TWI613178B - Method for manufacturing solidified slag, solidified slag, method for manufacturing coarse aggregate for concrete, and coarse aggregate for concrete - Google Patents

Abstract

A method for producing solidified slag which can be used as a raw material for high-quality coarse aggregate for concrete, a solidified slag produced by the method for producing the solidified slag, and a method for producing a coarse aggregate for concrete using the solidified slag And a coarse aggregate for concrete produced by the method for producing a coarse aggregate for concrete. The method for producing a solidified slag according to the present invention includes a step of solidifying a slag, and flowing molten blast furnace slag into a moving metal mold to be cooled, and solidifying the mold in a plate shape; slag In the dropping step, the mold is reversed so that the slag which has solidified to the inside in the mold falls from the mold; and the slag temperature maintaining step, the surface temperature of a part or the entire surface of the slag surface of the fallen slag is 900 Keep above °C for more than 5 minutes.

Description

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

The present invention relates to a method for producing a solidified slag, a solidified slag produced by the method for producing the solidified slag, a method for producing a coarse aggregate for concrete using the solidified slag, and a method for producing a concrete aggregate for concrete, and A coarse aggregate for concrete produced by the method for producing a coarse aggregate for concrete, which solidifies a blast furnace slag in a molten state on a metal mold and solidifies The solidified slag is dropped from the mold to produce a plate-shaped solidified slag.

As a method of solidifying molten slag which is generated in a metal purification step or the like, the following method is widely used: a method of blowing high-pressure cooling water to molten slag and quenching, or drying the molten slag to dry A method of discharging a dry pit or a slag cooling yard and performing a slow cooling in the atmosphere.

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

Recently, it has been realized to apply blast furnace slow cooling slag to coarse aggregate for concrete instead of gravel or the like. 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, the water-quenched slag has many pores and a small particle size, and thus cannot be applied to a coarse aggregate for concrete. On the other hand, although the slow cooling slag has no problem of pores, it is necessary to pulverize a block having a size of several m to a particle diameter of about 20 mm, which requires a large amount of time and is inefficient.

Therefore, as a coarse aggregate for concrete, in order to obtain a solidified slag having few pores and being easily pulverized, various techniques for solidifying molten slag using a metal mold have been proposed. When the molten slag is solidified in a metal mold, a solidified slag having a size larger than that of the water-quenched slag and smaller than the slow-cooled slag is obtained, and by pulverizing it, slag of a desired size can be easily obtained, and The slow cooling slag can shorten the pulverization time, so that the desired solidified slag having a particle diameter of about 20 mm can be easily obtained.

For example, an aggregate for asphalt pavement described in Patent Document 1, a method for producing the same, and an asphalt pavement are used as an example of solidifying the molten slag using a metal mold. Method for solidifying molten slag of Patent Document 1 The blast furnace slag in a molten state flows in a single layer on a moving mold made of metal in a plate shape having a layer thickness of 10 mm to 30 mm, and is cooled and solidified to form a single-layer plate-shaped solidified slag. . The single-layer plate-shaped slag is pulverized to produce an aggregate for asphalt pavement having a water absorption percentage of 1.5% or less and an abrasion loss percentage of 20% or less.

In addition, as a method of solidifying blast furnace slag by using a metal mold to produce a coarse aggregate for concrete, there is a coarse aggregate for concrete disclosed in Patent Document 2. In the coarse aggregate for concrete containing slag disclosed in Patent Document 2, the molten slag is poured into a metal mold and solidified, and the slag obtained after solidification is pulverized and adjusted to have a water absorption rate of 1.5% or less and a particle diameter of 5 mm. 20mm.

Prior art literature

Patent literature

Patent Document 1: Japanese Patent No. 3855706

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

The method of solidifying the molten slag described in Patent Document 1 is a method in which a molten blast furnace slag is poured into a metal moving mold in a single layer so as to have a plate shape of a solidified thickness of 10 mm to 30 mm. The solidification by cooling and solidification by rapid cooling suppresses the growth of pores generated in the solidified slag, thereby producing an aggregate having low water absorption and high abrasion resistance at a low porosity.

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

As described above, in the method of Patent Document 1, a glassy plate-shaped solidified slag is formed on one side, but when such a plate-shaped solidified slag is pulverized to produce an aggregate, a part of the surface can be formed into a glass. Quality coarse aggregate. In the case where a coarse aggregate having a glassy surface is used as a coarse aggregate for concrete, there is a problem that fresh concrete is easily bleed when solidified. Bleeding is a phenomenon in which a part of the agitated mixed water is released and rises to the surface due to sedimentation or separation of the solid material in the fresh concrete.

Further, the boundary between the vitreous portion and the crystalline portion which is about 1 mm from the surface in contact with the metal mold is easily broken. Therefore, there is also a problem that the glassy portion is likely to become fine particles when pulverized and adjusted to the coarse aggregate particle size, and the yield of the coarse aggregate is lowered.

