KR20170136664A - Reducibility improved carbon composite iron oxide agglomerate and the preparation method thereof - Google Patents

Abstract

The present invention relates to a reducibility improved iron oxide agglomerate having carbon therein, and a method of manufacturing the same. More specifically, the present invention relates to the method of manufacturing iron oxide agglomerate, and the reducibility improved iron oxide agglomerate having carbon therein comprising: iron oxide powder; a solid reducing agent having carbon; and flux. The present invention has a basicity of 0.5-1.6.

Description

TECHNICAL FIELD [0001] The present invention relates to a carbonaceous compacted iron oxide compacted material having improved reducibility and a method for producing the same,

The present invention relates to a carbonaceous compacted iron oxide compact having improved reducibility and a method for producing the same.

Steel production has been steadily increasing globally, and production by electric furnace steelmaking, which is a method of producing steel from iron ore with coal or coke as a reducing agent, is also increasing. Accordingly, the scrap used as the main raw material for the electric furnace steelmaking process is unstable in supply and the composition control including the impurity element is difficult to control when using low grade scrap iron such as scrap steel. In order to solve these problems, Direct Reduced Iron (DRI), which is a source of iron produced by adding a reducing gas such as carbon monoxide and hydrogen to solid iron ore, is attracting attention as a clean alternative iron source.

On the other hand, in the field of steelmaking, research is underway to utilize carbonaceous iron oxide briquettes, which are agglomerated with a mixture of iron ore and coal, in commercial blast furnaces and sintering machines.

In the case of the conventional sintering process, the quality of the sintered ores is deteriorated due to the uneven distribution of heat in the upper and lower portions of the sintered bed. Therefore, in order to compensate for the insufficient amount of heat in the upper part, the combustion gas condition is changed, an additional fuel is injected, a powder mixture of iron ore and coal is compacted in the lower part of the sintering bed And a method of segregating and charging a briquetting iron oxide briquettes having been made into a solidified material.

Korean Patent Laid-Open No. 10-2010-0011990 discloses a method for manufacturing a carbonaceous internal metal oxide briquette, and more particularly, to a method for producing a carbonaceous internal metal oxide briquette, A mixing step of mixing a metal oxide raw material containing a large amount of fine particles and a carbonaceous material into a powder mixture by a mixer, a molding step of compression molding the powder mixture into a briquetting machine, A classifying step of classifying the sieved body into a sieve body and a sieve body and using the body as the carbonaceous material-containing metal oxide briquette which is the product; and a step of classifying the part as a recycle material into the mixer or the briquetting machine A method for manufacturing a carbon-bearing metal oxide briquette, which comprises the steps of:

On the other hand, in the blast furnace, the carbon dioxide (CO ₂ ) Studies are underway on mitigation.

As a method for producing the reduced carbonaceous material-containing iron oxide briquettes, there is known a method of mixing and compression-molding iron oxide such as a mineral ore and a mill scale and a solid reducing agent, and then reducing the mixture at a high temperature of 1200 ° C or higher. The above-mentioned reduction method can utilize a low-grade iron ore and coal in the form of a derivative, which has an advantage in utilization of resources, and can contribute to improvement of economy through reduction of raw material cost. In addition, it has a faster reaction rate than a reduction reaction by natural gas, and is capable of a reduction reaction at a relatively low temperature, resulting in low fuel cost and environmental friendliness.

Korean Patent Laid-Open Publication No. 10-2014-0065555 discloses a pellet built-in pellet which is capable of securing strength at room temperature without firing by using molasses as a binder, thereby enabling high-efficiency blast furnace operation. A method for manufacturing a carbonaceous material-containing pellet including 75 to 79 parts by weight of iron ore, 19 to 20 parts by weight of coke, and 2 to 6 parts by weight of molasses has been disclosed and a method for producing the same.

However, the above methods have a problem in that the impurities such as gangue and ash which are inevitably present in the low-grade ores and the pulverized coal, suppress the direct contact between the iron oxide and the carbonaceous material and delay the reduction reaction.

Accordingly, the inventors of the present invention have conducted research on a method for reducing the carbonaceous built-up iron oxide compacted material, in order to improve the reducing characteristic of the carbonated iron oxide briquette, Iron oxide briquettes were prepared, and the present invention was completed.

