WO2015025501A1

WO2015025501A1 - Method for producing solidified slag, solidified slag, method for producing coarse aggregate for concrete, and coarse aggregate for concrete

Info

Publication number: WO2015025501A1
Application number: PCT/JP2014/004157
Authority: WO
Inventors: 博幸當房; 恵太田; 勇樹萩尾; 渡辺　圭児; 桑山　道弘; 大輔今西
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2013-08-20
Filing date: 2014-08-08
Publication date: 2015-02-26
Also published as: TW201512147A; TW201802057A; TWI659005B; KR101839667B1; CN105452187A; TWI613178B; JP6184476B2; JPWO2015025501A1; CN105452187B; KR20160013180A

Abstract

Provided are a method for producing solidified slag capable of serving as a raw material for a good-quality coarse aggregate for concrete, solidified slag produced by the method for producing solidified slag, a method for producing coarse aggregate for concrete using the solidified slag, and a coarse aggregate for concrete produced by the method for producing coarse aggregate for concrete. This method for producing solidified slag comprises a slag solidification step wherein blast furnace slag (3) in a molten state is poured into a moving metal template (5) and cooled so as to solidify in a plate-shape inside the template, a slag dropping step wherein the slag solidified to the interior while inside the template is dropped from the template by inverting the template, and a slag temperature holding step wherein the surface temperature is held at 900°C or higher for 5 minutes or longer for a portion of the slag surfaces or all the surfaces of the dropped slag.

Description

Solidified slag manufacturing method, solidified slag, concrete coarse aggregate manufacturing method, concrete coarse aggregate

The present invention relates to a solidified slag that solidifies molten blast furnace slag (blast 炉 furnace slag) on a metal mold and drops the solidified slag (solidified slag) from the mold to produce a plate-like solid slag. Produced by a production method, a solidified slag produced by the method for producing the solidified slag, a method for producing coarse aggregate for concrete (coarse 該 aggregate for concrete) using the solidified slag, and a method for producing the coarse aggregate for concrete It relates to coarse aggregate for concrete.

As a method of solidifying molten slag generated in a metal refining process, etc., high-pressure cooling water is sprayed onto the molten slag to quench it, or the molten slag is dried into a dry pit or slag cooling yard. A method of discharging to (slag cooling yard) and gradually cooling in the atmosphere is widely used.

In the method of rapidly cooling the molten slag, a large amount of high-pressure cooling water is blown, resulting in a sand-like solidified slag having a large particle size of 5 mm or less (so-called water granulated slag). . On the other hand, in a method in which molten slag is solidified by flowing it into a dry pit or slag cooling yard, etc., and gradually cooled, it becomes a lump of a size of several meters, which is crushed into a solidified slag (so-called gradually cooled slag (air-cooled slag) cooled slag)).

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

Therefore, granulated slag cannot be applied to coarse aggregate for concrete because it has many pores and small particle size. On the other hand, although slow cooling slag does not have a problem of pores, it is necessary to crush a mass of several meters to a particle size of about 20 mm, and this crushing requires a huge amount of time and is not efficient.

Therefore, as a coarse aggregate for concrete, various techniques for solidifying molten slag using a metal mold have been proposed in order to obtain solidified slag with few pores and easy to crush. Solidifying molten slag in a metal mold yields solidified slag that is larger than granulated slag and smaller than slowly cooled slag, and can be easily crushed by crushing it. Compared to slowly cooled slag, the time for crushing can be shortened, and a desired solidified slag having a particle size of about 20 mm can be easily obtained.

Examples of solidifying molten slag using a metal mold include, for example, aggregate for asphalt pavement described in Patent Document 1, a manufacturing method thereof, and asphalt pavement. In the solidification method of molten slag of Patent Document 1, the molten blast furnace slag is cooled and solidified by flowing it in a single layer on a metal moving mold so that the layer thickness is 10 to 30 mm. The solidified slag. This single-layer plate-like slag is crushed to produce an aggregate for asphalt pavement having a water absorption percentage of 1.5% or less and an abrasion loss of 20% or less.

Further, as a method for producing a coarse aggregate for concrete by solidifying blast furnace slag using a metal mold, there is a coarse aggregate for concrete disclosed in Patent Document 2. The coarse aggregate for concrete made of slag disclosed in Patent Document 2 is made by pouring molten slag into a metal mold to solidify, crushing the slag obtained after solidification, water absorption of 1.5% or less, and particle size Is adjusted to 5 to 20 mm.