In the same manner as in Patent Document 1, the coarse aggregate for concrete of Patent Document 2 is pulverized by a blast furnace slag solidified on a metal mold to form a water absorption rate of 1.5% or less and a particle diameter of 5 mm to 20 mm. Thick aggregate. The molten slag is poured into a metal mold and solidified into a thickness of 20 mm to 30 mm, thereby In the same manner, in the literature 1, the possibility of vitrification of the contact surface with the metal mold is high. In Patent Document 2, the blending conditions (mix proportion) of the concrete for concrete for concrete and the compressive strength at 7 days and 28 days for the curing period are clear, but it is not clear about bleeding.

The present invention has been made to solve the above problems, and an object of the invention is to provide a method for producing a solidified slag which can be used as a raw material of a coarse aggregate for concrete, and a solidified slag produced by the method for producing the solidified slag, which is used. A method for producing a coarse aggregate for concrete for solidifying slag, and a coarse aggregate for concrete produced by the method for producing a coarse aggregate for concrete.

The gist of the present invention for solving the above problems is as follows.

[1] A method for producing a solidified slag, comprising: a slag solidification step of flowing molten blast furnace slag into a moving metal mold to be cooled, and forming the mold into a plate shape Solidification; slag dropping step, inverting the mold to cause slag which has solidified to the inside in the mold to fall from the mold; and slag temperature maintaining step, part of the slag surface of the fallen slag Or the surface temperature of the entire surface is maintained at 900 ° C or more for 5 minutes or more.

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

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

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

[6] A solidified slag produced by the method for producing a solidified slag according to any one of the above [1] to [5], which is passed through a sieve having a pore diameter of 100 mm without passing through a pore diameter of 40 mm. The slag sample of the sieve, after dropping test 4 times from the height of 2 mm, the drop strength (fragmentation index) evaluated by the mass ratio of the sample which did not pass through the sieve having a diameter of 40 mm with respect to the sample before the drop test (Shatter Index)) is 70% or more.

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

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

According to the method for producing solidified slag of the present invention, the solidified slag is in the form of gold The vitreous portion formed on the contact surface of the mold is crystallized while maintaining the surface temperature of the slag at 900 ° C or higher for 5 minutes or longer. Therefore, solidified slag having a high drop strength is obtained. Further, the solidified slag produced by the method for producing solidified slag according to the present invention is further pulverized and screened to produce a coarse aggregate for concrete, which is stable because the proportion of the surface having a vitreous portion is small. High strength is obtained to obtain a coarse aggregate which is preferable for producing high-strength concrete.

1‧‧‧ Solidified slag manufacturing equipment

3‧‧‧ molten slag

5‧‧‧ mould

5a‧‧‧Depression

7‧‧‧ Surrounding mobile agencies

9‧‧‧Air Cooling Department

11‧‧‧Reverse discharge department

13‧‧‧Reverse movement department

15‧‧‧Reversal

17‧‧‧Reverse the mobile department

18‧‧‧ Solidified slag

19‧‧ ‧ pit

20‧‧‧Rough

21‧‧‧Cooling device

22‧‧‧ Solidified slag holding container

23‧‧‧ slag pot

24‧‧‧ slag cooling bed

Fig. 1 is a schematic view schematically showing a configuration of an embodiment of a solidified slag producing apparatus for realizing a method for producing a solidified slag according to the present invention.

Fig. 2 is a schematic view schematically showing a solidified slag holding container of the solidified slag producing apparatus shown in Fig. 1;

3 is a graph showing temperature transition at each measurement position when the slag is cooled on a metal mold.

4(a) and 4(b) are schematic views showing a one-dimensional heat transfer analysis model of slag and a mold.

Fig. 5 is a graph showing the relationship between the holding time at which the surface temperature of the slag is 900 ° C or more and the glass surface area ratio at the contact surface of the mold at the time of solidification.

Fig. 6 is a graph showing a calculation result of a temperature distribution in the thickness direction of the solidified slag.

7 is a graph showing the relationship between the measured value of the surface temperature of the slag and 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 the slag containment 3 a measured value of the surface temperature of the slag deposited under the solidified slag of the surface layer in the solidified slag holding container after the minute, the calculated value of the slag temperature is just after the mold contact surface of the solidified slag is discharged from the mold and The solidified slag retains the calculated value of the slag temperature after holding the solidified slag under the surface layer for 3 minutes.

8(a) and 8(b) are photographs showing the appearance of slag before and after the drop strength test in the case where the mold contact surface at the time of solidification is crystalline.

(a) and (b) of FIG. 9 are photographs showing the appearance of the slag before and after the drop strength test in the case where the mold contact surface at the time of solidification is glassy.

Fig. 10 is a graph showing the relationship between the drop strength and the ratio of the vitreous portion at the contact surface of the mold at the time of solidification.

