TWI659005B - Method for manufacturing solidified slag, solidified slag, method for manufacturing coarse aggregate for concrete, and coarse aggregate for concrete - Google Patents

Abstract

Provided are a method for producing a solidified slag that can be used as a raw material for high-quality coarse aggregate for concrete, a method for producing a solidified slag produced by the method for producing a solidified slag, and a method for producing a coarse aggregate for concrete using the solidified slag. And a coarse aggregate for concrete manufactured by the method for producing a coarse aggregate for concrete. The method for producing solidified slag according to the present invention includes a slag solidification step, in which a molten blast furnace slag is poured into a moving metal mold to be cooled, and the plate is solidified in a mold shape in the mold; the slag is solidified; A dropping step of inverting the mold so that the slag which has solidified to the inside of the mold is dropped from the mold; and a slag temperature maintaining step of reducing the surface temperature of a part or the entire surface of the dropped slag to 900 Hold above 5 ° C for 5 minutes.

Description

Method for producing solidified slag, method for producing solid aggregate for concrete, and coarse aggregate for concrete

The present invention relates to a method for manufacturing a solidified slag, a solidified slag manufactured by the method for manufacturing a solidified slag, a method for manufacturing a coarse aggregate for concrete using the solidified slag, and In the coarse aggregate for concrete manufactured by the method for producing a coarse aggregate for concrete, the solidified slag solidifies a blast furnace slag in a molten state on a metal mold and solidifies the solidified slag. The solidified slag dropped from the mold to produce a plate-like solidified slag.

As a method for solidifying molten slag generated in a metal purification step or the like, a method is widely used in which high-pressure cooling water is blown to the molten slag and quenched, or the molten slag is dried to dryness. A method in which a slag cooling pit or a slag cooling yard is discharged and slowly cooled in the atmosphere.

In the method of quenching molten slag, a large amount of high-pressure cooling water is blown, so that a sand-like solidified slag (so-called water granulated slag) having a plurality of pores with a particle diameter of 5 mm or less is formed. )). On the other hand, in a method in which molten slag flows to a dry slag pit or a slag cooling field to solidify and slowly cool, a block having a size of several m is formed, and the block is pulverized to form a block-like solidified slag (so-called Slow-cooling slag (air-cooled slag)).

Recently, blast furnace slow-cooling slag has been applied to rough aggregates for concrete instead of gravel. In order to apply the blast furnace slag to the coarse aggregate for concrete, it is necessary to reduce the pores in the slag and adjust the maximum value of the slag particle size to about 20 mm.

Therefore, in this state, since the water-quenched slag has many pores and a small particle size, it cannot be applied to a coarse aggregate for concrete. On the other hand, although slow-cooling slag does not have the problem of pores, it is necessary to pulverize a block having a size of several m to a particle diameter of about 20 mm. This pulverization requires a lot of time and is inefficient.

Therefore, as a coarse aggregate for concrete, in order to obtain a solidified slag with few pores and easy crushing, various techniques have been proposed for solidifying the molten slag using a metal mold. If the molten slag is solidified in a metal mold, a solidified slag having a size larger than that of the water quenching slag and smaller than the slow-cooling slag can be obtained. The slag having a desired size can be easily obtained by crushing the slag, and Compared with the slow-cooling slag, the pulverization time can be shortened, and the required solidified slag having a particle diameter of about 20 mm can be easily obtained.

Examples of the solidification of the molten slag using a metal mold include, for example, an aggregate for asphalt pavement described in Patent Document 1, a method for producing the aggregate for asphalt pavement, and an asphalt pavement. The method of solidifying the molten slag of Patent Document 1 is as follows: The molten blast furnace slag is flowed in a single layer on a metal moving mold to cool it in a plate shape with a layer thickness of 10 mm to 30 mm and allowed to cool. Solidified to form a single-layer plate-like solidified slag. This single-layer plate-shaped slag is pulverized to produce an aggregate for asphalt pavement with a water absorption percentage of 1.5% or less and an abrasion loss percentage of 20% or less.

In addition, as a method of manufacturing a coarse aggregate for concrete using a metal mold to solidify the blast furnace slag, there is a coarse aggregate for concrete disclosed in Patent Document 2. The coarse aggregate for concrete containing slag disclosed in Patent Document 2 allows molten slag to flow into a metal mold and solidify. The slag obtained after solidification is pulverized and adjusted to have a water absorption of 1.5% or less and a particle diameter of 5 mm. ~ 20 mm. [Prior Art Literature] [Patent Literature]

Patent Document 1: Japanese Patent No. 3855706 Patent Document 2: Japanese Patent Laid-Open No. 2004-277191

[Problems to be Solved by the Invention] The method for solidifying the molten slag described in Patent Document 1 is a method in which a molten blast furnace slag is formed into a plate shape with a solidified thickness of 10 mm to 30 mm. The layer flows into a metal moving mold and is cooled and solidified. By rapidly cooling and solidifying, the growth of pores generated in the solidified slag is suppressed, thereby producing a low porosity with low water absorption and abrasion resistance. ) High aggregate.

However, as described in the example of Patent Document 1, when the blast furnace slag is solidified on a metal mold in a plate shape, the portion from the lower surface in contact with the metal mold is about 1 mm. It is glassy (glassy state). This is caused by the fact that, in the molten slag, the contact surface with the metal mold is most rapidly cooled to become a glassy state, but the thermal conductivity of the molten slag is very small, so the interior of the molten slag is very small. The cooling rate does not increase but solidifies in a crystalline state.

As described above, in the method of Patent Document 1, glassy plate-shaped solidified slag is generated on one side. However, when such plate-shaped solidified slag is pulverized to produce an aggregate, a part of the surface that can be formed is glass. Rough aggregate. When a coarse aggregate having a glassy surface is used as the coarse aggregate for concrete, there is a problem that bleeding occurs when fresh concrete is solidified. Water bleeding is a phenomenon in which a part of the mixed mixed water is released and rises to the surface due to the sedimentation or separation of the solid material in the fresh concrete.

