JP2007031768A - Method for extruding iron-containing powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for extruding iron-containing powder by which strengthening of the resultant extruded material can be attained from the initial stage of extrusion. <P>SOLUTION: In the method where a water-soluble organic binder is mixed with the iron-containing powder to knead the resultant mixture using a kneader and the resultant kneaded material 11 is extruded using an extruder 12, kneading is performed using a paddle type kneader 10 as the kneader while carrying out deaeration so as to regulate air content in the kneaded material 11 to 20 to 40 vol.% and then extrusion is done using the extruder 12. Further, water is added to the iron-containing powder so that water contained in the kneaded material 11 becomes 10 to 20 mass% in the paddle-type kneader 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method for extruding iron-containing powder generated at, for example, an ironworks.

Conventionally, for example, as a granulation method of iron-containing powder (for example, dust) generated in an iron mill, a fired pellet method, which is an effective means for obtaining a strong granulated product, has been used. However, since this method requires thermal energy to express the strength of the granulated product, it is not an effective means particularly from the viewpoint of energy saving. In recent years, non-fired using cement or a water-soluble organic binder as a binder. A method for producing a granulated product by a granulation method has been put into practical use. Here, when cement is used as a binder, it must be cured in the atmosphere for several days before the pellets that are granulated products can be used. There is a problem of requiring a vast site. Moreover, since the sulfur component is contained in the cement, it is not preferable to supply the pellets to the desulfurized molten steel.

Therefore, a water-soluble organic binder is mainly used as a binder for producing the granulated product.
As described above, as a method of granulating the iron-containing powder using the water-soluble organic binder, for example, the iron-containing powder and the water-soluble organic binder are mixed with a drum mixer, and then a pan pelletizer or a briquette machine is used. A method of molding while compressing is used (for example, see Patent Document 1).

JP 2001-214222 A

However, even if the raw material and the water-soluble organic binder are kneaded using a pan pelletizer or a briquette machine, the kneaded product cannot be sufficiently degassed, and the strength of the kneaded product is reduced. For this reason, for example, in the handling (conveyance) process of the kneaded product, the kneaded product collapses due to the transfer of the belt, the shape cannot be maintained, and the yield cannot be improved by breaking.

This invention is made | formed in view of this situation, and it aims at providing the extrusion molding method of the iron-containing powder which can be strengthened from the initial stage of extrusion molding.

In the method of extruding iron-containing powder according to the present invention that meets the above-mentioned object, the water-containing organic binder is mixed with the iron-containing powder and kneaded with a kneader, and the kneaded product is extruded with an extruder.
A paddle type kneader is used as the kneader, and the kneaded product is kneaded while being deaerated so as to have an air content of 20% by volume or more and 40% by volume or less, and is extruded by the extruder.
Here, the air content is a value obtained by dividing the apparent density of the kneaded product by the true density of one particle (iron-containing powder) of the kneaded product, that is, (apparent density of the kneaded product) / (particles of the kneaded product). 1 true density) × 100 (%).

In the method for extruding iron-containing powder according to the present invention, the paddle-type kneader is used to add moisture to the iron-containing powder so that the moisture content of the kneaded product is 10% by mass or more and 20% by mass or less. Is preferred.

The method for extruding an iron-containing powder according to the present invention treats the iron-containing powder and a water-soluble organic binder with a paddle kneader, and reduces the air content in the kneaded product as compared with the case of using another kneader. As a result, voids between the particles of the iron-containing powder can be reduced, and the elasticity of the kneaded product can be increased from the beginning of extrusion molding.
Thereby, for example, in the handling process of the kneaded product, it is possible to suppress the kneaded product from collapsing due to the transfer of the belt, so that the yield of the kneaded product can be improved.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIG. 1 is a partial side cross-sectional view of a kneading machine and an extrusion molding machine used in an iron-containing powder extrusion molding method according to an embodiment of the present invention.

As shown in FIG. 1, an iron-containing powder extrusion molding method according to an embodiment of the present invention is obtained by mixing a water-soluble organic binder with iron-containing powder and kneading this with a paddle kneader 10. This is a method of extruding the degassed kneaded product 11 by an extruder 12 with the air inside. The reason why the paddle type kneader 10 is applied is that the kneading force is strong and the kneaded material can be deaerated reliably in a short time.
Hereinafter, after first describing the paddle type kneader 10 and the extrusion machine 12 used in the method for extruding iron-containing powder according to one embodiment of the present invention, the method for extruding iron-containing powder will be described.

