JP7359183B2 - Method for mixing raw material powder for briquettes and method for manufacturing briquettes - Google Patents

Description

The present invention relates to a method for mixing a raw material powder for briquettes and a binder used in a steel manufacturing process, and a method for manufacturing briquettes in which the resulting mixture is pressure-molded.

In the steelmaking process, various powder raw materials are briquettered and used. For example, cheap, low-grade iron ore can be crushed and sorted to remove impurities and then briquetted to produce high-grade raw materials, powdered coal can be briquetted to make briquette coal, or powdered coal can be made into briquettes. Ferrocoke is also produced by briquetting powdered iron ore.

Briquettes are manufactured by mixing raw material powder that has been crushed into powder and a binder, which is a material that binds the powders together, and then press-molding the mixture with a molding machine. Coal and iron ore briquettes used in the steelmaking process often use binders such as tar or pitch, but starch is also used in some cases.

Such briquettes are required to have a certain level of strength to prevent them from becoming powder during transportation. In order to increase the strength of briquettes, it is effective to increase the amount of binder, but the above-mentioned binders are generally expensive, and unnecessarily increasing the amount of binder is not recommended because it will lead to a rise in processing costs. do not have. On the other hand, when β starch, which is a relatively inexpensive binder, is used, there is a problem in that β starch is water-insoluble and therefore has a weak caking force and the strength of the briquettes is very low. Therefore, various methods have been proposed to improve the strength of briquettes when β starch is used as a binder.

Conventionally, as a method for improving the strength of briquettes using β starch as a binder, Non-Patent Document 1 describes a method in which β starch is mixed with caustic soda to gelatinize the β starch and improve its cohesive strength, thereby improving briquette strength. is proposed. However, caustic soda is harmful to the human body and handling it poses occupational hygiene risks. Furthermore, since sodium, which has a catalytic effect, is mixed into the briquettes, there is a problem in that, for example, when used in the production of briquettes, the reactivity of coke produced from the briquettes increases excessively.

Further, as a method for molding powdered charcoal, Patent Document 1 discloses a charcoal sheet in which powdered charcoal and starch powder are mixed, heated, and then molded into a sheet shape. However, since the powdered coal that is the subject of this application has a particle size of about 10 mm or less, this method tends to result in insufficient kneading, and when the coal is made into briquettes, the strength is insufficient. There is a problem in that the variation is very large. Furthermore, the use of water during mixing increases the water content of the mixture, making it unsuitable for subsequent carbon distillation of the mixture.

JP2008-308476A

Reiji Takahashi, Masaki Yamamoto, "Behavior of starch in caustic soda", Journal of the Starch Industry Association, Vol. 17, No. 3, pp. 289-293, 1969

As described above, in the steel manufacturing process, the conventional method of manufacturing briquettes using starch as a binder has a problem in that it is difficult to obtain briquettes with sufficient strength.

Therefore, the present invention efficiently mixes briquette raw material powder and starch, which is a binder, and molds it into briquettes, thereby obtaining briquettes that have high strength and are difficult to powder, suitable for the steel manufacturing process. The object of the present invention is to provide a method for mixing raw material powder for briquettes and a method for producing briquettes.

The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, the starch and raw material powder are first mixed in an unheated state, and then the starch and raw material powder are mixed in a heated state with steam. It has been found that a method including a step of Furthermore, we have discovered a steam blowing method that optimizes the insertion depth of the discharge port (blowout port) of the steam pipe (steam pipe) into the raw material powder and the direction in which the steam is blown out from the discharge port. This steam blowing method maximizes the opportunity for contact between the powder mixture and steam by placing the discharge port of the steam piping as close as possible to the rotating rotary blades (stirring blades) of the powder mixer. The time required to reach the gelatinization temperature can be shortened, and furthermore, by arranging the blowing direction of the discharge port to face the rotation direction of the rotary blade and having an angle within 45° in the vertical direction, It was found that vapor contact occurs efficiently.