Fig. 11 is a graph showing the product yield at the time of producing a 20 mm to 5 mm thick aggregate in the present invention example and a comparative example.

Fig. 12 is a graph showing the amount of bleeding in each of the examples of the present invention and the comparative examples in the concrete using the coarse aggregate.

Hereinafter, the present invention will be specifically described.

The method for producing a solidified slag according to the present embodiment includes a slag solidification step of flowing molten blast furnace slag into a moving metal mold to be cooled, and solidifying the mold in a plate shape. a slag dropping step of inverting the mold so that the slag which has solidified to the inside in the mold falls from the mold; and a slag temperature maintaining step, a part of the surface of the slag of the fallen slag or The surface temperature of the entire surface was maintained at 900 ° C or higher for 5 minutes or more.

An example of a solidified slag production apparatus that can realize the method for producing the solidified slag is shown in Fig. 1 . The solidified slag manufacturing apparatus 1 (FIG. 1) shown in FIG. 1 has a plurality of depressed portions 5a (recessed part) in which molten slag is contained in a molten state accommodated in the slag pot 23, that is, molten slag 3 flows therein. The metal mold 5 is supported so as to be able to move around, and the molten slag 3 is continuously flowed into the recessed portion 5a while the mold 5 is being surrounded, thereby continuously producing the solidified slag 18.

The solidified slag manufacturing apparatus 1 that performs such an operation includes a surrounding moving mechanism 7 that is circumferentially moved in a horizontal direction in a state in which a plurality of molds 5 are brought close to each other. The surrounding moving mechanism 7 includes an air-cooling moving portion 9 that moves the mold 5 in the circumferential direction while holding the molten molten slag 3 in the recessed portion 5a while the mold is being wound for one week. The slag 3 is air-cooled and solidified; the discharge portion 11 is reversed, and the mold 5 is reversed so that the depressed portion 5a faces downward, and the solidified slag 18 is discharged; the moving portion 13 is reversed to keep the inverted mold 5 reversed. Moving in the rotated state; the reversing portion 15 re-inverts the mold 5 in the inverted state so that the depressed portion 5a faces upward; and then reversing the moving portion 17 to move the re-inverted mold 5 to melt melting The cooling device 21 cools the inverted mold 5 until the portion where the slag 3 flows. The reversing movement unit 17 can also be omitted. Further, the solidified slag production apparatus 1 is provided with a flow tank 20 in order to allow the molten slag 3 to easily flow into the mold 5.

Further, the solidified slag manufacturing apparatus 1 has a pit 19 provided below the surrounding mold 5 of the reverse discharge portion 11, and a solidified slag holding container capable of accommodating 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 the following capacity, that is, The solidified slag 18 corresponding to the amount of one cup of the molten slag 3 of the slag pot 23 can be held, and after the cup of the solidified slag 18 of the slag pot 23 is accommodated, it can be carried out from the slag dropping position, and The container 22 is replaced with an empty solidified slag. According to this, even if the slag is held for a certain period of time in the solidified slag holding container 22, the waiting time is not generated and the productivity is lowered, and then the molten slag 3 of the next slag pot 23 can be processed. .

From the viewpoint of heat retention, it is preferable that at least a part of the bottom surface and the side surface of the solidified slag holding container 22 contain a low thermal conductivity fire resistance of about 5 W/(m.K) or less along the normal direction of each surface. Things. Further, a form or the like may be selected in which a lid is provided on the solidified slag holding container 22 after the solidified slag 18 is accommodated, or a simple heat source such as a burner is attached to the solidified slag holding container 22; The pit 19 in which the slag is dropped is itself used as a solidified slag holding container, and the outer lid is placed and held after the solidified slag is contained.

An example of a method of producing the solidified slag 18 by using the solidified slag production apparatus 1 of the present embodiment configured as described above will be described together with the operation of the solidified slag production apparatus 1.

The surrounding moving mechanism 7 is rotated at a predetermined speed, and the molten slag 3 flows into the surrounding mold 5 via the launder 20 at the molten slag inflow portion. The mold 5 that has flowed into the molten slag 3 moves in the air-cooling moving portion 9, and the molten slag 3 is air-cooled to become the solidified slag 18 (slag solidification step).

Here, it is preferable that the circumferential moving speed of the mold 5 and/or the flow of the molten slag 3 is such that the thickness of the solidified slag 18 is 20 mm or more and 30 mm or less. The speed of entry is controlled. When the thickness of the solidified slag is 20 mm or more, the solidified slag 18 is pulverized, whereby a widely used particle size distribution of a coarse aggregate product suitable for ordinary coarse aggregate size, that is, 5 mm to 20 mm can be obtained. In addition, when the thickness of the solidified slag 18 is 20 mm or more, as described later, when the solidified slag 18 is charged into the solidified slag holding container 22, the average amount of heat can be sufficiently increased. Therefore, the solidification slag 18 can be kept warm only by adding a heat source, and the slag surface temperature of the mold contact surface can be raised to 900 ° C or more for 5 minutes or longer.