As the paddle type kneader 10, for example, the kneaders disclosed in JP-A-9-10571 and JP-A-9-187635 can be used.
As shown in FIG. 1, the paddle type kneader 10 has a multiple barrel barrel 13 in which a part of two circles overlap each other when viewed in a front cross section. In addition, a raw material inlet 14 is provided in the lower portion of the downstream side, and an outlet 15 for the kneaded material 11 is provided in the lower portion thereof.
In the barrel 13, two rotating shafts 16 arranged substantially in parallel are arranged so as to be rotatable in the same direction by a motor (not shown). Each rotary shaft 16 is provided with a paddle 17 that is inclined in the direction of feeding the raw material from the inlet 14 to the outlet 15, and between the paddles 17 provided on each rotary shaft 16, from the water supply port 18. The raw material is sent to the outlet 15 side while being kneaded together with the supplied water.

An extruder 12 is provided on the downstream side of the paddle kneader 10.
The barrel 19 of the extrusion machine 12 has substantially the same configuration as the barrel 13 of the paddle type kneader 10 described above, and the inlet 20 for the kneaded material 11 provided on the upper upstream side of the barrel 19. Is connected to the outlet 15 of the paddle kneader 10.
In the barrel 19, two rotating shafts 21 arranged substantially in parallel are arranged so as to be rotatable in opposite directions by a motor (not shown). Each rotating shaft 21 is provided with a screw screw 23 for feeding that is inclined in a direction in which the raw material is fed from the charging port 20 to the discharging port 22.

A pair of rollers 24 for pushing the kneaded material 11 into the rotary shafts 21 are disposed on the upper base side of the two rotary shafts 21. Each roller 24 is rotationally driven in the opposite direction while synchronizing its rotational speed with the rotating shaft 21 disposed below the roller 24.
Thereby, the kneaded material 11 pushed into the rotating shaft 21 by the roller 24 is kneaded between the screw blades 23 provided on the rotating shaft 21, and then to the discharge port 22 provided at the downstream end of the barrel 19. It is fed and pushed out through a mold 25 provided in the discharge port 22.

The connecting portion between the discharge port 15 of the paddle type kneader 10 and the charging port 20 of the extruder 12 is sealed, and a vacuum pump (not shown) is connected by a hose 26 connected to the sealed connecting portion. It is the structure which can exhaust the air in a connection part using.
Thereby, at the time of kneading by the paddle type kneader 10, the kneaded material 11 in which the air content is reduced more than before can be produced by deaeration by kneading and deaeration by a vacuum pump.

Next, an iron-containing powder extrusion method according to an embodiment of the present invention will be described with reference to FIG.
First, a raw material composed of iron-containing powder and a water-soluble organic binder is cut out from a hopper (not shown) and supplied to the inlet 14 of the paddle type kneader 10.
Here, the iron-containing powder is, for example, dust having an average particle size of 100 μm or less containing 50% by mass or more of iron generated in an ironworks.
The water-soluble organic binder is pregelatinized starch or flour, for example, corn starch, wheat starch, or rice starch.

The raw material charged into the barrel 13 from the inlet 14 of the paddle type kneader 10 is deaerated while being kneaded by the paddle 17 provided around the rotary shaft 16 together with the moisture supplied from the water supply port 18 and discharged. It is sent to the exit 15.
This kneading is performed while deaeration so that the air content of the kneaded product is 20% by volume or more and 40% by volume or less.
Here, when the air content of the kneaded product exceeds 40% by volume, a large amount of air is contained in the extruded product, and the strength (eg, crushing strength) of the extruded product is reduced. There is a risk that it will not be able to withstand the impact applied to it and collapse. On the other hand, when the air content of the kneaded product is less than 20% by volume, the strength of the extruded product is not significantly improved, and it is necessary to increase the pressure in the extruder.
From the above, in order to produce an extruded product having sufficient strength stably and with good yield, the upper limit of the air content of the kneaded product is 40% by volume, preferably 35% by volume, and the lower limit is 20% by volume, preferably Is 30% by volume.

Moreover, it is preferable to perform the moisture content added to a raw material so that the moisture content of the kneaded material 11 may be 10 mass% or more and 20 mass% or less.
The crushing strength of the extruded product is maximized when the water content of the kneaded product is in the vicinity of 16 to 17% by mass. Here, when the water content of the kneaded product exceeds 20% by mass, the extrudates adhere to each other to form a dumpling, which necessitates the destruction of the extrudate, which reduces the productivity of the extrudate. Workability is poor. On the other hand, when the water content of the kneaded material is less than 10% by mass, the binding between the iron-containing powder and the water-soluble organic binder is insufficient. The kneaded material collapses during conveyance.