The present invention was made based on the above findings, and the gist thereof is as follows.
[1] A method of mixing a binder with powder, which is a raw material for briquettes, using a mixer with rotating blades, in which steam is blown into the mixed mixture of the powder and the binder to mix and stir it. A method for mixing briquette raw material powder, characterized by:
[2] In [1], the steam is blown into the mixer from the top of the mixer through a discharge port at the tip of the steam pipe inserted into the mixture, and the insertion depth position of the discharge port is at the same level as the powder. The briquette raw material powder is characterized in that the binder is present between an intermediate point between the upper surface of the powder initially charged in the mixer and the uppermost rotating surface of the rotating blade and the uppermost rotating surface of the rotating blade. How to mix the body.
[3] In [1] or [2], when blowing the steam from the discharge port at the tip of the steam pipe, the steam blowing direction of the discharge port is arranged to face the rotation direction of the rotary blade, and A method for mixing raw material powder for briquettes, characterized by having an angle within 45° in the direction.
[4] The method for mixing briquette raw material powder according to any one of [1] to [3], wherein the raw material powder is coal powder.
[5] The method for mixing briquette raw material powder according to any one of [1] to [4], wherein the binder is starch.
[6] A method for producing briquettes, comprising press-molding a mixture obtained by the method for mixing briquette raw material powder according to any one of [1] to [5].

According to the present invention, briquettes with sufficient strength can be obtained, and by optimizing the insertion depth of the steam piping outlet and the blowing direction of steam, the heating mixing time can be minimized and the amount of steam used can be reduced. It is possible to minimize the equipment cost and operating cost in briquette production.

It is a schematic sectional view showing an example of arrangement of a Henschel type mixer and steam piping. FIG. 3 is a schematic cross-sectional view showing an example of the mixing state of raw material powder and the arrangement position of steam piping. It is a perspective view showing the internal structure of a Henschel type mixer. FIG. 3 is a schematic cross-sectional view from three directions showing the positional relationship between the steam piping outlet and the rotary blade. FIG. 3 is a schematic cross-sectional view showing the vertical direction of a steam piping outlet. FIG. 2 is a correlation diagram showing the relationship between the steam flow rate required to reach the gelatinization temperature and the insertion depth. It is a transition diagram showing the relationship between the blowing direction of the steam piping outlet and the steam flow rate.

Hereinafter, embodiments of the present invention will be described using as an example a method for manufacturing molded coal briquettes used in the steel manufacturing process using starch as a binder. It can also be applied to the production method of mixed briquettes of coal powder and dust briquettes, or dust briquettes fed into converters.

[Powder mixing method and mixer]
A method of mixing raw material powders according to the present invention will be described using a Henschel type mixer 1 having a rotary blade 2 as shown in FIG. However, when implementing the present invention, it is not necessary to use a Henschel-type mixer, but a vertical paddle type or other device that rotates and mixes the powder, the axis of rotation is a vertical axis (vertical direction), and heating by steam is used. Any mixer can be used as long as it can do this.

Although FIG. 1 shows a configuration in which the rotary blade 2 is provided in two stages in the vertical direction, it may be provided in one stage or in three or more stages. This rotary blade 2 is a blade for mixing and stirring (also referred to as a "stirring blade"), and two blades are attached at a position facing the rotating shaft 3, but the number of blades is , there is no particular restriction, and the number may be one or three or more. Further, in order to maintain the strength of the two-blade blade, an auxiliary member may be attached that connects the two blades in the middle in a circular shape. If the rotation speed of the rotary blade is too low, the entire charge powder cannot be mixed. Furthermore, if the rotational speed is too high, the charged powder may fly out of the powder mixer. It is preferable to mix and stir at a peripheral speed of the tip of the stirring blade of about 5 to 40 m/s.

The internal volume of the mixer 1 is not particularly limited, and can be appropriately used from a small one of about 75 L to a large one of 4000 L or more.

