JP2013213264A - Method for manufacturing carbon-containing nonfired agglomerated ore for blast furnace using coal-char - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a carbon-containing nonfired agglomerated ore for blast furnace in which the carbon-content is high and the hot-crushing strength after reducing operation in the blast furnace is high.SOLUTION: There is provided a method for manufacturing the carbon-containing nonfired agglomerated ore for blast furnace, by adding and mixing a binder and water into a raw material including fine powdery iron oxide and fine powdery carbonaceous material and granulating. In the method for manufacturing the carbon-containing nonfired agglomerated ore in which the coal-char is used, the fine powdery carbonaceous material includes the coal-char, which is possesed as 20-60 mass% to the total mass of the fine powdery carbonaceous material.

Description

  The present invention relates to a method for producing an unfired carbon-containing agglomerated ore for blast furnace using coal char.

  Conventionally, steel mills mix various iron-containing and carbon-containing dusts collected from various dust collectors, etc., add cement-based aging binders, knead and mold to produce unfired pellets or briquettes It has been used as a blast furnace raw material.

  These unfired carbon-containing agglomerated ore for blast furnace deteriorates due to the reaction in the blast furnace under the gas condition and temperature condition in the thermal preservation zone and reduction reaction equilibrium zone of the blast furnace shaft portion. Therefore, the unfired carbon-containing agglomerated ore for blast furnaces needs a certain hot crushing strength for smooth blast furnace operation.

  Moreover, the reduction rate of these unfired carbon-containing agglomerated ores for blast furnaces is improved by causing a reduction reaction in the blast furnace with the carbon incorporated therein. For this reason, unburned carbon-containing agglomerated ores for blast furnaces have been designed to increase the amount of interior carbon with the goal of reducing the ratio of reducing materials during blast furnace operation.

  From the above, it is desired that the unfired carbon-containing agglomerated ore for blast furnace has a large amount of interior carbon and high hot crushing strength.

As a method of increasing the cold crushing strength of unfired carbon-containing pellets for blast furnaces, “addition of a hydraulic binder to a finely divided iron-containing raw material and finely divided carbonaceous material, and a carbon content ratio in all raw materials (TC) Is adjusted to a blending ratio of the pulverized carbonaceous material so that it is 15 to 25% by mass, further mixed and granulated while adjusting the moisture, and then subjected to a curing treatment to obtain a cold crushing strength of 85 kg / cm ^2. (8300 kN / m ² ) A method for producing unfired carbon-containing pellets for blast furnaces, wherein the curing treatment is performed after the pellets after granulation are left in the atmosphere for 12 to 48 hours in a primary curing yard. The pellet is charged into a shaft furnace for secondary curing, and steam blowing treatment is performed in the shaft furnace at a temperature of 60 to 90 ° C. and a treatment time of 5 hours or more. And before the steam blowing process The total processing time of the drying process should be within 8 hours "is the invention (Patent document 1).

In addition, for the purpose of reducing the ratio of reducing material in blast furnace operation, “in-carbon non-fired agglomerated minerals that are kneaded, molded, and cured by blending iron-containing raw material and carbon-based carbonaceous material and adding a binder. The binder is selected so that it contains 80 to 120% of the theoretical carbon required to reduce the reducible oxygen of stones to metallic iron, and the crushing strength at room temperature is 7850 kN / m ² or more. An invention of a carbon-incorporated non-fired agglomerated blast furnace for a blast furnace characterized by being kneaded, molded and cured is proposed (Patent Document 2).

  In addition, for the purpose of reducing the strength after reduction of the unfired briquette containing carbonaceous materials used in the blast furnace method and DR method (direct reduction method), “the porosity after molding and drying is 15 to 25%. There is a proposal of “carbonized material non-fired briquette” (Patent Document 3).

In addition, by adjusting the particle size of all iron raw materials, the blending ratio of fine powdered carbon materials, and adjusting the median diameter of fine powdered carbon materials, 50 kg / cm ² (4900 kN / m) required as raw material pellets for blast furnaces. ² ) While maintaining the above cold strength, it has a sufficient carbon content to greatly reduce the ratio of reducing material during blast furnace operation, and the crushing strength after reduction is 7 kg / cm ² (690 kN / m ² ) or more A non-fired carbon-containing pellet manufacturing method has been proposed (Patent Document 4).

