JP7790334B2 - Method and device for charging raw materials into a vertical carbonization furnace - Google Patents

Description

The present invention relates to a method and device for charging raw materials into a vertical carbonization furnace, and in particular to a method and device for charging raw materials into a vertical carbonization furnace for producing ferro-coke that prevents the segregation of fine particles that occurs during the transport process when charging briquette raw materials into the furnace, and enables the raw materials to be heated uniformly.

In recent years, in order to improve the efficiency of the steelmaking process in blast furnaces, it has been proposed to replace some of the coke charged into blast furnaces with ferro-coke. Ferro-coke is a molded coke produced by carbonizing a mixture of a carbon-containing material (such as coal) and a certain amount of iron-containing material (such as iron ore). The most commonly proposed carbonization method is a vertical carbonization furnace.

For example, Patent Document 1 discloses a method for producing ferro coke using a vertical carbonization furnace with a carbonization zone at the top and a cooling zone at the bottom. This ferro coke production method begins with a charging process, in which molded materials composed of carbon-containing and iron-containing materials are charged into the vertical carbonization furnace. Next, in the carbonization process, heated gas is injected into the carbonization zone to carbonize the molded materials and produce ferro coke. Subsequently, in the cooling process, cooling gas is injected into the cooling zone to cool the ferro coke. Furthermore, there are two processes: a furnace gas discharge process in which furnace gas is discharged from an outlet at the top of the vertical carbonization furnace, and a ferro coke discharge process in which ferro coke is discharged from the bottom of the cooling zone. During the carbonization process, low-temperature gas is injected from a tuyere located in the middle of the vertical carbonization furnace's height, and high-temperature gas is injected from a tuyere located at the bottom of the vertical carbonization furnace.

When producing ferro coke using a vertical carbonization furnace, increasing the amount of ferro coke produced requires increasing the volume of the furnace and increasing the production volume per batch. However, because cooling gas and high-temperature gas are injected in the depth direction of the vertical carbonization furnace (from the gas injection side to the opposite side), the depth direction of the furnace body cannot be increased beyond a certain point in order for the gas to penetrate to the center of the furnace. Therefore, the shape (horizontal cross-sectional shape) of a vertical carbonization furnace is longer in the furnace width direction (direction perpendicular to the depth direction) than in the depth direction.

Furthermore, if there is an imbalance in the loading balance of the briquettes when they are charged into the furnace, the gas flow within the furnace will become uneven, adversely affecting the carbonization of the briquettes. Therefore, as techniques for uniformly carbonizing briquettes in vertical carbonization furnaces, Patent Document 2 discloses a distributed raw material charging technique, and Patent Document 3 discloses a uniform gas injection technique.

JP 2011-57970 A JP 2017-155214 A JP 2018-172650 A

The device proposed in Patent Document 2 is said to enable raw materials to be charged uniformly in the width direction, making it possible to produce high-quality, highly productive ferro-coke. However, the technology in Patent Document 2 is not effective in charging raw materials uniformly in the depth direction, and there is a problem in that fine particles in particular segregate toward the charging port side, reducing the effectiveness of uniform gas injection.

Furthermore, the device proposed in Patent Document 3 claims that by adding a gas inlet, the raw materials can be heated uniformly, reducing temperature differences within the furnace and suppressing variations in the quality of ferro-coke. However, the technology in Patent Document 3 has the problem of increasing the complexity of the vertical carbonization furnace itself and the surrounding equipment, resulting in increased costs for construction and maintenance.

The present invention was developed in light of the above-mentioned circumstances, and aims to provide a raw material charging method and raw material charging device for a vertical carbonization furnace for producing ferro-coke that prevents fine particles generated from the briquetting raw material from segregating in the depth direction and enables the raw material to be heated uniformly.

The present inventors conducted extensive research to solve the above-mentioned problems. As a result, they discovered that fine particles generated during the transport process of the briquette raw material being charged into a vertical carbonization furnace segregate toward the charging inlet, which is located at the front depth of the furnace, causing variations in particle size of the charged deposit and resulting in uneven gas injection in the carbonization zone. They further discovered that by injecting gas near the furnace outlet of the charging inlet to uniformly disperse the fine particles within the furnace, the particle size of the charged deposit can also be made uniform.