[powder]
Examples of the raw material powder include coal powder, ore powder, and other powders such as converter dust, but it is preferable to use coal powder in the production of shaped coal briquettes in the steel manufacturing process. The particle size of the coal powder is not particularly limited, but the finer the particle size, the better the strength of the briquettes, so it is preferable, less than 10 mm is preferably 90% by mass or more, and more preferably 95% by mass or more. In addition, when using coal powder with a particle size of less than 10 mm and less than 90% by mass, it may be pulverized or mixed with another finer particle size coal powder to adjust the particle size to the above particle size range. .

[binder]
Although various materials can be used as the binder to be mixed with the powder, it is preferable to use starch as the binder used in the method for producing shaped charcoal briquettes of this embodiment.

The type of starch is not particularly limited, and starches manufactured from raw material plants such as tapioca, potatoes, sweet potatoes, corn, rice, and wheat can be used as appropriate, and starch derivatives processed from plant-derived starches and chemically synthesized starches can also be used. Starch and the like can also be used. Among these starches, it is preferable to use tapioca-derived starch, which has a relatively high gelatinization temperature.

Note that starch includes α starch that is gelatinized (gelatinized) and β starch before gelatinization, but as described above, in the present invention, it is preferable to use β starch, which is inexpensive.

[Mixing ratio]
It is preferable that starch, which is a binder, is mixed into coal powder in a mass ratio of 0.1 to 3.0% based on the total of coal powder and starch. If the amount of starch is less than 0.1% by mass, it is difficult to develop sufficient strength when the mixture is made into briquettes, and even if it is added in excess of 3.0%, the strength of the briquettes will not increase. This is because it slows down and there are no major changes. Further, 0.5 to 1.5% is more preferable.

[Steam blowing method]
The mixer 1 is provided with a steam pipe 5 inserted from above, and steam S can be blown into the mixer 1 from a discharge port 6 at the tip of the steam pipe 5.

Powder and binder, which are raw materials for briquettes, are charged into the mixer 1 and the rotary blade 2 is rotated to flow the charged raw material powder (hereinafter also referred to as "charged powder") P. can be mixed. At this time, as shown in FIG. 2, centrifugal force is generated on the charged powder P due to the rotation of the rotary blade 2, and a force is exerted to push the charged powder P toward the inner wall of the mixer 1, so that the upper surface F of the charged powder P is It forms a mortar shape, slides up against the inner wall, swells, and flows. Therefore, it is important that the discharge port 6 of the steam pipe 5 into which the steam S is blown is located in a region within the flowing mixed powder below the flowing upper surface F of the charged powder P. If the discharge port 6 is provided, good contact between the charged powder P and the steam S can be made.

Here, the insertion depth position of the discharge port 6 of the steam pipe 5 that sends out the steam S is between the top surface of the powder and the uppermost rotating surface of the rotary blade when the powder and binder are initially charged into the mixer. It is preferable that the point be located between the point and the uppermost rotating surface of the rotary blade.

To be more specific, the level of the depth position of the uppermost rotating surface of the uppermost rotary blade 2' is set to 1, and the level of the initially charged powder P when charged powder P is charged into the mixer 1 is set to 1. When the level of the depth position of the top surface is 0, it is preferable that the level of the depth position is within the range of 0.5 to 1.0. That is, from the midpoint (level 0.5) between the depth position of the top surface of the raw material powder at the time of charging (level 0) and the depth position of the top surface of the rotating surface of the rotary blade (level 1). By interposing the discharge port 6 of the steam pipe 5 up to the depth position (level 1) of the uppermost surface of the rotating surface, the steam S can efficiently contact the charging powder P. When the insertion depth position is close to the above-mentioned intermediate point (level 0.5) to the top surface of the charged powder (level 0), that is, when the depth position level is 0 to less than 0.5, When the charged powder P rotates and the top surface of the powder becomes a mortar shape, the discharge port 6 may be separated from the top surface of the powder, making it impossible to blow steam S into the charged powder P. Yes, mixing and stirring will not proceed, which is not preferable. More preferably, the level of the depth position is in the range of 0.7 to 1.0. Note that the uppermost rotary blade means the rotary blade in the case where there is only one rotary blade.

