JP2005097737A - Method for operating blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a blast furnace operating method which improves the ventilation of a blast furnace when ferrocoke is utilized as the raw material for the blast furnace, and to provide a method for operating a blast furnace which solves the problem in the conventional ferrocoke production technique and also improves the ventilation of the blast furnace in order to utilize ferrocoke as the raw material for a blast furnace. <P>SOLUTION: In the method for operating a blast furnace, at the time of charging ferrocoke produced by molding the raw material essentially consisting of coal and iron ore, coke and iron ore into a blast furnace, the ferrocoke is charged in the order of coke, ferrocoke and iron ore, and the charging cycle in the order of cokem ferrocoke and iron ore is repeated. Preferably, the ferrokoke is produced by subjecting the raw material essentially consisting of coal and iron ore to heating and hot molding into agglomerated moldings, heating the agglomerated moldings and carbonizing the coal in the agglomerated moldings. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for operating a blast furnace using ferro-coke as a blast furnace raw material.

The technology for blending powdered iron ore with raw coal and producing ferro-coke by dry distillation of this mixture in a normal chamber furnace coke oven is as follows: 1) A powder mixture of coal and powdered iron ore is used as a chamber furnace coke. A method of charging into a furnace, 2) a method of forming coal and iron ore cold, that is, at room temperature, and charging the molded product into a chamber furnace type coke oven have been studied (for example, Non-Patent Document 1). reference.). However, since ordinary furnace-type coke ovens are composed of silica brick, when iron ore is charged, it reacts with silica, which is the main component of silica brick, and low melting point firelite (2FeO · SiO ₂ ) Will cause damage to the quartz brick. For this reason, the technique which manufactures ferro-coke with a chamber-type coke oven is not implemented industrially.

  In recent years, a continuous molding coke manufacturing method has been developed as a coke manufacturing method that replaces the chamber furnace coke manufacturing method. In the continuous molding coke manufacturing method, a vertical shaft furnace composed of chamotte bricks instead of silica bricks is used as a carbonization furnace, coal is molded into a predetermined size in the cold, and then charged into the shaft furnace. The coal is carbonized by heating using a circulating heat medium gas to produce a molded coke. It has been confirmed that coke with the same strength as ordinary blast furnace coke can be produced even if a large amount of cheap non-caking coal with abundant resource reserves is used. When the caking property is high, the coal is softened and fused in the shaft furnace, which makes it difficult to operate the shaft furnace and causes a problem that the quality of the coke such as deformation and cracking is deteriorated.

In order to suppress fusion in the shaft furnace in the continuous coke production method, iron ore is added to the coal so as to be 15 to 40% of the total amount, and a molded product is produced coldly. A method of charging has been proposed (see, for example, Patent Document 1).
JP-A-6-65579 Fuel Society, “Coke Technology Annual Report” 1958, p. 38

  However, in the continuous coke manufacturing method described in Patent Document 1, in which iron ore is added to coal, a molded product is manufactured cold, and charged into a shaft furnace, iron ore has no caking properties. In order to produce a molded product in a cold state, it is necessary to add an expensive binder. Also, because room temperature moldings are charged from the top of the shaft furnace, thermal stress is generated due to the temperature difference between the inside and surface of the moldings due to contact with high-temperature gas, causing thermal cracking, pulverization, and product yield reduction. Resulting in.

  On the other hand, in blast furnace operation, the use of expensive coke is reduced by increasing the amount of pulverized coal injection, etc., and the operation is aimed at reducing the coke ratio. When the coke ratio is reduced, the load on the coke is increased in the blast furnace and the residence time is increased, so that there is a problem in that coke pulverization increases and air permeability deteriorates. It is desirable to reduce the coke ratio and achieve a low reducing material ratio by using ferro-coke for blast furnace operation, but at the same time it is preferable that the air permeability is good.

  Accordingly, an object of the present invention is to provide a method for operating a blast furnace capable of improving the air permeability of the blast furnace when using ferro-coke as a raw material for the blast furnace.

  Another object of the present invention is to provide a method for operating a blast furnace capable of solving the problems of conventional ferro-coke manufacturing techniques and improving the air permeability of the blast furnace in order to use ferro-coke as a raw material for blast furnace. There is to do.