Furthermore, the boundary between the glassy portion and the crystalline portion, which is about 1 mm from the surface in contact with the metal mold, is liable to crack. Therefore, there is also a problem that the glassy portion is liable to become fine particles when pulverization is performed to adjust the particle size of the coarse aggregate, and the yield of the coarse aggregate is reduced.

The coarse aggregate for concrete of Patent Document 2 is the same as that of Patent Document 1. Using blast furnace slag solidified on a metal mold, the blast furnace slag is crushed to form a water absorption of 1.5% or less and a particle diameter of 5 mm to 20 mm coarse aggregate. The molten slag flows into a metal mold and solidifies to a thickness of 20 mm to 30 mm. As in Patent Document 1, the contact surface with the metal mold is likely to vitrify. In Patent Document 2, the compressive strength of concrete (mix proportion) and curing period of 7 days and 28 days for concrete prepared with coarse aggregate for concrete is clear, but it is not clear about bleeding.

This invention is made in order to solve the said problem, The objective is to provide the manufacturing method of the solidified slag which can be used as the raw material of the coarse aggregate for concrete, the solidified slag manufactured by this manufacturing method of the solidified slag, The method for producing a coarse aggregate for concrete using the solidified slag, and the coarse aggregate for concrete produced by the method for producing a coarse aggregate for concrete.

[Means for Solving the Problems] The gist of the present invention for solving the problems is as follows.

[1] A method for producing a solidified slag, comprising the step of solidifying a slag, flowing the molten blast furnace slag into a moving metal mold to cool it, and making the mold into a plate shape in the mold. Solidification; a slag dropping step of inverting the mold so that the slag which has solidified to the inside of the mold is dropped from the mold; and a slag temperature maintaining step of a part of the slag surface of the dropped slag Or, the surface temperature of the entire surface is maintained at 900 ° C or higher for 5 minutes or longer.

[2] The method for producing solidified slag according to the above [1], wherein the thickness of the blast furnace slag solidified in a plate shape in the mold is 20 mm or more and 30 mm or less.

[3] The method for producing solidified slag according to the above [1] or [2], wherein in the slag temperature maintaining step, a surface of the solidified slag dropped from the mold During the solidification, the mold contact surface was 80% by area or more, and the surface temperature of the slag was maintained at 900 ° C or higher for 5 minutes or more.

[4] The method for producing a solidified slag according to any one of the above [1] to [3], wherein in the step of maintaining the temperature of the slag, solidification falling from the mold is solidified. The slag is laminated so that the average temperature in the thickness direction of the slag exceeds 900 ° C.

[5] The method for producing a solidified slag according to any one of the above [1] to [4], wherein in the slag temperature maintaining step, solidification falling from the mold is solidified. The slag is laminated in a holding container that can be carried out from a dropping position.

[6] A solidified slag manufactured by the method for manufacturing a solidified slag according to any one of the above [1] to [5], which is passed through a sieve having a hole diameter of 100 mm without passing through a hole diameter of 40 The slag sample with a sieve of mm mm was dropped four times from a height of 2 m, and the drop strength was evaluated based on the mass ratio of the sample that did not pass through the sieve with a diameter of 40 mm to the sample before the drop test. (Shatter Index) is over 70%.

[7] A method for producing a coarse aggregate for concrete, comprising: a step for producing a solidified slag, including the method for producing a solidified slag according to any one of the above [1] to [5]; and solidification A slag pulverizing step, which pulverizes the produced solidified slag; and a screening step, which smashes the pulverized solidified slag.

[8] A coarse aggregate for concrete, produced by the method for producing a coarse aggregate for concrete according to the above [7], with an average compressive strength of 100 N / mm ² or more.

[Effects of the Invention] According to the method for producing a solidified slag according to the present invention, the glassy portion of the solidified slag generated on the contact surface with a metal mold is maintained at a surface temperature of the slag of 900 ° C or higher for 5 minutes or more. During the period of time, it becomes crystalline, and a solidified slag having a high dropping strength is obtained. In addition, the coarse aggregate for concrete manufactured by further pulverizing and screening the solidified slag produced by the method for producing a solidified slag according to the present invention can be stabilized because the proportion of the portion having a glassy surface is small. To obtain high strength, thereby obtaining coarse aggregates that are better for making high strength concrete.

Hereinafter, the present invention will be specifically described.

The method for producing solidified slag according to this embodiment includes a slag solidification step of flowing a molten blast furnace slag into a moving metal mold to cool it, and solidifying the mold into a plate shape in the mold. A slag dropping step of inverting the mold to cause the slag which has solidified to the inside of the mold to fall from the mold; and a slag temperature maintaining step of a part of the slag surface of the dropped slag or The surface temperature of the entire surface was maintained at 900 ° C. or higher for 5 minutes or longer.

An example of the solidified slag manufacturing apparatus which can implement the manufacturing method of the said solidified slag is shown in FIG. A solidified slag manufacturing apparatus 1 (FIG. 1) shown in FIG. 1 has a plurality of recessed parts 5 a (recessed parts) having molten slag 3 which are accommodated in the molten state and accommodated in the slag pot 23. The mold 5 made of metal is supported so as to be movable around, and the molten slag 3 flows into the recessed portion 5 a while the mold 5 surrounds to continuously manufacture the solidified slag 18.

