JP2022137928A - Granule and method for producing granule - Google Patents

Abstract

To recycle powdered raw material with high production efficiency.SOLUTION: Granules are formed from a raw material containing at least one of refractory waste, slag or dust, have a grain size distribution of 5 mm or more and less than 50 mm, and a collapse strength of 35 kgf or more and 70 kgf or less. A method for producing granules includes the steps of: adding a binder and water to a raw material containing at least one of refractory waste, slag or dust, making a mixture; subjecting the mixture to non-compression molding, making granules; and sieving the granules to have a grain size distribution of 5 mm or more and less than 50 mm.SELECTED DRAWING: Figure 1

Description

The present invention relates to a granule and a method for producing the granule.

In recent years, the demand for recycling these waste materials has increased due to the decrease in disposal destinations of waste refractories containing slag and dust, the increase in disposal costs, and the increase in the price of auxiliary raw materials for iron manufacturing. Known recycling destinations include, for example, refractory repair materials and smelting furnace input auxiliary materials such as slag forming materials or slag foaming pacifiers. As a technology related to such recycling, Patent Document 1 describes crushing refractory blocks, sieving as necessary, adjusting the particle size to a predetermined range, and slag generated in the steelmaking refining process as it is. A technique for use as a foaming soothing agent is described. In addition, Patent Document 2 describes a technique for producing a slag concentration adjuster by pulverizing waste refractories containing MgO as a main component to 5 mm or less, adding and kneading a binder and water, and molding them into briquettes. there is

Japanese Patent Application Laid-Open No. 2004-2915 JP-A-10-317040

However, when raw materials such as waste refractories, slag, and dust are in the form of fine powder, it is difficult to recycle them as refractory repair materials. Moreover, when using waste refractories as an auxiliary raw material to be charged into a refining furnace as described in Patent Document 1, waste refractories having a relatively large particle size are used. This is because if waste refractories, slag, dust, etc., are thrown in as fine powder, they will be swept up by the gas flow generated in the furnace, resulting in a high proportion of them being discharged together with the exhaust gas, resulting in an inadequate effect. . As described in Patent Document 2, if a finely powdered raw material is formed into a briquette, it can be used as an auxiliary raw material to be charged into a smelting furnace. Since it is necessary, it cannot necessarily be said that the production efficiency is high.

Accordingly, an object of the present invention is to provide a granule and a method for producing the granule that enables recycling of finely powdered raw materials with high production efficiency.

[1] A granule made of a raw material containing at least one of waste refractories, slag and dust, having a particle size distribution of 5 mm or more and less than 50 mm and a crushing strength of 35 kgf or more and 70 kgf or less.
[2] The granules according to [1], in which portland cement is added as a binder.
[3] A slag foaming sedative containing 50% by mass or more of the granules according to [1] or [2].
[4] A slag-forming material containing 50% by mass or more of the granules according to [1] or [2].
[5] A step of adding a binder and water to a raw material containing at least one of waste refractories, slag or dust to produce a kneaded product, a step of non-compression molding the kneaded product to produce granules, and sieving the granules so that the particle size distribution is 5 mm or more and less than 50 mm.
[6] The method for producing granules according to [5], wherein water is added to the raw material so that the total of the raw material moisture content and the added moisture content is 13% by mass or more and 16% by mass or less.
[7] The method for producing granules according to [5] or [6], wherein the binder is Portland cement.
[8] The method for producing granules according to any one of [5] to [7], wherein the step of producing the kneaded product includes an empty kneading step for 1 minute or longer.
[9] The method for producing granules according to any one of [5] to [8], wherein the step of producing granules includes a step of reversing the direction of arm rotation of the granulator.
[10] The method for producing the granules according to any one of [5] to [9], further including a drying step for two days or longer.

According to the above configuration, the raw material containing at least one of waste refractories, slag, and dust is processed into granules having a predetermined particle size and strength even if the raw material is finely powdered, for example, a smelting furnace It becomes possible to recycle as an input auxiliary material. Since the granules are formed by non-compression molding, production efficiency can be improved compared to the case where the granules are formed by compression molding, for example.

It is a photograph for demonstrating the optimal particle size distribution of a pellet. 4 is a graph showing the strength of pellets in each study example. 2 is a graph showing the particle size distribution of pellets in each study example. It is a graph which shows the relationship between the drying period of the pellet after granulation, and strength.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the present specification and drawings, constituent elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description. In addition, % indicating a ratio means % by mass unless otherwise specified.

