JPH08120314A - Production of iron carbide - Google Patents

Abstract

PURPOSE: To efficiently carry out cementation and gas reformation reactions in a single reactor having multiple reducing bands by converting iron oxide into iron carbide in the reactor.

CONSTITUTION: There is arranged a reformation-reduction-cementation reactor 10 having a positioned part for partially metallized iron oxide material, a positioned part for direct reduced iron and a positioned part for iron carbide. A metal oxide material contg. iron is supplied to the reactor 10 and the top gas from the reactor is recycled, to obtain a supplying gas contg. methane. The supplying gas is heated and mixed with air in a mixing chamber, to burn the mixture partially. Further, in the reactor, partially burned gas mixture is supplied to direct reduced iron, to obtain the reformed reduced gas. The iron oxide material is brought into contact with the reformed reduced gas, to obtain direct reduced iron. The direct reduced iron is brought into contact with a cementating agent in the reactor 10, to obtain iron carbide.

COPYRIGHT: (C)1996,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a metal oxide containing iron into a compound containing non-iron oxide, and more particularly to a method for converting iron oxide into iron carbide.

[0002]

BACKGROUND OF THE INVENTION Iron carbide is known to be a suitable starting material for the production of steel. U.S. Pat. No. RE32237 and U.S. Pat. No. 5,137,566 relate to a process for converting the feed to a reactor to iron carbide and then to steel. It should be said that the method disclosed in these US Pat. No. 2,780,537 is improved.

[0003]

Although the methods disclosed in the above patents have made important improvements in this industry, further improvements and reductions are required in many facilities. .

Therefore, the main object of the present invention is to provide a method for converting iron oxide into iron carbide.

Another object is to carry out the above conversion in a single reactor having a plurality of reduction zones.

Another object is to efficiently carry out the carburization and gas reforming reaction in the reactor.

Furthermore, it is also possible to provide a method in which excess methane from the carburizing zone is circulated to the upper gas and reformed in the reactor to produce a reducing gas that reduces the iron oxide material entering the reactor. To aim.

It is also an object to provide a method in which the reactor operates at relatively low pressure.

Other objects and advantages of the present invention will be apparent from the following description.

[0010]

According to the present invention, the above objects and advantages can be easily obtained. The present invention is applied to a method for directly reducing and converting an iron-containing metal oxide to produce iron carbide.

The method of converting iron oxides into iron carbide according to the present invention includes the following steps (a) to (i).

(A) About 1.15 × 10 ⁵ to about 1.45 × 1
Operating under a pressure of 0 ⁵ (Pa) [about 1.15 to 1.45 (bar)], and an arrangement part of a partially metallized iron oxide material, and an arrangement part of direct reduced iron, A reforming-reduction-carburizing reactor having an arrangement part of iron carbide is provided, (b) a metal oxide material containing iron is supplied to the reactor, (c)
Circulating a top gas from the reactor to obtain a feed gas containing at least 8.5 (vol%) methane, and (d) about 650 to about 8 of the feed gas.
Heat to 50 (℃), (e) in the mixing chamber, about 650 to about 8
Mixing 50 (° C.) air with the heated feed gas,
(F) The mixture of the air and the feed gas is partially burned to a temperature higher than about 850 (° C.), the oxidation degree of the partially burned gas mixture is about 0.27 to about 0.32, and the reducing power is about. Two
To about 3 (g) by supplying the partially combusted gas mixture to the direct reduced iron in the reactor to produce a reformed reducing gas having an oxidation degree of about 0.05 to about 0.09. Then, (h) directly reducing iron is obtained by contacting the iron oxide material with the reforming reducing gas, and (i) directly reducing iron in the reactor at about 550 to 750.
Contact with the carburizing agent at (℃), about 4.0-about 5.5 (wt%)
To obtain iron carbide containing at least 80 (wt%) iron.

The process according to the invention makes it possible to convert iron oxides to iron carbide using a single reactor with several reaction zones. In this reactor, excess carburizing gas is mixed with the circulated top gas in the presence of heated direct reduced iron (DRI). This direct reduced iron acts as a catalyst for the reforming reaction using the gas mixture as the reducing gas. Thereafter, the reducing gas comes into contact with the iron oxide to directly reduce the iron oxide.

