WO2014104439A1

WO2014104439A1 - Method for manufacturing reduced iron

Info

Publication number: WO2014104439A1
Application number: PCT/KR2012/011716
Authority: WO
Inventors: 김현수; 조민영; 이달회; 고창국
Original assignee: 주식회사 포스코
Priority date: 2012-12-27
Filing date: 2012-12-28
Publication date: 2014-07-03
Also published as: CN104870655A; KR101384801B1

Abstract

Disclosed is a method for manufacturing reduced iron. The method for manufacturing the reduced iron according to the present invention comprises: charging iron ore into a reduction furnace; injecting reduction gas; and reducing magnetite, wherein the iron ore charged into the reduction furnace is mixed with a solid sulfur compound so that the sulfur (S) content with respect to the total mass ratio of the iron ore is between 0.1-1%, and wherein the pressure range of the reduction gas is no less than 1 atm.

Description

Manufacturing method of reduced iron

The present invention relates to a method for producing reduced iron, and more particularly to a method for producing reduced iron that can improve the reduction rate of sulfur-containing magnetite.

When manufacturing molten iron using a reduction furnace and a melting furnace, in the melting furnace, coal, pulverized coal, etc. are burned to melt the reduced iron to produce molten iron and slag. In addition, in a reduction furnace, oxygen is separated from iron ore using a reducing gas generated in a melting furnace and reduced.

In relation to iron ore charged in the reduction furnace, the necessity of using magnetite due to the depletion of high-grade hematite has recently increased. However, magnetite is classified as so-called hard-reducing ore, which is not easy to reduce.

When magnetite is reduced by carbon monoxide and hydrogen contained in the reducing gas, reduction proceeds from the surface of the magnetite to form a metal iron (Fe) layer on the surface of the magnetite.

Carburization reaction occurs in the metal iron layer, but at the same time, carbon precipitation reaction occurs to form graphite. When graphite is formed, it reduces the penetration of the reducing gas into the iron ore, thereby blocking the reaction of the iron oxide and the reducing gas in the iron ore.

Therefore, even if the amount of hydrogen in the reducing gas is increased in order to increase the reduction rate, as described above, the surface metal iron (Fe) layer formed on the surface of the magnetite becomes difficult to penetrate the reducing gas, thereby reducing the reduction rate.

An object of the present invention is to reduce the magnetite by reducing the surface iron (Fe) layer to facilitate the penetration of the reducing gas when the reduction rate is reduced by the formation of the surface iron (Fe) layer formed on the reduced iron surface during the reduction of magnetite, which is difficult to reduce It is to provide a method for producing reduced iron that can improve the efficiency.

Method for producing reduced iron according to an aspect of the present invention is a reduced iron manufacturing method for reducing the iron ore by charging the iron ore and reducing gas in the reducing furnace, the iron ore is a magnetite having a sulfur (S) content of 0.1 ~ 1%. , The reducing gas may have a pressure range of 1 atm or more.

The reducing gas may have a carbon activity of 1 or more.

In addition, the manufacturing method of the reduced iron according to another aspect of the present invention is a reduced iron manufacturing method for reducing the iron ore by charging the iron ore and reducing gas in the reducing furnace, the iron ore is a sulfur (S) content of less than 100ppm magnetite ore A solid sulfur compound including an ore having a high sulfur (S) content is mixed so that the mass ratio of sulfur is 0.1 to 1% based on the total ore mass ratio charged into the reduction furnace, and the reducing gas may have a pressure range of 1 atmosphere or more.

The reducing gas may have a carbon activity of 1 or more.

The reduction furnace may be a fluidized bed reduction furnace or a packed bed reduction furnace.

The reducing gas may include carbon monoxide 55-65%, hydrogen 15-25%, carbon dioxide less than 10%, nitrogen 10-15%.

According to the present invention, sulfur present in the ore or solid sulfur compound including magnetite is decomposed and adsorbed on the surface of the magnetite ore, thereby preventing carbon deposition but allowing the penetration of carbon, thereby improving the reduction efficiency and reduction rate of magnetite ore. Ore can be easily reduced.

1 is a graph showing the mass reduction rate according to the reaction time in the reduction of a typical magnetite.

2 is a graph showing the mass reduction rate according to the reaction time when the magnetite with low sulfur (S) content is reduced with hydrogen gas and replaced with a mixed gas of carbon monoxide and hydrogen.

3 is a graph showing the mass reduction rate according to the reaction time when the magnetite with high sulfur (S) content is reduced with hydrogen gas and replaced with a mixed gas of carbon monoxide and hydrogen.

4 is a view showing the principle of promoting the reduction of iron ore by sulfur (S).

5 is a graph showing the mass reduction rate according to the reaction time of iron ore having a high sulfur (S) content when the pressurized reducing gas is used.