Korean Patent Publication No. 10-2010-0011990 Korean Patent Publication No. 10-2014-0065555

SUMMARY OF THE INVENTION

And a method for producing the same.

In order to achieve the above object,

Wherein the iron oxide powder comprises iron oxide powder, solid reductant powder containing carbon and a flux, and the basicity is 0.5 to 1.6.

In addition,

Preparing a mixture having a basicity of 0.5 to 1.6 by mixing iron oxide powder, solid reductant powder containing carbon and a flux (step 1); And

And molding the mixture (step 2). The present invention also provides a method for manufacturing the carbonaceous material compacted iron oxide compact having improved reducibility.

Further,

And a step (1) of heat-treating and reducing the carbonaceous iron oxide compacted material having improved reducing properties (step 1).

The carbonaceous compacted iron oxide compact having the improved reducing ability of the present invention can be produced by melting the impurities such as ash and ash which are inevitably present in the low grade ore and coal by controlling the basicity of the carbonaceous built-up iron oxide compact, There is an advantage that the reducing ability of reducing the carbonaceous built-up iron oxide compacted material can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing an apparatus for reducing a briquetting iron oxide briquette according to an embodiment of the present invention,
FIG. 2 is a photograph showing the shape of a specimen according to the basicity of the carbonaceous built-in iron oxide briquettes produced by the examples and comparative examples of the present invention,
3 is a graph showing the gas volume fraction and the temperature pattern of carbon monoxide (CO) and carbon dioxide (CO ₂ ) generated during the reduction reaction of the carbonaceous built-in iron oxide briquettes produced by the examples and the comparative examples of the present invention,
FIG. 4 is a graph comparing the reduction characteristics of the carbonaceous built-in iron oxide briquettes produced by the examples and comparative examples of the present invention, and is a graph comparing the generation behavior of carbon dioxide (CO ₂ ) according to the basicity,
FIG. 5 is a graph comparing reduction characteristics of carbon monoxide-containing iron oxide briquettes produced by the examples and comparative examples of the present invention, and is a graph comparing generation behaviors of carbon monoxide (CO) according to basicity,
6 is a graph showing the results of calculation of reduction rates of the carbonaceous built-in iron oxide briquettes manufactured according to the examples and comparative examples of the present invention over time,
7 is a graph showing the final reduction ratio according to the basicity conditions of the carbonaceous built-in iron oxide briquettes produced by the examples and the comparative examples of the present invention,
8 is a photograph of the microstructure of the carbonaceous built-in iron oxide briquettes produced by Comparative Example 2 and Example 1 of the present invention through an optical microscope,
9 is a photograph of the microstructure of the carbonaceous built-in iron oxide briquettes produced by Comparative Example 2 and Example 1 of the present invention through a scanning electron microscope (SEM)
10 is a graph showing the results of calculation of the melting point of a flux used in Examples and Comparative Examples of the present invention using FactSage, which is a thermodynamic calculation program.

The present invention

Wherein the iron oxide powder comprises iron oxide powder, solid reductant powder containing carbon and a flux, and the basicity is 0.5 to 1.6.

Hereinafter, the carbonaceous compacted iron oxide compact having improved reducing ability of the present invention will be described in detail.

The carbonaceous compacted iron oxide compacted material may be one selected from the group consisting of briquettes, spherical pellets, and cylindrical pellets, depending on the shape and manufacturing method, which are obtained by agglomerating, i.e., agglomerating, the bulk mixture.

Carbonaceous iron oxide compacted iron oxide is used for producing pig iron from iron ore in the ironmaking process, and the iron contained in iron or iron oxide can reduce iron oxide. In the case of reducing iron ore or iron oxide by the conventional reducing gas, expensive natural gas is required and there is a limitation such that the location of the plant is usually limited to a natural gas production site. On the other hand, The method of reducing iron ore or iron oxide using compacted cargo has the advantage that it has a faster reaction rate and can perform a reduction reaction at a relatively low temperature, thus resulting in a low fuel cost and being environmentally friendly.

