JP2012162789A - Operating method of vertical type melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize operation and to improve productivity by constantly retaining the height of a coke bed.SOLUTION: In the operating method of a vertical type melting furnace in which a solid fuel is used, which is ventilated from a tuyere, and in which an iron source is melted or performed with melting and reducing to manufacture a pig iron: (i) two or more in-furnace observation containers are disposed in a height direction and/or in a furnace circumferential direction at upper side furnace wall by 0.5-1.5 m from a tuyere in a vertical type melting furnace having one step of a tuyere and from a lower step tuyere in a vertical type melting furnace having two steps of a tuyere; (ii-1) the in-furnace observation container having a suitable height for an interim operation is decided; and (ii-2) the height of the coke bed is observed from the in-furnace observation container while operating. The amount of the coke mixing in a charged material is increased and decreased according to the vertical variation of the height of the coke bed so that the height of the coke bed may become the same level of the height of the in-furnace observation container having a height suitable for the interim operation.

Description

  The present invention relates to a method for operating a vertical melting furnace for producing pig iron by melting or dissolving and reducing an iron source such as iron waste.

  A vertical furnace used for producing pig iron includes a blast furnace and a cupola. In the blast furnace, pig iron is produced using iron ore (iron oxide) as an iron source. While iron ore charged from the top of the furnace descends in the furnace, iron oxide in the iron ore is reduced with high-temperature reducing gas (CO) generated by the reaction of oxygen and coke in the hot air blown from the tuyere. .

In the blast furnace, in order to secure a reduction rate of about 60% or more, the blast temperature is set to 1000 ° C. or more, the blast speed is increased, and a raceway is formed in front of the tuyere in the furnace, and gas is used in this region. Rate: η _CO (= CO ₂ / (CO + CO ₂ )) is produced so that reducing gas (CO) is produced so that pig iron is produced.

  On the other hand, cupola is a vertical melting furnace with a smaller internal volume than a blast furnace. It melts an iron source mainly composed of iron scrap, foundry scrap, pig iron, etc., which has a higher metalization rate than iron ore. Manufacturing. In the vertical melting furnace, an iron source having a high metallization rate that does not require reduction is used. Therefore, it is only necessary to secure an amount of heat that can sufficiently dissolve the iron source in the furnace.

In the operation of the vertical melting furnace, when a raceway was formed in front of the tuyere, as in the blast furnace operation, heat was generated by the combustion reaction of oxygen (O ₂ ) and coke (C) (C + O ₂ → CO ₂ ) Thereafter, heat absorption by the solution loss reaction (CO ₂ + C → 2CO) between CO ₂ and coke (C) reduces the amount of heat in the furnace, making it difficult to sufficiently dissolve the iron source.

  Therefore, when melting an iron source with a high metallization rate in a vertical melting furnace, oxygen-enriched cold air or hot air of 600 ° C. or less from the tuyere does not form a raceway before the tuyere, Coke for casting is used as a solid fuel in order to blow into the furnace at a low blowing speed and to suppress a decrease in the amount of heat in the furnace due to the solution loss reaction.

  Since the coke for castings has a larger particle size than the coke for blast furnace, it does not easily cause a solution loss reaction (endothermic reaction). In addition, since the coke for casting has high strength and low ash content, the amount of pulverization in the furnace and the amount of slag generated are small, which contributes to maintaining the air permeability in the furnace.

  By the way, in recent years, there is a tendency to use a large amount of iron-making dust that contains a large amount of iron oxide and has a low metallization rate compared to pig iron scrap, and the vertical melting furnace has a melting function for melting the iron source. In addition, a reduction function for reducing iron oxide in the iron source is also required.

  Against this backdrop, as iron sources, in addition to iron sources that do not require reduction (sintering iron scraps, foundry scraps, pig iron, etc.) (iron sources with a high metallization rate), dust agglomerates, self Several methods have been proposed for operating vertical melting furnaces that use iron sources (low-metallization and iron sources that require reduction) such as reducible ores (agglomerates with a high carbon content). (See Patent Documents 1 to 3).

  However, as the types and properties of iron sources diversify, it becomes difficult to accurately estimate the required heat amount of the iron source, and the ratio of the solid fuel to the iron source (fuel ratio) is stably maintained at an appropriate value. It becomes difficult. As a result, the position where the iron source dissolves and / or the reduction reaction fluctuates in the furnace, and the furnace condition tends to become unstable.

  For example, if the fuel ratio is too low, the semi-molten iron will drop to the tuyere level, causing the tuyere to be blocked or damaged, leading to troubles that prevent the operation from continuing. On the other hand, an excessive fuel ratio does not have a fatal effect on the operation, but has a detrimental effect that not only wastes fuel by reducing the gas utilization rate but also reduces productivity.

