JP2010014319A - Vertical melting furnace and molten metal production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vertical melting furnace capable of promoting the combustion and heat generation of a carbon material and producing molten metal with high productivity. <P>SOLUTION: In this vertical melting furnace in which an iron source and the carbon material are charged from a furnace top, hot air is blown off from a plurality of tuyeres disposed at a furnace lower section, and molten metal is produced by melting the iron source by the combustion heat of the carbon material, an oxygen injection pipe A and a fuel gas injection pipe B are disposed in at least at a part of the tuyeres, and oxygen injected from the oxygen injection pipe A and a fuel gas injected from the fuel gas injection pipe B are brought into contact with each other in a region within a distance d in the furnace central direction from a tip of the tuyere (including region inside of tuyere) when an inner diameter of the tip of the tuyere is d. As an atmospheric temperature of the region near the tip of the tuyere is increased by a combustion gas of oxygen and fuel gas injected from the injection pipes A, B, and the combustion and heat generation of the carbon material are promoted, the productivity of molted metal is improved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vertical melting furnace in which an iron source is melted by the combustion heat of a carbon material to produce hot metal, and a hot metal manufacturing method using the vertical melting furnace.

Conventionally, a process of melting an iron source such as iron scrap using a vertical melting furnace is known (for example, Patent Document 1). In this process, iron sources such as iron scrap and coke are charged from the top of the vertical melting furnace, and hot air is blown from a plurality of tuyere (blower tuyere) provided at the bottom of the furnace to heat the combustion of coke. The molten iron is obtained by dissolving the iron source.
JP-A-56-156709

  In the hot metal production process using a vertical melting furnace, it is important to increase the productivity per cross-sectional area of the furnace. From such a viewpoint of productivity, it is desirable that the entire cross section of the furnace is effectively used for the combustion and heat generation of the coke, but in practice, it is not necessarily used effectively. In particular, (a) in the vicinity of the tuyere when the blast temperature is around 600 ° C., (b) in the center of the furnace when the diameter of the furnace is relatively large with respect to the size of the packing, coke combustion, Heat generation tends to be insufficient, which is a problem in increasing productivity.

Therefore, the object of the present invention is to solve such problems of the prior art, promote combustion and heat generation of the carbonaceous material, particularly combustion and heat generation of the carbonaceous material in the region near the tuyere, and produce hot metal with high productivity. An object of the present invention is to provide a vertical melting furnace.
Another object of the present invention is to provide a vertical melting furnace capable of promoting the combustion and heat generation of carbonaceous materials in the furnace center area together with the area near the tuyere and producing hot metal with higher productivity. There is to do.
Furthermore, another object of the present invention is to provide a hot metal production method capable of stably producing hot metal with high productivity using such a vertical melting furnace.

The present invention for solving the above problems is summarized as follows.
[1] A vertical mold in which molten iron is produced by charging an iron source and charcoal from the top of the furnace, blowing hot air from multiple tuyere at the lower part of the furnace, and melting the iron source with the combustion heat of the charcoal In a melting furnace, an oxygen injection pipe and a fuel gas injection pipe are installed in at least some tuyere, and when the tip inner diameter of the tuyere is d, the oxygen jet pipe is injected into the furnace. Oxygen and the fuel gas injected from the fuel gas injection pipe into the furnace are in contact with each other in an area at least within a distance d from the tip of the tuyere toward the center of the furnace (including the area inside the tuyere). A vertical melting furnace characterized by comprising:

[2] In the vertical melting furnace of [1], the oxygen injection pipe and the fuel gas injection pipe are provided in a double tubular shape, the outer pipe of the double pipe is an oxygen injection pipe, and the inner pipe is a fuel gas injection pipe. A vertical melting furnace.
[3] In the vertical melting furnace according to [1], the oxygen injection pipe and the fuel gas injection pipe are provided in a double tubular shape, the outer pipe of the double pipe is a fuel gas injection pipe, and the inner pipe is an oxygen injection pipe. A vertical melting furnace.
[4] A vertical melting furnace according to any one of the above [1] to [3], wherein the nozzle portion of the oxygen injection tube has a Laval shape or a tapered shape.

[5] A hot metal production method using the vertical melting furnace according to any one of [1] to [4] above, wherein iron scrap, iron-containing dust and / or iron-containing sludge agglomerated as an iron source A hot metal production method characterized by charging one or more of the above into a furnace and injecting oxygen from an oxygen injection tube and fuel gas from a fuel gas injection tube into the furnace.
[6] In the hot metal production method of [5] above, the fuel gas injected from the fuel gas injection pipe is mainly composed of one or more of natural gas, propane gas, iron-making process gas, and liquid fuel vaporized gas. The hot metal manufacturing method characterized by the above-mentioned.