In addition, the carbonaceous built-up iron oxide compacted material includes iron oxide powder and solid reductant powder containing carbon, and the iron oxide and solid reductant powder can be used in the form of low-grade iron ore and coal in the form of fine powder, It is possible to contribute to improvement of economic efficiency through That is, in various processes in the steelworks, dust may occur in the process of transporting coal, and slag may occur in the process of collecting exhaust gas during the manufacture of molten iron. Since the slag or dust includes carbon or iron, Can be saved.

At this time, the solid reductant powder containing carbon is preferably coal.

Meanwhile, the carbonaceous built-in iron oxide compact may include a flux, and the carbonaceous built-up iron oxide compact may have a basicity of 0.5 to 1.6.

This is to increase the reducing property of the carbonaceous built-up iron oxide compacted product during the reduction reaction through high-temperature heat treatment.

In this case, the basicity of the SiO ₂ Can be defined as CaO weight% relative to weight%.

In the case of conventional carbonaceous iron oxide compacted materials, impurities such as gangue and ash which are inevitably present in the low-grade ore and coal have a disadvantage in that the reduction reaction is delayed by suppressing direct contact between iron oxide and carbonaceous material.

On the other hand, in the case of the present invention, the carbonaceous built-in iron oxide compact can contain a flux having a basicity of 0.5 to 1.6, whereby the impurities can be controlled to a composition capable of melting at a low temperature, The reducing ability of the carbonaceous built-in iron oxide compact can be improved.

If the basicity is less than 0.5, a poorly reducible phase may be formed during the reduction reaction, resulting in a low reduction rate. For example, CaO, SiO ₂ And Al ₂ O ₃ , and having a basicity of 0.408, a Fe ₂ SiO ₄ phase having a poor reducing property can be formed and the reducing property of the carbonaceous built-in iron oxide compact can be reduced.

In addition, when the basicity exceeds 1.6, the melting point of the flux is increased, and the reduction ability can be reduced as the opportunity for direct contact between iron oxide and carbonaceous material is reduced.

At this time, it is preferable that the flux is included in 5 to 14% of the total weight of the carbonaceous built-up iron oxide compact.

This is based on the amount of gangue and ash contained in commercial iron ore and coal, but the content of the flux is not limited thereto.

Components of the flux are CaO, SiO ₂ And Al ₂ O _3. It is preferable that the carbonitride-incorporated iron oxide compact has a basicity value of 0.5 to 1.6 by controlling the content of the component.

For example, the flux may include Al ₂ O ₃ relative to the total flux weight 13 to 14%, the CaO and SiO ₂ 38 to 48%, and the carbonaceous built-in iron oxide compact can have a basicity value of 0.5 to 1.6.

In addition,

Preparing a mixture having a basicity of 0.5 to 1.6 by mixing iron oxide powder, solid reductant powder containing carbon and a flux (step 1); And molding the mixture (step 2). The present invention also provides a method for manufacturing the carbonaceous raw material containing iron oxide compact having improved reducing ability.

The method for producing a carbonaceous built-up iron oxide compact according to the present invention is characterized in that a mixture in which a flux is uniformly mixed with minute iron oxide and carbon so as to have a basicity value of 0.5 to 1.6 is subjected to spherical pelleting by electric granulation using a pelletizer , Cylindrical pelletization by mechanical extrusion, and briquetting by compression to produce a carbonaceous compacted iron oxide compact having improved reducibility.

Further,

And a step (1) of heat-treating and reducing the carbonaceous compacted iron oxide compact having improved reducibility produced by the above-described production method, thereby producing a reduced carbonaceous built-up iron oxide compact.

The reduced iron oxide compacted iron oxide compact material of the present invention is produced by reducing the iron oxide compacted iron oxide compacted material of the present invention. The reduction of the iron oxide contained in the carbonized iron oxide compacted material of the step 1 is reduced, It can be directly reduced by the carbon contained in the carbonaceous raw iron oxide compacted material and indirectly reduced by the carbon monoxide (CO) formed by the reaction with the iron oxide and carbon.

The reduction can be performed by heat-treating the carbonaceous built-in iron oxide compacted product at an elevated temperature of 1200 ° C or higher in an inert atmosphere.