JP 2009-161791 A JP 2003-342646 A JP 62-290833 A JP 2008-95177 A

  According to the invention described in Patent Document 1, the amount of carbon contained in the non-fired carbon-containing pellets for blast furnaces is large, and a non-fired carbon-containing pellet with high cold crushing strength can be obtained. Furthermore, in the secondary curing shaft furnace, there is a problem that steam blowing curing and subsequent drying treatment are required, resulting in high equipment costs and treatment costs. In this document, there is no mention of the hot crushing strength of the unfired carbon-containing agglomerated blast furnace.

According to the invention described in Patent Document 2, the blast furnace shaft portion in which the progress of the reduction reaction of iron oxide is generally restricted from the relationship between the temperature of the reducing gas and the gas composition (ηCO = CO ₂ / (CO + CO ₂ )). Even in the heat preservation zone and the reduction reaction equilibrium zone, the iron oxide in the unfired agglomerated ore in the temperature range of 900 to 1100 ° C. causes a reduction reaction by the carbon incorporated therein, and as a result, the reduction rate is improved. The reduction effect of the reducing material ratio at the time can be expected.

  However, in this method, the C content contained in the non-fired agglomerated mineral is 120% or less in terms of the theoretical carbon amount (hereinafter sometimes referred to as C equivalent) necessary for reducing iron oxide to form metallic iron. The total carbon content (TC) is limited to about 15% by mass or less), and if the C content is further increased, the cold crushing strength and hot crushing strength of the unfired agglomerated minerals are impaired. There is a problem.

  Furthermore, in this method, in order to maintain the cold crushing strength of the unfired agglomerated minerals with the carbonaceous material, a cement-based binder such as early-strength Portland cement is used instead of quick lime. Increasing the amount not only reduces the rate of temperature rise at the shaft in the blast furnace due to the dehydration reaction of cement, which is an endothermic reaction, but also generates a reduction stagnation zone (low temperature thermal preservation zone) at low temperatures, which causes iron for blast furnaces. The problem is that the reduced ore in the blast furnace of the sintered ore charged as a raw material is promoted.

  According to the invention described in Patent Document 3, it can be expected to some degree that the strength reduction during reduction in the blast furnace of the carbonaceous material-incorporated unfired briquette can be suppressed.

  However, the porosity after molding and drying of the carbonaceous material-incorporated non-fired briquette is affected by the properties and particle size of the raw material and the carbonaceous material, and it is difficult to control the porosity within the range of 15 to 25%. There is a problem of receiving.

  According to the invention described in Patent Document 4, the blending ratio of the finely powdered carbon material is set so that the particle size in all raw materials is 2 mm or less and the carbon content ratio (TC) in all raw materials is 15 to 25% by mass. By adjusting and setting the median diameter of the carbon material to 100 to 150 μm, producing a non-fired carbon-containing agglomerated mineral having good cold crushing strength and post-reduction crushing strength and having a high reducing material ratio reduction effect. Can do.

  However, in this method, the particle size in all the raw materials must be 2 mm or less, the median diameter of the carbonaceous material must be 100 to 150 μm, there are restrictions from both the raw material and the carbonaceous material, and 10 If the amount of non-fired carbon-containing agglomerated mineral used in the blast furnace is increased, the amount of slag charged into the blast furnace also increases. In addition, since the early strong cement undergoes a dehydration reaction (endothermic reaction) at 400 to 500 ° C., excessive use of the carbon-containing agglomerated mineral with 10% added cement lowers the temperature in the blast furnace, There is a problem that a temperature rise delay and a reduction delay occur.

  A non-fired carbon-containing agglomerated mineral having a sufficient carbon content that can reduce the ratio of reducing material during blast furnace operation and having high crushing strength after reduction in the blast furnace is desired. In this case, there are countermeasures disclosed in the patent document, but as described above, there are problems. The object of the present invention is to solve this problem.

  An object of this invention is to provide the manufacturing method of the non-baking carbon-containing agglomerated mineral for blast furnaces which uses the coal char which is good in hot crushing strength, and improves reduction efficiency.

The present inventor has produced a non-fired carbon-containing agglomerated mineral having a good hot crushing strength even when the amount of the carbon material to be embedded is large by using a coal char having a large non-surface area and high reactivity as the carbon material. The knowledge that is possible.
The present invention has been made to solve the above problems based on such knowledge, and the gist thereof is as follows.