[7] The hot metal manufacturing method according to [5] or [6], wherein an oxygen jet having a supersonic velocity at a nozzle outlet is injected from an oxygen injection pipe.
[8] In the hot metal production method according to any one of [5] to [7], the harmonic average particle diameter dp of the carbonaceous material charged into the furnace satisfies D / dp ≧ 30 with respect to the furnace inner diameter D. A hot metal production method characterized by the above.
Here, in the present invention, the term “contact” means that oxygen injected from the oxygen injection pipe and fuel gas injected from the fuel gas injection pipe are ejected from the injection ports (nozzles) of the oxygen injection pipe and the fuel gas injection pipe. When a gas diffusion region is formed in which each gas spreads at an angle of 10 ° on one side (20 ° on both sides) with respect to the center of the injection direction, the gas diffusion regions of oxygen and fuel gas partially overlap each other. . Therefore, if the injection port of the oxygen injection tube and the injection port of the fuel gas injection tube are adjacent to each other, the position of the injection port (nozzle tip) is substantially the “contact” position between the gases. .

According to the vertical melting furnace of the present invention, the oxygen temperature and the fuel gas injected from the oxygen injection pipe and the fuel gas injection pipe installed in the tuyere, respectively, burn at the tuyere, so that the ambient temperature in the vicinity of the tuyere And the combustion and heat generation of the carbonaceous material in that region can be effectively promoted. For this reason, productivity of hot metal can be improved.
In the present invention, when the oxygen injection pipe and the fuel gas injection pipe are provided in a double tubular shape, and the outer pipe of the double pipe is an oxygen injection pipe and the inner pipe is a fuel gas injection pipe, Since the contact state between the fuel gas and the fuel gas increases, the combustion efficiency is further improved. Therefore, the combustion and heat generation of the carbonaceous material in the region near the tuyere can be more effectively promoted.

  In the present invention, when the oxygen injection pipe and the fuel gas injection pipe are provided in a double tubular shape, and the outer pipe of the double pipe is a fuel gas injection pipe and the inner pipe is an oxygen injection pipe, As described above, not only is the effect that the ambient temperature rises in the region near the tuyere to promote the combustion and heat generation of the coke, but also the combustion gas generated at the tuyere tip causes the oxygen flow injected from the oxygen injection pipe to the outside By wrapping in, the oxygen flow can reach the furnace center region without so much diffusion, and the oxygen can promote the combustion and heat generation of coke in the furnace center region. As a result, the combustion and heat generation of coke can be promoted in a wide area from the tuyere to the center of the furnace, and the productivity of hot metal can be further increased.

In the present invention, when the nozzle portion of the oxygen injection tube has a Laval or tapered structure, a supersonic or near high-speed oxygen flow can be discharged from the oxygen injection tube. Can be easily achieved, and heat generation and dissolution in the same region can be further promoted. In particular, the above-described effect in the case where the oxygen injection pipe and the fuel gas injection pipe are provided in a double tubular shape, the outer pipe of the double pipe is a fuel gas injection pipe, and the inner pipe is an oxygen injection pipe. It can be further increased.
Moreover, according to the hot metal production method of the present invention using the vertical melting furnace as described above, the atmosphere temperature in the vicinity of the tuyere tip is raised, and the combustion and heat generation of the carbonaceous material in the same region can be promoted. In addition, since combustion and heat generation of the carbonaceous material can be promoted in a wide area from the tuyere to the furnace center, hot metal can be stably produced with high productivity.

  The vertical melting furnace targeted by the present invention is charged with an iron source and a carbon material from the top of the furnace, blown in hot air from a plurality of tuyere provided at the bottom of the furnace, and melts the iron source with the combustion heat of the carbon material. It is a vertical melting furnace which manufactures hot metal by doing. In this vertical melting furnace, the ratio H / D between the furnace inner diameter D and the raw fuel packed bed height H is 2 or more, preferably 2.5 or more. As a result, a stable red hot carbon material packed bed can be formed in the lower part of the raw fuel packed bed, and the carbon can be burned and heated by blowing from the tuyere, so that the packing can be efficiently dissolved.

  As the iron source to be used, one or more of ores, iron-based scraps, iron-containing dusts and / or agglomerates of iron-containing sludge are used, and coke is generally used as the carbonaceous material. Therefore, the vertical melting furnace targeted by the present invention includes a blast furnace. In particular, the present invention is agglomerates of iron-containing dust or / and iron-containing sludge (hereinafter referred to as iron-containing sludge) for the reason described below. For convenience of explanation, it is suitable for a vertical melting furnace using an “iron-containing dust / sludge agglomerate”). The furnace charges such as iron-containing dust / sludge agglomerates will be described in detail later.