On the other hand, when 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 rate of the coarse aggregate product can be reduced to 1.5% or less. Further, it is preferable to obtain high-strength coarse aggregate particles having a compressive strength of 100 N/mm ² or more.

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

The mold 5 from which the solidified slag 18 is discharged moves in the reverse rotation state in the reverse rotation state, and is cooled by the cooling device 21 while moving.

The mold 5 that has reversed the moving portion 13 is rotated in the circumferential direction in the reversing portion 15 and reversed so that the depressed portion 5a faces upward. In the mold 5 which has been re-inverted, the molten slag 3 flows into the slag inflow portion again immediately after the reversal or after moving in the reversing movement portion 17.

The solidified slag discharged to the pit 19 and loaded into the solidified slag holding vessel 22 18, laminating in the solidified slag holding container 22, by solidifying the heat of the slag 18 itself, the temperature of the mold contact surface of the solidified slag 18 which is lowered during solidification rises. At this time, by maintaining the slag surface temperature of the fallen solidified slag 18 at 900 ° C or higher for 5 minutes or longer, the glassy material of the mold contact surface of the solidified slag 18 can be changed to a crystalline form (the slag temperature is maintained). step). After the glass quality is changed to 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 of a slag solidification step, a slag dropping step, and a slag temperature maintaining step, and among the three steps, in particular, the slag temperature maintaining step has characteristics, and thus This will be described in detail below.

<Reason for the slag temperature retention step>

When the cross section of the plate-shaped solidified slag 18 dropped from the mold 5 is observed, the range from the contact surface of the mold to about 1 mm 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 only accelerated in this portion. Even if the solidified thickness of the solidified slag 18 changes, the vitreous portion is about 1 mm from the mold contact surface.

The surface temperature of the atmospheric side of the solidified slag 18 was measured using a radiation thermometer, and a thermocouple was placed on the back surface of the mold. In the case where the thickness of the solidified slag 18 was 23 mm, the molten slag 3 which was flowed onto the mold was The temperature transition until the process of cooling and solidification was measured. The measurement results are shown in Fig. 3. In addition, the slag temperature of the center position in the thickness direction of the slag and the position in contact with the mold 5 obtained by heat transfer analysis which will be described later is shown in FIG. shift. The slag at the position in contact with the mold 5 is remarkably increased by the heat conduction to the mold, and is lowered to 400 ° C in about 15 seconds, and then becomes a substantially constant temperature. The temperature drop in the center portion of the slag was slow and decreased to about 1150 ° C after 2 minutes, and the surface on the atmosphere side was only lowered to about 900 ° C after 2 minutes.

As described above, in the present embodiment in which the molten slag 3 is mainly cooled by heat conduction to the mold 5, the contact surface of the mold is quenched, and the thermal conductivity of the slag is small, and is 2 W/(m.K) or less, so that the inside of the slag is inside. The heat conduction is slow, and the cooling rate outside the contact surface of the mold is small. Therefore, only the slag of the mold contact surface is quenched and vitrified. When the mold 5 is reversed and the solidified slag 18 which has fallen from the mold 5 is conveyed one by one, the cooling during the transfer proceeds from the surface, and the glass quality of the surface remains directly.

When the vitreous material remains, as described above, when it is used as a coarse aggregate for concrete, there is a problem that bleeding easily occurs or the yield of the coarse aggregate is lowered. Therefore, it is necessary to reform the vitreous portion into crystal. quality.

Therefore, a temperature maintaining step of modifying the vitreous portion to a crystalline form is required.

<Study on cooling rate by analysis>

Corresponding to how to modify the vitreous part to crystalline form was studied. At the time of the study, the cooling rate inside the slag was investigated by heat transfer analysis. The process solidifies the slag into a plate shape, and thus the temperature during cooling and solidification can be considered to be a single plate of unsteady one-dimension heat conduction. This basic formula is the following formula (1).

[Expression 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 in which slag is contained in a mold, and Fig. 4(b) shows solidified slag which falls from a mold. As shown in Fig. 4 (a) and Fig. 4 (b), the slag and the thickness direction of the mold were divided into 10 parts and the mold was divided into 10 parts. Only the solidified slag was calculated after falling from the mold.

Here, the thermal conductivity hs of the interface of the atmosphere-slag, the thermal conductivity hm of the mold-atmosphere interface, and the thermal resistance R of the slag-mold interface are set as parameters, and the calculated values of the temperature and the measured values of FIG. The way to match determines the value of the parameter. The atmospheric-slag interface has a temperature difference of 1300 K or more at an initial stage, and thus 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-insulating state, and there is no heat transfer to the outside of 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 according to the following formulas (2) and (3).

