JP2011246584A - Simple method for measuring metallization rate of ferrocoke - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple method for measuring the metallization rate of ferrocoke by which the metallization rate of iron in the ferrocoke is easily and quickly measured, and thereby, the metallization rate of product ferrocoke is adjusted by adjusting the operation conditions of a carbonization furnace in the production of the ferrocoke.SOLUTION: The simple method for measuring the metallization rate of ferrocoke includes: measuring the electrical resistivity of the ferrocoke produced by the carbonization of a molded article obtained by mixing coal and iron ore and molding the resultant mixture; and estimating the metallization rate of the above ferrocoke by using the measured electrical resistivity. It is preferable that electrodes are arranged at both end portions of a compaction molded article obtained by compaction molding a powder of the ferrocoke, a current is applied between the electrodes, the electric potential difference generated between the electrodes is measured and the electrical resistivity is calculated by using the distance between the electrodes and the cross-sectional area vertical to the current direction of the compaction molded article, and it is preferable that a calibration curve related to the metallization rate and the electrical resistivity of the ferrocoke is prepared to estimate the metallization rate.

Description

  The present invention relates to a simple method for measuring the ferro-coke metalization rate, which quickly and easily evaluates the ratio of the amount of metallic iron to the total amount of iron in ferro-coke produced by dry distillation of a molded product in which coal and iron ore are mixed. .

  In order to efficiently operate the blast furnace, charging of the coke produced by dry distillation of coal in the coke oven is performed in the blast furnace. Coke in the blast furnace has a role of a spacer for improving ventilation in the blast furnace, a role as a reducing material, a role as a heat source, and the like. In recent years, a technique for obtaining ferro-coke for metallurgy by mixing iron ore with coal and dry distillation from the viewpoint of improving the coke reactivity has been studied (for example, see Non-Patent Document 1). When the reactivity of coke is increased by iron in iron ore, the reaction start temperature of coke and carbon dioxide can be lowered (for example, see Non-Patent Document 2), and the reaction is activated from a low temperature. As a result, the heat storage zone temperature of about 1000 ° C. is lowered, and the carbon dioxide concentration in the reducing equilibrium gas composition is increased. This aims to increase the difference between the carbon dioxide concentration in the actual gas and the carbon dioxide concentration in the reducing equilibrium gas composition to promote the reduction of FeO to iron.

  On the other hand, even if the iron-containing material (iron ore) added to the carbonaceous material (coke) as a catalyst is not all metallic iron but an oxidized iron-containing material such as wustite and magnetite, the reactivity of the carbonaceous material (See, for example, Non-Patent Document 3). However, the weight reduction rate due to the gasification of the carbonaceous material varies depending on the oxidation state of iron, and there may be an optimum metalization rate of the iron-containing material for the carbonaceous material reactivity. Further, when a molded product of a mixture of carbonaceous material and iron ore is dry-distilled, if all iron ore is reduced to metallic iron, the rate of reduction by solid carbon that is an endothermic reaction increases, which is thermally disadvantageous. For this reason, it is considered that there are upper and lower limits for the target metallization rate. For example, in Non-Patent Document 4, the target reduction rate is set to 80% (metallization rate; approximately 75%).

Seiji Nomura, Kenichi Higuchi, Kazuya Kunitomo, Makoto Naito “Iron and Steel” 95, 2009, p. 12 Naito Masaaki “Iron and Steel” 87, 2001, p. 5 Y. Ohtsuka et al., “Fuel” 65, 1986, p. 1478 NEDO homepage "Strategic development project for energy use rationalization technology, leading research on innovative iron making process" http://www.nedo.go.jp/activities/portal/gaiyou/p09016/h21jisshi.pdf Fuel Association "Coke Technology Annual Report" 1958, p. 38 Note that Non-Patent Document 5 is referred to in a problem to be solved by the following invention.