The present invention was completed based on these findings and further investigations, and the gist of the present invention is as follows.
[1] A method for charging raw materials into a vertical carbonization furnace, characterized in that when the raw materials are introduced into the vertical carbonization furnace through a charging port, gas is injected into the raw materials at the charging port to disperse fine particles in the raw materials.
[2] The method for charging raw materials into a vertical carbonization furnace according to [1], wherein the raw material is a briquette raw material and the particle diameter of the fine particles is 15 mm or less.
[3] The method for charging raw materials into a vertical dry distillation furnace according to [1] or [2], characterized in that the weight ratio of the fine particles in the raw material for briquettes is 8 wt % to 20 wt %.
[4] In any one of [1] to [3] above, the method for charging raw materials into a vertical carbonization furnace is characterized in that the gas is air or nitrogen gas, and the injection speed of the gas into the furnace is 7 m/s to 25 m/s.
[5] In any one of [1] to [4], the method for charging raw materials into a vertical carbonization furnace is characterized in that the injection angle θ of the gas into the furnace is 90° to 135° with respect to the inclined surface of the charging port.
[6] A raw material charging device for a vertical carbonization furnace, having a charging port for charging raw materials, characterized in that the charging port is equipped with a gas injection device for dispersing fine particles in the raw materials.
[7] The raw material charging device for a vertical carbonization furnace according to [6], wherein the raw material is a briquette raw material and the particle diameter of the fine particles is 15 mm or less.
[8] The raw material charging device for a vertical dry distillation furnace according to [6] or [7], characterized in that the weight ratio of the fine particles in the briquette raw material is 8 wt % to 20 wt %.
[9] In any one of [6] to [8], the gas is air or nitrogen gas, and the injection speed of the gas into the furnace is 7 m/s to 25 m/s.
[10] A raw material charging device for a vertical carbonization furnace, in any one of [6] to [9], characterized in that the injection angle θ of the gas into the furnace is 90° to 135° with respect to the inclined surface of the charging port.

When producing ferro-coke using a vertical carbonization furnace, the present invention allows raw materials to be uniformly charged in the depth direction of the vertical carbonization furnace without particle size segregation. As a result, by uniforming gas injection within the furnace and reducing variations in carbonization temperature, it becomes possible to produce ferro-coke of uniform quality at high quality and low cost, and also achieves the excellent effect of improving productivity.

1 is a schematic cross-sectional view showing an example of an upper part of a vertical carbonization furnace according to the present invention. FIG. 3 is a schematic cross-sectional view showing the injection angle of the injected gas into the furnace according to the present invention. FIG. FIG. 1 is a schematic cross-sectional view showing an example of the furnace upper portion of a conventional vertical carbonization furnace. 1 is a diagram showing the relationship between the coarse particle/fine particle distribution ratio of the charge in the furnace depth direction, and is an example in which the fine particle weight ratio is 8%. 1 is a diagram showing the relationship between the coarse particle/fine particle distribution ratio of the charge in the furnace depth direction, and is an example in which the fine particle weight ratio is 20%.

The following describes in detail embodiments of the raw material charging method and raw material charging device for a vertical carbonization furnace according to the present invention, with reference to the drawings. However, the present invention is not limited to these. Furthermore, since the drawings are intended to conceptually explain the present invention, the dimensions and ratios of the various components shown may differ from the actual dimensions.

[Vertical carbonization furnace]
The vertical carbonization furnace that is the subject of the present invention has a charging zone at the top where the molded material is charged, a carbonization zone in the middle consisting of a low-temperature heating section and a high-temperature heating section, a cooling zone below that, and a discharge zone at the bottom for the produced molded coke.

Here, the briquette raw material is a mixture of carbon-containing materials (such as coal) and iron-containing materials (such as iron ore) that are used to make briquette coke (ferrocoke) in a specified ratio, with a binder added and the mixture molded into a block. Examples of binders for briquette coke include soft pitch (SOP), asphalt pitch (ASP), starch, and direct coal liquefaction residue. The binder is preferably added at a weight ratio of 1 wt% to 15 wt% of the carbon-containing material (such as coal). Adding less than 1 wt% of binder results in insufficient penetration of the binder into the coal surface, making it difficult to achieve sufficient strength. Adding more than 15 wt% of binder is undesirable, as it significantly increases production costs. A more preferred ratio is 3 wt% to 10 wt%.

Figure 3 is a schematic diagram of a cross section of the charging zone in the upper furnace section 1 of a conventional vertical carbonization furnace. Briquettes 5 produced through the briquettes production process are stored in a storage tank (not shown) and then introduced into the upper furnace section 1 through the charging port 3 via the charging chute 2. A gate 4 is provided just before the outlet of the charging port 3. By closing the gate 4, an appropriate amount of briquettes 5 (for one batch) can be stored. By opening the gate 4, the briquettes 5 can be introduced into the furnace via the inclined charging chute 2. Here, the raw material charging device 9 refers to the overall configuration from the charging chute 2 to the charging port 3.