Japanese Patent No. 3855706 JP 2004-277191 A

The method for solidifying molten slag described in Patent Document 1 is to cool and solidify a molten blast furnace slag by pouring it into a metal moving mold in a single layer so that the solidified thickness is 10 to 30 mm. By rapidly cooling and solidifying, growth of pores generated in the solidified slag is suppressed, and aggregates with low porosity, low water absorption, and high abrasion resistance are produced.

However, as described in the example of Patent Document 1, when the blast furnace slag is solidified in a plate shape on a metal mold, about 1 mm from the lower surface in contact with the metal mold is glassy (glassy state). )Become. This is because, in molten slag, the contact surface with the metal mold is cooled most rapidly and becomes glassy (glassy state), but since the thermal conductivity of the molten slag is very small, the cooling rate inside the molten slag By solidifying in a crystalline state without becoming large.

As described above, in the method of Patent Document 1, a plate-like solidified slag having a glassy surface on one side is generated. When an aggregate is produced by crushing such a plate-like solidified slag, a part of the surface is formed. Coarse aggregate that is glassy is produced. When a coarse aggregate having a glassy surface is used as a coarse aggregate for concrete, there is a problem that it is likely to be bleeding when the fresh concrete is solidified. Breathing is a phenomenon in which a part of kneaded water is released and rises to the surface due to sedimentation or separation of a solid material in fresh concrete.

Also, it is easy to break at the boundary between the vitreous part and the crystalline part of about 1 mm from the surface that has been in contact with the metal mold. Therefore, when crushing and adjusting to a coarse aggregate particle size, the vitreous portion tends to be fine, and there is also a problem that the yield of the coarse aggregate decreases.

The coarse aggregate for concrete disclosed in Patent Document 2 uses blast furnace slag solidified on a metal mold as in Patent Document 1, and the blast furnace slag is crushed to obtain a water absorption of 1.5% or less. A coarse aggregate having a particle size of 5 to 20 mm is used. Molten slag is poured into a metal mold and solidified to a thickness of 20 to 30 mm, and the contact surface with the metal mold is likely to be vitrified as in Patent Document 1. The compressive strength of the concrete blended with the coarse aggregate for concrete of Patent Document 2 (mixcurproportion) and curing period (curing period) of 7 days and 28 days is clear, but breathing is not clear.

The present invention has been made to solve the above problems, and a method for producing solidified slag that can be a raw material for high-quality concrete coarse aggregate, and a solidified slag produced by the method for producing solidified slag. Another object is to provide 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 the coarse aggregate for concrete.

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

[1] A slag solidification step in which molten blast furnace slag is poured into a moving metal mold, cooled and solidified into a plate shape in the mold, and slag solidified to the inside in the mold. A slag dropping step of inverting the mold and dropping from the mold, and a slag temperature holding step of holding the surface temperature of a part or the entire surface of the slag of the dropped slag at 900 ° C. or more for 5 minutes or more. Production method.

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

[3] In the slag temperature holding step, the slag surface temperature is maintained at 900 ° C. or more for 5 minutes or more for 80 area% or more of the mold contact surface during solidification among the surfaces of the solidified slag dropped from the mold. The method for producing a solidified slag according to [1] or [2] above, wherein

[4] In any one of [1] to [3], in the slag temperature holding step, the solidified slag dropped from the mold is laminated with an average temperature in the slag thickness direction exceeding 900 ° C. The manufacturing method of solidification slag as described in a term.

[5] In any one of the above [1] to [4], in the slag temperature holding step, the solidified slag dropped from the mold is stacked in a holding container that can be carried out from the dropping position. 2. A method for producing a solidified slag according to item 1.

[6] A solidified slag produced by the method for producing a solidified slag according to any one of [1] to [5] above, passing through a sieve having an opening of 100 mm and passing through a sieve having an opening of 40 mm. The drop strength (Shatter Index) evaluated by the mass ratio of the sample that does not pass through the 40 mm aperture sieve to the sample before the drop test is 70% or more after the drop test in which the slag sample is dropped 4 times from a height of 2 m. Some solidified slag.