Japanese National Publication No. 01-501401 Japanese Patent Application Laid-Open No. 10-036906 JP 09-203584 A

  In order to maintain an appropriate fuel ratio, a method is currently employed in which the temperature of the hot metal is measured and the fuel ratio is adjusted based on the temperature. However, since the types and properties of iron sources are diversified, it is difficult to accurately predict furnace heat, and furnace heat varies greatly. Under such conditions, the conventional method of controlling the fuel ratio by observing the hot metal temperature can quickly and accurately cope with fluctuations in the furnace heat and cannot stabilize the furnace heat and the furnace conditions.

  This is considered to be because the hot metal temperature is affected by the cooling of the hot metal in the hearth and the hot metal, and the conditions inside the furnace are averaged and reflected in the operation.

  Therefore, an object of the present invention is to provide a new control factor that replaces the hot metal temperature, and to provide a method for operating a vertical melting furnace that solves the above-described problems.

  That is, the present inventors consider that keeping the coke bed height constant is an essential factor for stabilizing the furnace heat or the furnace condition, and based on this idea, the coke bed height is increased. An object of the present invention is to provide a method for reliably maintaining a constant temperature and stabilizing the furnace heat or the furnace condition.

  The coke bed is a layer filled with only coke from the tuyere to a height of 0.5 to 1.5 m above the tuyere. In the coke bed, the coke burns with the air introduced from the tuyere and generates heat, and the temperature on the upper surface of the coke bed is exactly the same as the iron source such as scrap that has fallen from the top completely dissolves and disappears. It has a melting point of

  The inventors have conceived that, in order to stably maintain the height of the coke bed, it is most certain to directly observe the height of the coke bed and identify the furnace wall above the tuyere level. An in-furnace observer was provided in the range in the height direction and / or the circumferential direction of the furnace, and the change in the height of the coke bed was directly observed to investigate the relationship with the change in the furnace heat or the furnace condition. As a result, it was found that the change in the coke bed height clearly reflects the change in furnace heat or furnace conditions.

  This invention was made | formed based on the said knowledge, and the summary is as follows.

(1) In a method of operating a vertical melting furnace that uses solid fuel, blows from a tuyere, melts an iron source, or melts and reduces to produce pig iron,
(I) The in-furnace observer is 0.5 to 1.5 m from the tuyere in the vertical melting furnace having one tuyere and from the lower tuyere in the vertical melting furnace having two tuyere. A plurality of upper furnace walls are provided in the height direction and / or the circumferential direction of the furnace,
(Ii-1) Determining an in-furnace observer suitable for the current operation,
(Ii-2) During operation, observe the height of the coke bed from the in-furnace observer so that the height of the coke bed is the same level as the height of the in-furnace observer suitable for the current operation. A method for operating a vertical melting furnace, wherein the amount of coke in the charge is increased or decreased according to the vertical fluctuation of the coke bed height.

  (2) In the vertical melting furnace having two stages of the tuyere, an in-furnace observation device is provided in the upper tuyere, and the operating method of the vertical melting furnace as described in (1) above.

  (3) The method for operating a vertical melting furnace according to (1) or (2), wherein the solid fuel is a solid fuel containing blast furnace coke.

  (4) The vertical melting according to any one of (1) to (3) above, wherein the height of the coke bed is the height of the central portion and / or the peripheral portion of the upper surface of the coke bed. How to operate the furnace.

  (5) The increase or decrease in the amount of coke in the charge is performed by increasing or decreasing the coke ratio and / or by introducing blank coke, as described in any one of (1) to (4) above How to operate the vertical melting furnace.

  According to the present invention, in the operation of a vertical melting furnace, the operating conditions (especially the fuel ratio) are effectively changed based on the change in the height of the coke bed, so that the melting of the iron source or the iron source Since melting and reduction can be performed stably, pig iron with uniform quality can be continuously produced while achieving a low fuel ratio and high productivity.

It is a figure which shows the one aspect | mode (conventional example) of a vertical melting furnace which has a 1 step tuyere. It is a figure which shows the one aspect (invention example) which provided the in-furnace observer in the vertical melting furnace of 1 step tuyere, and the one aspect | mode of the coke bed from which the consumption of coke differs in a peripheral part and a center part. In a vertical melting furnace having two-stage tuyere, it is a diagram showing an embodiment (invention example) in which an in-furnace observer is provided at the upper tuyere.

  The present invention will be described with reference to the drawings.