FIG. 1 schematically shows a vertical melting furnace to which the present invention is applied and its basic operation mode. In this example, one or more of iron-based scrap and iron-containing dust / sludge agglomerates are used. This shows a vertical melting furnace with the main iron source.
In the figure, 1 is a furnace body, 2 is a raw material charging section provided at the top of the furnace, 3 is a plurality of tuyere (blower tuyere) provided at appropriate intervals in the circumferential direction of the lower part of the furnace, and 4 is this tuyere 3 Reference numeral 5 denotes a hot air pipe for supplying hot air to the exhaust duct, 5 is an exhaust duct connected to the upper part of the furnace body, and 6 is a dust collector provided in the middle of the exhaust duct 5.
Although there is no essential limitation on the size of the melting furnace, etc., the furnace inner diameter at the tuyere position is usually about 2 to 4 m and the furnace height is 5 to 5 as a size that is substantially operable or advantageous in operation. It is about 10m. Although there is no restriction | limiting in the number of tuyere, Usually, it is about 4-12.

  In such a melting furnace, an iron source (iron source mainly composed of one or more of iron-based scrap and iron-containing dust / sludge agglomerate) and coke are charged from the raw material charging section 2 at the top of the furnace, Hot air is blown from the plurality of tuyere 3 and the iron source is melted by the heat of the combustion gas of coke to form hot metal. The generated hot metal is taken out of the furnace through the outlet at the bottom of the furnace. In the furnace, dust is also generated with the rising hot air, and this dust is collected by the dust collector 6 via the exhaust duct 5.

In the present invention, when the oxygen injection pipe A and the fuel gas injection pipe B are installed in at least some tuyere 3, and the tip inner diameter of the tuyere is d, the oxygen injection pipe A is directed into the furnace. And the fuel gas injected from the fuel gas injection pipe B into the furnace within a distance d from the tip of the tuyere toward the center of the furnace (including the area inside the tuyere) Configure to touch. As the fuel gas injected from the fuel gas injection pipe B, natural gas, propane gas, or the like is used as described later.
The oxygen injection pipe A and the fuel gas injection pipe B may be installed in all tuyere 3 of the furnace body 1 or some tuyere 3. Moreover, you may change the tuyere to apply periodically.

About each following embodiment, the case where coke is used as a carbon material is demonstrated to an example.
2 shows a tuyere structure according to an embodiment of the present invention. FIG. 2 (a) is a longitudinal sectional view of the tuyere and FIG. 2 (b) is a front view of the tuyere. In the figure, 30 is a tuyere tube and 31 is a tuyere tip.
In this embodiment, the oxygen injection pipe A and the fuel gas injection pipe B are installed in parallel. As described above, in the oxygen injection pipe A and the fuel gas injection pipe B, oxygen and fuel gas injected from each contact in a region within a distance d from the tuyere tip 31 in the furnace center direction (and therefore at least one). Are mixed and combusted in the part). Here, the region within the distance d in the furnace center direction from the tuyere tip 31 includes the region inside the tuyere. In the present embodiment, oxygen and fuel gas injected from both the injection pipes A and B come into contact with each other in the area inside the tuyere immediately after injection and burn.

  Here, when the position where the oxygen and the fuel gas injected from the oxygen injection pipe A and the fuel gas injection pipe B contact each other exceeds the distance d from the tuyere tip 31 toward the furnace center, the fuel gas is mainly blown air. Since pure oxygen is diluted in the blown air, an increase in the combustion temperature is suppressed. According to the chemical equilibrium calculation, for example, the adiabatic flame temperature of methane gas, which is the main component of city gas, is 1954 ° C. (2227K) in air (25 ° C.), and remains at 2216 ° C. (2489 K) even in hot air (600 ° C.). It is not much different from the coke surface temperature at the tuyere at around 2000 ° C. (2273 K). On the other hand, in the case of pure oxygen combustion, the adiabatic flame temperature rises to 2781 ° C. (3054 K), and therefore an effect of improving the combustion speed due to the temperature rise can be expected.