[7] A solidified slag production process including the method for producing a solidified slag according to any one of [1] to [5], a solidified slag crushing process for crushing the produced solidified slag, and a crushed solidified slag A method for producing a coarse aggregate for concrete, comprising a classification step of classifying the material.

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

According to the method for producing a solidified slag according to the present invention, the vitreous portion formed on the contact surface of the solidified slag with the metal mold is crystalline while the slag surface temperature is maintained at 900 ° C. or higher for 5 minutes or longer. Since it changes, solidified slag with high drop strength can be obtained. In addition, the coarse aggregate for concrete produced by further crushing and classifying the solidified slag produced by the method for producing solidified slag according to the present invention has a small proportion of vitreous portions on the surface, High strength can be obtained stably, and a coarse aggregate suitable for producing high-strength concrete can be obtained.

FIG. 1 is a schematic view schematically showing a configuration of an embodiment of a solidified slag production apparatus that realizes a solidified slag production method according to the present invention. FIG. 2 is a schematic view schematically showing a solidified slag holding container in the solidified slag manufacturing apparatus shown in FIG. FIG. 3 is a graph showing the temperature transition at each measurement position when the slag is cooled on a metal mold. FIG. 4 is a schematic diagram showing a one-dimensional heat transfer analysis model of a slag and a mold. FIG. 5 is a graph showing the relationship between the holding time of the slag at a surface temperature of 900 ° C. or more and the glassy area ratio in the mold contact surface during solidification. FIG. 6 is a graph showing the calculation result of the temperature distribution in the thickness direction of the solidified slag. FIG. 7 shows the measured surface temperature of the slag below the solidified slag on the surface layer deposited in the solidified slag holding container 3 minutes after slag storage, and immediately after discharge from the mold at the mold contact surface of the solidified slag and It is a graph which shows the relationship between the calculated value of the slag temperature after hold | maintaining as solidified slag under a surface layer for 3 minutes within a solidified slag holding container, and slag thickness. FIG. 8 is a photograph showing the appearance of the slag before and after the drop strength test when the mold contact surface during solidification is crystalline. FIG. 9 is a photograph showing the appearance of the slag before and after the drop strength test when the mold contact surface during solidification is glassy. FIG. 10 is a graph showing the relationship between the drop strength and the vitreous portion ratio in the mold contact surface during solidification. FIG. 11 is a graph showing the product yield at the time of manufacturing a coarse aggregate of 20 to 5 mm by comparing the example of the present invention with the comparative example. FIG. 12 is a graph showing a comparison of the amount of breathing in concrete using the coarse aggregates of the present invention example and the comparative example.

Hereinafter, the present invention will be specifically described.

The method for producing solidified slag according to the present embodiment includes a slag solidification step in which molten blast furnace slag is poured into a moving metal mold, cooled, and solidified into a plate shape in the mold, A slag dropping step in which the slag solidified inside the mold is dropped from the mold by reversing the mold, and a slag that holds the surface temperature of a part or the entire surface of the dropped slag at 900 ° C. or more for 5 minutes or more. And a temperature holding step.

FIG. 1 shows an example of a solidified slag manufacturing apparatus that can realize the above-described solidified slag manufacturing method. The solidified slag manufacturing apparatus 1 (FIG. 1) shown in FIG. 1 is made of a plurality of metals having recessed portions 5a (recessed rod parts) into which molten blast furnace slag accommodated in a slag pan 23, that is, molten slag 3 is poured. The mold 5 is supported so as to be able to move around, and the molten slag 3 is poured into the recessed portion 5a while the mold 5 goes around to continuously produce the solidified slag 18.

The solidified slag manufacturing apparatus 1 that performs such an operation is provided with a revolving mechanism 7 that revolves horizontally in a state where a plurality of molds 5 are brought close to each other and supported. This circular movement mechanism 7 moves the mold 5 in the circular direction while holding the molten slag 3 poured into the recessed portion 5a while the mold makes one round, and air-cools the air by cooling and solidifying the molten slag 3. The moving part 9, the reversing discharge part 11 for reversing the casting mold 5 so that the recessed part 5a faces downward and discharging the solidified slag 18, and the reversing moving part 13 for moving the reversed casting mold 5 in the reversed state. A re-inversion unit 15 that re-inverts the mold 5 in the inverted state so that the recessed portion 5a faces upward, and a re-inversion moving unit 17 that moves the re-inverted mold 5 to a portion into which the molten slag 3 is poured. And a cooling device 21 for cooling the inverted mold 5. The re-inversion moving unit 17 may be omitted. The solidified slag manufacturing apparatus 1 is provided with a gutter 20 so that the molten slag 3 can be easily poured into the mold 5.