This reforming reaction is an endothermic reaction, and the temperature of the heated DRI is lowered to a temperature suitable for carburizing in the carburizing zone of the reactor.

Such an arrangement improves the efficiency of the overall conversion process and allows the process to operate at low energy consumption levels.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

The present invention relates to a process for converting iron-containing metal oxides to carbides in a reforming-reduction-carburizing reactor.

FIG. 1 is a schematic explanatory view of a reactor 10 used for operating the process according to the present invention.

According to the present invention, the iron-containing metal oxide is fed to the reactor 10 through the inlet 16. The reactor 10 has each arrangement part of an iron oxide material, direct reduced iron, and iron carbide, and preferably, the flow of gas or the like in the reactor is directed downward from the inlet 16 supplying the raw material toward the outlet 18. To do. At the outlet 18, the iron carbide produced according to the present invention is discharged.

In accordance with the present invention, iron oxide is fed by metallic gas (D
RI) directly. The gas thus supplied is the one in which the upper gas from the outlet 20 is circulated, and is reformed into the reducing gas in the reactor 10 prior to the step of obtaining DRI.

The DRI thus obtained has an inlet 1
It is carburized by the carburizing gas supplied to the reactor 10 through 7.

In this connection, the reactor 10
It preferably has an iron oxide preheating pre-reduction zone 14, an iron oxide reduction zone 11, an integrated reforming reduction zone 12, and a carburizing zone 13, respectively. The supplied iron oxide material is reactor 1
0 is passed or passed through, preferably downward as it is converted to iron carbide.

The metal oxide provided is preferably about 63.
Contains about 70 (wt%) iron. This metal oxide is lumpy
It may be a lump, pellet or other suitable shape for feeding to the reactor.

Top gas exits reactor 10 through outlet 20. This top gas is typically about 8.5 to about 1
9.7 (vol%) methane, about 11.3 to about 14.9 (vol%) carbon dioxide, about 9 to about 17.8 (vol%) nitrogen, about 19 to about 24.7 (vol
%) Carbon monoxide, and about 33.2 to about 48.5 (vol%) hydrogen. The upper gas usually has a volume ratio of CH ₄ / CO ₂ of about 0.58 to about 1.0, CO / CO ₂ of about 1.4 to about 1.83, and H ₂ / H ₂ O of about 1.38 to about 2.0. Has become. The temperature of the upper gas is usually lowered to 350 to 450 (° C).

The top gas is circulated to the reactor 10 to provide a feed gas and at least 8.5 (vol%) CH ₄
Contains. The upper gas can be suitably circulated as follows. The upper gas is conveyed to the water separation unit 22 through the pipe 23. The water separation unit 22 preferably cools the upper gas to about 40 to about 60 (° C.) and reduces the water content to about 1 to about 3 (vol%). A suitable existing water separation unit may be used as the water separation unit 22.

After the removal of water is completed, the upper gas is divided into two. One of them is used as fuel for the heaters 24 and 26. Its function will be described later. The remaining top gas is preferably sent to the preheater 25 for about 200 to about 300.
It is heated to (℃). Then, if necessary, it is mixed with natural gas to form a make-up gas. Preferably at least 8.5 (vol%) of top gas circulated or feed gas
The above CH ₄ should be contained. The mixture of top gas and natural gas is then sent to a heater 24 (which is fed with the top gas initially separated above) and is about 650 to about 850 (° C), preferably about 680 to about 720.
It is heated to (℃). Heated gas mixture (feed gas)
After that, through the pipe 28, the mixer 3 of the reactor 10
Sent to 0. The heated gas is preferably sent to the mixer 30 at a rate of about 1000 to about 1100 Nm ³ per ton.

Air is also supplied to the mixer 30, preferably about 650 to about 850 of air through the heater 26.
It is heated to (℃). More preferably air is 680-72
Heat to 0 (° C). The air may be enriched with oxygen, preferably with a volume ratio of air to oxygen of 1: 7 to.
Make it 7: 1. Air or a mixture of air and oxygen is sent to the mixer 30 at a ratio of about 70 (Nm ³ ) to 1 DRI (ton).