FIG. 6 is a photograph showing a magnetite cross section in which a metal iron layer is broken and porous by using a sulfur compound in a reduction reaction.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

Method for producing reduced iron according to an embodiment of the present invention is a reduced iron manufacturing method for reducing the iron ore by charging the iron ore and reducing gas in the reducing furnace, the iron ore is a magnetite (S) content of 0.1 ~ 1% The reducing gas is characterized in that the pressure range of 1 atm or more.

The activity of carbon can be expressed as

2CO = C + CO ₂ (Equation 1)

The equilibrium constant of equation (1) is defined as

_{_{_{K 1 = a C · P CO2}}} / (PCO) 2 ( Equation 2)

CO + H ₂ = C + H ₂ O (Equation 3)

Similarly, the equilibrium constant of equation (3) is defined as

_{_{_{K 2 = a C · P H2O}}} / (P CO) · (P H2) ( Equation 4)

Where a _C is the activity of carbon in the gas. At constant temperature, K1 and K2 are constant, and the pressure of the entire gas is constant.

P _total = P _CO + P _CO2 + P _H2 + P _H2O + P _N2 = Schedule (Equation 5)

Solving Equations 2, 3, and 5 gives the carbon activity a _C. The activity of carbon in these reducing gases increases in proportion to the total gas pressure. The greater the pressure of the reducing gas, the greater the activity of carbon.

The reducing gas is characterized in that the carbon activity (carbon activity) of 1 or more.

If the activity of carbon is less than 1, the rate of carburizing on the reduced magnetite surface Fe layer is not effective. Carbon activity must be greater than 1 to increase confidence in the Fe layer.

In addition, the method for producing reduced iron according to another embodiment of the present invention in the reduced iron manufacturing method for reducing the iron ore by charging the iron ore and reducing gas in the reducing furnace, the iron ore is less than 100ppm sulfur (S) content The solid sulfur compound including ore in iron ore is mixed so that the mass ratio of sulfur is 0.1 to 1% based on the total ore mass ratio charged in the reduction furnace, and the reducing gas may have a pressure range of 1 atm or more.

The reduction furnace is characterized in that the fluidized bed reduction furnace or packed-bed reduction furnace.

The reducing gas is characterized in that containing 55 to 65% carbon monoxide, 15 to 25% hydrogen, less than 10% carbon dioxide, nitrogen 10 to 15%.

In the present invention, the reduction furnace may be a fluid reduction furnace of the FINEX process, a molten iron manufacturing process in which a molten gasifier and a plurality of fluidized-bed reduction furnaces are connected in multiple stages. In addition, the reduction furnace may be a packed-bed reduction furnace. When the packed-bed reduction furnace is used, the charged iron ore may be charged in the form of a block.

The reducing furnace is charged with a subsidiary material such as iron ore, limestone, dolomite, and the like to reduce the iron ore by reducing the iron ore by injecting a reducing gas containing carbon monoxide, hydrogen generated and supplied in the molten gasifier.

Preferably, the present invention may be used when the magnetite is reduced in the fluidized-bed reduction furnace used in the FINEX process.

In the fluidized-bed reduction reactor, the gas or natural gas formed through coal gasification reaction can be used. In this gas, trace amounts of hydrogen sulfide (H ₂ S) are commonly present.

However, in the molten iron manufacturing process, in general, H ₂ S can increase the content of S in molten iron as an impurity, thereby suppressing the incorporation of S in the process. Therefore, in the coal gasification reaction, the content of S in the coal is reduced as much as possible.

Likewise, if the content of S in the ore is high, its use may be restricted.

However, due to the development of current desulfurization technology, S in molten iron can be effectively removed, and the reduction rate of magnetite can be improved by using S, which is regarded as impurities or harmful substances.

The CO + H2 mixed gas generated during coal gasification or natural gas reforming enters a fluidized-bed reduction furnace loaded with ore to reduce magnetite to form Fe on the surface.

Carburization reaction occurs in Fe thus formed, but at the same time, carbon precipitation reaction, that is, graphite is formed, inhibits carburization and reduction and prevents gas from penetrating.

When this reaction occurs, all the carbon in the gas is converted to graphite, which does not contribute to the reduction, greatly reducing the gas utilization rate. Effective use of the S compound contained in the ore inhibits the formation of graphite to continuously infiltrate the inside of the ore to promote the reduction.

The infiltrated carbon reacts with the internal iron oxide to form a gas and simultaneously destroys the Fe layer.

On the other hand, the prediction that the reduction rate of magnetite increases as the hydrogen content increases during the reduction of magnetite is applied only when the diffusion rate of Fe ions is high in the high temperature region.

When the magnetite is reduced by using hydrogen, Fe layer is formed on the surface to inhibit gas penetration, thereby blocking the reaction between iron oxide and gas that has not been reduced inside, thereby rapidly reducing the reduction rate.

The reduction pattern of the magnetite ore reduced at 900 ° C. or lower at low temperature is a well known fact that the initial reaction rate is rapidly reduced by hydrogen as shown in FIG. 1, and can be easily confirmed by an experiment.