Further, the discharge port 6 at the tip of the steam pipe 5 may be the end of the pipe itself, or a nozzle that is a part for the tip may be attached. If it is a nozzle, it is also possible to prepare and replace a nozzle with a shape that changes the angle of the steam blowing direction.

Further, the position of the insertion port 7 into which the steam pipe 5 is inserted should be set as far as possible in the mixer so that when the charged powder P is mixed while rotating, the powder becomes a mortar shape. It is preferable to provide it at a position close to the inner wall side. The further away from the inner wall side the center (center) becomes, the further away the discharge port 6 of the steam pipe 5 will be from the top surface of the charged powder P when it is shaped like a mortar, making it difficult to blow steam into the powder. This is because it becomes difficult. The specific position of the insertion port 7 depends on the equipment scale of the mixer 1 and the amount of raw material powder to be charged, but it can be provided at a position within 100 mm from the inner wall side of the mixer 1 toward the center. preferable.

[Relationship between insertion depth of discharge port and steam flow rate]
Subsequently, Test A was conducted to examine the relationship between the insertion depth of the steam injection outlet and the steam flow rate, which will be described below.

In this test A, blended coal (coal powder) was used as a raw material powder for manufacturing briquettes for coke raw material, and the steam flow rate was measured when β starch was mixed and stirred as a binder. As the blended coal, powdered coal whose particle size was less than 10 mm accounted for 95% by mass was used. As the binder, β starch derived from tapioca was used in a total amount of 1% by mass.

The above raw material powder was heated to 75° C., at which the β starch gelatinized, while blowing steam into it using a Henschel type mixer 1 shown in FIG. At that time, the test was conducted by changing the insertion depth of the steam pipe and the steam flow rate. The test conditions were as follows.

(a) Insertion depth The raw material powder was charged so that the depth from the top surface of the powder at the time the raw material powder was charged to the uppermost rotating surface of the rotary blade was 200 mm. Then, the level at the depth position of the top surface of the powder (depth 0 mm) when the raw material powder was initially charged was set to 0, and the level at the depth position of the uppermost rotating surface of the rotary blade (depth 200 mm) was set to 1. At the same time, tests were conducted with the depth position level set to the following four conditions.
(a) Level 0 (=depth 0mm, powder surface), (b) Level 0.50 (=depth 100mm),
(c) Level 0.75 (=depth 150mm), (d) Level 0.98 (=depth 196mm).

(B) Steam flow rate The steam flow rate (kg/hr) per 1 kg of the mixture (total of blended coal and β starch) was set to the following three conditions (a), (b), and (c).
(a) 100kg/hr, (b) 200kg/hr, (c) 300kg/hr.

(c) Conduct a mixing test under a total of 12 conditions for each combination (a to d in a) and a to c in b), measure the steam flow rate and time required to reach the gelatinization temperature (75°C), and measure the steam flow rate. The basic unit (the amount of steam in kg per 1 ton of coal blend, expressed as kg/t-cl) was determined.

The results are shown in FIG. In any of the steam flow rates (the above three conditions B), the steam flow rate could be reduced by increasing the insertion depth. In particular, by increasing the insertion depth level to 0.50 or more, even if the steam flow rate was reduced, the unit flow rate of steam up to the gelatinization temperature could be lowered, and heating could be performed efficiently.

From the above tests, it was found that setting the insertion depth to 0.5 to 1.0 is effective in achieving a target steam consumption rate of 70 kg/t-cl or less.

[Relationship between steam blowing direction and steam flow rate]
Next, Test B, which examined the relationship between the steam blowing direction and the steam flow rate, was conducted and will be described below.