The mixture of air, top gas and natural gas is
Then, it is partially burned to a temperature higher than about 850 (° C), preferably about 1000 to about 1100 (° C). This upper gas,
Natural gas and air preferably have a CH ₄ / (CO ₂ + H ₂ O) value of about 0.60: 1 to about 0.63: 1 by volume and a degree of oxidation of about 0.30 to about partially burned or oxidized gas. About 0.3
Operate the supply amount so that it becomes 5. That is, they are supplied in a stoichiometrically balanced manner.

The degree of oxidation (N _o ) is defined as follows using the volume of each component.

[0030]

## STR1 ## _{N o = (% CO 2 +} % H 2 O) / (% CO +% C
O ₂ +% H ₂ +% H ₂ O) In a mixer (mixing chamber) 30, the gas is preferably about 30-35 (vol%) H ₂ , about 15-17 (vol%).
CO, about 18 to 20 (vol%) CO ₂ , about 9 to 12 (vol
%) CH ₄ , and about 4 to 7 (vol%) steam.

This gas is then passed into the reactor 10, preferably the reforming reduction zone 12, and has a degree of oxidation of about 0.27 to about 0.32 and a reducing power (N _R ) of about 2.0 to about 3.0.

The reducing power is defined as follows using the volume of each component.

[0033]

N _R = (% CO +% H ₂ ) / (% CO ₂ +% H ₂ O) At the same time, the carburizing agent is supplied to the carburizing zone 13 through the inlet 17. The carburizing agent is preferably gas or natural gas, containing at least 80 (vol%) CH ₄ , the balance being H ₂ , CO, CO ₂ .

The carburizing gas is preferably about 400 to about 450.
It is supplied to the carburizing zone 13 at a ratio of (Nm ³ / ton). The fuel oil can be used as a carburizing agent by mixing it with methane so that it has the above composition, or by coexisting with methane. In this case, the carbon that can be used for carbonization is mixed in an amount sufficient to drive the above-mentioned reforming and carburizing reaction. Carburizing gas is about 550 to about 75 directly on reduced iron in the carburizing zone.
They come in contact at 0 (° C.) and act to form iron carbide according to the reaction formula shown below.

[0035]

## STR00003 ## 3Fe + CH ₄ → 2H ₂ + Fe ₃ C The remaining carburizing gas rises together with the contained CH ₄ into the reforming reduction zone 12, and by mixing with the inflow gas from the mixer 30, this gas The mixture is C as a whole
The value of H ₄ / (CO ₂ + H ₂ O) should be 0.65: 1 to 0.90: 1. In the reforming reduction zone 12, the mixed gas makes intimately contact with the heated DRI material. On DRI, solid metallic iron acts as a catalyst to provide a catalyst having a specific surface area of about 12 to about 16 (m ² / g).

The heat from the surface region induces a gas reforming reaction which is very endothermic. This reforming reaction is represented by the following equation.

[0037]

CH ₄ + CO ₂ → 2H ₂ + CO The reformed gas produced is about 45 to about 48 (vol%) hydrogen, about 32 to about 34 (vol%) carbon monoxide, about 2 to about 2 4 (vol%) carbon dioxide, about 1 to about 3 (vol%) methane, about 14 to about 16 (vol%) nitrogen, and about 1 to about 3
The composition has (vol%) water vapor, the degree of oxidation is about 0.05 to about 0.09, the reducing power is about 11 to about 29, and CH ₄
/ (CO + H ₂₎ volume ratio of from about 1: is 10: 10 to about 1.4.

According to the present invention, the endothermic reforming reaction and the excess carburizing gas flowing upward further cool the downward DRI material to a temperature suitable for the carburizing reaction. While the reformed gas flows upward through the iron oxide reduction zone 11, the iron oxide is reduced and metallized into DRI. The DRI produced in this way has a metallization degree (defined as the total weight% of reduced or metallized iron) of about 90 to about 93 (%), and is also immobilized by excess carburizing gas. And about 0.1 to about 1.0 weight percent of the carbon formed. Iron oxide is mainly iron oxide reduction zone 11
Within about 64 by the H ₂ and CO contained in the reformed gas.
It is reduced at 0 to about 750 (° C). The reaction formula is shown below.