  FIG. 1 shows an embodiment of a conventional vertical melting furnace having a single stage tuyere. The vertical melting furnace has a furnace bottom 2 provided with a tap outlet 3, a furnace body 1 provided with a tuyere 10 on a lower furnace wall 14, a gas suction part 4 provided with a gas suction port 5, and a housed iron source to seal the furnace top. It consists of a furnace top 6 to be stopped and a charging part 7 for charging the iron source 8 into the furnace.

  In the operation of a conventional vertical melting furnace, air at room temperature or 600 ° C. or lower is fed into the furnace body 1 from the tuyere 10 to mainly burn coke (solid fuel) and generate iron source by combustion heat. Dissolve.

  FIG. 2 shows an embodiment (invention example) in which an in-furnace observer 15 is provided in the range of 0.5 to 1.5 m above the tuyere 10 on the lower furnace wall 14 of the vertical melting furnace shown in FIG. .

  In the operation of a vertical melting furnace, there should be an optimum height of the coke bed where the operation continues stably and the fuel ratio is low. If this optimum height can be predicted in advance, the height at which the in-furnace observation device is installed should essentially match the optimum height of the coke bed.

  However, the optimum height of a coke bed naturally varies depending on the type and properties of the iron source and solid fuel, and is not always constant. In addition, it is difficult to predict the optimum height of the coke bed in advance with the current technical level.

  Therefore, in the present invention, the height at which the in-furnace observer is installed is defined as a range of 0.5 to 1.5 m above the tuyere level. This is due to the fact that there is an optimum height of the coke bed in this height range based on the past operational results. If the installation height of the in-furnace observation device is less than 0.5 m, the installation position is too low, and if the installation height exceeds 1.5 m, the installation position is too high and the coke bed height is reduced. It cannot be observed accurately.

  In the range of 0.5 to 1.5m above the tuyere level, if you install multiple in-furnace observers with different installation heights, the coke bed height can be adjusted to various heights during operation. It is also possible to converge to the optimum height while observing at the position.

  In actual operation, since the height of the coke bed varies in the furnace circumferential direction, a plurality of in-furnace observers are also provided in the furnace circumferential direction.

  That is, if a plurality of in-furnace observers are provided in the height direction and / or the circumferential direction in the range of 0.5 to 1.5 m above the tuyere level, a plurality of in-furnace observers can be used as coke beds The height of the coke bed can be observed and averaged, and the height of the coke bed can be grasped more accurately.

  Although it is preferable to provide a plurality of in-furnace observers in the range of 0.5 to 1.5 m above the tuyere level in the height direction and / or the furnace circumferential direction, the number of installation is not particularly limited.

  The in-furnace observation device is made of a heat-resistant material and structure, but there is no particular limitation other than the heat-resistant material and structure. The in-furnace observer may be a window through which the inside of the furnace can be directly observed, or may be configured with an optical device that captures the inside of the furnace as an image.

  When a change in coke bed height is detected by an in-furnace observer, the operating conditions are changed to restore the coke bed height. If the coke bed height falls below the optimum height, the amount of coke in the charge is increased. On the other hand, when the height of the coke bed rises from the optimum height, the amount of coke blended in the charge is reduced.

  In the operation of vertical melting furnaces, keeping the coke bed height constant is an essential factor in stabilizing the furnace conditions and improving operating performance (fuel ratio and productivity). Although it is possible to estimate the amount of coke consumed in the bed, there is an error, and the estimation of the amount of coke consumed including the error causes the fluctuation of the furnace condition.

  The present invention is characterized in that an in-furnace observer is provided on the furnace wall above the tuyere and the change in the height of the coke bed is directly observed to accurately collect accurate position information.

  Here, FIG. 3 shows an embodiment in which a furnace 15 is provided in the upper tuyere 11 in the vertical melting furnace having two tuyere, that is, the upper tuyere 11 and the lower tuyere 10 ′ (invention). Example).

  The aim of providing the upper tuyere 11 is the air that is introduced from the lower tuyere 10 'and the combustion gas generated by the combustion of the coke at the tip of the tuyere rises through the coke bed. The generated CO gas is completely burned by air at a normal temperature or 100 ° C. or less fed from the upper tuyere 11 to increase the combustion efficiency of coke.

  Therefore, in order to achieve the above aim, the height of the coke bed in the vertical melting furnace having two upper and lower tuyere is inevitably controlled to the height of the upper tuyere. .

  In consideration of such a situation, in the vertical melting furnace having two upper and lower tuyere, the in-furnace observation device is provided in accordance with the position of the upper tuyere, but it is independently located at another position on the equipment structure. It is preferable to provide it on the furnace wall.

  In a vertical melting furnace having two upper and lower tuyere, solid fuel can be completely burned by the effect of air sent from the upper tuyere or air at 100 ° C. or lower. Therefore, blast furnace coke, which is unsuitable for use in conventional cupola furnaces, can be used in place of some or all of the expensive foundry coke.