In this test B, the same raw materials as those used in the steam flow rate test A described above were used, the same Henschel type mixer was used, the steam flow rate was 50 kg/hr, and the level at the insertion depth position of the outlet of the steam pipe was were mixed under conditions of 0.98°C, and steam was blown to the gelatinization temperature (75°C). At this time, the steam blowing direction of the discharge port was arranged to face the vertically downward direction and the rotating direction of the rotary blade. The results are shown in FIG.

When the direction of the discharge port was downward, the steam flow rate became 0 30 seconds after starting steam blowing, and steam blowing could not be performed thereafter. When the discharge port of the steam piping was observed after the experiment was completed, it was found that the discharge port was clogged with raw material powder, which made it impossible to blow steam into the pipe.

On the other hand, when the discharge port was oriented in the direction of rotation, steam could be blown without any problem until the gelatinization temperature was reached.

From the above tests, it was found that it is preferable that the direction of steam blowing is not simply downward in the vertical direction of the steam piping, but in the direction of rotation of the rotary blade. Further, it is desirable to blow out the steam in a direction along the direction of rotation, rather than in a direction opposite to the direction of rotation of the rotary blade, that is, in a direction in which the charged powder flows back into the discharge port as it rotates.

Furthermore, it is preferable that the steam blowing direction of the discharge port 6 when blowing steam is arranged to face the rotational direction of the rotary blade and has an angle (θ) of up to 45° in the vertical direction. That is, with respect to the vertical direction of the balloon direction, it is preferable that both upward and downward angles are within 45 degrees from the horizontal plane. This is because even if steam is blown in a direction exceeding 45° in the vertical direction, the mixing effect and heating effect of the steam are poor.

Here, the steam blowing direction will be explained using figures. 3, 4, and 5 are schematic diagrams of the positional relationship between the steam blowing direction of the discharge port and the rotary blade. FIG. 3 is a perspective view showing the internal structure of the Henschel type mixer, FIG. 4(a) is a front sectional view of the mixer as seen from the front A direction of FIG. 3, and FIG. 4(b) is a 4(c) is a side cross-sectional view of the mixer seen from the side B direction of FIG. 3, and FIG. 4(c) is a plan sectional view of the mixer seen from the upper direction C of FIG. 3. FIG. Further, FIG. 5(a) is a schematic cross-sectional view with the discharge port facing upward, and it is preferable that the upward angle θ≦45°. FIG. 5(b) is a schematic cross-sectional view with the discharge port facing downward, and the downward angle θ≦45° is preferable.

In addition, as shown in Fig. 4(c), the discharge port is located inside the rotation (center side, Fig. 4(c) ) or to the outside of the rotation (circumferential side, ψ≦45° in FIG. 4(c)).

[Temperature of mixture by steam blowing]
Steam blowing is continued until the temperature of the mixture after steam blowing during mixing and stirring becomes equal to or higher than the gelatinization temperature of starch used as a binder. Since this gelatinization temperature differs depending on the type of starch, the temperature of the mixture after steam injection may be adjusted depending on the starch used. For example, when starch derived from tapioca is used, its gelatinization temperature is 58.5 to 70.0°C, so the temperature of the mixture after steam injection should be 70.0 to 95.0°C. is preferred. More preferably, the temperature is 70.0 to 80.0°C. Similarly, when starch derived from potatoes is used, its gelatinization temperature is 56.0 to 66.0°C, so the temperature of the mixture after steam injection is 66.0 to 95.0°C. is preferable. More preferably, the temperature is 66.0 to 80.0°C.

Since the temperature of the steam is 100° C. when it is blown out from the nozzle into the atmosphere, the temperature of the mixture can be controlled by adjusting the flow rate of the steam blowing and the length of the blowing time. Moreover, the temperature of the mixture can be measured by inserting a thermometer into the mixture inside the stirrer.