  In order to manufacture ferro-coke, a method using a chamber-type coke oven and a method of carbonizing a molded product of coal and iron ore are conceivable (for example, see Non-Patent Document 5). In order to produce ferro-coke by dry distillation of the molded product, it is desirable to use, for example, a vertical dry distillation furnace different from the chamber furnace type. Unlike vertical furnace coke ovens, vertical vertical distillation furnaces are heated and dry-distilled in a countercurrent moving bed of solid and gas. The metallization rate of iron ore in ferro-coke depends largely on the maximum temperature of ferro-coke in the dry distillation furnace, but the target production volume (that is, the solid descent rate) and the specific heat of the solid due to changes in raw material conditions It is assumed that the heat exchange conditions between the solid and the gas change due to changes or the like. For this reason, it is considered that it is often difficult to adjust the heating conditions so as to achieve the target metallization rate. The vertical carbonization furnace is not a batch type furnace like a chamber furnace type coke oven, but is operated continuously. Therefore, as soon as the operation changes, the metalization rate of the product ferro-coke is ascertained. It is desirable to optimize the operating conditions of the furnace.

  The metallization rate can be evaluated by measuring the total iron amount and the metal iron amount, and is often measured according to JIS. The total iron amount is according to JIS M8212 (Iron Ore-Total Iron Determination Method) and the metallic iron amount is according to V. in JIS M8213 (Iron Ore-acid soluble iron (II) determination method). It is necessary to reduce the iron by dissolving it in the solution and quantitatively determine it by titration. Reduction and titration require many working procedures and solution adjustments. According to the JIS method, it is possible to accurately measure the metallization rate, but it may take a week for the analysis results to be obtained. For this reason, it is desirable that the metallization rate can be measured by a simpler and quicker method in order to measure the metallization rate in a timely manner during the operation of the carbonization furnace and reflect it in the operation of the furnace.

  Therefore, the object of the present invention is to solve such problems of the prior art and to measure the metallization rate of iron in ferrocoke simply and quickly, and thereby the operating conditions of the dry distillation furnace during ferrocoke production. Is to provide a simple method for measuring the ferro-coke metallization rate, which can adjust the metallization rate of the product ferro-coke.

The features of the present invention for solving such problems are as follows.
(A) Coal and iron ore are mixed and molded to produce a molded product, and the ratio of the amount of metallic iron to the total amount of iron in ferrocoke produced by dry distillation of the molded product (metal iron mass / total iron Mass) metallization rate,
A simple method for measuring the ferro-coke metalization rate, wherein the electrical resistivity of the ferro-coke is measured and estimated using the electrical resistivity obtained by the measurement.
(B) Electrodes are installed at both ends of a compression molded product obtained by compression molding ferro-coke powder, current is applied between the electrodes, a potential difference generated between the electrodes is measured, and the distance between the electrodes and the compression are measured. The method for easily measuring the ferro-coke metallization rate according to (a), wherein the electrical resistivity is obtained from the following equation (1) using a vertical cross-sectional area with respect to the current direction of the molded product.
Electrical resistivity (Ω · cm) = (V / I) × (S / L) (1)
Where V: potential difference (V), I: applied current (A), S: vertical cross-sectional area (cm ² ) with respect to the current direction of the compression molded product, and L: distance between electrodes (cm).
(C) A calibration curve of the relationship between the metallization rate of ferrocoke and the electrical resistivity is created, and the metallization rate is estimated using the calibration curve, as described in (a) or (b) Simple measurement method of ferro-coke metalization rate.

  According to the present invention, when producing ferro-coke, the metallization rate can be measured quickly and easily, so the measured value is fed back to the operation to maintain the target metallization rate of the product ferro-coke. Can do.

Schematic of the electrical resistivity measuring device. The graph which shows the relationship between the electrical resistivity of ferro-coke, and the highest ultimate temperature at the time of dry distillation. The graph which shows the relationship between an electrical resistivity and a metallization rate.