When T>1400K, λ=-5.0×10 ^-3 T+9.20...(2)

When T≦1400K, λ=7.78×10 ^-4 T+1.11...(3)

The heat capacity measurement result of blast furnace slag based on Ogino et al. (K. Ogino and J. Nishiwaki, "Steel Property Value Handbook" Ironmaking (2006) p.350, Japan Iron and Steel Association (shares), (independent) Japan Society for the Promotion of Science, the 54th Committee of the Iron and Steel Association, the specific heat of the slag Cp at T < 1443K, set Cp = 1039 J / (kg. K), at 1443K ≦ T < When it is 1673K, it is set to Cp=2242.5 J/(kg.K), and when 1673K≦T<1773K, it is set to Cp=1326 J/(kg.K).

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

Thereby, the temperature change of the slag can be calculated, and the temperature condition and the holding time of the slag temperature maintaining step are investigated based on the temperature change.

<temperature condition>

The surface temperature required to crystallize the vitreous portion was investigated. The surface temperature of the solidified slag immediately after the slag dropping step is changed depending on the solidification thickness of the slag and the cooling time of the slag until the slag is reversed. Therefore, by changing the solidification thickness of the slag and the cooling time, the surface temperature of the solidified slag is changed, and the solidification of the surface temperature is variously changed. The slag was held in the solidified slag holding container for 24 hours, and the relationship between the highest temperature of the mold contact surface of the solidified slag and the area ratio of the vitreous portion was investigated. As a result, it was confirmed that in order to crystallize the vitreous portion, it is effective to raise the surface temperature to 900 ° C or higher.

<hold 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 removed, the holding time in the solidified slag holding container is changed, and the mold for self-solidified slag is molded. The holding time from the time when the surface temperature of the contact surface side rises to 900 ° C, that is, the time when the surface temperature of the slag is maintained at 900 ° C or more, and the area ratio of the vitreous portion of the mold contact surface of the solidified slag We conducted a survey.

Specifically, in the solidified slag production apparatus shown in the embodiment to be described later, 12 tons of molten slag 3 is continuously processed in 6 minutes by repeating the circumference of the metal mold 5 for 2 weeks, and the solidified slag 18 is oriented. After the storage of the solidified slag holding container 22 is completed for a predetermined period of time, the solidified slag 18 is discharged to the slag cooling bed 24 and diffused immediately after the predetermined holding time is reached, and is cooled in the atmosphere, wherein the cooling is performed in the atmosphere. The solidified slag holding container 22 is disposed at a position where the slag is dropped when the mold 5 is reversed.

In order to calculate the holding time of 900 ° C or more, it is necessary to specify the time point at which the surface temperature of the mold contact surface side of the molten slag rises to 900 ° C and the time point to fall to less than 900 ° C. Therefore, the surface temperature of the molten slag on the contact surface side of the mold rises to 900 ° C, and the final solidified slag is placed in the solidified slag holding container. When the surface temperature of the slag contact surface side of the slag reaches 900 ° C, the heat transfer analysis assumes that the surface of the slag in the solidified slag holding vessel is an adiabatic boundary condition. Time point. Further, the time point at which the surface temperature was lowered to less than 900 ° C was set as the time point at which the solidified slag was discharged from the solidified slag holding container to the slag cooling bed and diffused. This is based on the assumption that the surface temperature of the solidified slag is immediately lowered to less than 900 ° C at the point of time when the solidified slag is discharged from the solidified slag holding vessel to the slag cooling bed and diffused.

Fig. 5 is a graph showing the relationship between the glass area ratio (%) and the time (min) at which the temperature is maintained at 900 °C or higher. As shown in the graph of Fig. 5, it is understood that the area ratio of the vitreous portion of the mold contact surface is reduced to about 10% by holding at 900 ° C or higher for 5 minutes, and the area of the vitreous portion is further increased even if the holding time is further increased. 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 longer.

In addition, even if the holding time of 900 ° C or more in FIG. 5 is extended from 5 minutes, the area ratio of the vitreous portion is not significantly lower than about 10%, and it is considered that it is based on the following: In the outermost layer portion of the solidified slag in the slag holding container, the solidified slag having the mold contact surface facing upward does not rise to 900 ° C or higher and does not crystallize even if the holding time is extended. Therefore, when the slag holding container is provided with a lid after the slag is accommodated or reheated by using a simple heating source such as a burner, the area ratio of the vitreous portion can be further reduced.

Further, the reason why the calculated value of the holding time at 900 ° C or higher in FIG. 5 is zero, and a part of the glassy slag is crystallized is considered to be based on the following: for holding the slag in the initial stage of the slag treatment. In the solidified slag in the lower portion of the deposition layer in the container, the surface temperature rises until the final solidified slag is accommodated, and is maintained at 900 ° C or higher for 5 minutes or longer. In other words, it is considered that the solidified slag contained in the slag holding container in the initial stage of the slag treatment satisfies the conditions of crystallization and is crystallized.

Then, it was confirmed whether the temperature condition and the holding time were ensured by laminating the solidified slag which fell by the slag dropping step.

