JP2008266104A - Method of manufacturing white blast furnace slag particles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing white blast furnace slag particles by a dry granulation process having non of a complex step such as that comprising mixing secondary materials. <P>SOLUTION: The black blast furnace slag particles manufactured by the method of dry granulation, for example, with a slag processor and the like, are heated until the occurrence of whitening. Alternatively, black blast furnace slag particles manufactured by the method of dry granulation are kept at above 850°C for a specific period for whitening. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing white particles that can be used for fine aggregate for concrete, decorative sand and the like from blast furnace slag.

  Blast furnace slag particles are produced by cooling the molten blast furnace slag in a molten state discharged from the blast furnace. As a method for producing blast furnace slag particles, a processing method by granulation in which molten blast furnace slag is rapidly cooled with a large amount of water to produce blast furnace slag particles, and a gas jet is sprayed on the flowing molten blast furnace slag to form particles (Patent Document 1) Or by applying a mechanical blow (Patent Document 2, a dry granulator using this mechanical blow is also called a slaglator), and cooling to produce blast furnace slag particles by a dry granulation method There is a processing method.

  Another possible method is to crush the so-called slow-cooled slag that has been discharged into the yard and naturally cooled into particles, but the slow-cooled slag is very strong and is used for fine aggregates for concrete, etc. When it is necessary to make it finer, it is difficult to crush to a particle size equivalent to 5 mm or less of sand, and this is a problem in terms of cost.

  In the treatment method by water granulation, porous particles are obtained by solidifying in a state where bubbles are generated in the particles by the reaction of water and molten blast furnace slag. Particles produced by this method become white due to fine pores on the surface, and the color tone is suitable for applications such as fine aggregate for concrete where decorativeness is important and decorative sand spread on the surface of dirt pavement. As a result, there were problems of low strength and easy wear.

In addition, since water is absorbed into the pores, there is a problem that workability deteriorates when applied as a concrete fine aggregate. JIS
In A5011-1 “Concrete slag aggregate-Part 1: Blast furnace slag aggregate”, there is a regulation of 3.5% or less as the water absorption required for blast furnace slag fine aggregate, The value is about 2 to 5%, and when it exceeds 3.5%, an additional step of reducing the water absorption rate such as grinding is required.

  In the dry granulation method, bubbles are not generated in the particles, so that dense particles can be obtained. In addition, since the generated particles have a particle size equivalent to 5 mm or less sand, when applied as fine aggregate for concrete, it is often unnecessary to crush separately. Since it is not high in strength, it is relatively easy to crush. Furthermore, since there are no pores, particles with a water absorption of 1% or less can be obtained relatively easily, and the concrete fine aggregate properties are excellent. However, the particles produced by the dry granulation method have a problem that the color tone is dark, such as dark green, and the application destination is limited.

  Here, regarding a method for whitening slag particles, for example, Patent Document 3 describes a method for producing white slag in which bone incinerated ash obtained by incineration of waste containing bone components is mixed with molten slag.

JP-A-55-21546 JP-A-64-52636 JP 2000-233953 A

  However, the conventional whitening method for molten slag has a problem that a special auxiliary material such as bone incineration ash is required, and there is a limit to the amount that can be applied to a large amount of blast furnace slag. Furthermore, when mixing the auxiliary materials, a complicated device such as an ash blowing device is required, and there is a problem that costs increase.

  Then, an object of this invention is to provide the manufacturing method of the white blast furnace slag particle | grains by the dry granulation method which does not require complicated processes, such as mixing of a raw material.

  (1) A method for producing white blast furnace slag particles, comprising heating black blast furnace slag particles produced by a dry granulation method to a temperature at which whitening occurs. In this case, the blast furnace slag particles may be temporarily heated to a predetermined temperature at which whitening occurs, or may be held for a predetermined time at the predetermined temperature or higher.

  (2) A method for producing white blast furnace slag particles, characterized in that black blast furnace slag particles produced by a dry granulation method are whitened by holding at 850 ° C. or higher for a predetermined time.