Further, the position where the oxygen and the fuel gas injected from the oxygen injection pipe A and the fuel gas injection pipe B come into contact with each other may be inside the tuyere, but at a distance of 2d or more from the tuyere tip 31 to the inside of the tuyere. If contact is made at a position, heat from a high-temperature flame due to pure oxygen combustion is loaded on the inner surface of the tuyere, which leads to wear and heat loss on the inner surface of the tuyere, which is not desirable. For this reason, it is preferable that the position where the oxygen and the fuel gas injected from the oxygen injection pipe A and the fuel gas injection pipe B contact each other is within a range of less than 2d from the tuyere tip 31 to the tuyere inward.
The oxygen injection pipe A and the fuel gas injection pipe B are installed such that their tips do not protrude from the tuyere tip 31. When the tips of these injection pipes A and B protrude from the tuyere tip 31, wear is caused by the flowing iron flowing down in the coke packed bed at the tip of the tuyere, which is not desirable.

On the other hand, when each tip of the oxygen injection pipe A and the fuel gas injection pipe B is located inside the tuyere as in this embodiment, the distance L between the tip and the tuyere tip 31 satisfies the following conditions. Is preferred. This is to reduce the thermal load on the inner surface of the tuyere by avoiding a jet or flame of oxygen or fuel gas from directly contacting the inner surface of the tuyere.
L <d / (2 tan θ)
However, θ is an expansion angle on one side of the ejection gas at the tip of the nozzle (injection port) (an expansion angle on one side with respect to the center of the gas injection direction), and is 10 °.

  In the melting furnace having a tuyere structure according to the present invention, oxygen and fuel gas are respectively injected from the oxygen injection pipe A and the fuel gas injection pipe B into the furnace, and the oxygen and the fuel gas are in contact with each other at the tuyere to burn. However, high-temperature combustion gas is supplied in the vicinity of the tuyere, and the ambient temperature in that region can be effectively increased. For example, the blowing temperature of a vertical melting furnace such as a general cupola is around 600 ° C, but even if blowing air (hot air) of such temperature hits reddish coke, the combustion speed is not so high, and the blowing air is effective It is during the stage of contact and combustion with the high-temperature CO gas generated inside the furnace that contributes to combustion. Therefore, the burning and heat generation of coke near the tuyere are not very active. On the other hand, according to the present invention, the region where the fuel gas is burned with pure oxygen is formed at the tip of the tuyere, and the atmospheric gas temperature can be raised to about 2000 ° C. or more, which is a temperature suitable for coke combustion. In order to efficiently burn the fuel gas and make the high-temperature combustion gas exist near the tip of the tuyere, the fuel gas and oxygen are injected by separate injection means as in the present invention, and the fuel gas is burned with pure oxygen is necessary. As described above, as a result of increasing the atmosphere temperature at the tip of the tuyere, coke combustion and heat generation in the vicinity of the tip of the tuyere are promoted, and the productivity of hot metal can be improved.

  Further, the dust and sludge constituting the iron-containing dust / sludge agglomerate contain more iron oxide than iron-based scrap. Therefore, when iron-containing dust / sludge agglomerates are used as the iron source of the melting furnace, iron oxide in the agglomerates is reduced by coke and CO gas in the furnace, and heat is generated in this reduction reaction part. There is a risk that combustion and exothermic reaction may be delayed due to temperature drop. On the other hand, in the present invention, as described above, since the combustion and heat generation action of coke can be enhanced, the above-mentioned problems when using iron-containing dust / sludge agglomerates as an iron source can be advantageously solved.

FIG. 3 shows a tuyere structure according to another embodiment of the present invention. FIG. 3 (a) is a longitudinal sectional view of the tuyere and FIG. 3 (b) is a front view of the tuyere.
In the present embodiment, the oxygen injection pipe A and the fuel gas injection pipe B are provided in a double tube (concentric cross section), the outer pipe of this double pipe structure is the oxygen injection pipe A, and the inner pipe is the fuel gas injection pipe B. It is what.
By adopting such a structure, the contact state between the oxygen injected from the oxygen injection pipe A and the fuel gas injected from the fuel gas injection pipe B is further increased, so that the combustion efficiency is further improved. For this reason, the combustion and heat generation of coke in the vicinity of the tuyere can be more effectively promoted.