Further, the solidified slag manufacturing apparatus 1 has a pit 19 provided below the casting mold 5 that circulates around the reversal discharge unit 11, and the pit 19 has a solidified slag holding container 22 that can accommodate the solidified slag 18 to be discharged. Has been placed.

As shown in FIG. 2, the solidified slag holding container 22 has a capacity capable of holding the solidified slag 18 in an amount corresponding to the molten slag 3 for one cup of the slag pot 23, and solidifies for one cup of the slag pot 23. After the slag 18 is accommodated, it may be carried out from the slag dropping position and replaced with an empty solidified slag holding container 22. In this way, even if slag is held in the solidified slag holding container 22 for a long time, the molten slag 3 in the next slag pot 23 is continuously added without causing a waiting time and reducing productivity. Can be processed.

From the viewpoint of heat retention, at least a part of the bottom and side surfaces of the solidified slag holding container 22 along the normal direction of each surface has a low thermal conductivity fire resistance of about 5 W / (m · K) or less. It is desirable to be composed of objects. Further, after the solidified slag 18 is accommodated, the solidified slag holding container 22 is provided with a lid, a simple heating source such as a burner is added to the solidified slag holding container 22, or the pit 19 itself at the slag dropping position. Can be used as a solidified slag holding container, and a mode in which a cover is installed and held after the solidified slag is accommodated can be selected.

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

The orbiting moving mechanism 7 is rotated at a predetermined speed, and the molten slag 3 is poured into the circulating mold 5 at the molten slag inflow portion through the gutter 20. The mold 5 into which the molten slag 3 is poured moves through the air-cooling moving part 9, and the molten slag 3 is cooled by air to become a solidified slag 18 (slag solidification step).

Here, it is preferable to control the rotational speed of the mold 5 and / or the flow rate 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, a particle size distribution suitable for a coarse aggregate product having a general coarse aggregate size of 5 to 20 mm, which is widely used, is obtained. Can be obtained. If the thickness of the solidified slag 18 is 20 mm or more, as will be described later, when the solidified slag 18 is charged into the solidified slag holding container 22, the average heat content (average (amount of heat) is sufficiently increased. Therefore, it is possible to raise the slag surface temperature of the mold contact surface to 900 ° C. or higher and hold it for 5 minutes or more simply by keeping the solidified slag 18 warm without adding a heating source.

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 pore generation inside the slag is suppressed, so the water absorption rate of the coarse aggregate product is reduced to 1.5% or less. This is also preferable for obtaining coarse aggregate particles having a high strength such as a compressive strength of 100 N / mm ² or more.

The mold 5 that has arrived at the reverse discharge unit 11 rotates and reverses in the circumferential direction in the reverse discharge unit 11, and the solidified slag 18 is discharged to the pit 19 or the solidified slag holding container 22 in the pit 19 (slag Dropping process).

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

The mold 5 that has passed through the inversion moving unit 13 rotates in the circumferential direction in the reinversion unit 15 and reinverts so that the recessed portion 5a faces upward. The molten slag 3 is poured into the re-inverted mold 5 immediately after re-inversion or after moving the re-inversion moving part 17 at the slag inflow portion.

The solidified slag 18 discharged into the pit 19 and charged into the solidified slag holding container 22 is laminated in the solidified slag holding container 22 and is a mold of the solidified slag 18 that is reduced during solidification due to the amount of heat held by the solidified slag 18 itself. The temperature of the contact surface rises. At this time, by maintaining the slag surface temperature of the dropped solidified slag 18 at 900 ° C. or more for 5 minutes or longer, the glassy surface of the mold contact surface in the solidified slag 18 can be modified to crystalline (slag temperature holding step). ). In this way, after the vitreous is modified into crystalline, the solidified slag 18 is discharged from the solidified slag holding container 22 to the slag cooling bed 24.