  (3) The method for producing white blast furnace slag particles according to (1) or (2), wherein the heating temperature or the holding temperature is 950 ° C. or lower.

  (4) The method for producing white blast furnace slag particles according to (2), wherein the holding temperature is 900 ° C. or higher and 950 ° C. or lower.

  (5) The method for producing white blast furnace slag particles according to any one of (1) to (4), wherein the dry granulation method is a dry granulation method by mechanical impact.

  In the method for producing white blast furnace slag particles of the present invention, white blast furnace slag particles can be produced from black blast furnace slag particles produced by a dry granulation method without requiring complicated steps such as mixing of auxiliary materials. It becomes possible.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  The present inventor performs various tests, and when the temperature of the black blast furnace slag particles produced by the dry granulation method is increased, the whitening occurs when the temperature exceeds a certain temperature regardless of the production lot. I found the phenomenon.

  That is, when the black blast furnace slag particles were gradually heated, when the heating temperature became 850 ° C. to 900 ° C., at least a part of the particles changed from black to gray and became 900 to 950 ° C. Occasionally, most of the particles were found to turn gray or white (milky white).

  It has been found that the variation in temperature when the color change of particles occurs tends to vary depending on the heating rate when the heating temperature is raised. Thus, a more detailed study revealed that the degree of whitening differs depending on the absolute value of the temperature and the time that the particles are held in that temperature range.

  Specifically, when the blast furnace slag particles are held at a temperature of 850 ° C. or higher (holding temperature) for a predetermined time or more in a heat insulating tank, or once heated to a temperature of 900 ° C. or higher (heating temperature), at least the particles Some of the particles are changed to gray. Further, when the particles are kept at 900 ° C. or higher for a predetermined time or heated to a temperature of 950 ° C. or higher, almost all of the particles become gray or white (milky white).

  This phenomenon is that after dry granulation, the blast furnace slag particles become vitreous and have a black color tone under normal cooling conditions. However, with the method of the present invention, the blast furnace slag particles are heated to a high temperature or held at a predetermined temperature for a predetermined time. Then, it is considered that the vitreous material is converted into crystalline material, and fine crystals are precipitated, so that the color becomes black or gray or white (milky white).

  In order to promote crystallization, it is effective to maintain the temperature close to the freezing point of the blast furnace slag particles as long as possible, and in order to ensure gray-white or whitening of the entire particles, the temperature should be 900 ° C. or higher. It is preferable to hold for a predetermined time or more, and further, it is desirable to hold for a longer time at a temperature of 900 ° C. or higher for reliable whitening when particles are accumulated assuming cosmetic sand or the like. However, since the freezing point of the blast furnace slag particles varies depending on the composition of the slag, for example, about 1100 to 1400 ° C., it is preferable to set the upper limit of the heating and holding temperature according to the conditions at that time.

  If the temperature is higher than 950 ° C., the blast furnace slag particles are softened and fused so that the product cannot be transported, and a sieve or the like for removing the fused lump from the product is required. The heating temperature is preferably 950 ° C. or lower.

  Regarding the holding time, the influence of the apparatus is large, and the larger the apparatus, the longer the time required for the entire amount of particles to reach a predetermined temperature. Therefore, the holding time for whitening tends to increase. Therefore, it is preferable to confirm the holding time in advance by a test using an actual apparatus.

  FIG. 1 shows an example of an apparatus for producing white blast furnace slag particles for carrying out the method of the present invention. This apparatus includes a blast furnace slag dry granulator 5 (slaglator) and heating apparatuses 3 to 6 for heating blast furnace slag particles granulated by the dry granulator 5. As the dry granulator 5 for blast furnace slag, a mechanical blow type slaglator is used. Below, the manufacturing method of the white blast furnace slag particle | grains using this apparatus is demonstrated.

  The heating device introduces the blast furnace slag particles 1 produced by the dry granulation method in the dry granulator 5 into the heat insulating tank 3 and moves the blast furnace slag particles 1 at a predetermined speed by pushing in the horizontal direction by the reciprocating pusher 4. The slag particles 2 are retained in the heat insulating tank 3 during heat retention, and then discharged as a product 8. The heating element 6 may be, for example, an electric heater or a gas combustor as long as it has a function of keeping the temperature inside the heat insulating tank 3 at a temperature at which whitening of the slag particles 2 occurs, and the type is not particularly specified.