In the case of high temperature, the magnetite surface structure may be changed in various ways because the diffusion rate at which Fe ions of the iron oxide which is not reduced is increased to the surface is increased.

However, as mentioned above, magnetite reduction in magnetite reduction can not be significantly improved even when hydrogen is used, because the rate controlling step is diffusion of Fe ions at low temperatures. In order to improve the reducibility of magnetite, it is necessary to effectively destroy the Fe layer which prevents the penetration of gas. However, if physical energy is used for the destruction, it is very difficult in terms of the efficiency of the reaction, and the implementation of the method is also difficult and the application is difficult.

In other words, chemical energy is inevitably used, and as the cheapest resource, S compound, which is an impurity contained in ore, is used. It is known that even a very small amount of S as a surface active material can cover the surface and suppress the formation of graphite to solve problems such as metal dusting and to promote iron carbide formation.

However, there is no research or technology development to improve the reducibility of magnetite using the advantages of S.

When S is effectively used, the reducibility can be greatly improved by changing the structure of the reduced magnetite.

2 shows a change in the reduction pattern when the magnetite with low S content is reduced with hydrogen and the gas is converted into a CO + H ₂ mixed gas. When hydrogen is used, the initial mass loss rate is fast, but decreases quickly, and when it is substituted with CO + H ₂ , the mass increases significantly. This increase in mass is due to an increase in the precipitation rate of carbon, which reduces the reduction and forms graphite on the surface.

3 shows the change when hydrogen is reduced in magnetite with high S content and gas is replaced with CO + H ₂ mixed gas. As shown in FIG. 2, the reduction rate decreases soon, but the mass decreases again after a slight increase in mass during CO + H ₂ substitution. An increase in mass means an increase in the C content in the Fe layer formed upon reduction, and a decrease in mass means that the oxygen is removed, that is, the reduction starts again.

That is, it can be understood that the infiltration of the reducing gas which has been blocked is restarted. The reason for the infiltration of gas is that the precipitation of carbon is suppressed by S present in the ore, and carburization is continued, so that carbon meets iron oxide directly, and as a result of the reaction, CO is formed, and CO reacts with iron oxide to form CO2. It can be understood that the Fe layer is exploded by increasing the pressure at the Fe-Fe-oxide interface by repeating the reaction where C meets C and generates CO.

The mechanism for this is shown in FIG. 4.

On the other hand, a similar result can be obtained when mixing an ore having a high S content with an ore having a low S content.

This is because S of the ore having a high S content is transferred to the ore having a low S content, thereby increasing the S content. The mixing ratio of the ore having a high S content is preferably mixed so as to be 0.1 to 1% based on the total ore mass.

Induction of magnetite structure upon reduction using S described above can be applied even under pressurized conditions. At atmospheric pressure, gas corresponding to a gas component (carbon activity of 1.2 or more) containing 55 to 65% of CO, 15 to 25% of H ₂ , less than 10% of CO ₂ , and 10 to 15% of N ₂ can be pressurized without changing the composition. Through magnetite reduction can be improved.

This can increase the reduction rate without additional fuel consumption in economic terms. When pressurized to 4 atm, the carbon activity increases to 4.

The reducing effect of magnetite having a high S content has been described in FIG. 5. Ore with an S content of 0.1% or more and less than 1% in the ore is capable of increasing reducibility without H2S load. 6 shows a cross section of the porous reduced magnetite.

While the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings.

Claims

In the reduced iron manufacturing method for charging the iron ore into the reduction furnace and blowing the reducing gas to reduce the iron ore,

The iron ore is a magnetite having a sulfur (S) content of 0.1 to 1%,

The reduced gas is reduced iron production method characterized in that the pressure range of 1 atm or more.
The method of claim 1,

The reducing gas is a reduced iron production method, characterized in that the carbon activity (carbon activity) is one or more.
In the reduced iron manufacturing method for charging the iron ore into the reduction furnace and blowing the reducing gas to reduce the iron ore,

The iron ore is a magnetite having a sulfur (S) content of less than 100 ppm,

The reduced gas is reduced iron production method characterized in that the pressure range of 1 atm or more.
In the reduced iron manufacturing method for charging the iron ore into the reduction furnace and blowing the reducing gas to reduce the iron ore,

The iron ore is a mixture of a solid sulfur compound including a high sulfur (S) content to a magnetite ore having a sulfur (S) content of less than 100 ppm so that the mass ratio of sulfur is 0.1 to 1% based on the total ore mass ratio charged into the reduction furnace.

The reduced gas is reduced iron production method characterized in that the pressure range of 1 atm or more.
The method according to any one of claims 1 to 4,

The reducing furnace is a reduced iron production method characterized in that the fluidized bed reduction furnace or packed-bed reduction furnace.
The method according to any one of claims 1 to 4,

The reducing gas is carbon monoxide 55 ~ 65%, hydrogen 15-25%, carbon dioxide 10% or less, reduced iron production method characterized in that it comprises 10-15% nitrogen.