The features of the present invention for solving such problems are as follows.
(1) When charging ferro-coke, coke, and iron ore, which are made by molding raw materials mainly composed of coal and iron ore, into the blast furnace, coke, ferro-coke and iron ore A method for operating a blast furnace, comprising charging and repeating a charging cycle in the order of the coke, ferro-coke, and iron ore.
(2) Ferro-coke heats the raw material mainly composed of coal and iron ore and forms it into a lump-molded product by heating. The method of operating a blast furnace according to (1), characterized in that the blast furnace is manufactured in the same manner.
(3) The blast furnace operating method according to (1) or (2), wherein the ferro-coke raw material further contains biomass.
(4) The method for operating a blast furnace according to any one of (1) to (3), wherein the ferro-coke raw material further contains waste plastic.

  According to the present invention, ferro-coke suitable for blast furnace operation can be obtained, and coke ratio can be reduced by using ferro-coke as a raw material for blast furnace, and the air permeability of the blast furnace is maintained well and stable. It can be operated with high productivity.

  In the present invention, when ferro-coke, coke, and iron ore are charged into a blast furnace for operation, the coke, ferro-coke, and iron ore are charged into the blast furnace in the order of the coke, ferro-coke, Repeat the charging cycle in the order of iron ore ("coke / ferrocoke / iron ore" cycle). Therefore, in the blast furnace, a multi-layered state in the order of coke, ferro-coke, and iron ore is repeatedly formed from the bottom.

  The ferro-coke used in the present invention is produced by heating a mass molded product produced by molding a raw material mainly composed of coal and iron ore, and dry-coalizing the coal in the mass molded product. . The main component of coal and iron ore means that the raw material of ferro-coke is mainly coal and iron ore. Ferro-coke is made of a raw material containing 70 mass% or more of coal and iron ore. Although coke is produced, a raw material containing 80 mass% or more of coal and iron ore is usually used.

  Ferro-coke is manufactured by heating a raw material mainly composed of coal and iron ore and forming it into a lump-molded product by heating, and then heating the lump-molded product to dry-distill the coal in the lump-formed product. It is desirable that

  When producing ferro-coke using coal and iron ore as raw materials, it takes advantage of the fact that caking is expressed when coal is heat-treated. By molding, a molded product is manufactured without using a binder. Further, by subjecting the hot molded product to a dry distillation in a high temperature state, the thermal stress generated in the molded product during the heating process is reduced, so that pulverization can be suppressed and manufactured ferrocoke. Product yield can be improved. In addition, a large amount of hydrogen-containing gas can be recovered from coal by utilizing the catalytic effect of iron ore in the carbonization process, and this reducing gas can be supplied to the metallurgical furnace as a reducing gas for the iron source. .

  Although only coal and iron ore can be used as raw materials for ferro-coke, it is preferable to use biomass in addition to coal and iron ore. Biomass refers to all living organisms, that is, all organisms that can be regenerated as energy resources, and examples include wood, pulp waste liquid, paper, and oil. Due to the catalytic effect of iron ore in the dry distillation process, a large amount of gas containing hydrogen can be recovered from biomass. Therefore, by adding biomass, a suitable reducing gas can be obtained by blowing into a blast furnace or the like. . Moreover, it is preferable that the ferro-coke raw material is dry-distilled in a shaft furnace. When the molded product formed by molding the raw material is fused in the shaft furnace, the flow of hot air in the furnace becomes worse. However, in some cases, the mass molding may not be unloaded in the shaft furnace. However, in addition to iron ore, biomass such as wood that does not show caking properties is blended to form the mass in the dry distillation process. It is possible to suppress the object from fusing in the shaft furnace.

  When blending biomass with ferrocoke, since biomass has a low bulk density, the strength of the produced ferrocoke tends to decrease. Therefore, the blending ratio of biomass is preferably 20 mass% or less of the entire ferro-coke raw material.