Hereinafter, the present invention will be described in detail with reference to the drawings through examples and experimental examples.

However, the following Examples and Experimental Examples are merely illustrative of the present invention, and the contents of the present invention are not limited by the following Examples.

≪ Example 1 >

Carbonaceous iron oxide compacted materials with improved reducing properties were prepared by the following steps.

Step 1: 73.46%, 16.54%, and 10% of the total weight of the graphite powder (C) and the flux of the solid reducing agent (hematite, Fe ₂ O ₃ ) And the mixture was uniformly mixed using a mixer for about 24 hours to prepare a mixture.

At this time, the molar equivalence ratio (C / O) of the iron oxide (hematite, Fe ₂ O ₃ ) and the graphite (C) was 1.0 and the flux was CaO, SiO ₂ , Al ₂ O ₃ The powder was mixed and the ratio of Al ₂ O ₃ 13.4%, CaO 38.9% and SiO ₂ 47.7% was included, thereby preparing a mixture having a basicity of 0.816. At this time, the basicity was calculated by the following formula 1.

<Formula 1>

CaO (wt.%) / SiO ₂ (weight %)

Step 2: 5 g of the mixture of step 1 was placed in a mold having a diameter of 20 mm, unidirectionally compression-molded at a pressure of 2000 kgf / cm ² , and then dried in a dry oven at 120 ° C for about 24 hours To remove the adhered moisture to produce a carbonaceous internal iron oxide briquettes.

Step 3; The carbonaceous built-in iron oxide briquettes prepared in the above step 2 were placed on an alumina plate (Al ₂ O ₃ plate) and placed in a heat zone in a SiC horizontal tubular furnace as shown in FIG. Thereafter, a nitrogen (N ₂ ) gas was flowed into the tubular furnace to make it an inert atmosphere, and the temperature was increased from 200 to 1000 ° C at a rate of 20 ° C / min, at a rate of 10 ° C / min from 1000 to 1200 ° C, The mixture was reduced at a temperature of 1200 DEG C for 20 minutes and then cooled to obtain a reduced carbonaceous material-containing iron oxide briquettes.

&Lt; Example 2 >

In step 1 of Example 1 above, the flux was added to the total flux of Al ₂ O ₃ 13.4%, CaO 47.7%, and SiO ₂ 38.9%, so that a mixture having a basicity of 1.224 was prepared. The same procedure as in Example 1 was repeated to produce a carbonitride-incorporated iron oxide briquettes.

&Lt; Comparative Example 1 &

In step 1 of Example 1, the graphite (C) powders, which do not include flux but contain iron (hematite, Fe ₂ O ₃ ) and solid reducing agent, are varied to include 81.64% and 18.36% Except that the briquettes of the present invention were produced in the same manner as in Example 1,

&Lt; Comparative Example 2 &

Except that in step 1 of Example 1 the flux was made to comprise 13.4% Al ₂ O ₃ , 86.6% CaO, and 86.6% SiO ₂ relative to the total weight of the flux, Was carried out in the same manner as in Example 1 to prepare a carbonitride-incorporated iron oxide briquettes.

&Lt; Comparative Example 3 &

In step 1 of Example 1 above, the flux was added to the total flux of Al ₂ O ₃ 13.0%, CaO 25.1%, and SiO ₂ 61.5%, to prepare a mixture having a basicity of 0.408. The carbonitride-incorporated iron oxide briquettes were produced in the same manner as in Example 1,

&Lt; Comparative Example 4 &

In step 1 of Example 1 above, the flux was added to the total flux of Al ₂ O ₃ 13.4%, CaO 53.7%, and SiO ₂ 32.9%, so that a mixture having a basicity of 1.632 was prepared. The same procedure as in Example 1 was carried out to produce a carbonitride-incorporated iron oxide briquettes.

The above Examples and Comparative Examples are summarized in Table 1 below.