Raw materials are stored in the furnace up to the vicinity of the charging port 3, and the charged materials are designed to fall onto the stored raw materials (charged material 8) near the midpoint in the depth direction. A gas outlet 6 for discharging gas from inside the furnace is located near the top of the upper furnace section 1, and the pressure inside the furnace is controlled by adjusting the exhaust gas 7. After the raw materials are charged and stored in this vertical carbonization furnace, gases (low-temperature gas, high-temperature gas, and cooling gas) are circulated through multiple tuyeres in the lower carbonization zone, allowing for efficient heating during carbonization and subsequent cooling.

Note that while Figure 3 shows a cross-section of the vertical carbonization furnace from the raw material charging side toward the depth, a cross-section perpendicular to that cross-section is not shown. However, the width perpendicular to the depth (furnace width) is designed to be long because the depth cannot be increased. The shape of the furnace upper part 1 is, for example, 1.0 to 2.0 m deep and 4 to 8 m wide. Therefore, multiple rows of charging chutes 2 are installed at equal intervals across the furnace width (for example, at intervals of 0.8 to 1.2 m), and each charging inlet 3 is provided with a gate 4. The shape of the charging chutes 2 is not particularly limited, but examples include a square prism with a rectangular cross-section or a cylindrical shape with a circular cross-section.

[Particle size composition of molded product]
Next, the particle size distribution of the shaped product and particle size segregation of the charged material will be explained.
When the briquettes are transported to a vertical dry distillation furnace after the briquettes production process, they are partially crushed and disintegrated to produce fine particles. The size (particle size) of the briquettes immediately after production is 20 mm to 30 mm on average, but many fine particles are present before they are loaded into the furnace. Here, in the present invention, particles with a particle size of 15 mm or less are defined as "fine particles" and particles with a particle size of more than 15 mm are defined as "coarse particles." The weight ratio of the fine particles (the ratio of the weight of the fine particles to the weight of the entire briquettes raw material) is 8 wt% to 20 wt%. This numerical range is based on the minimum and maximum values of actual measurements.

It was also found that even when raw materials were charged so that they were directed towards the middle of the furnace, fine particles tended to fall short of the middle section rather than reaching it, resulting in particle size segregation of the charged material and adversely affecting gas injection in the carbonization zone, etc.

[Gas injection]
Therefore, the present inventors have conducted research to eliminate variations in the fine particles of the raw material being fed, and have discovered a method of injecting gas into the raw material being fed to prevent the fine particles from falling unevenly.
That is, the present invention is characterized in that a gas injection device 10 is provided near the furnace outlet of the charging port 3 in the upper part of the furnace 1, as shown in FIG.

Here, the injection speed of the gas 11 injected in the depth direction when charging the raw materials is preferably set to 7 m/s to 25 m/s. By adjusting it to this range, the charging tendency of the shaped material (described below) remains unchanged, while the charging tendency of the fine granules mixed with the shaped material can be uniformly dispersed in the depth direction. A speed of 15 m/s to 20 m/s is more preferable.

As the gas 11 to be injected, it is preferable to use air or nitrogen gas.
This gas injection prevents the segregation of fine particles toward the charging port side, and by uniformly blowing gas into the vertical carbonization furnace, it is possible to reduce variations in the carbonization temperature and produce high-quality, uniform ferro-coke at low cost.
Specific examples of the gas injection device 10 include a blower and a compressor.
Furthermore, the specific installation position of the gas injection device 10 is the charging port 3, and particularly preferably near the outlet of the furnace. More preferably, it is located below the furnace outlet of the charging port 3, near the boundary with the furnace inner wall.

Also, as shown in Figure 2, the injection angle θ of the gas injection direction is preferably 90° or more, in the direction toward the furnace from perpendicular to the inclined surface 12 of the charging inlet 3. This is because an injection angle θ of less than 90° will result in a reverse flow relative to the direction of raw material charging. Furthermore, if the injection angle θ is 45° toward the furnace from perpendicular to the inclined surface 12 of the charging inlet 3, in other words, exceeds 135°, the effect of dispersing fine particles will be poor. Therefore, the injection angle θ of the gas into the furnace is preferably 90° to 135° relative to the inclined surface of the charging inlet. It is more preferably 95° to 120°.

The inclined surface 12 of the charging port 3 is at an angle δ with respect to the vertical side wall 13 of the vertical carbonization furnace. This angle δ is the angle at which the raw materials are charged into the furnace, and is preferably between 30° and 70°. More preferably, it is between 40° and 60°.

The following examples further illustrate the present invention, but the present invention is not limited to these examples.

To confirm the effects of the present invention, a charging test was conducted simulating the operation of a vertical carbonization furnace. For the charging test, a charging model was used that mimicked the shape of the gas injection device 10 installed in the charging inlet 3 of the furnace upper part 1 shown in Figure 1. The dimensions of the furnace upper part 1, into which the charge material descends, were 0.3 m wide x 1.5 m deep, and the height from the charging inlet 3 to the charge material 8 was 1.0 m.