<Slag temperature in the holding state>

For the solidified slag having a slag thickness of 25 mm, the temperature distribution immediately before falling from the mold was calculated. As an example, FIG. 6 shows a calculation result of the temperature distribution inside the solidified slag 18 after 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 . It is considered that the temperature of the solidified slag immediately after being discharged from the mold is substantially the same as the temperature of the solidified slag immediately before falling from the mold, and therefore is expressed as "just after being discharged from the mold" in Fig. 6 .

In the solidified slag immediately after being discharged from the mold, the temperature at the contact surface of the mold and the air surface is lowered, and the internal temperature is high. When the solidified slag is dropped into the holding container in this state, and the layers are accumulated and accumulated, the slag inside the build-up layer is kept in a kept state, so that the heat inside the slag is transferred to the mold contact surface side at the time of solidification as time passes. And the atmosphere side, the slag as a whole is close to a uniform temperature distribution. The temperature distribution calculation result after 3 minutes is indicated by a broken line in Fig. 6 . Temporarily reduced in this condition The temperature at the contact surface of the mold also rises to a temperature of about 1000 °C.

In the method for producing a solidified slag according to the present invention, after the solidified slag is dropped from the mold and discharged, it is necessary to raise the surface temperature of a part or the entire surface of the molten slag containing the solidified slag of the mold contact surface to 900 ° C or higher. And keep it for more than 5 minutes. It is confirmed that the average temperature of the solidified slag discharged from the mold in the thickness direction of the slag exceeds 900 ° C, and the solidified slag is laminated in the pit 19 or the solidified slag holding container, thereby implementing the facility without using a new heating source. Step

<temperature of molten slag layer>

When the surface temperature of the slag is raised to 900 ° C or higher by the heat content of the solidified slag itself, the slag of the solidified slag can be appropriately selected and the mold can be reversed until the solidified slag is dropped. The cooling time and the holding time in the solidified slag holding container are achieved. This point will be specifically described below.

For example, FIG. 7 shows that the cooling time after the molten slag is injected into the mold is set to 2 minutes, and the holding time in the solidified slag holding container after the final solidified slag is dropped and stored is set to 3 minutes ( In the case of 180 seconds), the average value of the slag thickness is related to the surface temperature of the slag in the slag accumulation layer in the solidified slag holding container.

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

On the other hand, the solid line shows the calculated value of the temperature of the mold contact surface of the solidified slag, and is the temperature immediately after being discharged from the mold, and is kept as the solidified slag under the surface layer in the solidified slag holding container. Temperature after minutes (180 seconds). As shown in Fig. 7, as long as the average thickness is 20 mm or more, the calculated temperature of the mold contact surface of the solidified slag after holding for 3 minutes exceeds 900 °C, and the higher 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 of the layer in the container is kept as high as the calculated slag thickness, and the solidified slag having an average thickness of 22 mm or more after the test is 3 minutes. After that is 900 ° C or more. In other words, it is confirmed that the measured value of the surface temperature of the solidified slag under the surface layer is in good agreement with the calculation result, and the solidified slag having an average thickness of 20 mm or more is laminated based on the calculation result and the measured value, whereby the solidification can be melted after 3 minutes. The surface temperature of the slag is 900 ° C or higher.

Further, in the case where the heat source for raising the surface temperature of the solidified slag is only the heat of the solidified slag itself, in order to reduce the influence of heat radiation on the outside, it is necessary to store the layer in the solidified slag holding container. The amount of solidified slag is ensured to a certain amount. Specifically, it is preferable to store the solidified slag layer of 5 tons or more, more preferably 10 tons or more, in a thickness of 1 m or more.

Plate-shaped solidified slag cast from metal mold and slow-cooled slag When the average solidification rate is large, the crystal grains tend to be small, and as described later, the residual stress in the vicinity of the contact surface of the mold can be alleviated and the strength characteristics are better than that of the slow cooling slag. Material.

Further, in the solidified slag produced by the method for producing a solidified slag of the present invention, the drop strength (Watter Index) defined below is 70% or more, and the drop strength is obtained by the method for producing the solidified slag of the present invention (Shatter Index) ) is a high-strength plate-shaped solidified slag of 70% or more. In addition, by using a plate-shaped solidified slag having a drop strength of 70% or more and cast by a metal mold, the solidified slag is pulverized and sieved to produce a slag product such as a coarse aggregate for concrete. The rate is increased.

Further, the solidification of slag in the slag by the method of the present invention for producing solidified manufactured crushing, screening the coarse aggregate obtained, an average compressive strength measurement method described later is ² or more concrete 100N / mm with crude The aggregate is suitable as a raw material for coarse aggregates in the manufacture 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 a plan view, and has a thickness of 45 mm, and an outer dimension of a mold corresponding to a trapezoidal upper bottom is set to 0.7 m, and a mold corresponding to a trapezoidal lower bottom is used. The outer dimension was set to 1.0 m, and the outer dimension of the mold corresponding to the height of the trapezoid was set to 2.7 m. Further, the depth of the depressed portion 5a of the mold 5 flowing into the molten slag was set to 100 mm. Casting mold 5 by surrounding moving mechanism 7 The conveyance speed of the surrounding conveyance and the surrounding conveyance was set to 14 m/min at the center of the mold.