The solidified slag manufacturing apparatus 1 that performs such an operation includes a surrounding moving mechanism 7 that moves in a horizontal direction in a state where a plurality of molds 5 are approached and supported. The orbiting moving mechanism 7 includes an air-cooled moving portion 9 that moves the casting mold 5 in the orbiting direction while holding the molten slag 3 flowing in the recessed portion 5a during a period of one round of the casting mold to melt the molten mold. The slag 3 is air-cooled to solidify it; the discharge part 11 is reversed, and the mold 5 is inverted so that the recessed part 5a of the mold 5 is directed downward to discharge the solidified slag 18; The reversing part 15 re-reverses the mold 5 in the reversed state with the recessed portion 5a facing upward; the reversing moving part 17 moves the re-reversed mold 5 to the molten state. And a cooling device 21 that cools the reversed mold 5. The reversing moving section 17 may be omitted. In addition, the solidified slag manufacturing apparatus 1 is provided with a flow channel 20 in order to allow the molten slag 3 to easily flow into the mold 5.

Furthermore, the solidified slag manufacturing apparatus 1 has a pit 19 provided below the surrounding mold 5 surrounding the reversing discharge section 11, and a solidified slag holding container capable of containing the discharged solidified slag 18 is disposed in the pit 19. twenty two.

As shown in FIG. 2, the solidified slag holding container 22 has a capacity that can hold the solidified slag 18 in an amount equivalent to one cup of the molten slag 3 and can also accommodate the slag pot 23. After 1 cup of solidified slag 18 is removed, it is carried out from the slag dropping position and replaced with an empty solidified slag holding container 22. According to this, even if the slag is held in the solidified slag holding container 22 for a certain period of time, there is no waiting time to reduce productivity, and the molten slag 3 of the next slag pot 23 can be processed. .

From the viewpoint of thermal insulation properties, it is desirable that at least a part of the bottom surface and the side surfaces of the solidified slag holding container 22 include a low thermal conductivity of about 5 W / (m · K) or less along the normal direction of each surface. Refractory. In addition, the following forms may be selected: a cover is provided on the solidified slag holding container 22 after the solidified slag 18 is contained; or a simple heating source such as a burner is attached to the solidified slag holding container 22; The pit 19 at the slag dropping position itself is used as a solidified slag holding container, and an outer cover is installed and held after the solidified slag is received.

An example of the method of manufacturing the solidified slag 18 using the solidified slag manufacturing apparatus 1 of this embodiment configured as described above will be described together with the operation of the solidified slag manufacturing apparatus 1.

The orbiting movement mechanism 7 is rotated at a predetermined speed, and the molten slag 3 is caused to flow into the surrounding mold 5 through the flow channel 20 at the molten slag inflow portion. The mold 5 that has flowed into the molten slag 3 moves inside the air-cooled moving part 9, and the molten slag 3 is subjected to air cooling to become a solidified slag 18 (slag solidification step).

Here, it is preferable to control the orbiting speed of the mold 5 and / or the inflow speed of the molten slag 3 so that the thickness of the solidified slag 18 is 20 mm or more and 30 mm or less. If the thickness of the solidified slag is 20 mm or more, by pulverizing the solidified slag 18, it is possible to obtain a widely used coarse aggregate product having a particle size of 5 to 20 mm, which is suitable for ordinary coarse aggregate sizes. distributed. When the thickness of the solidified slag 18 is 20 mm or more, as described later, when the solidified slag 18 is loaded into the solidified slag holding container 22, the average amount of heat can be sufficiently increased. Therefore, the heating of the solidified slag 18 without the need for an additional heating source can increase the surface temperature of the slag at the contact surface of the mold to more than 900 ° C. and maintain it for more than 5 minutes.

On the other hand, if the thickness of the solidified slag 18 is 30 mm or less, the cooling rate of the slag is in an appropriate range and the generation of pores in the slag is suppressed, so that the water absorption of the coarse aggregate product can be reduced to 1.5% or less. In addition, it is preferable to obtain high-strength coarse aggregate particles having a compressive strength of 100 N / mm ² or more, for example.

The mold 5 that has reached the reverse discharge section 11 rotates in the reverse discharge section 11 in a circumferential direction and is reversed, and the solidified slag 18 is discharged into the pit 19 or the solidified slag holding container 22 in the pit 19 (the slag falls step).

The mold 5 from which the solidified slag 18 has been discharged moves in the reverse moving part 13 in the reversed state, and is cooled by the cooling device 21 during the movement.

The mold 5 having passed through the reversing moving portion 13 is rotated in the re-reversing portion 15 in the circumferential direction and re-reversed so that the recessed portion 5 a faces upward. In the mold 5 that has been reversed again, immediately after re-reversing or after moving within the re-reversing moving portion 17, the molten slag 3 flows into the slag inflow portion again.

The solidified slag 18 discharged to the pit 19 and loaded into the solidified slag holding container 22 is stacked in the solidified slag holding container 22, and the heat of the solidified slag 18 is reduced during solidification by the heat of the solidified slag 18 itself. The temperature at the contact surface of the mold increased. At this time, by maintaining the slag surface temperature of the falling solidified slag 18 at 900 ° C. or higher for 5 minutes or more, the glass quality of the mold contact surface of the solidified slag 18 can be changed to crystalline (the slag temperature is maintained). step). In this manner, after the glassy material is modified to be crystalline, the solidified slag 18 is discharged from the solidified slag holding container 22 to the slag cooling bed 24.

As described above, the solidified slag manufacturing method of the present invention has three steps: a slag solidification step, a slag dropping step, and a slag temperature maintaining step. Among these three steps, especially the slag temperature maintaining step has characteristics, so This will be described in detail below.

<Reason why a slag temperature maintaining step is required> When the cross-section of the plate-like solidified slag 18 dropped from the mold 5 is observed, the range from about 1 mm from the mold contact surface is vitrified. The reason for vitrification only in the range of about 1 mm from the mold contact surface is that the cooling rate is accelerated only in this part. Even if the solidified thickness of the solidified slag 18 is changed, the glassy portion is still about 1 mm from the mold contact surface.