As described above, the method for producing solidified slag of the present invention has three steps of a slag solidification step, a slag dropping step, and a slag temperature holding step, and among these three steps, the slag temperature holding step is particularly characteristic. This will be described in detail below.

<Reason why slag temperature holding process is necessary>
When the cross section of the plate-shaped solidified slag 18 dropped from the mold 5 is observed, the range from the mold contact surface 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 faster only in this part. Even if the solidification thickness of the solidification slag 18 changed, the vitreous portion did not change from the mold contact surface to about 1 mm.

The surface temperature of the solidified slag 18 on the atmosphere side is measured using a radiation thermometer, and a thermocouple is installed on the back of the mold, and the temperature transition until the molten slag 3 flowing on the mold is cooled and solidified is measured. The measurement was performed for a case where the solidified slag 18 had a thickness of 23 mm. The measurement results are shown in FIG. FIG. 3 also shows the transition of the slag temperature at the central position in the thickness direction of the slag and the position in contact with the mold 5, which was obtained by heat transfer analysis described later. The initial cooling rate of the slag at the position in contact with the mold 5 is remarkably large due to heat transfer 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 is slow, and after about 2 minutes, the temperature decreases only to about 1150 ° C., and the atmosphere side surface also decreases only to about 900 ° C. after 2 minutes.

Thus, in the present system in which the molten slag 3 is cooled mainly by heat transfer to the mold 5, the mold contact surface is rapidly cooled, but the thermal conductivity of the slag is as small as 2 W / (m · K) or less, The heat conduction inside the slag is slow, and the cooling rate other than the mold contact surface is small. Therefore, only the slag on the mold contact surface is quenched and vitrified. When the solidified slag 18 after the mold 5 is inverted and dropped from the mold 5 is conveyed one by one, the cooling progresses from the surface during the conveyance, so that the glassy surface remains as it is.

If the vitreous remains, as described above, when used as a coarse aggregate for concrete, there are problems that it is easy to breathe and the yield of the coarse aggregate is reduced. It needs to be modified. Therefore, a temperature maintaining step for modifying the vitreous portion to be crystalline is necessary.

<Examination of cooling rate by analysis>
We examined how to modify the vitreous part to be crystalline. During the study, the cooling rate inside the slag was examined by heat transfer analysis. Since this process solidifies the slag into a plate shape, the temperature transition during the cooling and solidification process can be thought of as a simple flat plate unsteady one-dimension heat conduction. This basic formula is the following formula (1).

Where 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 slag or mold temperature (K ), X is the length (m) in the thickness direction, and t is the time (s).

FIG. 4 shows an analysis model, FIG. 4 (a) shows a state where slag is accommodated in the mold, and FIG. 4 (b) shows solidified slag dropped from the mold. As shown in FIG. 4, the thickness direction of the slag and mold was calculated by dividing the slag into 10 parts and dividing the mold into 10 parts. Only the solidified slag was calculated after dropping from the mold.

Here, the heat transfer coefficient hs at the air-slag interface, the heat transfer coefficient hm at the mold-atmosphere interface, and the thermal resistance R at the slag-mold interface are used as parameters, and the calculated temperature matches the measured value in FIG. The parameter values were determined as follows. Since the air-slag interface has a high temperature difference of 1300 K or more in the initial stage, heat radiation was considered. The ambient temperature Ta was assumed to be constant at 293 K and there was no temperature rise. After dropping from the mold, it was assumed that it was in a heat-insulating state, and there was no heat transfer to the outside of the slag. The calculation was performed by explicit solution (technique) with Δt = 0.5 sec.

As the thermal conductivity λ (W / (m · K)) of the slag, the value calculated from the following formulas (2) and (3) was used.
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 specific heat Cp of the slag is the heat capacity measurement result of the blast furnace slag by Ogino et al. Based on the 54th Committee), Cp = 1039J / (kg · K) when T <1443K, Cp = 2242.5J / (kg · K) when 1443K ≦ T <1673K, 1673K ≦ T <1773K In this case, Cp = 1326 J / (kg · K).

The heat transfer coefficient of the slag surface and the heat transfer coefficient of the mold back are hs = 30 W / (m ² · K) and hm = 10 W / (m ² · K), respectively, and the heat resistance of the slag-mold interface is R = 9 × 10 By setting ^-4 m ² · K / W, it was possible to substantially match the measured temperature value in FIG.