At the slag inflow portion, the blast furnace slag in a molten state of 1360 ° C or more and 1410 ° C or less is allowed to flow into the mold 5 at about 2 ton / min. The mold 5 that has flowed into the molten slag 3 is conveyed in the air-cooling moving portion 9 for about 120 seconds (the length of the air-cooling moving portion 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 reversed in the reverse discharge portion 11, and the solidified slag 18 that has been peeled off from the mold is dropped to 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 in the reverse rotation state in the reverse movement portion 13, and the cooling water is sprayed from the upper and lower surfaces at the portion where the cooling device 21 is provided to be rapidly cooled.

Then, the mold 5 in the inverted state is reversed again by the reversing portion 15, and the original depressed portion 5a is returned to the upward state again. Then, the molten slag is again flowed into the restored mold. The above procedure was repeated for 5 weeks for one slag pot, and 30 tons of molten slag was continuously treated in 15 minutes.

After all of the solidified slag has fallen from the mold, it is held in the solidified slag holding vessel for a predetermined period of time, and then the solidified slag is discharged from the solidified slag holding vessel to the slag cooling bed and diffused, and is cooled in the atmosphere.

In the example of the present invention, the molten slag temperature is 1385 ° C, the holding time after the slag storage in the solidified slag holding container is completed is 10 minutes, and the average thickness of the solidified slag is 25 mm. Immediately after the specified holding time, the solidified slag is discharged from the solidified slag holding container to the slag cooling bed and diffused. And it is cooled in the atmosphere.

In the comparative example, the molten slag temperature was 1380 ° C, and the average thickness of the solidified slag was 23 mm, so that the solidified slag fell from the mold to the pit, and immediately after all the solidified slag fell from the mold, the forklift was used ( Shovel car) removes the solidified slag from the pit and cools it in the slag cooling bed for the treatment of the molten slag in the next 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 effect of the solidification thickness on the glassy existence of the mold contact surface is not in the range of 20 mm to 26 mm.

In the solidified slag after cooling, the ratio of the vitreous portion 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) of the mold contact surface was sorted from the solidified slag produced by the present invention by visual observation, and on the other hand, solidified by the comparative example by visual observation. In the slag, the contact surface of the mold was sorted into a vitreous solidified slag, and a drop test was performed.

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

In the solidified slag of the comparative example in which the mold contact surface of the solidified slag is divided into glass, as shown in FIG. 9(b), the whole is finely pulverized by dropping. This is because a large residual stress is generated in the vicinity of the surface which is a large temperature gradient at the time of solidification, and therefore, even a relatively small impact of a drop of 1 m is likely to be broken.

On the other hand, in the solidified slag produced by the method for producing a solidified slag according to the present invention, as shown in FIG. 8(b), there is almost no breakage of the entire end portion due to falling, and thus A high-strength plate-shaped solidified slag is formed. This is because the residual stress near the surface is alleviated or eliminated when the vitreous portion of the mold contact surface is crystallized.

The drop strength (Shatter Index) was measured by the method described below. The apparatus for the drop strength test used the apparatus described in the Japanese Industrial Standards (JIS) M8711 iron ore sinter-drop strength test method. A sample of a plate-shaped solidified slag of 40 mm to 100 mm (a sample of a plate-shaped solidified slag which passed through a sieve having a diameter of 100 mm and passed through a sieve having a diameter of 40 mm; about 3 kg) was used, and a height of 2 m was used. 4 drop test. After the drop test, a ratio of not pulverized to 40 mm or less (mass ratio of a sample which did not pass through a sieve having a hole diameter of 40 mm) was determined, and the ratio was defined as a drop strength. Regarding other test conditions, JIS M8711 iron ore sintered ore-falling strength measuring method is used as a test method for sintered ore.

The drop strength of the slab slag is calculated by the following formula (4).

S (%): A / B × 100 ... (4)

S: Drop strength of plate slag determined to be 40 mm or more (Shatter Index)

A: mass of 40mm or more after the test (kg)

B: mass of the sample from 40mm to 100mm before the test (kg)

The relationship between the ratio of the vitreous portion of the mold contact surface and the drop strength S is shown in Fig. 10 as a result of comparison between the inventive example and the comparative example. In the example of the present invention, the ratio of the vitreous portion was decreased from 52% by area to 9 area% of the comparative example, and the falling strength S was increased from 46% to 89% of the comparative example.