A radiation thermometer was used to measure the surface temperature on the atmospheric side of the solidified slag 18, and a thermocouple was provided on the back of the mold. When the thickness of the solidified slag 18 was 23 mm, the molten slag 3 flowing up to the mold 3 was measured. The temperature transition until the process of being cooled and solidified is measured. The measurement results are shown in FIG. 3. FIG. 3 also shows the transition of the slag temperature at the center position in the thickness direction of the slag and the position in contact with the mold 5, which are obtained by the heat transfer analysis described later. The slag at the position in contact with the mold 5 increases the initial cooling rate significantly by heat conduction to the mold, decreases to 400 ° C. in about 15 seconds, and then reaches a substantially constant temperature. The temperature of the central part of the slag dropped slowly and only decreased to about 1150 ° C after 2 minutes, and the surface on the atmospheric side also decreased to only about 900 ° C after 2 minutes.

In this way, in the present method in which the molten slag 3 is mainly cooled by heat conduction to the mold 5, the mold contact surface is rapidly cooled, and the thermal conductivity of the slag is small, which is 2 W / (m · K) or less. Internal heat conduction is slow, and the cooling rate outside the mold contact surface is small. Therefore, only the slag on the contact surface of the mold is quenched and vitrified. When the mold 5 is reversed and the solidified slag 18 dropped from the mold 5 is transported separately one by one, the cooling during the transport starts from the surface, so the glass on the surface remains directly.

If the glassy substance remains, as described above, when it is used as a coarse aggregate for concrete, there is a problem that it is easy to leak water or a problem that the yield of the coarse aggregate is reduced. Therefore, it is necessary to reform the glassy part into a crystal. quality. Therefore, a temperature-maintaining step of reforming the glassy part to crystalline is required.

<Research on Cooling Rate by Analysis> A study has been made on how to change the glassy part to crystalline. During the research, the cooling rate inside the slag was studied by heat transfer analysis. In this process, the slag is solidified into a plate shape, so the temperature during the cooling and solidification process can be considered to be an unsteady one-dimension heat conduction of a flat plate. This basic formula is the following formula (1).

[Equation 1]

Here, λ is the thermal conductivity (W / (m · K)), ρ is the density (kg / m ³ ), Cp is the specific heat (J / (kg · K)), and T is the temperature of the slag or mold (K ), X is the length (m) in the thickness direction, and t is the time (s).

4 (a) and 4 (b) show an analytical model, FIG. 4 (a) shows a state where slag is contained in a mold, and FIG. 4 (b) shows a solidified slag dropped from the mold. As shown in FIGS. 4 (a) and 4 (b), the thickness direction of the slag and the mold is calculated by dividing the slag into 10 parts and the mold into 10 parts. Only the solidified slag is calculated after falling from the mold.

Here, the thermal conductivity hs of the interface between the atmosphere and the slag, the thermal conductivity hm of the mold-atmosphere interface, and the thermal resistance R of the interface between the slag and the mold are set as parameters. Match the way to determine the value of the parameter. Since the air-slag interface has a high temperature difference of 1300 K or more in the initial stage, heat radiation is considered. The ambient temperature Ta is fixed at 293 K, and the temperature does not rise. After falling from the mold, it is assumed to be in a heat-insulated state, and there is no movement from the heat outside the slag. It is set to Δt = 0.5 sec, and calculation is performed by an explicit solution technique.

The thermal conductivity λ (W / (m · K)) of the slag is a value calculated based on the following expressions (2) and (3). When T> 1400 K, λ = -5.0 × 10 ^-3 T + 9.20… (2) When T ≦ 1400 K, λ = 7.78 × 10 ^-4 T + 1.11… (3) Based on Ogino et al. The heat capacity measurement results of blast furnace slag (K. Ogino and J. Nishiwaki), "Steel Physical Property Value Manual" Ironmaking (2006) p.350, Japan Iron and Steel Association (stock), (Independence) The 54th Committee of the Japan Society for the Promotion of Science) The specific heat Cp of the slag is set to Cp = 1039 J / (kg · K) when T <1443 K, and set to 1443 K ≦ T <1673 K. It is Cp = 2242.5 J / (kg · K), and is set to Cp = 1326 J / (kg · K) when 1673 K ≦ T <1773 K.

The thermal conductivity on the surface of the slag and the thermal conductivity on the back of the mold are set to hs = 30 W / (m ² · K), hm = 10 W / (m ² · K), and the thermal resistance at the slag-mold interface is set to R = 9 × 10 ^-4 m ² · K / W, which can be approximately consistent with the measured value of temperature in FIG. 3.

With this, the temperature change of the slag can be calculated, and the temperature conditions and the holding time of the slag temperature maintaining step can be studied based on the temperature change.

<Temperature conditions> The surface temperature required for crystallizing a glassy part was examined. The surface temperature of the solidified slag immediately after the slag dropping step is changed according to the solidified thickness of the slag and the cooling time of the slag until the mold is inverted until the slag is peeled. Therefore, by changing the solidification thickness of the slag and the cooling time in various ways, the surface temperature of the solidified slag is changed, and the solidified slag having various changes in surface temperature is held in the solidified slag holding container for 24 hours. The relationship between the maximum temperature of the mold contact surface of the solidified slag and the area ratio of the glassy part was investigated. As a result, it was confirmed that in order to crystallize the vitreous part, it was effective to raise the surface temperature to 900 ° C or higher.

<Holding time> Then, under the condition that the solidification thickness of the slag and the cooling time of the slag until the mold is reversed until the slag is peeled off are fixed, the holding time in the solidified slag holding container is changed, and self-solidification is performed. The retention time from the point when the surface temperature of the mold contact surface side of the slag rises to 900 ° C, that is, the time when the surface temperature of the slag is maintained at 900 ° C or more, the glassy part of the surface in contact with the mold of the solidified slag The relationship of area ratio was investigated.