(1) A method of producing a non-fired carbon-containing agglomerated blast furnace for a blast furnace by adding a binder and moisture to a raw material having finely powdered iron oxide and finely powdered carbonaceous material, and mixing and granulating the mixture.
The pulverized carbon material has a coal char,
The said char char is 20 mass% or more and 60 mass% or less with respect to the total mass of the said pulverized carbonaceous material, The manufacturing method of the non-baking agglomerated coal ore for blast furnaces using the coal char characterized by the above-mentioned.
(2) Of the pulverized carbonaceous material, the pulverized carbonaceous material other than coal char is pulverized general coal. A method for producing agglomerates.
(3) The above (1), wherein the finely powdered carbon material is 15% by mass or more and 25% by mass or less with respect to the total mass of the raw material having the finely divided iron oxide and the finely powdered carbon material. Or the manufacturing method of the non-baking carbon-containing agglomerated mineral for blast furnaces using the coal char as described in (2).
(4) The coal char has a BET specific area of 5.0 m ² / g or more, and is a non-fired coal-containing agglomerated blast furnace using the coal char according to any one of (1) to (3). Manufacturing method.

The figure which shows the measuring apparatus of the hot crushing strength of the non-baking carbon-containing agglomerated mineral for blast furnaces. The figure which shows the measurement conditions of the hot crushing strength of the non-baking carbon-containing agglomerated mineral for blast furnaces. The figure which shows the relationship of the hot crushing strength at the time of using coal char and steam coal. The figure which shows the relationship of the hot crushing strength at the time of using coal char and powdered coke. The figure which shows the sample cross section after reaction of the non-baking carbon-containing agglomerate for blast furnaces. (A) is a sample cross-sectional photograph after reaction in Comparative Example 1, and (B) is a sample cross-sectional photograph after reaction in Example 1.

In the present invention, the pulverized iron oxide and the pulverized carbonaceous material are both finely pulverized so that they can be molded by pelletizing or briquetting, and are, for example, 2 mm or less, particularly about −250 μm. It is particularly preferred. However, as for the particle size of finely divided iron oxide, the ratio of the particle size of 1 mm or more is preferably less than 5%. Since the blending ratio is larger than that of the carbonaceous material, it has an important influence on the moldability. When the ratio exceeds 5%, the granulation cannot be performed smoothly.

  A blast furnace that achieves the intended purpose by blending pulverized iron oxide, pulverized carbonaceous material and binder adjusted to such a blend into a blended raw material, adding water to such raw material, mixing, granulating, and curing Unfired carbon-containing agglomerated mineral can be produced. Here, the granulation equipment for mixing and granulating is not particularly limited as long as it has a function of kneading, adding water, and granulating the blended raw materials. It is not particularly limited.

  Examples of the non-fired carbon-containing agglomerated blast furnace according to the present invention include non-fired carbon-containing pellets and non-fired carbon-containing briquettes. Examples of pellets include those that are formed into a spherical shape by a disk pelletizer, and examples of briquettes include symmetric pillow-type briquettes and almond-type briquettes that are formed by a pair of opposed forming rolls with a hollow mold. It is not limited to.

The unfired carbon-containing agglomerated mineral needs a certain strength to withstand the pulverization during the transportation to the blast furnace and the charging of the blast furnace after molding. Therefore, the raw unfired carbon-containing agglomerated mineral for blast furnace after curing is cured to promote a hydraulic reaction between an inorganic binder such as cement and water. The cold crushing strength after curing is preferably 5000 kN / m ² or more for non-fired carbon-containing pellets (diameter of about 10 to 15 mm), and 1000 N / sample or more for non-fired carbon-containing briquettes (about 20 to 25 cc). preferable.

[About pulverized carbonaceous materials]
The present invention is characterized in that a coal char is used as a part of a fine powdery carbon material used for production of a non-fired carbon-containing agglomerated mineral. That is, it utilizes the characteristics of coal char with a large specific surface area and high reactivity.
If the particle size of the carbonaceous material is reduced in order to increase the reactivity of the finely powdered carbonaceous material, the carbonaceous material contained therein is gasified in a large amount before forming a metal network by reduction of iron oxide to metal at a low temperature. A large amount of voids are produced, and sufficient strength after reduction cannot be maintained.
Even if too much coal char is used, a large amount of gasification occurs at a low temperature, a metal network is formed by fine coal char, and a large amount of voids are also generated, resulting in hot crushing. Strength cannot be maintained. Therefore, it is important to harmonize the mixing ratio of coal char and other finely divided carbonaceous materials.
Then, this inventor discovered that 20 mass% or more and 60 mass% or less were suitable with respect to the total mass of a fine powder carbon material by the experiment mentioned later.