Iron oxide (%)
black smoke(%)
Flux (%)
Flux composition basicity
CaO SiO ₂ Al ₂ O ₃ (%) Comparative Example 1 81.67 18.36 0 - - - - Comparative Example 2

73.46



16.54



10

0 86.6 13.4 0 Comparative Example 3 25.1 61.5 13.4 0.408 Example 1 38.9 47.7 13.4 0.816 Example 2 47.7 38.9 13.4 1.224 Comparative Example 4 53.7 32.9 13.4 1.632

<Experimental Example 1> Observation of the shape of the reduced carbonaceous briquettes

In order to compare the shapes of the reduced carbon monoxide-containing iron oxide briquettes produced according to Examples and Comparative Examples of the present invention, the reduced carbon monoxide-containing iron oxide briquettes produced by Examples 1 and 2 and Comparative Examples 1 to 4 were visually observed , And the results are shown in Fig.

2 (a). (b), (c), (d), (e) and (f) This is a photograph showing the iron oxide built-in iron oxide briquettes.

In the case of Fig. 2 (a), it was confirmed that the specimen shrinks and the volume decreases as compared with the specimen before the reduction experiment. It can be considered that the residual carbon (C) is carburized in the metallic iron (Fe) formed by the reduction of the iron oxide, and as a result, the diffusion of the metallic iron (Fe) increases and the agglomeration proceeds.

At this time, it was visually confirmed that the residual graphite remained on the inside and the surface of the reduced iron oxide-incorporated iron oxide briquettes.

In the case of FIG. 2 (b), it was confirmed that the metal iron (Fe) coagulated in the form of coarse spherical particles, and the melted slag flowed out of the specimen and collapsed the shape of the reduced carbonaceous internal iron oxide briquettes.

At this time, it was confirmed that the residual graphite was separated from the metal iron (Fe) and the slag and remained on the surface.

2 (c) to 2 (f), it was confirmed that the initial briquetting shape was maintained, but the volume was expanded compared to before briquetting.

At this time, the reduced metal iron (Fe) was present in the form of a plurality of fine spherical particles, and it was confirmed that it was weakly bonded to powdered slag and graphite by hand so as to be crushed by hand.

<Experimental Example 2> Reduction behavior of iron oxide (hematite, Fe ₂ O ₃ ) and graphite

The following experiment was conducted to confirm the reduction behavior of iron oxide and graphite used in Examples and Comparative Examples of the present invention.

The single reduction reaction of iron oxide (hematite, Fe ₂ O ₃ ) and graphite is classified into direct reduction reaction caused by direct contact between iron oxide and graphite and indirect reduction reaction by carbon monoxide (CO) gas generated by direct reduction And the reaction formula thereof is expressed by the following equation (2).

<Formula 2>

Fe _x O _y + C = Fe _x O _{y -1} + CO

Fe _x O _y + CO = Fe _x O _{y -1} + CO ₂

C + CO ₂ = 2CO

The carbon monoxide (CO) and carbon dioxide (CO ₂ ) gases generated by the reduction reaction in the step 3 were measured through a gas analyzer (MRU company, DELTA 1600S model) in the manufacturing process of the comparative example 1, ) And carbon dioxide (CO ₂ ) gas volume distribution and temperature pattern are shown in FIG.

As shown in FIG. 3, the gas was not measured in the step 1 section of the reaction time interval from 0 to 900 ° C., and a small amount of carbon dioxide (CO ₂ ) gas was measured in the step 2 of the reaction time. It can be seen that the carbon monoxide (CO) gas generated by the direct reduction is used for the indirect reduction reaction and discharged as the carbon dioxide (CO ₂ ) gas.

In addition, it can be seen that the amount of carbon monoxide (CO) gas generated increases in a step 3 of the reaction time period from that of carbon dioxide (CO ₂ ) gas, and the direct reduction reaction is increased. In addition, it can be seen that the amount of gas is drastically reduced in the step 4 of the reaction time, and the reduction reaction of the carbonaceous internal iron oxide briquetting is completed in the step 4.

As a result, it can be confirmed that most of the generated gas is carbon monoxide (CO) gas. As a result, the reduction reaction of briquetting iron oxide briquettes occurs in a complex manner by indirect reduction reaction and direct reduction reaction, but it can be seen that it proceeds mainly by direct reduction reaction.

Experimental Example 3 Reduction Behavior of Carbonaceous Iron Oxide Briquettes According to Basicity (1)

The following experiment was conducted to confirm the reduction behavior of iron oxide and graphite used in Examples and Comparative Examples of the present invention.