Specifically, in the solidified slag manufacturing apparatus shown in the examples described later, the surrounding of the metal mold 5 was repeated for 2 weeks, and 12 tons of the molten slag 3 was continuously processed in 6 minutes. After the storage of the solidified slag holding container 22 is completed for a predetermined time, the solidified slag 18 is immediately discharged and diffused to the slag cooling bed 24 at a time point that becomes the predetermined holding time, and is cooled in the atmosphere. The solidified slag holding container 22 is arranged at a slag dropping position when the mold 5 is inverted.

In order to calculate the holding time of 900 ° C or higher, it is necessary to specify a time point when the surface temperature of the mold contact surface side of the slag rises to 900 ° C and a time point when the surface temperature decreases to less than 900 ° C. Therefore, when the surface temperature of the mold contact surface side of the slag rises to 900 ° C., it is assumed that the storage of the last solidified slag in the solidified slag holding container is completed and the surface temperature of the mold contact surface side of the slag reaches At the time point of 900 ° C, the time point was obtained by assuming that the surface of the slag in the solidified slag holding container was an adiabatic boundary condition using the heat transfer analysis. The time point at which the surface temperature is lowered to less than 900 ° C. is the time point at which the solidified slag is discharged from the solidified slag holding container to the slag cooling bed and diffused. This is based on the assumption that at the time point when the solidified slag is discharged from the solidified slag holding container to the slag cooling bed and diffused, the surface temperature of the solidified slag is immediately lowered to less than 900 ° C.

FIG. 5 is a graph showing a relationship between a glassy area ratio (%) and a time (min) for holding at 900 ° C. or higher. As shown in the graph of FIG. 5, it can be seen that the area ratio of the glassy part of the mold contact surface is reduced to about 10% by holding at 900 ° C. for 5 minutes. Even if the holding time is further increased, the area of the glassy part The ratio will not change significantly. From this, it was confirmed that in order to crystallize the vitreous portion of the mold contact surface, it is effective to maintain the surface temperature of the solidified slag at 900 ° C. or higher for 5 minutes or more.

In addition, even if the holding time of 900 ° C. or higher in FIG. 5 is longer than 5 minutes, the area ratio of the glassy portion is not significantly lower than about 10%. It is considered to be based on the following: In the outermost part of the solidified slag in the slag holding container, the solidified slag with the mold contact surface facing upwards will not rise to a temperature of 900 ° C or higher even if the holding time is extended, and will not crystallize. Therefore, if a lid is provided on the slag holding container after the slag is stored, or a simple heating source such as a burner is used for reheating, the area ratio of the glassy portion can be further reduced.

In addition, even if the calculated value of the holding time at 900 ° C. or higher in FIG. 5 is zero, the reason why a part of the glassy slag is crystallized is considered to be based on the following: In the solidified slag in the lower part of the buildup layer in the container, the surface temperature rose during the time until the final solidified slag was stored, and it was maintained at 900 ° C or higher for 5 minutes or more. That is, it is considered that the solidified slag contained in the slag holding container at the initial stage of the slag treatment satisfies the conditions for crystallization and is crystallized.

Then, it was examined whether the temperature condition and the retention time can be secured by laminating the solidified slag that has been dropped through the slag dropping step.

<Slag temperature in the heat preservation state> For solidified slag with a thickness of 25 mm, calculate the temperature distribution immediately before falling from the mold. As an example, FIG. 6 shows a calculation result of the temperature distribution inside the solidified slag 18 120 seconds after the molten slag 3 is injected into the mold. The temperature distribution inside the solidified slag is, for example, a solid line graph of FIG. 6. The temperature of the solidified slag immediately after being discharged from the mold is considered to be approximately the same as the temperature of the solidified slag immediately before being dropped from the mold. Therefore, it is expressed as "immediately after being discharged from the mold" in FIG. 6.

In the solidified slag immediately after being discharged from the mold, the temperature of the mold contact surface and the atmospheric surface decreased, and the internal temperature became high. If the solidified slag is dropped into the holding container in this state and continuously stacked and stacked, the slag inside the stacked layer becomes a heat-preserving state, so that the heat in the slag is conducted to the contact surface side of the mold during solidification with time. And the atmosphere, the slag as a whole has a nearly uniform temperature distribution. The calculation result of the temperature distribution after 3 minutes is shown by the dotted line in FIG. 6. In this condition, the temperature of the mold contact surface that is temporarily lowered also rises to a temperature of about 1000 ° C.

In the method for producing solidified slag of the present invention, after the solidified slag is dropped and discharged from the mold, it is necessary to raise the surface temperature of a part or the entire surface of the slag including the solidified slag at the mold contact surface to 900 ° C or higher. And hold for more than 5 minutes. By confirming that the average temperature in the thickness direction of the solidified slag discharged from the mold exceeds 900 ° C. and that the solidified slag is laminated in the pit 19 or the solidified slag holding container, it can be implemented without using a new heating source. Mentioned steps.

<Temperature of slag stacking> When the surface temperature of the slag rises to 900 ° C or higher due to the heat content of the solidified slag itself, the solidification thickness of the solidified slag can be appropriately selected, and the mold can be inverted until the solidification melts. Conditions such as the cooling time of the slag until the slag falls and the holding time in the solidified slag holding container are realized. This point will be specifically described below.

For example, FIG. 7 shows that the cooling time after the molten slag is poured into the mold is 2 minutes, and the holding time in the solidified slag holding container after the last solidified slag is dropped and stored is set to 3 minutes ( 180 seconds), the relationship between the average slag thickness and the slag surface temperature in the slag accumulation layer in the solidified slag holding container.

Using infrared thermography, the temperature of the solidified slag is measured from the upper part of the solidified slag holding container, and the solidified slag (hereinafter sometimes referred to as "under the surface layer" The surface temperature of the solidified slag ") is indicated in FIG. 7. The solidified slag is a non-surface solidified slag and is located below the surface solidified slag. Any measured value of the surface temperature of the solidified slag having an average thickness of 22 mm or more tested under the surface layer exceeded 900 ° C. The slag thickness on the horizontal axis in FIG. 7 is an average of values obtained by measuring the thickness of the slag near the surface layer after cooling.