In an embodiment of the present invention, granules are produced from finely powdered raw materials containing at least one of waste refractories, slag and dust. The raw material used in the present embodiment is, for example, a mixture of used alumina-based refractories and slag, or a mixture of used dolomite brick chips and stainless steel dust, but is not limited to these examples. Finely powdered means that the particle size is less than 5 mm, but not all of the raw materials are finely powdered. may be

In this embodiment, cement and water are used as binders in order to improve the particle size distribution of raw materials containing at least one of waste refractories, slag and dust so that they can be put into a smelting furnace and improve production efficiency. is used to form the raw material into pellets. Here, briquettes and pellets are both granules, but differ in that briquettes are compression-molded granules and pellets are non-compression-molded granules. In other words, the step of forming the raw material into pellets in this embodiment does not include the step of compression. As a result, in the present embodiment, the production efficiency can be improved as compared with, for example, the case where the raw material is formed into briquettes by compression molding. The fact that the manufactured granules are non-compression-molded pellets can be identified by the difference in strength from compression-molded briquettes, as will be described later.

FIG. 1 is a photograph for explaining the optimum particle size distribution of pellets used as an auxiliary material to be charged into a smelting furnace. The inventors of the present invention conducted an experiment to determine the optimum particle size distribution when molding the raw material into pellets and using it as an auxiliary raw material to be charged into the refining furnace. In the experiment, a mixture of used refractories and slag was formed into pellets, and the pellets were sieved into three stages of particle size distribution. In the example shown in FIG. 1(a), the particle size d is less than 5 mm, in the example shown in FIG. 1(b), the particle size d is 5 mm or more and less than 25 mm, and in the example shown in FIG. 1(c), the particle size d is 30 mm or more and less than 50 mm. . Table 1 shows the results of using three types of pellets as a slag foaming suppressant for about 30 charges each in a converter.

In a converter, if the slag foaming is not sufficiently calmed down, tapping will not be completed in one time and tapping will need to be repeated. be able to. In the results shown in Table 1, when the grain size d is less than 5 mm, the average number of times of tapping is 1.8 times, and most of the charges require tapping twice or more. On the other hand, when the grain size d is 5 mm or more and less than 25 mm, and when the grain size d is 30 mm or more and less than 50 mm, the average number of times of tapping is 1.1 times, and tapping is completed in one time in most charges. there is From this result, when the particle size d is less than 5 mm, most of the pellets put in as a slag foaming calming agent are swirled up by the gas flow and do not reach the molten steel surface, and the slag calming effect is insufficient. Recognize. Therefore, in the present embodiment, the pellet production conditions are optimized so as to obtain granules having a particle size distribution of 5 mm or more and less than 50 mm.

In the present embodiment, the method for producing pellets as a granulated product includes the steps of adding a binder and water to raw materials to produce a kneaded product, non-compression molding the kneaded product to produce pellets, and producing pellets. and sieving so that the particle size distribution is 5 mm or more and less than 50 mm. In optimizing the pellet production conditions, the production conditions in the kneading and granulation steps were studied so that the yield of pellets having a particle size distribution of 5 mm or more and less than 50 mm was sufficiently high in the sieving step.

Table 2 shows the conditions for producing pellets in the study example. No. 1 to No. 9, the raw material used is a mixture of spent alumina-based refractories and slag, and the grain size of the raw material is less than 5 mm. A pelletizer (Pellegaia (registered trademark) mixer) equipped with the functions of a kneader and a granulator was used to form the pellets, and kneading of the raw materials with a binder and water and granulation were carried out as a series of steps. Portland cement was used as a binder, and the amount of binder (outer coating to raw material) was varied in the range of 5% to 15%. The amount of water added was set by the total water content, which is the sum of the raw material water content and the added water content, and the total water content was varied in the range of 12% to 17%. Here, the water content is calculated for raw materials and water that do not contain a binder. Empty kneading in the kneading step, that is, preliminary kneading of the binder and raw materials before adding water is usually carried out for 15 seconds. 6 and no. 9 was performed for 1 minute. Regarding the rotation of the arm in the Pellegaia (registered trademark) mixer during granulation, it is normally rotated in one direction at a constant speed. In No. 7, the rotating speed was changed to a low speed in the second half of the granulation process while rotating in one direction. 8 and no. In 9, the direction of rotation was reversed in the second half of the granulation process while rotating at a constant speed.