The carbon dioxide (CO ₂ ) gas generated by the reduction reaction in the step 3 was subjected to gas analysis (MRU company, DELTA 1600S model) in the manufacturing process of the reduced carbon monoxide-containing iron oxide briquettes of Examples 1 and 2 and Comparative Examples 1 to 4 , And the carbon dioxide (CO ₂ ) gas volume fraction and the temperature pattern are shown in FIG.

As shown in FIG. 4, it can be seen that the amount of generated carbon dioxide (CO ₂ ) gas is slightly reduced in the case of Comparative Example 2, compared with the case of Comparative Example 1 which does not include flux, In the case of Comparative Example 3, Examples 1 and 2 and Comparative Example 4, which are not less than 0.408, is somewhat increased as a whole.

As a result, it can be seen that when the basicity is 0.408 or more, the reducing property of the carbonaceous built-in iron oxide briquette is improved.

<Experimental Example 4> Reduction Behavior of Carbonaceous Iron Oxide Briquettes According to Basicity (2)

The following experiment was conducted to confirm the reduction behavior of iron oxide and graphite used in Examples and Comparative Examples of the present invention.

The carbon monoxide (CO) gas generated by the reduction reaction in Step 3 was measured through a gas analyzer (model MRU, DELTA 1600S) in the manufacturing processes of Examples 1 and 2 and Comparative Examples 1 to 4, ) The gas volume fraction and the temperature pattern are shown in Fig.

As shown in FIG. 5, in the case of Comparative Example 1 not including flux, carbon monoxide (CO) gas tended to be generated continuously until the reaction was terminated. However, it can be seen that most of the carbon monoxide (CO) gas is generated in the specific section in Examples 1 and 2 and Comparative Examples 2 to 4 including the flux.

In Comparative Example 2, a relatively low amount of carbon monoxide (CO) gas was generated, and most of the reduction reactions occurred in the temperature holding period after reaching 1200 ° C. However, in Comparative Example 3 in which the basicity was 0.408 or more, It can be seen that most of the reduction reactions occurred in the vicinity of 1100 ° C, which is a lower temperature in the case of Example 2 and Comparative Example 4.

As a result, it can be seen that when the basicity is 0.408 or more, the reducing property of the carbonaceous built-in iron oxide briquette is further improved.

<Experimental Example 5> Comparison of the reduction ratio according to the basicity and the reaction time

The following calculations were carried out in order to confirm the basicity and the reduction rate according to the reaction time of the carbonaceous built-in iron oxide briquettes used in Examples and Comparative Examples of the present invention.

In order to compare the reduction rates according to the reaction times in the reduction reactions of Step 3 in Examples 1 and 2 and Comparative Examples 1 to 4, the reduction ratio was calculated using the following calculation method and the formulas 3 to 5, The results are shown in Fig.

Calculation method of reduction rate

Reduction rate calculation calculates the flow rate of the total exhaust gas flow rate using a Proportional of fraction (% N ₂₎ of nitrogen (N ₂₎ gas as measured by (Q _N2) and gas analyzer (Q _total) of the supplied nitrogen (N ₂₎ Respectively. Measured by calculating the total exhaust gas flow rate and the gas analyzer of carbon monoxide (CO) and carbon dioxide, carbon monoxide (CO) in the (CO ₂₎ any time 't' as the product of the volume fraction of gas (% CO,% CO ₂₎ and carbon dioxide (CO ₂₎ and can calculate the amount (Q _{CO, CO2} Q) of the gas, can be expressed as the equation to equation (3).

<Formula 3>

Q _total : 100 = Q _N2 :% N ₂

Q _total = (Q _N2 /% N _2? 100

(Q _CO ) t = (Q _total ) _t (% CO) _t

_(CO2 Q) t = (Q _total) and _t (% CO _{2) t}

Through the calculation of CO and CO2 generation amount can be calculated on the mass of the reduced oxygen at a specific time, through the following equation (4), oxygen by weight of the mass of the reduced oxygen as the initial iron oxide _{(Fe 2 O 3) (W} O) 0 It is possible to calculate the oxygen mass (W _O ) _t remaining in the carbonaceous material-containing iron oxide briquettes at any time.