4 shows a tuyere structure according to another embodiment of the present invention. FIG. 4A is a longitudinal sectional view of the tuyere, and FIG. 4B is a front view of the tuyere.
In the present embodiment, the oxygen injection pipe A and the fuel gas injection pipe B are provided in a double tube (concentric cross section), the outer pipe of this double pipe structure is the fuel gas injection pipe B, and the inner pipe is the oxygen injection pipe A. It is what.
By adopting such a structure, as described above, the atmosphere temperature in the vicinity of the tuyere tip is increased by the combustion gas, and the effect of promoting the combustion and heat generation of coke in that region is obtained, and further, The following effects are obtained. Combustion gas (combustion gas generated by combustion of fuel gas, oxygen, and blown air) at the tip of the tuyere wraps the oxygen flow injected from the oxygen injection pipe A from the outside, thereby suppressing the expansion and diffusion of the oxygen flow. . That is, the combustion gas generated outside the oxygen flow injected from the oxygen injection pipe A has a lower density and a larger kinematic viscosity coefficient than the oxygen gas, so that the oxygen flow velocity is not attenuated and the oxygen flow is diffused. It helps to maintain the flow rate and straightness of the oxygen flow. Therefore, the oxygen flow can reach the center region in the furnace without diffusing so much while maintaining a sufficient speed, and can promote the combustion and heat generation of coke in the center region of the furnace. As a result, the combustion and heat generation of coke can be promoted in a wide area from the tuyere to the center of the furnace, and the productivity of hot metal can be further increased.

  In addition, as described above, when iron-containing dust / sludge agglomerates that originally contain a large amount of iron oxide are used as the iron source of the melting furnace, iron oxide is reduced by coke and CO gas in the furnace. In the reduction reaction part, endotherm is generated, and if it is left as it is, there is a possibility that the temperature drops and the combustion / exothermic reaction is delayed. In particular, under conditions such as D / dp ≧ 30 where the furnace inner diameter D is relatively large with respect to the carbon particle diameter (harmonic mean particle diameter) dp of the packed bed, blown air (oxygen) is present in the furnace center region. Because it is difficult to reach, the concern is increased. On the other hand, in the embodiment as shown in FIG. 4, since the combustion / heating action of coke in the central region of the furnace can be enhanced as described above, the iron-containing dust / sludge agglomerate is used as the iron source. The said subject at the time of use can be solved advantageously.

FIG. 5 shows a tuyere structure in another embodiment of the present invention. FIG. 5A is a longitudinal sectional view of the tuyere, and FIG. 5B is a front view of the tuyere. FIG. 5A shows an enlarged cross-sectional view of the nozzle portions of both the injection pipes A and B.
In the present embodiment, the oxygen injection pipe A and the fuel gas injection pipe B are provided in a double tube (concentric cross section), the outer pipe of this double pipe structure is the fuel gas injection pipe B, and the inner pipe is the oxygen injection pipe A. In addition, the nozzle portion (discharge portion) of the oxygen injection tube A is formed in a Laval shape (7 in the drawing is a throttle portion) that can discharge oxygen at supersonic speed.

With such a structure, a supersonic (nozzle outlet flow velocity) oxygen jet can be injected from the oxygen injection tube A, and it is even easier to make oxygen reach the furnace center region. Thereby, the effect described in the embodiment of FIG. 4 can be further enhanced. In particular, when the furnace is operated under the condition that the ratio D / dp between the furnace inner diameter D and the harmonic mean particle diameter dp of coke (carbon material) is D / dp ≧ 50, Since oxygen is difficult to reach the zone, coke in the furnace center region causes a solution loss reaction (CO ₂ + C = 2CO, endothermic reaction) due to carbon dioxide in the combustion gas, and heat generation and melting in the furnace center region Tended to stagnate. On the other hand, in the embodiment of the present invention as shown in FIG. 5, even if the operation is performed under the condition of D / dp ≧ 50, oxygen easily reaches the furnace center region, and heat is generated in the region. -It can promote dissolution.

In addition, as described above, when iron-containing dust / sludge agglomerates that originally contain a large amount of iron oxide are used as the iron source of the melting furnace, iron oxide is reduced by coke and CO gas in the furnace. In the reduction reaction part, endotherm is generated, and if it is left as it is, the temperature may drop and the combustion / exothermic reaction may be delayed. In particular, under the condition of D / dp ≧ 50 as described above, the blown air (oxygen) is supplied to the furnace center region It ’s hard to reach, so the concern grows. On the other hand, in the embodiment as shown in FIG. 5, since the coke combustion and heat generation action in the central region of the furnace can be particularly enhanced as described above, the iron-containing dust / sludge agglomerate is used as the iron source. The above-mentioned problem when used as can be particularly advantageously solved.
The nozzle part (discharge part) of the oxygen injection tube A may be tapered instead of Laval. Further, the jetted high-speed oxygen flow may have a flow velocity equal to or lower than the speed of sound. 2 and 3 also, the nozzle portion of the oxygen injection tube A can be formed in a Laval shape or a tapered shape.