  The blast furnace slag particles 1 to be charged may be particles once manufactured and cooled to room temperature as long as the blast furnace slag is below the temperature at which the blast furnace slag is softened and fused, or may be high temperature particles immediately after being discharged from the dry granulator 5. However, in the latter case, less energy is consumed by the heating element 6, which is advantageous in that the operating cost can be reduced.

  In FIG. 1, the heat insulating tank 3 is a horizontal type, but a vertical heat insulating tank in which the blast furnace slag particles 1 are introduced from the upper part, moved by gravity, and the product is discharged from the lower part may be adopted. The atmosphere of the heat insulating tank 3 is not particularly defined, and normally air may be used, but nitrogen or water vapor may be used.

  FIG. 2 shows a detailed view of an example of the dry granulator 5. The dry granulator (slaglator) 5 executes a dry granulation method in which the molten slag is mechanically blown into particles. In this dry granulator 5, the molten slag flowing down from the molten slag pan 10 is hit with a rotating impeller 5 a and blown off into the rotating hood 9, thereby producing the blast furnace slag particles 1. Black slag particles 12 are discharged from the rear end portion and introduced into the heat insulating tank 3 (not shown).

  In the example of FIG. 2, two impellers 5a are installed, molten slag is caused to flow down to the first stage impeller 5a, and particles having a short flight distance are struck by the second stage impeller 5a. The flying distance of a certain distance or more is obtained for the particles.

  Further, the dry granulator 5 is not limited to a granulation method in which a mechanical blow is applied to the molten slag by a rotating impeller 5a or the like. For example, as shown in Patent Document 1, a molten slag is generated by an air flow ejected from a nozzle. The method of granulating may be used. In addition to the rotating hood 9, an apparatus such as a vibrating inclined plate may be used as a device for collecting particles. The present invention is equally applicable to blast furnace slag particles that have no surface pores and are glassy and blackish. In a granulation system in which slag is atomized by a water stream or in a granulator of other types in which water is present in the granulation part, bubbles are generated in the particles and whitened, so that the present invention is not applicable.

  As described above, in the method for producing white blast furnace slag particles according to the present embodiment, the black blast furnace slag particles produced by the dry granulation method are heated to a predetermined heating temperature, or at a predetermined holding temperature. The black blast furnace slag particles can be whitened only by holding for a predetermined time. Therefore, white blast furnace slag particles can be produced without requiring a complicated process such as mixing of auxiliary materials.

  Hereinafter, the result of the test which investigated the color tone change of the blast furnace slag particle | grains by changing the holding temperature and holding time when heating the blast furnace slag particle | grains manufactured by the dry granulation method is demonstrated. In this test, the slag particles produced by mechanical blow with a rotating impeller in the apparatus of the method of FIG. 2 (throughput 3T / H, no heat storage tank) are once cooled, and then have a program temperature control function. Using an electric furnace, the temperature was raised from room temperature to a specified temperature at 10 ° C./min, kept at a constant temperature for a specified time, and then allowed to cool naturally. Nitrogen was circulated in the electric furnace. It was confirmed that similar results were obtained in tests of 3 to 4 levels per condition.

  Table 1 shows the test results under each condition. In Table 1, the meaning of “whitening” represents the presence or absence of any discoloration (at least partially grayed or whitened) in one particle compared to the black state before heating. The whitening in the present invention is based on the definition. “Particle” represents the color tone of a single particle, and “Whole” represents the color tone of the entire particle packed in a transparent container and observed at a distance of 50 cm or more. The vitreous particles have a transparent surface, and the color tone in this state is represented by “semi-transparent”.

  As can be seen from the results in Table 1, no change in color tone was observed at 800 ° C. or lower regardless of the holding time. At 850 ° C., the particles became opaque under a holding condition of 60 minutes, but no whitening occurred. This is considered to be a stage where crystallization has progressed but the color tone has not changed.