[0039]

Embedded image 2FeO + H ₂ + CO → 2Fe + H ₂ O + CO _{2 The} remaining gas flows upward from the iron oxide reduction zone 11,
The zone 14 contacts the iron oxide introduced. In the present invention, the residual gas flowing upward still has sufficient heat and reducing power to preheat and prereduce the iron oxides of zone 14, preferably at a temperature of about 500 to about 550 (° C. ), The metallization degree is about 70 to about 80 (%) with respect to the total weight of iron.

The gas remaining after the above preheating and prereduction is
It flows further upward through the zone 14 to the outlet 20, where it is discharged as upper gas. Usually, the temperature is about 350 to about 450 (° C). The upper gas discharged in this way is then recycled further as described above.

FIG. 2 shows another embodiment of the present invention. In this embodiment, the carburizing zone 13 is divided and provided with an additional carburizing zone 13a for cooling and further carburizing as desired. The inlet 15 is provided in the carburizing zone 13a for supplying the cooling gas to the iron which is carburized and / or partially combusted and is moved downward from the carburizing zone 13. According to the present invention, carburization proceeds further by cooling to about 350 to about 400 (° C.). The cooling gas preferably contains about 8 to about 10 (vol%) CH _4, which results in a CO / CO ₂ value of about 1.4 to about 2.0 by volume. As described above, the carburizing gas is preferably about 400 to about 450 (Nm ³ /
ton) is supplied to the carburizing zone 13. The supply ratio in the embodiment of FIG. 2 is 50:50 to 80:20 (volume ratio) between the carburizing zone 13 and the carburizing zone 13a, respectively. As described above, the gas contacts the carbonized DRI / iron at the temperature determined in the carburizing zone 13a, and further carburizes iron by the Boudouard reaction shown below.

[0042]

Embedded image 3Fe + 2CO → Fe ₃ C + CO _{2 If} desired, cooling gas may be removed from the carburizing zone 13a through outlet 19 and circulated through inlet 15 after removing water and other undesirable constituents from the cooling gas.

The iron carbide material withdrawn from the reactor 10 contains about 4.0 to about 5.5 (%) by weight of immobilized carbon and at least 80 (wt%) iron.

Further, in the present invention, as shown in the figure, the smoke exhausted from the heaters 24 and 26 is used,
Preheating the top gas in the heater 25 may make the process more efficient.

In the process according to the invention, the reactor can be operated at a relatively low pressure, preferably about 1.15 × 10 ⁵
About 1.45 × 10 ⁵ (Pa) [about 1.15 to about 1.45 bars], more preferably about 1.3 × 10 ⁵ to about 1.4 × 10 ⁵ (Pa), most preferably about 1.34 × 10 ⁵ (Pa). Works. This has the advantage that the conversion can be carried out by a single reactor with multiple zones. As this reactor, one according to the prior art may be used.

According to the invention, iron-containing metal oxides are converted to iron carbide in a single reactor with multiple zones. Feed and gas temperatures are important at various steps in the process and, according to the present invention, the process can efficiently obtain each such temperature.

The metal oxide feed can be charged to the reactor at the desired temperature and is preferably preheated to about 500 to about 550 (° C.) by the top gas rising in zone 14.

The preheated and partially reduced iron oxide is sent to the iron oxide reduction zone 13. Here, the gas continuously heats the metal oxide to about 640 to about 750 ° C., followed by metallization and reduction of the iron oxide to DRI.

The DRI is then sent to the reforming reduction zone 12 and contacted with the gas introduced from the mixer 30 at a temperature higher than about 850 (° C.), preferably about 1000 to about 1100 (° C.).

At these temperatures, the DRI material acts as a catalyst for the gas reforming reaction, which is a highly endothermic reaction. Due to the endothermic nature of this reaction, the DRI material is about 80
The temperature rises only from 0 to about 850 (° C), and thereafter, about 550 to about 750 (° C), preferably about 620 to about 680 due to the excess carburizing gas rising from the carburizing zone 13.
It is cooled to (℃).