FIG. 2 is a graph showing the strength of pellets in each study example. In each study example shown in Table 2, the pellets obtained in the granulation step were dried for 2 to 3 days with a loosening step for preventing adhesion between particles, and then dried according to JIS Z8841. The crushing strength was measured using a crushing strength tester as follows. In the results shown in the graph of FIG. 1, No. 2 and no. 3 with a total moisture content of 14%. 2 with a total moisture content of 12% and 17%, respectively. 1 and no. 3, and it can be seen that the strength of the pellet is improved by setting the total moisture content within an appropriate range. Also, No. 2, No. 4 and no. 5, No. 5 with a binder amount (outer coating) of 5%. 10% stronger than No. 4 strength. No. 2 strength is high, and No. 15%. Since the strength of 5 is even higher, it can be seen that the strength of the pellet is improved by increasing the amount of binder. Furthermore, No. 2, No. 6, No. 7 and no. Comparing No. 8, No. 8 was changed from 15 seconds to 1 minute for empty kneading. No. 6 and No. 6 in which the direction of rotation of the arm was reversed during granulation. In No. 8, the strength of the granules was greatly improved, whereas in No. 8, the rotation speed of the arm was changed during granulation. In No. 7, the strength of the granules is not so much improved, and it can be seen that extending the empty kneading time and reversing the rotation direction during granulation are more effective in improving the strength of the pellets. No. No. 9 is an example in which the manufacturing conditions were optimized based on the above knowledge, and the average strength was 55 kgf, which was the maximum among all the examples.

Here, the strength of the pellets is not directly related to the effect itself when the pellets are used as auxiliary raw materials for smelting furnaces, such as slag foaming tranquilizers. This is an important index in terms of preventing the effect from being insufficiently exhibited due to the particle size being lower than that at the time of production. Specifically, by imparting a crushing strength of 35 kgf or more, it becomes possible to use the same transportation and charging means as those for ordinary auxiliary raw materials, and sufficient handleability can be imparted. Among the examined examples, No. 1 satisfies this strength standard. 5, No. 6, No. 8, No. 9. Moreover, if the strength is high, the particles are less likely to collapse during the sieving process, and the yield is improved. In the case of pellets that are non-compression-molded with an appropriate amount of binder, the upper limit of crushing strength is 70 kgf. A briquette that is compression-molded from the same material has a crushing strength of about 90 kgf when dried, and can be distinguished from the pellets, which are the granules according to the present embodiment, in this respect.

FIG. 3 is a graph showing the particle size distribution of pellets in each study example. In each study example shown in Table 2, after drying, the granules were sieved to measure the particle size distribution. In the results shown in the graph of FIG. In No. 1, the particle size of the granules was remarkably small, and the proportion of the granules having the above-described particle size distribution of 5 mm or more and less than 50 mm was about 20%. Also, No. In 3, the moisture content was too large, and as a result, it was difficult to measure the particle size distribution by sieving. No. Although the particle size distribution itself could be measured in 4, it was not suitable for practical use because the amount of binder was too small and the amount of water was too large. Otherwise, no. 2 and no. 5 to No. In No. 9, the ratio of granules having a particle size distribution of 5 mm or more and less than 50 mm was approximately 50% or more, which was a state suitable for practical use. This is because, for example, when the pellets in each study example are used as a slag foaming tranquilizer or slag forming material as described later, the slag foaming tranquilizer or slag forming material has a particle size distribution of 5 mm or more and less than 50 mm. It means that the grain content is 50% or more. The highest yield was No. 9, and the proportion of granules with a particle size distribution of 5 mm or more and less than 50 mm reached 75%.

FIG. 4 is a graph showing the relationship between the drying period of pellets after granulation and strength. The raw material and binder (Portland cement) were mixed as shown in Table 3, and the pellets after granulation were dried indoors and outdoors, and the crushing strength was measured after a predetermined number of days had elapsed. As shown in the graph of FIG. 3, in all cases, the intensity increases significantly until the lapse of two days, but after that the change in intensity becomes smaller. Therefore, it is considered that two days or more is preferable as the period of the drying process that can sufficiently develop the strength of the pellets after granulation.

From the results of the above studies, the following are the conditions for producing pellets for obtaining granules having a particle size distribution of 5 mm or more and less than 50 mm. In addition, as shown by the above examination examples, it is not necessary to satisfy all the manufacturing conditions, and pellets can be produced by combining arbitrary conditions from the following conditions according to the physical properties of the raw material and the characteristics of the manufacturing equipment. Particle size distribution can be optimized.