Next, a hot metal manufacturing method using the vertical melting furnace as described above will be described.
In this hot metal manufacturing method, an iron source and a carbon material are charged from the top 2 of the furnace, hot air is blown from the tuyere 3, oxygen is injected from the oxygen injection pipe A, and fuel gas is injected from the fuel gas injection pipe B. Hot metal is produced by melting the iron source with the combustion heat of the carbonaceous material.
There is no particular restriction on the fuel gas injected from the fuel gas injection pipe B. Usually, a gas mainly composed of one or more of natural gas, propane gas, iron-making process gas, and liquid fuel vaporized gas is used. . The amount of fuel gas injected from the fuel gas injection pipe B is preferably set to be equal to or less than the amount that is completely burned by oxygen injected from the oxygen injection pipe A.

In addition, although there is no restriction | limiting in particular in an oxygen enrichment rate, in order to acquire the effect of this invention, generally it is preferable to set it as an oxygen enrichment rate of 2 vol% or more. On the other hand, if the oxygen enrichment rate is excessive, the amount of heat extracted from the tuyere increases due to an increase in tuyere tip temperature, and the frequency of erosion of tuyere refractories may increase. In addition, the temperature distribution in the furnace radial direction becomes large, and problems such as difficulty in controlling the gas flow tend to occur. For this reason, the oxygen enrichment rate is preferably about 50 vol% as the upper limit.
The harmonic average particle diameter dp of the carbonaceous material (such as coke) charged in the furnace satisfies D / dp ≧ 30, preferably D / dp ≧ 40, more preferably D / dp ≧ 50 with respect to the furnace inner diameter D. It is desirable. Since carbon materials with a small dp are cheaper, it is preferable from the viewpoint of economy to operate under conditions where the D / dp is as large as possible. On the other hand, the larger the D / dp, the more difficult the blown air (oxygen) reaches the furnace center side, so the combustion and heat generation at the furnace center side becomes insufficient, and the heat absorption due to the carbon solution loss reaction decreases. It becomes easier to proceed, and the productivity per furnace cross-sectional area tends to decrease. Therefore, it can be said that the present invention is particularly useful in such a condition with a large D / dp.

  As the iron source, for example, one or more of ores, iron-based scraps, iron-containing dust / sludge agglomerates, etc. are used, and as the carbon material, coke is generally used, but as mentioned above In addition, the vertical melting furnace of the present invention is particularly suitable for a hot metal manufacturing process in which one or more of iron-based scrap and iron-containing dust / sludge agglomerates are used as the main iron source. The manufacturing process will be described.

When iron-containing dust / sludge agglomerates are charged as the iron source, the amount of exhaust gas increases because the coke unit increases compared to the case of iron-based scrap alone charging. By performing the conversion, the amount of exhaust gas can be reduced. When the iron-based scrap and the iron-containing dust / sludge agglomerate are charged together, the charging method into the furnace is arbitrary, but it is better for the stability of operation to charge as uniformly as possible.
The iron source and coke may be charged into the furnace at the same time or alternately. In addition, the main furnace charging materials are one or more iron sources and coke of iron-based scrap, iron-containing dust / sludge agglomerates, but also iron such as pig iron, reduced iron, iron ore, etc. Sources, charcoal materials such as charcoal and anthracite may be charged.

  The iron-containing dust / sludge agglomerate may be any one of iron-containing dust, iron-containing sludge, or any material obtained by solidifying a raw material mainly composed of iron-containing dust and sludge. However, in general, one or more types of iron-containing dust and iron-containing sludge are mixed with a hydraulic binder, and if necessary, water is added to the raw material containing carbonaceous powder for reduction, and then molded. The molded product is then hydrated and cured to form an agglomerated product.

The iron-containing dust is dust containing iron oxide and / or metallic iron, and the type thereof is not particularly limited, but typical examples include steel-making dust generated in a steel manufacturing process. The steelmaking dust includes hot metal pretreatment dust generated in the hot metal pretreatment process, converter dust generated in the converter decarburization process, electric furnace dust generated in the electric furnace, and the like. These steelmaking dusts are collected by collecting dust from the exhaust gas generated in the steelmaking process. Among these, converter dust generated in the converter decarburization step, so-called OG dust, is particularly preferable because it has a low impurity content and therefore a high iron content. Examples of iron-containing dust other than steelmaking dust include blast furnace dust and rolling dust.
The iron-containing sludge is a sludge containing iron oxide and / or metallic iron, and there is no particular limitation on the type thereof, but it is sludge formed by collecting various types of dust as described above with a wet dust collector. Is a typical example.