The DRI material is then sent to the carburizing zone 13,
The carburizing reaction is carried out there. If it is desired to cool the iron carbide produced before it is taken out, the further cooling / carburizing zone 13a shown in FIG.

The iron carbide produced is contacted with a cooling gas when it is sent to the zone 13a and is cooled to about 350 to about 400 (° C.). At this temperature, the cooling gas causes further carburization and the iron carbide material is finally removed at about 50 to about 60 ° C.

It should also be noted that other stoichiometrically compatible iron-carbon products, such as Fe ₂ C, can also be produced from the gas and feed.

The following table shows representative tests and their results by an extended test program using an industrial plant using the above-mentioned reduction and carburization process using a shaft furnace.

[0055]

[Table 1]

It goes without saying that the present invention can be variously modified and modified without departing from the spirit and scope thereof.

Therefore, the above embodiments are merely explanations of the embodiments, and do not limit the gist of the present invention described in the claims, and various means and ranges which are considered to be substantially the same may be changed. It is included in the invention.

[0058]

INDUSTRIAL APPLICABILITY According to the present invention, iron-containing metal oxides are converted to iron carbide by a single reactor having a plurality of zones. It is important to keep the temperature of the feed and the gas within a suitable range in each step, but in the present invention, each step can be kept at a suitable temperature by utilizing the heat of flue gas and the like.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a process and an apparatus according to the present invention.

FIG. 2 is an explanatory view of a process and an apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 10 ... Reactor 11 ... Iron oxide reduction zone 12 ... Reforming reduction zone 13 ... Carburizing zone 15 ... Inlet 16 ... Inlet 17 ... Inlet 18 ... Outlet 20 ... Outlet 22 ... Water separation unit 23 ... Pipe 24 ... Heater 25 ... Preheater 26 ... Heater 28 ... Tube 30 ... Mixer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Oscar Gee. Dam G. Venezuela, Ed. Bolivar, Puerto Ordus, URB. Los Saltos, Number 7, Month 12, Calle 4 (72) Inventor Henry Earl. Buenossee. Venezuela, Ed. Bolivar, Puerto Ordus, URB. Roraima, Casa Number 3, Month 5, Parsella 4

Claims (26)