On the other hand, the solid line indicates the calculated value of the temperature of the mold contact surface of the solidified slag, and it is the temperature immediately after being discharged from the mold, and is held in the solidified slag holding container as the solidified slag under the surface 3 Temperature after minutes (180 seconds). As shown in FIG. 7, as long as the average thickness is 20 mm or more, the temperature of the mold contact surface of the solidified slag after being held for 3 minutes exceeds 900 ° C. The larger the average thickness, the higher the temperature of the mold contact surface. .

The measured value of the surface temperature of the solidified slag under the surface layer held in the container is the same as the calculation result. The larger the thickness of the slag, the higher the tendency. The solidified slag with an average thickness of 22 mm or more after the test is 3. 900 minutes or more after minutes. That is, it is confirmed that the measured surface temperature of the solidified slag under the surface layer is in good agreement with the calculated result. Based on the calculated result and the measured value, the solidified slag having an average thickness of 20 mm or more is laminated, and the solidification can be achieved after 3 minutes The surface temperature of the slag is 900 ° C or higher.

In addition, when the heat source for increasing the surface temperature of the solidified slag is only the heat content of the solidified slag itself, in order to reduce the external influence of heat radiation, it is necessary to laminate and store the solidified slag holding container. The amount of solidified slag is ensured to some extent. Specifically, it is preferable that the solidified slag which is 5 ton or more, and more preferably 10 ton or more is stacked to a thickness of 1 m or more to be accommodated.

Compared with slow-cooled slag, plate-like solidified slag casted from a metal mold tends to have a higher average solidification rate, so that crystal grains tend to be smaller, and, as will be described later, residuals near the contact surface of the mold can be eased and eliminated Residual stress to obtain a material with superior strength characteristics than slow-cooled slag.

Further, in the solidified slag manufactured by the method for manufacturing a solidified slag according to the present invention, the drop strength (Shatter Index) defined below is 70% or more, and by the method for manufacturing the solidified slag according to the present invention, the drop strength (Shatter Index) is obtained. ) Is a plate-like solidified slag with a high strength of 70% or more. Furthermore, by using a plate-shaped solidified slag having a drop strength of 70% or more and cast from a metal mold, the solidified slag is crushed and screened to produce slag products such as coarse aggregates for concrete. Rate increases.

Furthermore, the coarse aggregate obtained by pulverizing and screening the solidified slag produced by the method for producing a solidified slag of the present invention is used for concrete having an average compressive strength of 100 N / mm ² or more measured by a method described later. Coarse aggregate is suitable as a raw material for coarse aggregate in the production of high-strength concrete. [Example]

The effects of the present invention will be described based on specific embodiments.

In this embodiment, the apparatus shown in FIG. 1 is used to manufacture solidified slag. The mold 5 is made of cast steel having a trapezoidal shape in plan view, the thickness is set to 45 mm, the outer dimension of the mold corresponding to the trapezoidal upper bottom is set to 0.7 m, and the mold corresponding to the bottom of the trapezoidal shape is set. The external dimensions of the mold are set to 1.0 m, and the external dimensions of the mold having a trapezoidal height are set to 2.7 m. The depth of the recessed portion 5 a of the mold 5 flowing into the molten slag was set to 100 mm. The mold 5 is orbitally conveyed by the orbiting mechanism 7. The conveying speed of the orbital conveyance is set to 14 m / min at the center of the mold.

In the slag inflow portion, the blast furnace slag in a molten state of 1360 ° C. to 1410 ° C. is caused to flow into the mold 5 at about 2 ton / min. The mold 5 that has flowed into the molten slag 3 is transported in the air-cooled moving part 9 in about 120 seconds (the length of the air-cooled moving part is 2/3 (240 degrees) of the entire circumference), and the molten slag 3 is solidified by air cooling. Slag 18.

The mold 5 is inverted in the reversing discharge part 11, and the solidified slag 18 that has been peeled from the mold is dropped into the solidified slag holding container 22 disposed in the pit 19. The mold 5 from which the solidified slag 18 has been discharged is moved while maintaining the reversed state in the reversing moving portion 13, and the cooling device 21 is sprayed with cooling water from both the upper and lower sides to perform rapid cooling.

Then, the mold 5 in the reversed state is reversed again by the re-reverse portion 15, and the original recessed portion 5a is restored to the upward state again. Then, molten slag was again poured into the restored mold. The above steps were repeated for a single slag pot for 5 weeks, and 30 tons of molten slag was continuously processed within 15 minutes.

After all the solidified slag is dropped from the mold, it is held in the solidified slag holding container for a predetermined time. Then, the solidified slag is discharged from the solidified slag holding container to the slag cooling bed and diffused, and cooled in the atmosphere.

In the example of the present invention, the conditions are as follows: the molten slag temperature is 1385 ° C, the holding time after the slag storage in the solidified slag holding container is 10 minutes, and the average thickness of the solidified slag is 25 mm, so that Immediately after a predetermined holding time, the solidified slag is discharged from the solidified slag holding container to the slag cooling bed and diffused, and cooled in the atmosphere.

In the comparative example, the conditions were that the molten slag temperature was 1380 ° C and the average thickness of the solidified slag was 23 mm. The solidified slag was dropped from the mold to the pit. After all the solidified slag was dropped from the mold, the forklift was used immediately. (Shovel car) The solidified slag is removed from the pit and cooled in a slag cooling bed to prepare for the next treatment of the molten slag in the slag pot. In the comparative example, when the solidification of the solidified slag was measured after cooling, the thickness was 20 mm to 26 mm, and the average thickness was 23 mm. The influence of the solidification thickness on the existence rate of glassy on the contact surface of the mold is not in the range of 20 mm to 26 mm.

