to carry out the required fischer-tropsch reaction and to produce the target hydrocarbons.

In a preferred embodiment, CO ₂ and H ₂ contained in CO ₂ -rich stream 22 react to form methane CH ₄ according to the following reaction:

CO₂+4H₂—>CH₄+2H₂O

In the present embodiment, the hydrocarbon production device is a methanation device 6, such as a catalytic reactor, a bioreactor, a cold plasma/DBD reactor or a hot plasma reactor.

If H ₂ enters the top reduction reaction gas and is therefore not present in the second stream 22 in an amount sufficient to effect hydrocarbon production reactions, an additional H ₂ stream 40 may be provided to the hydrocarbon production unit 6. Such a hydrogen stream may be provided by a dedicated hydrogen production facility 9, such as an electrolysis facility. It may be a water or steam electrolysis installation. Preferably CO ₂ is used to neutralize electricity, which consists essentially of electricity from renewable sources, defined as energy collected from renewable sources that are naturally supplemental on a human time scale, including sources like sunlight, wind, rain, tides, waves, and geothermal, among others. In some embodiments, power from the nuclear source may be used because the nuclear source does not expel CO ₂ to be produced.

H ₂ stream 40 may also be added to the reducing gas 11.

The flue gas 27 may also be supplied to the hydrocarbon production unit 6.

In a preferred embodiment, the hydrocarbon product 23 from the hydrocarbon production apparatus 6 is re-injected into the furnace 1.

In a first embodiment, stream 24 represents that the hydrocarbon product 23 is a gas that is mixed with a reducing gas in a production unit.

In a second embodiment, stream 25 represents either injection into the furnace with the reducing gas or injection into the transition zone of the furnace separately. In a third embodiment, stream 26 represents either injection into the furnace with cooling gas 13 or injection into the cooling zone of the furnace separately. The hydrocarbon product 23 may be gaseous and/or liquid. All of these embodiments may be combined with each other.

In all embodiments, the hydrocarbon product acts as a carbon provider of the DRI product. In a preferred embodiment, the carbon content of the direct reduced iron is set to 0.5 to 3wt.%, preferably 1 to 2wt.%, allowing for a direct reduced iron that is easy to handle and maintains good combustion potential for its future use. The amount of gas injected into the hydrocarbon production unit can be controlled based on the amount of carbon required for the DRI product.

The method according to the invention allows reducing the carbon footprint of the direct reduction process by capturing and utilizing the emitted CO ₂. It also avoids the need for external sources to increase the carbon content of the DRI product.

Claims

1. A direct reduction facility for manufacturing direct reduced iron, comprising:

A direct reduction furnace configured to reduce iron ore by a reducing gas, wherein the reducing gas exits from a top of the furnace as a top reduction reaction gas,

A carbon dioxide recovery device configured to capture and at least partially subject the overhead reduction reaction gas to carbon dioxide recovery, split it into two streams in recovery, a carbon dioxide rich stream and a carbon dioxide lean stream,

A hydrocarbon production unit configured to subject the carbon dioxide rich stream to hydrocarbon production to produce a hydrocarbon product.

2. The direct reduction facility of claim 1, wherein the hydrocarbon production unit is further configured to at least partially inject the hydrocarbon product into a direct reduction furnace.

3. The direct reduction plant of claim 1, wherein the carbon dioxide recovery device is further configured to re-inject the carbon dioxide-lean stream as a reducing gas into the furnace.

4. The direct reduction plant according to claim 1 or 2, wherein the carbon dioxide recovery means is further configured to obtain a carbon dioxide rich stream containing 80% to 100% by volume of carbon dioxide.

5. The direct reduction facility according to any one of the preceding claims, wherein the hydrocarbon production unit is further configured to subject 1% to 20% by volume of the top reduction reaction gas to hydrocarbon production.

6. The direct reduction facility of any of the preceding claims, further comprising a dedicated hydrogen production facility configured to provide a hydrogen stream to a hydrocarbon production unit to react with the carbon dioxide-rich stream.

7. The direct reduction plant according to any one of the preceding claims, wherein the hydrocarbon generation unit is further configured to generate hydrocarbon product of a gas that is mixed with the reduction reaction gas prior to injection into the furnace.

8. The direct reduction facility according to any of the preceding claims, wherein the hydrocarbon generation unit is further configured to generate liquid hydrocarbons.

9. The direct reduction plant according to any one of the preceding claims, wherein the hydrocarbon generation unit is further configured to inject the generated hydrocarbon separately from the reducing gas into the transition zone of the furnace.

10. The direct reduction facility according to any one of the preceding claims, wherein the hydrocarbon generation unit is further configured to inject the generated hydrocarbon into a cooling zone of the furnace.

11. The direct reduction facility according to any one of the preceding claims, wherein the hydrocarbon generation unit is further configured to generate hydrocarbons comprising hydrocarbon chains of 1 to 5 carbons.

12. A direct reduction plant according to any of the preceding claims, characterized in that the hydrocarbon production unit is a methanation unit.

13. The direct reduction plant according to claim 12, characterized in that the methanation means is a cold plasma reactor.

14. The direct reduction plant according to any of the preceding claims, further comprising a preparation device configured to heat the reducing gas prior to injection into the direct reduction furnace, wherein the preparation of such released preparation off-gas, the released preparation off-gas being at least partly supplied to the hydrocarbon production unit.