  Hereinafter, an embodiment of a method for producing ferrocoke suitable for use in a blast furnace will be described. In the case of using raw iron ore, coal, and biomass, the biomass is further pulverized to a predetermined particle size or less by a pulverizer and then heated by a preheater. A fluidized bed furnace or kiln is used as the preheater. As a method for preheating the raw material, there are a pattern in which all of the raw iron ore, coal, and biomass are preheated to the same temperature, and a pattern in which a temperature difference is set between them. In this embodiment, two types of preheaters are used. Then, the temperature of coal and biomass is preheated to about 200 ° C to 300 ° C, and the iron ore is preheated to 400 ° C to 500 ° C, and then mixed in a kneader to produce a mixture having an average of about 350 ° C. . When coal and biomass are heat-treated at 200 ° C. or higher, pyrolysis gas may be generated, and handling tends to be difficult. Therefore, it is desirable to keep the preheating temperature of coal and biomass low. On the other hand, since iron ore does not generate gas even when heat-treated, it is possible to increase the preheating temperature.

  Since iron ore has higher thermal efficiency during preheating due to its higher specific gravity than coal, biomass, etc., energy saving can be achieved by making the iron ore preheating temperature higher than that of coal and biomass. You can also.

  Coal has the property of becoming more caustic when heated rapidly. By heating and mixing the preheating temperature of the coal at a temperature lower than the preheating temperature of the iron ore, the coal can be rapidly heated, so that the caking property of the coal can be improved.

  Next, the raw iron ore, coal, and biomass are hot formed by a hot forming machine. Coal softens and melts at about 350 ° C. due to preheating and kneading. If this softening and melting property of coal is used as a binder, the raw material can be formed into a lump-molded product without adding a separate binder. Note that if the raw material is to be molded at a temperature higher than 350 ° C., the molding temperature may be 350 ° C. or lower because the raw material may not be molded by the gas generated from coal.

  It is desirable that the lump-molded product molded by the hot molding machine is dry-distilled by a direct heating method using hot air in a shaft furnace type heat treatment furnace or the like. The heated gas is blown into the shaft furnace from the hot air furnace. A low temperature gas is blown into the upper portion of the shaft furnace, a high temperature gas is blown into the middle portion, and a gas is circulated from the middle portion to the upper portion in order to increase thermal efficiency. Cooling gas is blown into the lower part of the shaft furnace, and room temperature-based molded ferro-coke is taken out.

  In the shaft furnace, the lump molding is at a temperature of about 900 ° C., so the iron ore in contact with the coal is reduced. The reduction rate of iron ore can be as high as 80% or more. The crushing strength of the molded ferro-coke is 1960 N or more, and a sufficient strength not to be pulverized in a blast furnace is obtained.

  According to the present embodiment, the mass molded product molded hot is inserted into the shaft furnace in a high temperature state, so that the thermal stress generated in the molded product during the heating process in the shaft furnace is reduced. Powdering can be suppressed and the product yield can be improved. Moreover, by blending biomass such as wood that does not show caking properties in addition to iron ore, it is possible to suppress the fusion of the molded product in the shaft furnace during the dry distillation process.

  Ferro-coke containing the partially reduced powder iron source is put into the blast furnace. Usually, iron ore, sintered ore, coke, etc. are introduced into the blast furnace in addition to ferro-coke. Ferro-coke promotes the reduction of sintered ore due to its high reactivity and contains partially reduced iron ore, so it can lower the temperature of the heat preservation zone in the blast furnace, and thus the coke ratio Can be reduced. Furthermore, by suppressing pulverization, air permeability can be improved and the coke ratio is reduced.

  In order to lower the reducing material ratio (fuel ratio) of the blast furnace, the reduction equilibrium temperature in the blast furnace using highly reactive coke is controlled and the temperature of the heat preservation zone is lowered, and iron ore is partially reduced beforehand. Two methods are conceivable: putting them into the blast furnace. When the ferro-coke produced by the above method is used for the operation of a blast furnace, it is very effective because both methods can be combined. That is, the ferro-coke produced by the method of the present invention can reduce the coke reactivity by the catalytic effect of the iron ore at the same time that the iron ore is partially reduced, increasing the gas utilization rate in the blast furnace. Therefore, by using this, the reducing material ratio of the blast furnace can be reduced.

Since iron ore has a catalytic action for the CO ₂ reaction, the reactivity of ferrocoke can be increased by adding highly reactive iron ore to the raw material of ferrocoke, and therefore ferrocoke in the blast furnace. It is preferable because coke pulverization can be further suppressed.

  Moreover, it is desirable that the iron ore as the raw material for ferrocoke contains porous iron ore. When porous iron ore (that is, so-called high crystal water ore) is used among iron ores, the decomposition catalytic effect can be improved and the yield of hydrogen can be increased.