Examples of other finely powdered carbon materials other than coal char include powdered coke pulverized to a predetermined particle size, powdered lime, blast furnace ash containing coke dust, finely powdered general coal, and other powdered solid carbon materials. In the prior art, the particle size of the carbonaceous material needs to be 100 to 150 μm (paragraphs “0017” and “0018”), but in the present invention, the particle size of the other carbonaceous materials may be about −250 μm.
That is, even if the particle size of coal char and other carbonaceous materials is about −250 μm, it is possible to produce a blast furnace non-calcined agglomerated ore for blast furnace with good hot crushing strength and high reduction efficiency.

As for the compounding quantity of a pulverized carbon material, 10 mass% or more is preferable with respect to the raw material total mass. As a result, the iron oxide in the carbon-containing agglomerated mineral can be substantially reduced only by the carbon material inherent in the carbon-containing agglomerated mineral.
Conventionally, the ratio of the carbon content to the theoretical carbon amount required to reduce iron oxide in the pellet is defined as “carbon equivalent”, which is used as a measure of the degree of reduction of iron oxide by carbon. Conventionally, in order to maintain the hot crushing strength required as a blast furnace raw material, the carbon content has to be limited to 15% by mass (corresponding to a carbon equivalent of 1.2) (Patent Document 1). reference). However, in this invention, 15 mass% or more fine carbonaceous materials can be added to the said iron containing raw material. The blending amount of the finely powdered carbon material is more preferably 15% by mass or more and 25% by mass or less with respect to the total mass of the raw material. This is because, even if iron oxide in the carbon-containing agglomerated ore is reduced, the surplus carbon content is still gasified, so that iron raw materials other than the unfired carbon-containing agglomerated ore in the blast furnace (for example, sintered ore) ) Can be promoted to save energy and reduce CO ₂ . This is because the residual carbon content promotes the reduction of the sintered ore existing in the vicinity thereof.

[About finely divided iron oxide]

  As finely divided iron oxide, iron ore, pulverized scale to a predetermined particle size, iron-containing dust, sludge, etc., collected with a dust collector or the like can be used. For iron ore, it is more preferable to use a pellet feed, so that the labor of grinding can be saved. Since iron-containing dust and sludge hardly have a diameter of 1 mm or more and a particle diameter of 250 μm or less accounts for 80% or more of the whole, they can be used directly.

[About the binder]
As the binder, there is a hydraulic binder having a function of increasing the cold crushing strength of the granulated product by being cured by a hydration reaction with moisture contained in the raw material or added moisture. Examples of the hydraulic binder include an aging binder composed of fine powder mainly composed of blast furnace granulated slag and an alkali stimulator, Portland cement, alumina cement, blast furnace cement, and the like. In addition, the iron oxide raw material is dispersed and densely packed to react with an organic dispersant (sodium polyacrylate) or moisture that increases cold strength, and then gels by entering into the voids between the raw materials and hardens by drying. There are also organic binders such as pregelatinized corn starch that increase the strength between the layers.

By adding the hydraulic binder, the necessary cold crushing strength of the unfired carbon-containing agglomerated ore for blast furnace can be maintained. However, the addition of a hydraulic binder increases the amount of slag in the blast furnace, leading to an increase in required energy and an increase in the amount of generated CO ₂ . In addition, since the hydraulic binder undergoes a dehydration reaction with an endothermic reaction at 400 to 500 ° C. in the blast furnace, excessive addition of the binder causes a low temperature in the blast furnace, and the efficiency of the blast furnace decreases.
Therefore, in the case of a non-fired carbon-containing agglomerated blast furnace, a hydraulic binder of about 5% by mass to 10% by mass with respect to the total raw material mass is preferable.

Next, examples of the present invention will be described, but the present invention is not limited thereto.
As the raw material, three kinds of coal chars having different specific surface areas, fine coke and general coal were used as fine powdery carbon materials. The pulverized iron oxide used was a lobe river crushed to -0.25 mm. Portland cement was added to finely divided iron oxide and finely divided carbonaceous material, and after kneading, pellets (average particle size 13 mm) were granulated with a disk pelletizer. Table 1 shows the composition and components of coal char, steam coal and coke breeze. Coal char has a specific surface area of 5.0 m ² / g or more as compared with pulverized coke or steam coal, and is more reactive than pulverized coke or steam coal.