<Formula 4>

(W _O ) _t = (W _O ) ₀ - (16 裡 Q _CO + 32 裡 Q _{CO 2} ) / V _g

V _g : Volume of the flue gas

Finally, the reduction ratio of the carbonaceous built-in iron oxide briquet can be calculated through the ratio of the removed oxygen mass to the initial oxygen mass through the following equation (5).

&Lt; EMI ID =

Reduction rate _{= {(W O) 0 -} (W O) t} / (W O) 0 and 100

As shown in FIG. 6, in the case of Comparative Example 2, the reduction rate was lower than that of Comparative Example 1 in which no flux was used.

On the other hand, in the case of Comparative Example 3, in comparison with the case of Comparative Example 1 in which no flux was used

The reduction rate was higher before reaching 1200 ℃, but the reduction rate was lower at 1200 ℃.

On the other hand, in Examples 1 and 2 and Comparative Example 4, it was confirmed that the reduction rate was higher than that in Comparative Example 1 during the entire reduction time.

 As a result, it can be seen that the reduction rate is varied depending on the basicity of the carbonaceous built-in iron oxide briquette, and the reduction rate is high during the entire reduction time when the basicity is greater than 0.408.

<Experimental Example 6> Comparison of reduction rates according to basicity

The following calculation was carried out in order to confirm the reduction ratio according to the basicity of the carbonaceous built-in iron oxide briquettes used in Examples and Comparative Examples of the present invention.

The reduction ratios of the reduced carbon monoxide-containing iron oxide briquettes prepared in Examples 1 and 2 and Comparative Examples 1 to 4 as compared to the carbonaceous built-in iron oxide briquettes produced in Step 2 of Examples 1 and 2 and Comparative Examples 1 to 4 were evaluated in Experimental Example 5 And the equations 3 to 5, and the results are shown in Fig.

As shown in Fig. 7, the reduction rate was lowered when compared with the case of Comparative Example 1 which did not contain the flux in Comparative Example 2 and Comparative Example 3, The reduction rate tended to increase as compared with the case of Comparative Example 1 in which the flux was not included.

On the other hand, the reduction rate values close to 100% were obtained at 98.9% and 98.8%, respectively, when prepared according to Examples 1 and 2, but in the case of the base prepared at Comparative Example 4 at a higher basicity condition, Tended to decrease again.

 As a result, the reduction ratio of the carbonaceous material-containing iron oxide briquet varies depending on the basicity, and when the basicity exceeds 0.408 and the basicity is less than 1.632, the reduction rate is high.

Experimental Example 7 Microstructure observation of reduced iron oxide briquettes

In order to observe the microstructure of the reduced carbon monoxide-containing iron oxide briquettes prepared in Examples and Comparative Examples of the present invention, the following analysis was conducted.

Microstructure of reduced carbonaceous internal iron oxide briquettes prepared in Comparative Example 2 and Example 1 having a basicity of 0 and a basicity of 0.516 was observed with an optical microscope (OM) and a scanning electron microscope (SEM) 8 and 9, respectively.

As shown in FIG. 8, it was confirmed that a large amount of bright metallic iron (Fe) and dark colored slag existed in the cross-sectional image when the comparative example 2 in which the reduction rate value was the lowest was produced. However, when manufactured according to Example 1 in which the reduction ratio was the highest, it was confirmed that spherical metallic iron (Fe) having a small size was observed in the cross-sectional image. Most of the slag was found to be separated from metallic iron (Fe), but a small amount of slag was found to be bound to metallic iron (Fe).

9 (a) and 9 (b) are cross-sectional images showing the boundary between metal iron (Fe) and slag in the case of Comparative Example 2 and Example 1, respectively. The results of analyzing the components by the energy dispersive X-ray analyzer (EDS) for the points 1 and 2 in FIG. 9A and the points 1 and 2 in FIG. 9B are shown in Table 2 below .

element Area 1 Area 2 Point 1 Point 2 C 10.62 13.29 6.35 10.75 O 45.6 0 51.94 0 Al 7.53 0 5.57 0 Si 17.24 0.34 20.84 0.7 Ca 0 0 13.58 0 Fe 19.01 86.37 1.72 88.55

9A was confirmed to be slag containing aluminum (Al), silicon (Si) and iron (Fe) components, and region 2 of FIG. 9 (a) Iron (Fe). At this time, a large amount of iron (Fe) component not reduced on the slag could be considered as a cause of the reduction ratio of the briquetting iron oxide iron oxide used in Comparative Example 2 to be low.