  The amount of consumption of the coke bed differs between the peripheral part and the central part of the coke bed. FIG. 2 shows an embodiment of a coke bed in which the consumption amount differs between the peripheral part and the central part. In general, the coke in the peripheral part is preferentially burned by the air introduced from the periphery, so the amount of coke consumption in the peripheral part is larger than the amount of coke consumption in the central part, and the upper surface of the coke bed is shown in FIG. The shape is as shown in FIG.

  When observing the top surface of the coke bed with such a shape from the outside of the furnace and judging its height, it is difficult to grasp the height of the central part, so pay attention to the height of the central part and the peripheral part. It is preferable to observe. The central part of the coke bed means the area closest to the center when the coke bed is divided into three or more along the radial direction of the furnace, and the peripheral part of the coke bed is Means the region closest to the furnace wall.

  Increasing / decreasing the amount of coke in the charge is performed by increasing / decreasing the coke ratio and / or introducing blank coke. The introduction of blank coke is preferable because the height of the coke bed can be recovered more quickly.

  In addition, although the increase / decrease in the amount of coke contained in the charge is preferable in terms of directly leading to the recovery and maintenance of the height of the coke bed and the increase in the amount of heat in the furnace, It is also effective to change the oxygen amount and the like together.

  Next, examples of the present invention will be described. The conditions of the examples are one example of conditions adopted for confirming the feasibility and effects of the present invention, and the present invention is limited to this one example of conditions. Is not to be done. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

(Example)
The present invention was carried out in a vertical melting furnace having two-stage tuyere and provided with an in-furnace observer at the upper tuyere. Table 1 shows the equipment specifications. The upper tuyere was 1.2 m above the lower tuyere, and an in-furnace observer was provided at the upper tuyere. In operation using 100% scrap, 100% use of coke for blast furnace has already been achieved. Table 2 shows the operation specifications.

  Under the operating conditions shown in Table 2, the operation method for controlling the amount of coke according to the present invention was compared with the method for managing the amount of coke at the hot metal temperature of the conventional method.

  In the operation method of the present invention, the operation was continued according to the action method shown in Table 3 based on the result of monitoring the in-furnace condition through the in-furnace observer at the upper tuyere.

  As a result, as shown in Table 4, compared to the conventional method, it is possible to respond quickly to changes in operation, and the number of wind-downs and rests is greatly reduced, resulting in continuous production. The speed could be increased.

  As described above, according to the present invention, in the operation of a vertical melting furnace, the operating conditions (especially the fuel ratio) are effectively changed based on the change in the height of the coke bed to stabilize the furnace condition. Since the iron source can be evenly dissolved or dissolved and reduced, pig iron with uniform quality can be continuously produced. Therefore, the present invention has great applicability in the steel manufacturing industry.

DESCRIPTION OF SYMBOLS 1 Furnace body 2 Furnace bottom part 3 Outlet 4 Gas suction part 5 Gas suction part 6 Furnace top part 7 Insertion part 8 Iron source 9 Coke bed 10 Feather 10 'Lower tuyere 11 Upper tuyere 12 Hot metal 13 Hot water reservoir 14 Furnace wall 15 In-furnace observer

Claims (5)

In the method of operating a vertical melting furnace that uses solid fuel, blows from the tuyere, dissolves the iron source, or dissolves and reduces it to produce pig iron,
(I) The in-furnace observer is 0.5 to 1.5 m from the tuyere in the vertical melting furnace having one tuyere and from the lower tuyere in the vertical melting furnace having two tuyere. A plurality of upper furnace walls are provided in the height direction and / or the circumferential direction of the furnace,
(Ii-1) Determining an in-furnace observer suitable for the current operation,
(Ii-2) During operation, observe the height of the coke bed from the in-furnace observer so that the height of the coke bed is the same level as the height of the in-furnace observer suitable for the current operation. A method for operating a vertical melting furnace, wherein the amount of coke in the charge is increased or decreased according to the vertical fluctuation of the coke bed height.   The vertical melting furnace operating method according to claim 1, wherein in the vertical melting furnace having two stages of tuyere, an in-furnace observer is provided in the upper tuyere.   The method for operating a vertical melting furnace according to claim 1 or 2, wherein the solid fuel is a solid fuel containing blast furnace coke.   The operation method of the vertical melting furnace according to any one of claims 1 to 3, wherein a height of the coke bed is a height of a central portion and / or a peripheral portion of an upper surface of the coke bed. .   The vertical melting furnace according to any one of claims 1 to 4, wherein the amount of coke blended in the charge is increased / decreased by increasing / decreasing the coke ratio and / or introducing blank coke. Operating method.

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