The ratio of coal char Z and steam coal was changed, and other raw material conditions were tested constant. Table 2 shows the raw material composition and the characteristics of the unfired carbon-containing agglomerated mineral.
In Table 2, Examples 1 to 4 are cases where the coal char in the pulverized coal is 20% by mass to 60% by mass. In Examples 1 to 4, a target cold crushing strength of 10000 kN / m ² or more and a hot crushing strength of 700 kN / m ² or more were ensured. RAR indicates the fuel cost (kg / tp) when 10% of unfired carbon-containing agglomerated ore is used in a blast furnace. In Examples 1 to 4, the RAR was good at 470 kg / tp or less.

Here, the measuring method of cold crushing strength is based on JISM8718 "Iron ore pellet crushing strength test method" (2009). That is, a compressive load was applied to one sample at a speed of 10 mm / min, the load was applied until the sample reached 50% of the maximum compressive load, and the maximum value of the compressive load was defined as the crushing strength. The strength index was a load value per unit cross-sectional area (kN / m ² ).

  As the hot crushing strength, the post-reaction crushing strength simulating the temperature and gas conditions in the blast furnace was measured. FIG. 1 shows an apparatus for measuring the post-reaction crush strength of a non-fired carbon-containing agglomerated blast furnace. A predetermined reactive gas flows from the inlet 3 between the inner reaction tube 1 (Φ73 mm) and the outer reaction tube 2 and is introduced into the inner reaction tube 1 from the bottom of the inner reaction tube 1. Alumina balls 5 are spread on the lower part of the reaction inner tube 1, and a sample 6 consisting of 350 g of sintered ore and 150 g of unfired carbon-containing pellets is filled thereon. The sample is heated by the heating device 7, and the sample temperature is measured by the thermocouple 8. The gas after the reaction is discharged from the reaction inner pipe 1 to the outside through the gas outlet 4 after the reaction. FIG. 2 shows the measurement conditions for the post-reaction crush strength of the unfired carbon-containing agglomerated blast furnace. The gas composition and temperature simulate the conditions in the shaft portion of the blast furnace. After completion of the reaction, the sample was taken out after cooling with nitrogen, and the crushing strength was measured. The crushing strength after the reaction was measured according to JIS M8718 “Iron ore pellet crushing strength test method”.

FIG. 3 shows the relationship between the amount of coal char used and the hot crushing strength when steam coal and coal char are used. The relationship between the use ratio of coal char X, Y, Z of Table 2 and hot crushing strength is plotted.
FIG. 4 shows the relationship between the amount of coal char used and the hot crushing strength when using powdered coke and coal char. In all blending types, the amount of coal char used was 20% by mass to 60% by mass, and a target hot crush strength of 700 kN / m ² or more was ensured.

  FIG. 5A shows a cross-sectional photograph of the sample after the reaction in Comparative Example 1. The white part in the sample cross-sectional photograph is metallic iron produced by the reduction reaction. Although the reduction to wustite and metallic iron is proceeding uniformly, a metal network in which the metallic iron after the reaction is firmly bonded is not seen. FIG. 5B shows a sample cross-sectional photograph after the reaction in Example 1. Metallic iron after reduction forms a strong metal network, confirming a dramatic improvement in post-reaction strength of unfired carbon-containing pellets.

It is possible to provide a method for producing an unfired carbon-containing agglomerated blast furnace ore for blast furnaces having a high carbon content and high hot crushing strength after reduction in the blast furnace.

DESCRIPTION OF SYMBOLS 1 ... Inner tube, 2 ... Outer tube, 3 ... Reactive gas inlet, 4 ... Post-reaction gas outlet, 5 ... Alumina ball, 6 ... Sample, 7 ... Heating device, 8 ... Thermocouple.

Claims (4)

It is a method for producing a non-fired carbon-containing agglomerated blast furnace for a blast furnace by adding a binder and moisture to a raw material having finely powdered iron oxide and a finely powdered carbon material, and mixing and granulating,
The pulverized carbon material has a coal char,
The said char char is 20 mass% or more and 60 mass% or less with respect to the total mass of the said pulverized carbon material, The manufacturing method of the non-baking carbon-containing agglomerated mineral for blast furnaces using the coal char characterized by the above-mentioned.   2. Of the pulverized carbonaceous material, the pulverized carbonaceous material other than the coal char is pulverized steam coal. Production method.   The said pulverized carbon material is 15 mass% or more and 25 mass% or less with respect to the total mass of the raw material which has the said pulverized iron oxide and the said pulverized carbon material. The manufacturing method of the non-baking carbon-containing agglomerated mineral for blast furnaces using the coal char of description. The method for producing an unfired carbon-containing agglomerated mineral for a blast furnace using the coal char according to claim 1, wherein the coal char has a BET specific area of 5.0 m ² / g or more. .