  The blending ratio of the iron ore and coal when producing the lump-molded product is preferably 40 mass% or less of the total amount of iron ore and coal. This is because the strength of ferro-coke is abruptly reduced when the blending ratio of iron ore is more than 40 mass%. Moreover, since the ratio of the surface of the iron ore in contact with coal increases as the blending ratio of the iron ore decreases, the reduction rate of the iron ore increases. When the reduction rate of iron in iron ore is as high as about 80%, the coke drum strength and crushing strength of ferro-coke increase due to the blending of iron ore.

  In the present invention, waste plastic can be used as a raw material for ferrocoke instead of biomass or in combination with biomass. Similar to biomass, a large amount of gas containing hydrogen is generated from waste plastic due to the catalytic effect of iron ore in the dry distillation process in a shaft furnace or the like. Waste plastic refers to plastic that is used in all industrial fields and everyday life fields and discharged as waste after use. Waste plastic is mainly contained in both general waste discharged from households and industrial waste discharged from business establishments. In addition to waste plastic, organic waste such as sludge and tires may be used as a raw material for ferrocoke. When waste plastic is used, heat treatment at 200 ° C. or more may cause generation of pyrolysis gas, which tends to be difficult to handle, and the preheating temperature is about 200 ° C. to 300 ° C. preferable. In addition, when hot-forming ferro-coke raw materials, it is possible to produce the molded product without using a binder by using the thermoplasticity of the waste plastic and molding the waste plastic in a heated state. it can.

  FIG. 1 is an explanatory view showing an embodiment of the present invention. In FIG. 1, in order to charge coke, ferro-coke, and iron ore from the top of the blast furnace 1, individual reservoirs are prepared in the above-ground part. For example, the reservoir 4 is filled with coke, the reservoir 5 is filled with ferro-coke, and the reservoir 6 is filled with iron ore. As ferro-coke, ferro-coke produced by hot molding as described above can be used, or ferro-coke produced by other methods can be used. Also, sintered ore can be used instead of iron ore. These raw fuels are placed on the belt conveyor 3 and stacked in the blast furnace 1 in the order of coke, ferro-coke and iron ore using the furnace top charging equipment 2 of the blast furnace 1. There are a plurality of types of furnace top charging equipment 2, but any type can be used. In addition, the charging cycle is sequentially repeated so that the charging level of the raw material in the blast furnace becomes constant with charging of coke, ferro-coke, and iron ore as one cycle.

  FIG. 2 shows a schematic diagram of the layered structure after the raw fuel is deposited in the blast furnace 1 as described above. Ferro-coke 8 is preferably coarser in order to ensure air permeability in the blast furnace. However, if the particle size is too large, the strength decreases, so that, for example, Macek type (I: 43 mm, H: 43 mm, t: 18 mm) To mold. In this way, the ferro-coke 8 is molded as a particle size approximately intermediate between the coke 9 having a particle size of 50 to 100 mm and the iron ore 7 (or sintered ore) having a particle size of 5 to 20 mm. For this reason, the three types of raw fuels are neatly deposited as shown in FIG. 2 without being mixed with each other.

  FIG. 3 is a schematic diagram of a layered structure when raw fuel is stacked and deposited in the blast furnace 1 in the order of coke 9, iron ore 7, and ferro-coke 8. The iron ore 7 having a small particle diameter enters a gap between coke particles having a large particle diameter, thereby reducing the porosity of the coke layer and deteriorating the air permeability.

By the way, the pressure loss of the packed bed is quantified by Ergan et al., As shown in the following Equation 1 (for example, see Chemical Engineering Association, Chemical Engineering Handbook, Revised 5th Edition, P278). However, in Equation 1, ΔP / ΔL: pressure loss per unit length of packed bed (Pa / m), ε: porosity of layer (−), u: gas superficial velocity (m / sec), dp : Harmonic average diameter (m) of packed particles, ρ: gas density (kg / m ³ ).

  In Equation 1, the first term on the right side of the equation is a quadratic expression with a numerator of porosity ε and a cubic equation with a denominator of ε. Further, since the numerator of the second term on the right side is the first-order ε and the denominator is the third-order expression, the pressure loss increases as the porosity ε decreases. As the porosity of the packed bed in the blast furnace decreases, pressure loss increases and blast furnace operation becomes unstable.