As described above, the iron-containing dust / sludge agglomerate generally contains a hydraulic binder in the iron-containing dust or / and iron-containing sludge, and further contains carbon powder for reduction as required. It can be obtained by adding water to the blended raw material, mixing, molding, and hydrating and curing the molded product.
As said hydraulic binder, 1 or more types, such as various cements, such as a Portland cement, a blast furnace cement, an alumina cement, a fly ash cement, blast furnace granulated slag fine powder, quick lime, can be used, for example. In general, the blending amount of the hydraulic binder in the raw material is preferably about 2 to 25 mass% from the viewpoints of strength development and suppression of slag generation.

  The carbonaceous material powder is a powder mainly composed of carbon, and becomes a reducing material for iron oxide in a vertical melting furnace. Generally, lump coke is used as a reducing material in a vertical melting furnace for iron making, but carbon powder such as coke powder is less expensive and advantageous in terms of cost than lump coke. Since the contact area of carbon increases, there is an advantage that the reduction reaction of iron oxide proceeds rapidly. As the carbonaceous material powder, one or more types such as coke powder, coal powder (preferably anthracite coal powder), plastic powder and the like can be used, and those having a low volatile content such as coke powder are particularly preferable. Further, if a large carbon material is present in the iron-containing dust / sludge agglomerated material, cracks are generated from the portion, which causes a decrease in strength. Therefore, the carbon material powder preferably has a particle size of 3 mm or less. In general, the blending amount of the carbonaceous powder in the raw material is preferably about 2 to 25 mass%.

Further, in the raw material of the iron-containing dust / sludge agglomerated material, materials other than the iron-containing dust or / and iron-containing sludge, hydraulic binder and carbonaceous powder described above may be appropriately blended as necessary. For example, curing rate modifiers, surfactants, bentonites, chlorides for increasing the compressive strength of iron-containing dust / sludge agglomerates, materials for imparting an appropriate particle size distribution to the raw materials and enhancing moldability As an additive, one or more of iron-containing granular materials such as sintered sieve powder and mill scale, and limestone for adjusting the basicity of slag, and granular materials such as meteorite may be blended.
Further, from the viewpoint of reducing the amount of slag to be generated as much as possible, the total amount of SiO ₂ , Al ₂ O ₃ , CaO, and MgO in the raw material is preferably set to 25 mass% or less. Of course, these components include those contained in hydraulic binders.

In order to obtain an iron-containing dust / sludge agglomerate using a hydraulic binder, water is added to the above-mentioned raw material and mixed, then molded, and this molded product is hydrated and cured.
Although the amount of water varies depending on the composition of the raw material, the maximum amount of water that does not ooze out even when compressed during molding is desirable. Quantitatively, it is preferable to adjust the slump so that the maximum water amount is zero in the measurement according to JIS-A-1101 (method of measuring concrete slump). If the amount of water is too small, it cannot be molded properly, and curing of the hydraulic binder does not proceed. On the other hand, if the amount of water is too large and water oozes out during molding, special measures are required for the treatment of the water.

The molding process can be performed by any method such as molding using a mold, extrusion molding, roll press molding, etc. However, if the molding is made dense, the iron-containing dust / sludge agglomerate tends to increase in strength. For this reason, it is preferable to mold as high a density as possible. For this reason, it is preferable to compression-mold the mixture of raw material and water or to perform compression molding while vibrating. Specifically, it is preferable to perform molding using a compression molding machine such as a briquette molding machine, a press molding machine, an extrusion molding machine, or the like having a vibration function.
Although the shape of a molded product is arbitrary, in order to suppress powdering at the time of charging to a furnace as much as possible, it is preferable that there are few corners. Also, the size of the molded product is arbitrary, but if it is too small, the pressure loss of the furnace will increase when it is charged into the vertical melting furnace, while if it is too large, it will agglomerate when charged in the vertical melting furnace. In general, a size of about 20 to 2000 cm ^{3 in} volume is preferable because a reduction and dissolution delay due to a temperature rise delay in the center of the compound occurs.

A molded product obtained by molding a mixture of a raw material and water is cured for a certain period of time in order to be hydrated and cured by a hydraulic binder. The curing method and period may be arbitrary. For example, after performing primary curing with steam, secondary curing in the atmosphere may be performed. The curing period is preferably as short as possible from the aspects of curing space and productivity, but may be appropriately selected according to the required strength after curing. Generally, about 1 to 7 days is preferable.
Further, the iron-containing dust / sludge agglomerate may be produced by a method other than the production method in which the molded body is hydrated and cured using a hydraulic binder as described above.