  In the present invention, coal and iron ore are mixed, molded to produce a molded product, and the ratio of the amount of metallic iron to the total iron content in ferrocoke produced by dry distillation of the molded product (metal iron mass / The metallization rate (total iron mass) can be easily measured by measuring the electrical resistivity of ferrocoke and estimating it.

  Ferro-coke is produced by dry distillation of a mixture of coal and iron ore, and therefore the interior is composed of a coke part, iron ore (including reduced metallic iron) and pores. The local non-uniformity is large, and the measurement error of electric resistance may be increased unless a homogenization process is performed. Therefore, it is preferable to measure the electrical resistance of the ferrocoke which is pulverized to form a powder and the powder is consolidated. Ferro-coke is preferably pulverized into a fine powder having a particle size of about 0.1 mm or less. The pulverized ferrocoke is preferably compression molded to form a compression molded product. Compression molding can be easily performed using a tablet molding machine or the like.

Electrodes are installed at both ends of the compression molded product that has been crushed and compression molded, current is applied between the electrodes (applied current), the potential difference generated between the electrodes is measured, and the distance between the electrodes and the current direction of the compression molded product are measured. The electrical resistivity can be obtained from the following formula (1) using the vertical sectional area.
Electrical resistivity (Ω · cm) = (V / I) × (S / L) (1)
Where V: potential difference (V), I: applied current (A), S: vertical cross-sectional area with respect to the current direction of the compression molded product (area of the compacted surface) (cm ² ), L: distance between electrodes (high in the compaction direction) (Cm). In the following example, the compression molded product has a cylindrical shape, and by installing electrodes on the upper and lower surfaces, which are planar circular portions of the column, the area of the circular portion of the column corresponds to S and the height of the column corresponds to L. Will do.

  The metallization rate of ferrocoke is determined by measuring the electrical resistivity of ferrocoke. In the ferrocoke carbonization process, the electrical resistance is due to the structural change of coal and the production of metallic iron accompanying the reduction of iron ore. This is because it is considered to change. Therefore, the electrical resistance of the product ferrocoke is predicted to correlate with the metallization rate via the highest temperature reached during dry distillation of the ferrocoke. Therefore, the following experiment was performed.

  Using a small carbonization furnace, 3 kg of a mixture of coal and iron ore (mass ratio coal: iron ore = 0.7: 0.3) was carbonized at a set temperature of 800 to 950 ° C., Electrical resistance was measured for ferro-coke produced at temperature. The molded product was heated in a fixed layer state, and it was confirmed that the temperature measured by embedding a thermocouple in the molded product coincided with the set temperature of the furnace.

  Ferro-coke is produced by dry distillation of a mixture of coal and iron ore, and therefore the interior is composed of a coke part, iron ore (including reduced metallic iron) and pores. The local non-uniformity is large, and the measurement error of electric resistance may be increased unless a homogenization process is performed. Therefore, ferrocoke was pulverized and the electrical resistance of the compacted product (compression molded product) was measured.

  FIG. 1 shows a schematic diagram of an electrical resistivity measuring apparatus used for measurement. As shown in FIG. 1, a Teflon (registered trademark) cylindrical container 1 having an inner diameter of 15 mm is filled with ferrocoke pulverized to a particle size of 100 μm or less, and 700 N through SUS pressing tools 2 and 3 that also serve as electrode terminals. The layer height (consolidated body height) of the pulverized sample 4 that was consolidated by the above method was measured. The compacted body area is an area of a circle having a diameter of 15 mm. Thereafter, a constant current of 5 mA is applied to the pulverized sample 4 through the upper and lower electrode terminals 2 and 3 of the pulverized sample 4 (consolidated body) using the direct current generator 5 (applied current), and the potential measuring device The voltage (potential difference) was measured at 6. The electrical resistivity was calculated by the above equation (1).