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

Then, in order to make the solidified slag of the inventive example and the comparative example produced as described above a concrete coarse aggregate, 10 tons of plate-shaped solidified slag was pulverized using an impact crusher. Then, the pulverized slag was sieved with a sieve of 20 mm and 5 mm. Thereby, a coarse aggregate for concrete of 20 mm to 5 mm is produced.

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

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

Further, the compressive strengths of the slag coarse aggregates of the inventive examples and the comparative examples were compared. In the sample for measuring the compressive strength, a slightly larger rough aggregate particle including a flat surface was used, and the flat surface was used as a bottom surface, and a size of 10 mm × 10 mm × 10 mm was cut by a diamond cutter, and Anstron type compression was used. The test machine (Universal testing machine) measures the compressive strength of each of the six samples.

The sample obtained from the coarse aggregate of the comparative example had an average value of compressive strength of 50 N/mm ² and a minimum value of 10 N/mm ² , and there was a coarse aggregate sample having extremely large unevenness and very low strength. On the other hand, the average value of the compressive strength of the sample taken from the coarse aggregate of the present invention was 167 N/mm ² and the lowest value was 80 N/mm ² , thereby stably obtaining high compressive strength.

The slag coarse aggregates of the inventive examples and comparative examples were used to formulate concrete and the characteristics were evaluated. The amount of bleeding was compared in the fresh concrete in which the coarse aggregate of the present invention was formulated and the fresh concrete in which the coarse aggregate of the comparative example was blended. The results of the survey are shown in Fig. 12. The example of the present invention having a small glassy surface has a smaller amount of bleeding than the comparative example of the vitreous surface.

Next, using each of the coarse aggregates, the concrete was agitated by purging a high-intensity water-cement ratio of 35%, thereby preparing a test body for compressive strength measurement, and performing 28-day strength. Comparison. For comparison, the same is true for the production of commercially available natural limestone for coarse aggregates. Test the body and evaluate it.

In the concrete using the coarse aggregate of the comparative example, the strength at the 28th was 53 N/mm ² , whereas the concrete using the coarse aggregate of the present invention had a strength of 75 N/mm ^{2 at} 28 days. 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 present invention obtained a 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 the present invention is a material suitable as a coarse aggregate for high-strength concrete.

1‧‧‧ Solidified slag manufacturing equipment

3‧‧‧ molten slag

5‧‧‧ mould

5a‧‧‧Depression

7‧‧‧ Surrounding mobile agencies

9‧‧‧Air Cooling Department

11‧‧‧Reverse discharge department

13‧‧‧Reverse movement department

15‧‧‧Reversal

17‧‧‧Reverse the mobile department

18‧‧‧ Solidified slag

19‧‧ ‧ pit

20‧‧‧Rough

21‧‧‧Cooling device

22‧‧‧ Solidified slag holding container

23‧‧‧ slag pot

Claims (8)

A method for producing a solidified slag, comprising: a slag solidification step of flowing molten blast furnace slag into a moving metal mold to be cooled, and solidifying in a plate shape in the mold; a slag dropping step of inverting the mold to cause the slag which has solidified to the inside in the mold to fall from the mold; and a slag temperature maintaining step, without adding a heat source but by dropping the slag itself The heat is provided to lower the falling slag to a surface temperature of a part or the entire surface of the slag surface of less than 900 ° C at 900 ° C or more for 5 minutes or more. The method for producing a solidified slag according to the first aspect of the invention, wherein the blast furnace slag solidified in the mold in a form of a plate has a thickness of 20 mm or more and 30 mm or less. The method for producing a solidified slag according to the first or second aspect of the invention, wherein in the slag temperature maintaining step, mold contact at the time of solidification in the surface of the solidified slag falling from the mold 80% by area or more of the surface, and the surface temperature of the slag is maintained at 900 ° C or higher for 5 minutes or longer. The method for producing a solidified slag according to the first or second aspect of the invention, wherein the slag temperature maintaining step causes the solidified slag falling from the mold to have an average temperature in the slag thickness direction of more than 900 Laminating at °C. The manufacturer of the solidified slag as described in claim 1 or 2 of the patent application In the slag temperature maintaining step, the solidified slag falling from the mold is laminated in a holding container that can be carried out from the falling position. A solidified slag produced by the method for producing a solidified slag according to any one of claims 1 to 5, which is passed through a sieve having a pore diameter of 100 mm without passing through the pore diameter The slag sample of the 40 mm sieve, after falling down from the height of 2 m for 4 times, the drop strength of the sample which was not passed through the sieve having a diameter of 40 mm with respect to the mass ratio of the sample before the drop test (broken The crack index) is 70% or more. A method for producing a coarse aggregate for concrete, comprising: a solidification slag production step, comprising the method for producing a solidified slag according to any one of claims 1 to 5; and a solidification slag crushing step And pulverizing the solidified slag produced; and screening step of screening the pulverized solidified slag. A coarse aggregate for concrete, which is produced by the method for producing a coarse aggregate for concrete according to claim 7, and has an average compressive strength of 100 N/mm ² or more.