The following tests were conducted using a vertical melting furnace having a structure shown in FIG. 1 having a hearth diameter of about 2 m, six tuyere, and an effective height of 5 m from the tuyere. In the example of this test, the oxygen injection pipe A and the fuel gas injection pipe B having the structure shown in FIGS. 2 to 5 are installed in all tuyere, and in addition to the tuyere air blow, oxygen and fuel gas (natural gas) ) Was supplied. On the other hand, in the comparative example, only tuyere ventilation was performed.
Use iron scrap 90 mass% + iron-containing dust / sludge agglomerate 10 mass% as the iron source, and cast iron coke 40 mass% + blast furnace coke 60 mass% on the sieve sieved with 40 mm sieve. The operation was performed under conditions of a soot temperature of 1500 to 1550 ° C. and a coke ratio of 130 to 200 kg / t · pig.
In addition, the oxygen injection pipe A used in Invention Example 4 has a nozzle portion with a Laval shape, and the nozzle outlet flow velocity of the oxygen flow becomes supersonic (about Mach 2).

The operation results are shown in Table 1 together with the operation conditions. In Table 1, the production index is an index of the output amount when the output amount of Comparative Example 1 (conventional example) is 100. It can be seen that the productivity of the examples of the present invention is greatly improved.

Explanatory drawing schematically showing a vertical melting furnace to which the present invention is applied and its basic operation mode The tuyere structure in one embodiment of the vertical melting furnace of this invention is shown, Fig.2 (a) is a longitudinal cross-sectional view of a tuyere, FIG.2 (b) is a front view of a tuyere FIG. 3 shows a tuyere structure in one embodiment of a vertical melting furnace of the present invention, in which FIG. 3 (a) is a longitudinal sectional view of the tuyere and FIG. 3 (b) is a front view of the tuyere. The tuyere structure in one embodiment of the vertical melting furnace of this invention is shown, FIG. 4 (a) is a longitudinal cross-sectional view of a tuyere, FIG.4 (b) is a front view of a tuyere. The tuyere structure in one embodiment of the vertical melting furnace of this invention is shown, Fig.5 (a) is a longitudinal cross-sectional view of a tuyere, FIG.5 (b) is a front view of a tuyere.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Furnace 2 Raw material charging part 3 Tuyere 4 Hot air pipe 5 Exhaust duct 6 Dust collector 7 Constriction part 30 Tuyere pipe 31 Tip of tuyere A A Oxygen injection pipe B Fuel gas injection pipe

Claims (8)

In a vertical melting furnace in which hot metal is introduced from the top of the furnace, hot air is blown from a plurality of tuyere provided at the bottom of the furnace, and the iron source is melted by the combustion heat of the carbon material. ,
When an oxygen injection pipe and a fuel gas injection pipe are installed in at least a part of the tuyere, and the tip inner diameter of the tuyere is d, oxygen and fuel injected from the oxygen jet pipe into the furnace The fuel gas injected from the gas injection tube into the furnace is configured to come into contact with the area at least within the distance d in the furnace center direction from the tip of the tuyere (including the area inside the tuyere). A vertical melting furnace.   The saddle type according to claim 1, wherein the oxygen injection pipe and the fuel gas injection pipe are provided in a double tubular shape, an outer pipe of the double pipe is an oxygen injection pipe, and an inner pipe is a fuel gas injection pipe. melting furnace.   The saddle type according to claim 1, wherein the oxygen injection pipe and the fuel gas injection pipe are provided in a double tubular shape, an outer pipe of the double pipe is a fuel gas injection pipe, and an inner pipe is an oxygen injection pipe. melting furnace.   The vertical melting furnace according to any one of claims 1 to 3, wherein the nozzle portion of the oxygen injection tube has a Laval shape or a tapered shape. A hot metal production method using the vertical melting furnace according to any one of claims 1 to 4,
As an iron source, one or more agglomerates of iron-based scrap, iron-containing dust and / or iron-containing sludge are charged into the furnace,
A hot metal manufacturing method, wherein oxygen is injected from an oxygen injection pipe and fuel gas is injected from a fuel gas injection pipe into a furnace.   6. The hot metal production according to claim 5, wherein the fuel gas injected from the fuel gas injection pipe is mainly composed of one or more of natural gas, propane gas, iron-making process gas, and liquid fuel vaporized gas. Method.   The hot metal production method according to claim 5 or 6, wherein an oxygen jet having a supersonic velocity at a nozzle outlet is jetted from an oxygen jet pipe.   The hot metal manufacturing method according to any one of claims 5 to 7, wherein the harmonic average particle diameter dp of the carbonaceous material charged in the furnace satisfies D / dp≥30 with respect to the furnace inner diameter D.

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