In the solidified slag after cooling, the ratio of the glassy part of the mold contact surface at the time of solidification was evaluated, and the drop strength of the slag was evaluated.

First, the glass-free solidified slag (crystalline solidified slag) having a contact surface with a mold is selected from the solidified slag produced in the example of the present invention by visual inspection. On the other hand, the solidified slag produced by the comparative example is visually selected. From the slag, a solidified slag having a contact surface with a mold of glass is sorted and subjected to a drop test.

Fig. 8 (a), Fig. 8 (b), Fig. 9 (a), and Fig. 9 (b) are photographs showing test results, Fig. 8 (a) shows a state before the test of the present invention example, and Fig. 8 (b) Fig. 9 (a) shows the state after the drop test of the comparative example, and Fig. 9 (b) shows the state after the drop test of the comparative example.

As shown in FIG. 9 (b), the solidified slag of the comparative example in which the contact surface portion of the mold of the solidified slag was classified as glassy was finely pulverized as a whole as shown in FIG. 9 (b). This is because a large residual stress is generated in the vicinity of the surface having a large temperature gradient during solidification, and therefore it is easy to break even a relatively small impact of a drop of 1 m.

On the other hand, in the solidified slag produced by the method for producing a solidified slag of the present invention, as shown in FIG. A high-strength plate-like solidified slag is formed. This is because when the glassy part of the mold contact surface is crystallized, residual stress near the surface is relaxed or eliminated.

The drop strength (Shatter Index) was measured by the method described below. As a device for the drop strength test, the device described in the Japanese Industrial Standards (JIS) M8711 iron sintered ore-fall strength test method was used. A sample of plate-shaped solidified slag with a diameter of 40 mm to 100 mm (a sample of plate-shaped solidified slag that passed through a sieve opening of 100 mm and a plate-shaped solidified slag that did not pass through a sieve with a diameter of 40 mm; about 3 kg) was implemented. Drop test 4 times from a height of 2 m. After the drop test, a ratio (mass ratio of a sample that did not pass through a sieve with a pore size of 40 mm) that was not pulverized to 40 mm or less was determined, and this ratio was set as the drop strength (Shatter Index). Regarding other test conditions, the JIS M8711 iron ore sinter ore-fall strength measurement method as a test method for sinter ore was used.

The drop strength (Shatter Index) of the plate-like slag is calculated by the following formula (4). S (%): A / B × 100 ... (4) S: Drop strength of plate-shaped slag judged to be 40 mm or more (Shatter Index) A: Mass of 40 mm or more after test (kg) B: Before test The mass (kg) of a sample of 40 mm to 100 mm (kg). The relationship between the ratio of the glassy part of the mold contact surface and the drop strength S is shown in FIG. 10 as a result of comparison between the present invention example and the comparative example. In the example of the present invention, the ratio of the glassy portion was reduced from 52 area% to 9 area% of the comparative example, and the drop strength S was increased from 46% to 89% of the comparative example.

Based on the results, in order to effectively improve the strength of the solidified slag by crystallization of the vitreous part, it can be said that it is preferably 80% or more of the area of the mold contact surface during solidification on the surface of the solidified slag, More preferably, it is 90% by area or more, and the surface temperature of the slag is maintained at 900 ° C or higher for 5 minutes or more. That is, it is preferable that the area of the mold contact surface of the solidified slag during solidification is 80% by area or more, and more preferably 90% by area or more of the crystalline material. In other words, the area of the glassy portion of the surface of the mold contact surface of the solidified slag is solidified. The ratio is set to less than 20 area%, and more preferably set to less than 10 area%.

Then, in order to make the solidified slags of the examples of the present invention and the comparative examples manufactured as described above into coarse concrete aggregates, a 10-ton plate-shaped solidified slag was crushed using an impact crusher. Then, the crushed slag is sieved with a sieve of 20 mm and 5 mm. Thereby, a coarse aggregate for concrete of 20 mm to 5 mm was manufactured.

The result of comparing the yield of the coarse aggregate product of 20 mm to 5 mm with respect to the solidified slag used as the raw material is compared in the present invention example and the comparative example and is shown in FIG. 11. The yield of the coarse aggregate product of the example of the present invention was 71%, and that of the comparative example was 65%. That is, the yield of the coarse aggregate product of the comparative example is 6% higher than that of the present invention.

The water absorption of the coarse aggregate of the example of the present invention was measured to be 0.9%, which was significantly reduced compared with the existing water absorption of the blast furnace slow-cooled slag coarse aggregate, which is 3% to 4%, thereby obtaining the same water absorption as the natural aggregate. rate.

Furthermore, the compressive strength of the slag rough aggregates of the examples of the present invention and the comparative examples was compared. For a sample for measuring the compressive strength, a size of 10 mm × 10 mm × 10 mm was cut out using a diamond cutter from a slightly larger coarse aggregate particle including a flat surface with the flat surface as a bottom surface. A compression tester (universal testing machine) measured the compression strength of each of the six samples.

The average value of the compressive strength of the sample taken from the coarse aggregate of the comparative example was 50 N / mm ² , and the lowest value was 10 N / mm ^2. There were coarse aggregate samples with very large unevenness and very low strength. In contrast, the average value of the compressive strength of the sample taken from the coarse aggregate of the example of the present invention was 167 N / mm ² , and the minimum value was 80 N / mm ² , so that high compressive strength was stably obtained.

Concrete was prepared using the slag coarse aggregate of the examples and comparative examples, and the characteristics were evaluated. The amount of bleeding was compared between freshly mixed concrete prepared with the coarse aggregate of the example of the present invention and freshly mixed concrete prepared with the coarse aggregate of the comparative example. The investigation results are shown in FIG. 12. The example of the present invention with a small glassy surface has a smaller amount of bleeding than the comparative example with a larger glassy surface.