Table 1 shows an example of the blast furnace operation in the case where coke, ferro-coke, and iron ore are stacked and deposited in the order of coke, ferro-coke, and iron ore when charging a blast furnace with an internal volume of 3443 m ³ .

  In Table 1, in the example of the present invention, since the fine porosity of the iron ore enters the coke layer, the porosity of the packed bed does not decrease, so the air permeability of the blast furnace is maintained well, and the number of slips is one time. / Day, the number of wind reductions was 0 times / day, and stable operation was possible.

  Here, the number of slips is the number of times that the raw material charging surface of the blast furnace rapidly decreases. Normally, the raw material charging surface descends continuously, and when a certain amount of descent is reached, new raw fuel is charged. However, when the air permeability of the blast furnace deteriorates, the pressure of the blast rises, so the force that pushes up the raw fuel charged with gas increases, and the raw material charging surface does not temporarily drop (shelf suspension) ) Occurs. When shelving occurs, a space is generated between the raw material charging surface and the tuyere, but if the layer structure is broken and the raw fuel falls into this space, the raw material charging surface is rapidly lowered.

  A sudden drop in the raw material charging surface of 300 mm or more is defined as a slip. However, in the case of a large slip of 600 mm or more, the blast furnace air volume is temporarily reduced by 20% to reduce the raw material charging surface. Wait for recovery. This number is shown as the number of wind reductions. Since the production volume is roughly proportional to the blown air volume, the wind reduction directly leads to a decrease in productivity.

  As a comparative example, the operation was performed in which the order of charging the raw fuel into the blast furnace was changed in the order of coke, iron ore, and ferro-coke. A blast furnace operation example in the case of stacking and depositing coke, iron ore, and ferro-coke in this order is shown in Table 1 as Comparative Example 1. The pressure loss in the packed bed increased, the number of slips and wind reductions increased, and the production volume decreased by 200 tons per day. In addition, since unreduced ore is supplied to the lower part of the blast furnace due to the slip, indirect reduction as an exothermic reaction decreases and the amount of direct reduction as an endothermic reaction increases, so that the reducing material ratio increases by 3 kg / t. It was.

  As a comparative example, normal operation without charging ferro-coke was performed using raw fuel charging to the blast furnace as coke and iron ore. An example of blast furnace operation in this case is shown in Table 1 as Comparative Example 2. Compared to Example 1 (Example of the present invention) and Example 2 (Comparative Example 1) in which the effect of partial reduction of the ore in ferro-coke and the effect of lowering the temperature of the heat preservation zone could be expected, the reducing material ratio increased by about 40 kg / t. .

  As described above, the use of ferro-coke in a blast furnace has a great effect on reducing the reducing material ratio. I understand.

It is explanatory drawing which shows one Embodiment of this invention. It is one Embodiment of this invention, and is a schematic diagram of the layered structure at the time of depositing raw fuel in a blast furnace in order of coke, ferro-coke, and iron ore. It is a schematic diagram of a layered structure when raw fuel is laminated and deposited in a blast furnace in the order of coke, iron ore, and ferro-coke.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Blast furnace 2 Furnace top charging equipment 3 Belt conveyor 4 Reservoir (coke)
5 Reservoir (ferrocoke)
6 Reservoir (Iron Ore)
7 Iron ore 8 Ferro-coke 9 Coke

Claims (4)

  When charging ferro-coke produced by molding raw materials mainly composed of coal and iron ore, coke and iron ore into the blast furnace, the coke, ferro-coke and iron ore are charged in this order. A method for operating a blast furnace, characterized by repeatedly performing a charging cycle in the order of the coke, ferro-coke and iron ore.   Ferro-coke is manufactured by heating raw materials mainly composed of coal and iron ore and forming them into a lump-molded product by heating, and then heating the lump-formed product to dry-distill the coal in the lump-formed product. The method of operating a blast furnace according to claim 1, wherein   The method for operating a blast furnace according to claim 1 or 2, wherein the ferro-coke raw material further contains biomass.   The method for operating a blast furnace according to any one of claims 1 to 3, wherein the ferro-coke raw material further contains waste plastic.

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