  FIG. 2 shows the relationship between the electrical resistivity of ferrocoke measured by the above method and the maximum temperature reached during dry distillation. It can be seen that the electrical resistivity changes in accordance with the highest temperature achieved during the dry distillation of ferro-coke, and the electrical resistivity is low when the dry distillation is at a high temperature. This is considered to be the effect that the crystallite in the coke part expands as the temperature increases, and the effect that the iron ore is reduced and the ratio of metallic iron increases.

  Therefore, there is a correlation between the electrical resistivity of ferro-coke and the ratio of metallic iron, and the calibration curve is created by measuring the relationship between the metalization rate of ferro-coke and the electrical resistivity and preparing a calibration curve in advance. By measuring the electrical resistivity of ferro-coke with a compacted body prepared under the same conditions as in the above, it is possible to estimate the value of metallization rate (metal iron mass / total iron mass).

  In the above, the ferro-coke is filled in the cylindrical container 1, but the vertical plane in the current passing direction may have the same area and shape, and may be a polygonal column such as a square column or a hexagonal column in addition to a column. Therefore, even a prismatic container can be implemented.

A molded product of a mixture of coal and iron ore (mass ratio of coal: iron ore = 0.7: 0.3) was carbonized in a small dry distillation furnace at 800, 820, 850, 870, 900, and 950 ° C. Ferro-coke was manufactured. The total iron content and metallic iron content of each ferrocoke were measured according to the JIS method. In addition, each ferrocoke is pulverized to a particle size of 100 μm or less, and compressed using a tablet molding machine to form a cylindrical tablet-shaped compression molded product having a diameter of 1.5 cm and a thickness of 1 cm, and electrodes are installed at both ends. Then, a current of 10 mA is passed between the electrodes, the potential difference generated between the electrodes is measured, and the electrical resistivity is calculated from the above equation (1) using the distance between the electrodes (1 cm) and the area of the compression molded product (1.767 cm ² ). Asked.

  FIG. 3 shows the relationship between the measured metallization rate and electrical resistivity. The numerical value shown in FIG. 3 is the dry distillation temperature of ferro-coke. It has been shown that the metallization rate decreases as the electrical resistivity increases.

  By using the calibration curve of the relationship between the metallization rate and the electrical resistivity thus created, it is possible to measure the electrical resistivity of ferrocoke and to estimate the metallization rate quickly and easily. .

DESCRIPTION OF SYMBOLS 1 Cylindrical container 2 Upper electrode terminal and pressing tool 3 Lower electrode terminal and pressing tool 4 Ground sample (consolidated body)
5 DC current generator 6 Potential measuring device

Claims (3)

Coal and iron ore are mixed and molded to produce a molded product, and the ratio of the amount of metallic iron to the total iron content in the ferro-coke produced by dry distillation of the molded product (metal iron mass / total iron mass) A certain metallization rate,
A simple method for measuring the ferro-coke metalization rate, wherein the electrical resistivity of the ferro-coke is measured and estimated using the electrical resistivity obtained by the measurement. Electrodes are installed at both ends of a compression molded product obtained by compression molding ferro-coke powder, an electric current is applied between the electrodes, a potential difference generated between the electrodes is measured, and the distance between the electrodes and the compression molded product The simple method for measuring the ferro-coke metalization rate according to claim 1, wherein the electrical resistivity is obtained from the following formula (1) using a vertical cross-sectional area with respect to a current direction.
Electrical resistivity (Ω · cm) = (V / I) × (S / L) (1)
Where V: potential difference (V), I: applied current (A), S: vertical cross-sectional area (cm ² ) with respect to the current direction of the compression molded product, and L: distance between electrodes (cm).   3. A ferro-coke metal according to claim 1 or 2, wherein a calibration curve of the relationship between the metallization rate of ferro-coke and the electrical resistivity is prepared, and the metallization rate is estimated using the calibration curve. Simple measurement method of conversion rate.

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