Next, using various coarse aggregates, mixing the concrete with a water-cement ratio of 35% in pursuit of high strength to mix the concrete to produce a test body for measuring the compressive strength, and the 28-day strength was measured. Compare. For comparison, a test body prepared by using commercially available natural limestone for coarse aggregate was also produced and evaluated.

The 28-day strength of the concrete using the coarse aggregate of the comparative example was 53 N / mm ² , while the 28-day strength of the concrete using the coarse aggregate of the example of the present invention was 75 N / mm ² . The 28-day strength of the concrete using the coarse aggregate of natural limestone was 72 N / mm ² , and the concrete using the coarse aggregate of the example of the present invention achieved higher compressive strength than the concrete using the coarse aggregate of natural limestone. Therefore, it can be said that the coarse aggregate of the example of this invention is a material suitable as a coarse aggregate for high-strength concrete.

1‧‧‧Solidified slag manufacturing device

3‧‧‧ molten slag

5‧‧‧mould

5a‧‧‧ Depression

7‧‧‧Circular movement mechanism

9‧‧‧Air-cooled mobile unit

11‧‧‧ reverse discharge

13‧‧‧Reverse moving part

15‧‧‧ Reversal Department

17‧‧‧Reverse moving part

18‧‧‧ solidified slag

19‧‧‧ pit

20‧‧‧ flume:

21‧‧‧cooling device

22‧‧‧ solidified slag holding container

23‧‧‧Slag Pot

24‧‧‧ Slag Cooling Bed

FIG. 1 is a schematic diagram schematically showing the configuration of an embodiment of a solidified slag manufacturing apparatus that realizes the solidified slag manufacturing method of the present invention. FIG. 2 is a schematic view showing a solidified slag holding container of the solidified slag manufacturing apparatus shown in FIG. 1. FIG. 3 is a graph showing temperature transitions at each measurement position when the slag is cooled on a metal mold. 4 (a) and 4 (b) are schematic diagrams showing a one-dimensional heat transfer analysis model of slag and a mold. FIG. 5 is a graph showing the relationship between the retention time at which the surface temperature of the slag is 900 ° C. or higher and the ratio of the surface area of the glass which occupies the mold contact surface during solidification. FIG. 6 is a graph showing a calculation result of a temperature distribution in the thickness direction of the solidified slag. FIG. 7 is a graph showing the relationship between the measured surface temperature of the slag, the calculated value of the slag temperature, and the thickness of the slag, and the measured value of the surface temperature of the slag is accumulated in the solidified slag after 3 minutes of storage The measured surface temperature of the slag below the solidified slag in the surface layer of the holding container. The calculated value of the slag temperature is the surface layer of the solidified slag immediately after being discharged from the mold and in the solidified slag holding container as the surface layer. The calculated value of the slag temperature after holding the solidified slag for 3 minutes. FIGS. 8 (a) and 8 (b) are photographs showing the appearance of slag before and after a drop strength test when the mold contact surface is crystalline during solidification. FIGS. 9 (a) and 9 (b) are photographs showing the appearance of slag before and after a drop strength test when the mold contact surface during the solidification is glassy. FIG. 10 is a graph showing the relationship between the drop strength and the ratio of the glassy portion occupying the mold contact surface during solidification. FIG. 11 is a graph showing a product yield when manufacturing a coarse aggregate of 20 mm to 5 mm in comparison with an example of the present invention and a comparative example. FIG. 12 is a graph showing a comparison between the amount of water bleeding in concrete using coarse aggregates in the examples of the present invention and the comparative example.

Claims (8)

A manufacturing method of solidified slag, comprising: a slag solidification step of flowing a molten blast furnace slag into a moving metal mold to cool it, and solidifying it in a plate shape in the mold; A slag dropping step of inverting the mold so that the slag which has solidified to the inside of the mold is dropped from the mold; and a slag temperature maintaining step of a part or the entire slag surface of the dropped slag The surface temperature of the surface was maintained at 900 ° C or higher for 5 minutes or longer. The method for manufacturing solidified slag according to item 1 of the scope of the patent application, wherein the thickness of the blast furnace slag solidified in a plate-like manner in the mold is 20 mm or more and 30 mm or less. The method for manufacturing solidified slag according to item 1 or 2 of the scope of application for a patent, wherein in the slag temperature maintaining step, a mold contact during solidification in the surface of the solidified slag dropped from the mold is contacted. The surface area is 80% by area or more, and the surface temperature of the slag is maintained at 900 ° C or more for 5 minutes or more. The method for manufacturing solidified slag according to item 1 or 2 of the scope of patent application, wherein in the slag temperature maintaining step, the average temperature of the solidified slag dropped from the mold in the thickness direction of the slag exceeds 900 ℃ and laminated. The method for manufacturing solidified slag according to item 1 or 2 of the scope of application for a patent, wherein in the slag temperature maintaining step, the solidified slag dropped from the mold is laminated and held at a position where the solidified slag can be removed from the dropping position. Inside the container. A solidified slag, which is a solidified slag manufactured by the method for manufacturing a solidified slag according to any one of claims 1 to 5 in a patent application, which is passed through a sieve with a diameter of 100 mm without passing The slag sample with a sieve with a diameter of 40 mm was evaluated by the mass ratio of the sample that did not pass through the sieve with a pore size of 40 mm relative to the sample before the drop test. The drop strength (fragmentation index) is 70% or more. A method for manufacturing coarse aggregate for concrete, comprising: a method for manufacturing solidified slag, comprising the method for manufacturing a solidified slag according to any one of claims 1 to 5 in the scope of patent application; , Crushing the produced solidified slag; and a screening step of screening the crushed solidified slag. A coarse aggregate for concrete is manufactured by the method for manufacturing a coarse aggregate for concrete described in item 7 of the scope of patent application, and has an average compressive strength of 100 N / mm ² or more.