[Claims] 1. About 1.15 × 10 ⁵ to about 1.45 × 10
A reforming-reducing-carburizing reactor is provided which operates under a pressure of ⁵ (Pa) and has an arrangement of partially metallized iron oxide material, an arrangement of direct reduced iron and an arrangement of iron carbide. A step, a step of supplying a metal oxide material containing iron to the reactor, and a step of obtaining a feed gas containing at least 8.5 (vol%) methane by circulating an upper gas from the reactor, Heating the supply gas to about 650 to about 850 (° C.), mixing air of about 650 to about 850 (° C.) with the heated supply gas in a mixing chamber, the air and the supply gas Partial combustion of the mixture with about 85
When the temperature is higher than 0 (° C), the partially burned gas mixture has an oxidation degree of about 0.27 to about 0.32 and a reducing power of about 2 to about 3.
And feeding the partially combusted gas mixture directly to the reduced iron in the reactor,
A step of obtaining a reformed reducing gas having an oxidation degree of about 0.09; a step of directly obtaining the reduced iron by bringing the iron oxide material and the reforming reducing gas into contact with each other; About 550 to 750 in the reactor
Contact with the carburizing agent at (℃), about 4.0-about 5.5 (wt%)
And a step of obtaining iron carbide containing at least 80 (wt%) of iron, the method comprising the step of converting iron oxide to iron carbide at low pressure. 2. The reforming reducing gas is H ₂ , CO and C.
The method of claim 1, wherein the method comprises H ₄ and the volume ratio of CH ₄ / (CO + H ₂ ) is about 1:10 to about 1.4: 10. 3. The reduced iron is directly added to the reduced iron by a step of bringing the iron oxide material into contact with the reforming reducing gas.
3. The carbon of 0 (wt%) is contained.
The described method. 4. The reforming reducing gas is about 9 to about 12 (vol).
The method according to claim 2, characterized in that it contains CH ₄ percent). 5. The method of claim 1, wherein circulating the top gas comprises preheating the top gas with the combustion flue gas from the heating the feed gas. 6. The upper gas is about 200 to about 300 (° C.)
6. The method of claim 5, wherein the method is preheated. 7. The degree of oxidation is about 9 by the step (h).
The process of claim 1 wherein direct reduced iron of 0 to about 93 (%) is obtained. 8. The carburizing agent comprises at least about 80 vol.
Methane and the balance H _2, CO, The method of claim 1, wherein the any one or a gas mixture consisting of any combination thereof of CO ₂ contained in%). 9. The mixture of air and feed gas is about 10.
The method according to claim 1, wherein the partial combustion is carried out at a temperature of 00 to about 1100 (° C). 10. The partially burned mixture is CH ₄
The value of / (CO ₂ + H ₂ O) is about 0.60: 1 to about 0.63: 1 by volume.
The method of claim 1, wherein: 11. CH of the partially combusted gas and carburizing agent mixture by mixing the partially combusted gas mixture with excess carburizing agent having CH ₄ in the reactor.
_The volume ratio of ₄ / (CO ₂ + H ₂ O) is about 0.65: 1 to about 0.9: 1.
The method according to claim 10, wherein: 12. A mixture of the partially combusted gas mixture and an excess of carburizing agent having CH ₄ in the reactor to produce CH of the partially combusted gas and carburizing agent mixture.
_The volume ratio of ₄ / (CO ₂ + H ₂ O) is about 0.65: 1 to about 0.9: 1.
The method of claim 1, wherein: 13. In the step of contacting the iron oxide material with the reforming reducing gas, directly reduced iron is produced by an endothermic reaction, and the temperature of the directly reduced iron is about 800 to about 850.
The method according to claim 1, wherein the temperature is (° C). 14. The method of claim 13 wherein excess carburizing agent further cools the direct reduced iron to about 600 to about 750 (° C.). 15. Excess carburizing agent flows upward and is mixed with inflowing partially combusted gas by sending the iron oxide material, the direct reduced iron and the iron carbide downward in the reactor. The gas mixture is reformed by contacting with the reduced iron directly to produce a reformed reducing gas that reduces the iron oxide material in the reduction zone of the reactor. Method. 16. The iron oxide material by contacting the reforming reducing gas with the iron oxide material and contacting the gas remaining after reduction with the iron oxide material falling into the reduction zone. 16. The method of claim 15 wherein the is preheated to about 500 to about 550 (° C). 17. The residual gas further pre-reduces the iron oxide material falling in the reduction zone to reduce the metallization degree to about 7.
17. The method according to claim 16, which is 0 to about 80 (%). 18. The method of claim 1, wherein the iron carbide is cooled by contacting the iron carbide with a cooling gas. 19. The cooling gas is CH ₄ from about 8 to about 10.
(vol%) and the volume ratio of CO / CO ₂ thereof is about 1.4 to 2.0, and the iron carbide is further carburized by the cooling gas.
The described method. 20. The further carburization is about 350-400.
20. The method according to claim 19, characterized in that it is performed at (° C). 21. In the cooling step, the iron carbide is about 5
The cooling is performed at 0 to about 60 (° C.).
8. The method according to 8. 22. The upper gas discharged from the reactor has a volume ratio of CH ₄ / CO ₂ of about 0.58 to about 1.0 and CO 2.
/ CO volume ratio of ₂ of about 1.4 to about 1.83, The method of claim 1, wherein the volume ratio of H ₂ / H ₂ O is about 1.38 to about 2.0. 23. The method of claim 1, wherein the metal oxide material contains about 63-70 (wt%) iron. 24. The step (e) comprises mixing the heated feed gas with oxygen-enriched air having a volume ratio of air to oxygen of about 7: 1 to about 1: 7. The method according to claim 1, wherein: 25. The partially combusted gas mixture is about 1100 to about 1200 (NM) with respect to 1 (ton) of direct reduced iron.
^3. The method according to claim 1, wherein the reduced iron is directly supplied in a ratio of ³ ). 26. The direct reduced iron is from 620 to about 680.
The method according to claim 1, wherein the carburizing agent is contacted at (° C).