[Steam blowing time (mixing time)]
The mixing and stirring time for steam blowing can be adjusted as appropriate depending on the type of powder and binder, but when starch is used, time is required for it to gelatinize and become uniformly mixed with the powder. For example, the heating time in the above-mentioned process for producing shaped coal briquettes is preferably 60 seconds or more, more preferably 120 seconds or more.

Furthermore, the mixing time in an unheated state before steam blowing mixing may be adjusted appropriately depending on the type of powder and binder. The time for mixing in a heated state may be about 15 seconds or more.

[Molding method]
Molded coal briquettes are obtained by press-molding the mixture obtained by the above-described mixing method. This molding method is not particularly limited, and as the briquette molding device, any of roll compression, rolling, and extrusion molding machines may be used. In particular, it is preferable to use a double roll molding machine that has recesses on the roll surface that can uniformly apply pressure to the inside of the briquettes. In addition, in this embodiment, although the molded coal briquette was explained as an example, it can also be applied to other briquettes (ore powder briquettes, converter input dust briquettes, etc.) in the steel manufacturing process.

Hereinafter, embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

In this example, the same raw materials as those used in the steam flow rate test A described above were used, the same Henschel mixer was used, the steam flow rate was 100 kg/hr, and the level at the insertion depth position of the outlet of the steam pipe was were mixed under four conditions: 0.98 (invention example 1), 0.75 (invention example 2), 0.50 (invention example 3), and 0.25 (comparative example 1), and the temperature of the mixture was Steam was blown into the solution until the temperature reached 75°C.

In order to confirm the quality of the mixture under these four conditions, the mixture obtained after the completion of steam blowing was molded into briquettes, and the briquette strength was measured.

Note that the temperature of the mixture was measured with a thermocouple installed inside the mixer. In addition, the briquette strength was determined by applying compressive force to the obtained heated mixture using a pressure roll type molding machine, molding it into Masek type molded charcoal briquettes of 46 mm x 46 mm x 38 mm, and molding the above molded charcoal briquettes for 2 hours. Ten briquettes after natural curing were dropped three times from a height of 2 m, and the ratio of the mass of lumps of 15 mm or more to the mass of the dropped briquettes was measured as falling strength (%).

The results are shown in Table 1.

The briquette strengths of Invention Examples 1 to 3 showed high strength, but the briquettes of Comparative Example 1 had low strength and were easily powdered. From the above, it was found that the level of the insertion depth position of the discharge port is preferably 0.5 or more.

1 Mixer 2 Rotary blade,
2' Uppermost rotating blade 3 Rotating shaft 4 Raw material powder loading port 5 Steam piping 6 Steam piping discharge port 7 Steam piping insertion port S Steam P Charged powder F Top surface of charged powder

Claims (5)

A method of mixing a binder with powder, which is a raw material for briquettes, using a mixer having a rotating blade, the method comprising: blowing steam into the mixed mixture of the powder and the binder to mix and stir the mixture; Steam is blown into the mixer through a discharge port at the tip of the steam pipe inserted into the mixture from above, and the insertion depth of the discharge port is such that the powder and binder are charged into the mixer. 1. A method for mixing raw material powder for briquettes, characterized in that the powder is mixed from a midpoint between the top surface of the powder initially mixed and the top surface of rotation of the rotary blade to the top surface of rotation of the rotary blade. When blowing the steam from the discharge port at the tip of the steam pipe, the steam blowing direction of the discharge port is arranged to face the rotation direction of the rotary blade and has an angle within 45° in the vertical direction. The method for mixing briquette raw material powder according to claim 1 . The method for mixing briquette raw material powder according to claim 1 or 2 , wherein the raw material powder is coal powder. The method for mixing briquette raw material powder according to any one of claims 1 to 3 , wherein the binder is starch. A method for producing briquettes, comprising pressurizing and molding a mixture obtained by the method for mixing briquette raw material powder according to any one of claims 1 to 4 .

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