On the other hand, as a result of confirming the inside of the small spherical particles in the reduced carbonaceous internal iron oxide briquettes produced by Example 1 having the highest reduction ratio, it was confirmed that a small amount of slag was present in the metal iron (Fe) As a result, point 1 in FIG. 9 (b) was confirmed to be a slag containing aluminum (Al), silicon (Si), calcium (Ca) and a small amount of iron (Fe) ) Was identified as carburized metal iron (Fe). That is, the amount of unreduced iron (Fe) remaining in the slag is very small, which is in good agreement with the tendency that a high reduction rate value appears.

 <Experimental Example 7> Analysis of reduction behavior according to basicity

With respect to the results of Experimental Example 6, the following calculation was carried out in order to analyze the reduction behavior according to the basicity of the carbonaceous material-containing iron oxide briquettes.

In order to confirm the melting point of the positive used in the cases of Comparative Examples 1 to 4 and Examples 1 and 2, calculation was performed using FactSage, which is a thermodynamic calculation program, and the results are shown in FIG. The state diagram was also calculated using FactSage for the fluxes used in Comparative Example 2 where the reduction ratio is the lowest, Example 1 which is the highest, and Comparative Example 4 where the reduction ratio decreases again.

First, as shown in FIG. 10, the melting point of the flux used in Comparative Example 3 was the lowest and then increased.

The lower the melting point of the flux is, the higher the reduction rate of the briquetting iron oxide briquettes can be. Thus, in the case of the flux used in Comparative Example 5, the reduction ratio is reduced again due to a higher melting point.

On the other hand, as a result of calculating the state diagram using the FactSage, it was confirmed that Fe ₂ SiO ₄ (fayalite) which can lower the reducing property of FeO at a comparatively low temperature and a FeO mass fraction can be formed in Comparative Example 2. That is, in the case of Comparative Example 2, the reason why the reduction ratio is low despite the low melting point is that Fe ₂ SiO ₄ , which is a low melting point compound, is formed, but the reducing ability of FeO is decreased and the reduction ratio of the iron oxide briquettes containing carbon is reduced.

As a result, it can be seen that when the basicity has a value of at least 0.408 and less than 1.632, the carbonaceous built-in iron oxide has a higher reduction rate.

Claims (8)

Wherein the iron oxide powder, the iron oxide powder, the solid reductant powder containing carbon and the flux, and the basicity is 0.5 to 1.6.
The carbonaceous compacted iron oxide compact according to claim 1, wherein the compacted material is one selected from the group consisting of briquettes, spherical pellets, and cylindrical pellets.
The carbonaceous compacted iron oxide compact according to claim 1, wherein the solid reducing agent is coal.
The carbonaceous iron oxide compact having improved reducing properties according to claim 1, wherein the flux comprises 5 to 15% by weight of the total weight of the carbonaceous built-up iron oxide compact.
The method of claim 1, wherein the flux is selected from the group consisting of CaO, SiO ₂ And Al ₂ O ₃ , wherein the carbonaceous compacted iron oxide compacted material having improved reducing ability is at least one selected from the group consisting of Al ₂ O ₃ and Al ₂ O ₃ .
6. The method of claim 5, wherein the flux comprises Al ₂ O ₃ to total flux weight 13 to 14%, the CaO and SiO ₂ 38 to 48%. &Lt; RTI ID = 0.0 &gt; 8. &lt; / RTI &gt;
Preparing a mixture having a basicity of 0.5 to 1.6 by mixing iron oxide powder, solid reductant powder containing carbon and a flux (step 1); And
2. The method of claim 1, further comprising the step of forming the mixture (step 2).
A method for producing reduced carbonaceous iron oxide compacted body comprising the step of heat treating and reducing the carbonaceous compacted iron oxide compact having improved reducing properties (step 1).

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