An air blower (gas injection device 10) with adjustable airflow speed was installed near the furnace exit of the charging inlet 3, and coarse granules (grain size: over 15 mm) and fine granules (grain size: 15 mm or less) of the moldings were mixed and charged. Air was used as the gas, and the air injection speed was varied from 0 m/s (i.e., no air injection), 7 m/s, 15 m/s, 20 m/s, and 25 m/s. Tests were conducted with a minimum fine granule weight ratio of 8 wt% (ratio of fine granule weight to total molding weight) of 20 wt% (Tests No. 1-10). The gas injection angle θ was set at an upward angle of 105° relative to the inclined surface 12 of the charging inlet 3 (angle δ relative to the furnace sidewall 13 was 60°).

The comparative conditions for the above charging tests are shown in Table 1.

After the charging test, samples were taken from 10 equally spaced drop positions (scattering locations shown in Figures 4 and 5 below) in the depth direction, from the front to the opposite side. The coarse particle abundance rate (the ratio of the coarse particle weight at each drop position to the total coarse particle weight) and fine particle abundance rate (the ratio of the fine particle weight at each drop position to the total fine particle weight) at each of the 10 drop positions were compared.

The results are shown in Figures 4 and 5. Figure 4 shows the case where the fine particle weight ratio was 8 wt%, the lowest actually measured value, and Figure 5 shows the case where the fine particle weight ratio was 20 wt%, the highest actually measured value.

From these results, in the present invention example, regardless of whether the weight ratio of fine particles with a particle size of 15 mm or less was a minimum of 8 wt% or a maximum of 20 wt%, it was possible to shift the falling position of the fine particles to the center position in the depth direction (the middle part of the furnace) when the air injection speed was 7 m/s to 25 m/s. In particular, since the falling position of the fine particles was closer to the center position at an air injection speed of 7 m/s and the effect of air injection on the coarse particles began to be felt at 25 m/s, it was found that an air injection speed of 7 m/s to 25 m/s was the appropriate condition. It was found that by injecting air within this range, the fine particles could be mixed uniformly throughout the charge, resulting in high-quality molded coke.

The above confirms the effectiveness of this invention.

1 Upper part of furnace 2 Charging chute 3 Charging inlet 4 Gate 5 Molded material 6 Gas outlet 7 Exhaust gas 8 Charge material 9 Raw material charging device 10 Gas injection device 11 Injected gas 12 Inclined surface (of charging inlet) 13 Side wall of furnace θ Gas injection angle δ Angle of inclined surface

Claims (8)

A method for charging raw materials into a vertical carbonization furnace, characterized in that when the raw materials are charged into the vertical carbonization furnace through a charging port, the inclined surface of the charging port has an angle δ of 30° to 70° with respect to the vertical side wall of the vertical carbonization furnace, and gas is injected into the raw materials at the charging port at an injection angle θ of 90° to 135° with respect to the inclined surface of the charging port into the furnace, thereby dispersing fine particles in the raw materials. The raw material charging method for a vertical carbonization furnace described in claim 1, characterized in that the raw material is a briquette raw material and the particle diameter of the fine particles is 15 mm or less. 3. The method for charging raw materials into a vertical dry distillation furnace according to claim 2 , wherein the weight ratio of the fine particles in the raw material for forming the briquettes is 8 wt % to 20 wt %. A method for charging raw materials into a vertical carbonization furnace according to any one of claims 1 to 3, characterized in that the gas is air or nitrogen gas, and the injection speed of the gas into the furnace is 7 m/s to 25 m/s. A raw material charging device for a vertical carbonization furnace, having a charging port for charging raw materials, characterized in that the charging port is equipped with a gas injection device for dispersing fine particles in the raw material , the inclined surface of the charging port has an angle δ of 30° to 70° with respect to the vertical side wall of the vertical carbonization furnace, and the injection angle θ of the gas into the furnace is 90° to 135° with respect to the inclined surface of the charging port . 6. The raw material charging device for a vertical carbonization furnace according to claim 5 , wherein the raw material is a briquette raw material and the fine particles have a particle size of 15 mm or less. 7. The raw material charging device for a vertical dry distillation furnace according to claim 6 , wherein the weight ratio of the fine particles in the briquette raw material is 8 wt % to 20 wt %. A raw material charging device for a vertical carbonization furnace as described in any one of claims 5 to 7, characterized in that the gas is air or nitrogen gas, and the injection speed of the gas into the furnace is 7 m/s to 25 m/s.