  Whitening occurred at 850 ° C. for 120 minutes, but the color tone remained gray.

  At 900 ° C., most of the particles turned white with a holding time of 15 minutes, but some of the particles remained black spots. When the holding time is extended, the black portion tends to shrink, and all the particles are whitened under the condition of 120 minutes.

  Under the condition of 950 ° C., light fusion occurred between some particles regardless of the holding time. This fusion is easily broken by transfer of the container and the like, and it is considered that there is no hindrance to the use as a fine aggregate.

  Under the condition of 1000 ° C., the particles were firmly fused. Under these conditions, a process such as crushing is required for use as a fine aggregate, resulting in high manufacturing costs. Since whitening has occurred, it can be used.

  Therefore, it is necessary to increase the temperature and heat until whitening occurs, and it is necessary to hold at a temperature of at least 850 ° C. for a predetermined time. The temperature is preferably 950 ° C. or less from the viewpoint that the crushing treatment is unnecessary, and more preferably held at 900 to 950 ° C. for a predetermined time from the viewpoint of sufficiently whitening in a short time.

  FIGS. 3 to 6 show photographs of black blast furnace slag particles produced with a slaglator and blast furnace slag particles treated under several conditions in Table 1. FIG.

  FIG. 3 is a photograph of blast furnace slag particles as produced by atomization by the mechanical blow-type dry granulator 5 (slaglator) shown in FIG. 4 shows the slag particles after holding the slag particles at 850 ° C. for 60 minutes, FIG. 5 shows the slag particles after holding the slag particles at 900 ° C. for 15 minutes, and FIG. 6 shows the slag particles. Are slag particles after being held at 900 ° C. for 120 minutes.

  Under the condition of holding at 850 ° C. for 60 minutes as shown in FIG. 4, whitening has not yet occurred and the same black particles as in FIG. 3 remain. In the condition of holding at 900 ° C. for 15 minutes as shown in FIG. 5, whitening occurs, but black remains partially in a spot shape. In addition, it can be seen that the entire particle is whitened under the condition of holding at 900 ° C. for 120 minutes as shown in FIG.

  Thus, it turns out that the black slag particle | grains manufactured by the dry granulation method can be whitened by using the manufacturing method of the white blast furnace slag particle | grains of this invention.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

It is a figure which shows the structural example of the manufacturing apparatus of the white blast furnace slag particle concerning one Embodiment of this invention. It is a figure which shows the structural example of the dry granulator concerning the embodiment. 3 is a photograph of blast furnace slag particles (black) discharged from the dry granulator of FIG. 2. It is a photograph of blast furnace slag particles (black) under the condition of holding at 850 ° C. for 60 minutes. It is a photograph of blast furnace slag particles partially whitened under the conditions of holding at 900 ° C. for 15 minutes. It is the photograph of the blast furnace slag particle | grains in which the whole was whitened on condition of holding for 900 minutes at 900 degreeC.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input slag particle 2 Slag particle in heat retention 3 Heat retention tank 4 Pusher 5 Dry granulator (slaglator)
5a Rotating impeller 6 Heating element 7 Exhaust piping 8 Collected product 9 Rotating hood 10 Molten slag pan 11 Cooling spray 12 Black blast furnace slag particles

Claims (5)

  A method for producing white blast furnace slag particles, comprising heating black blast furnace slag particles produced by a dry granulation method to a temperature at which whitening occurs.   A method for producing white blast furnace slag particles, characterized in that black blast furnace slag particles produced by a dry granulation method are whitened by holding at 850 ° C. or higher for a predetermined time.   The method for producing white blast furnace slag particles according to claim 1 or 2, wherein the heating temperature or the holding temperature is 950 ° C or lower.   The method for producing white blast furnace slag particles according to claim 2, wherein the holding temperature is 900 ° C or higher and 950 ° C or lower.   The method for producing white blast furnace slag particles according to any one of claims 1 to 4, wherein the dry granulation method is a dry granulation method by mechanical impact.