・Add 10% or more Portland cement as a binder.
Portland cement has a longer setting time, i.e., the time from mixing with water to development of strength, than other types of cement such as alumina cement, so the kneaded product of raw materials, binders and water is formed early. Stable granulation is possible without solidification to make granulation difficult. From the viewpoint of ensuring the strength of the granules, the amount of Portland cement to be added is preferably 10% or more in terms of external coating. If the amount of binder added is too large, the moldability during granulation will be lowered.

- Adjust the amount of water added so that the total water content is between 13% and 16%.
If the total moisture content, which is the sum of the raw material moisture content and the added moisture content, is too low, the grain size of the granules will be too small, resulting in a low yield. Also, if the total water content is too high, the strength of the granules may be low, or if the water content is too high, it may not be suitable for practical use. Therefore, it is preferable to adjust the total moisture content, for example, to an appropriate range as described above. Here, the waste refractories, slag, and dust used as raw materials are originally discharged from a dry environment, but for example, they contain water due to rainwater during storage. Too much water may be present. Therefore, it is preferable to adjust the amount of added water according to the total water content as in the present embodiment.

- In the kneading process, extend the time of the empty kneading process.
- In the granulation process, the arm rotation direction of the granulator is reversed.
In addition to adjusting the amount of the binder and the amount of water added, the mixing of the raw materials with the binder and water is accelerated by carrying out an empty kneading step for 1 minute or more or reversing the arm rotation direction of the granulator. Also, the strength of the granules is increased, and as a result, handleability and yield can be improved. Pellegaia (registered trademark) mixer is exemplified as a pelletizer capable of performing kneading and granulation as a series of steps and reversing the arm rotation direction in the granulation step, but other kneaders and granulators are used. It is also possible to

・The drying process is carried out over a period of 2 days or longer.
Since the strength of the granules is exhibited by the binder solidifying after granulation, it is preferable to carry out the drying process for a period of 2 days or more.

According to the embodiments of the present invention as described above, even if the raw material containing at least one of waste refractories, slag, and dust is finely powdered, granules having a predetermined particle size and strength can be obtained. By processing it, it becomes possible to recycle it, for example, as an auxiliary raw material for smelting furnaces. Since the granules in the present embodiment are pellets formed by non-compression molding, production efficiency can be improved compared to the case of forming granules by compression molding. The produced granules can be used as a slag foaming suppressant as in the above example, and also as a smoke preventive agent. These slag foaming suppressants or anti-smoke agents are added to, for example, slag pots, hot metal pots, or ladles. In addition, the above granules may be used as auxiliary raw materials for smelting furnaces for other purposes such as slag forming materials. Further, the use of the granules is not limited to the auxiliary raw material to be charged into the smelting furnace, and other uses such as a repair material for damaged lining bricks of a converter or an electric furnace are also possible.

Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person having ordinary knowledge in the technical field to which the present invention belongs can conceive of various modifications or modifications within the scope of the technical idea described in the claims. It is understood that these also belong to the technical scope of the present invention.

Claims (10)

A granule made of a raw material containing at least one of waste refractories, slag, and dust, having a particle size distribution of 5 mm or more and less than 50 mm, and a crushing strength of 35 kgf or more and 70 kgf or less. 2. Granules according to claim 1, wherein portland cement is added as a binder. A slag foaming sedative containing 50% by mass or more of the granules according to claim 1 or 2. A slag-forming material containing 50% by mass or more of the granules according to claim 1 or 2. A step of adding a binder and water to a raw material containing at least one of waste refractories, slag or dust to produce a kneaded product;
a step of non-compression molding the kneaded material to produce a granulated material;
A method for producing granules, comprising the step of sieving the granules so that the particle size distribution is 5 mm or more and less than 50 mm. 6. The production of granules according to claim 5, wherein in the step of adding water, water is added to the raw material so that the total of the raw material moisture content and the added moisture content is 13% by mass or more and 16% by mass or less. Method. The method for producing granules according to claim 5 or 6, wherein the binder is Portland cement. The method for producing granules according to any one of claims 5 to 7, wherein the step of producing the kneaded product includes an empty kneading step for 1 minute or longer. The method for producing the granules according to any one of claims 5 to 8, wherein the step of producing the granules includes a step of reversing an arm rotation direction of the granulator. The method for producing the granules according to any one of claims 5 to 9, further comprising a drying step for two days or longer.

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