The kneaded material 11 produced by the paddle kneader 10 is pushed into the inlet 20 of the extruder 12 by the roller 24 through the outlet 15. Then, the kneaded product 11 is extruded from the mold 25 while being kneaded by the screw blades 23 of the rotating shaft 21 to produce a rod-shaped extruded product 27.
The extruded product 27 is transported to a dryer via a conveyor (not shown) and dried. For example, the moisture content of about 16% by mass is reduced to about 0.3% to 0.5% by mass. After that, it is supplied to the converter.

Next, examples carried out for confirming the effects of the present invention will be described.
Here, as the iron-containing powder, converter exhaust gas dust collection dust (converter dust: average particle size 0.5 μm or more and 5 μm or less) and blast furnace pre-dust collection dust (blast furnace dust collection dust: average particle size 10 μm or more and 50 μm or less) And α starch was used as a water-soluble organic binder. This mixed dust also contains some moisture.
The reason why the mixed dust is used is that better kneading results (reduction in air content) are more easily obtained than kneading each individual dust. This is presumed to be due to the fact that by mixing both dusts, the particle size distribution becomes wider and the packing density per unit volume becomes higher.
After adding α starch to this mixed dust, water was further added and kneaded for 90 seconds with the paddle kneader described above, and an extruded product was produced with an extruder. In addition, the metal mold | die provided in the downstream edge part of the extrusion molding machine was equipped with six molding holes with a diameter of 16 mm in the circumferential direction, and manufactured the extrusion molding of diameter 16mm and length 40mm by this. . Using this extruded product, the crushing strength was measured according to JIS H8718. The test conditions and results are shown in Table 1.

As shown in Table 1, in Examples 1 and 2, the air content of the kneaded product was set to 30% by volume, and the air content was within the specified range (range of 20% to 40% by volume). Compared with the comparative example 1 (18 volume%) whose content is less than the minimum of a regulation range, and the comparative example 2 (45 volume%) exceeding an upper limit, the crushing strength of the extrusion molding was able to be improved.
In Examples 3 to 5, the air content of the kneaded material is set within the specified range, and the water content of the kneaded material is set within the range of 10% by mass or more and 20% by mass or less. Compared to Examples 1 and 2, the crushing strength of the extruded product could be further improved.
In this way, by regulating the air content of the kneaded product, it is possible to suppress the collapse of the extruded product due to the belt connection in the process of transporting the extruded product obtained from the kneaded product to the dryer. By supplying the extruded product to the converter, the iron recovery yield can be improved as compared with the prior art. In addition, this effect becomes more remarkable by prescribing the moisture content of the kneaded product.

As described above, the present invention has been described with reference to one embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and is described in the claims. Other embodiments and modifications conceivable within the scope of the above are also included. For example, a case where the iron-containing powder extrusion molding method of the present invention is configured by combining some or all of the above-described embodiments and modifications is also included in the scope of the right of the present invention.
In the above-described embodiment, the case where an apparatus in which a paddle kneader and an extruder are integrated is used for manufacturing a molded product. However, the paddle kneader and the extruder are separately provided. The resulting device may be used. In addition, as an extrusion molding machine, it is also possible to use what is equipped with the barrel of a single cylinder type instead of a barrel type barrel, for example.

It is a fragmentary sectional side view of the kneading machine used for the extrusion molding method of the iron-containing powder which concerns on one embodiment of this invention, and an extrusion molding machine.

Explanation of symbols

10: Paddle type kneader, 11: Kneaded product, 12: Extruder, 13: Barrel, 14: Input port, 15: Discharge port, 16: Rotating shaft, 17: Paddle, 18: Water supply port, 19: Barrel , 20: input port, 21: rotating shaft, 22: discharge port, 23: screw blade, 24: roller, 25: mold, 26: hose, 27: extruded product

Claims (2)

In a method of mixing a water-soluble organic binder with iron-containing powder and kneading with a kneader, and extruding this kneaded product with an extruder,
A paddle type kneader is used as the kneading machine, the kneaded product is kneaded while being deaerated so that the air content is 20% by volume or more and 40% by volume or less, and is extruded by the extruder. A method for extruding iron-containing powder. The method for extruding iron-containing powder according to claim 1, wherein water is added to the iron-containing powder so that the water content of the kneaded product is 10% by mass or more and 20% by mass or less with the paddle kneader. A method for extruding iron-containing powder characterized by the above.

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