This makes it possible to calculate the temperature change of the slag, and based on this, the temperature condition and the holding time in the slag temperature holding process were examined.

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

<Retention time>
Next, the solidification slag mold was changed by changing the holding time in the solidification slag holding container under the condition that the solidification thickness of the slag and the cooling time of the slag until the slag was peeled after reversing the mold were fixed. The relationship between the holding time from the time when the surface temperature on the contact surface side rose to 900 ° C., that is, the time for holding the slag surface temperature at 900 ° C. or higher, and the area ratio of the vitreous portion of the mold contact surface of the solidified slag investigated.

Specifically, in the solidified slag manufacturing apparatus shown in the examples described later, the metal mold 5 is repeatedly wound twice to continuously process 12 tons of molten slag 3 in 6 minutes, and the mold 5 is inverted. The solidified slag 18 is held in the solidified slag holding container 22 disposed at the slag dropping position at that time, and then held for a predetermined time. When the predetermined holding time is reached, the solidified slag 18 is immediately discharged to the slag cooling floor 24. Spread and cooled in the atmosphere.

In order to calculate the holding time at 900 ° C. or higher, it is necessary to specify the time point when the surface temperature on the mold contact surface side of the slag rises to 900 ° C. and the time point when the surface temperature falls below 900 ° C. Therefore, when the surface temperature on the mold contact surface side of the slag rises to 900 ° C., the last solidification slag is stored in the solidified slag holding container, and the surface temperature of the slag on the mold contact surface side reaches 900 ° C. This time was determined by assuming that the surface of the slag is adiabatic boundary condition in the solidified slag holding container in the heat transfer analysis. Moreover, the time when the surface temperature decreased to less than 900 ° C. was the time when the solidified slag was discharged from the solidified slag holding container to the slag cooling bed and spread. This is based on the assumption that as soon as the solidified slag is discharged from the solidified slag holding container to the slag cooling bed and spread, the surface temperature of the solidified slag drops below 900 ° C.

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

In FIG. 5, the reason why the area ratio of the vitreous portion does not greatly decrease from about 10% even if the holding time at 900 ° C. or higher is extended beyond 5 minutes is the solidification that is laminated and deposited in the slag holding container. It is considered that the solidified slag having the mold contact surface facing upward at the outermost layer portion of the slag was not crystallized because the temperature did not rise to 900 ° C. or higher even when the holding time was increased. Therefore, the area ratio of the vitreous portion can be further reduced by installing a lid after the slag is accommodated in the slag holding container or by reheating using a simple heating source such as a burner.

Further, in FIG. 5, the reason why some vitreous slag is crystallized even when the calculated value of the retention time at 900 ° C. or higher is zero is that the lower part of the deposited layer contained in the slag holding container at the initial stage of the slag treatment. In the solidified slag, it is considered that the rise in surface temperature progressed within the time until the final solidified slag was accommodated, and the temperature was maintained at 900 ° C. or higher for 5 minutes or longer. In other words, it is considered that the solidified slag accommodated in the slag holding container at the initial stage of the slag treatment has been crystallized by satisfying the crystallization conditions.

Next, it was examined whether the above temperature condition and holding time could be secured by laminating the solidified slag dropped in the slag dropping process.

<Insulated slag temperature>
For the solidified slag having a slag thickness of 25 mm, the temperature distribution immediately before dropping from the mold was calculated. 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, as shown by a solid line graph in FIG. Since the temperature of the solidified slag immediately after being discharged from the mold is considered to be substantially the same as the temperature of the solidified slag immediately before dropping from the mold, it is indicated as “immediately after being discharged from the mold” in FIG.

¡In the solidified slag immediately after being discharged from the mold, the temperature of the mold contact surface and the air surface is lowered, but the internal temperature is high. If the solidified slag is dropped into the holding container in this state and stacked one after another, the slag inside the deposited layer becomes a heat-retaining state. Conducted to the air side and the atmosphere side, the entire slag approaches a uniform temperature distribution. The temperature distribution calculation result after 3 minutes is shown by a broken line in FIG. Under these conditions, the temperature of the mold contact surface once lowered also rises to about 1000 ° C.

In the method for producing a solidified slag according to the present invention, after the solidified slag is dropped and discharged from the mold, the surface temperature of a part or the whole surface of the solidified slag including the mold contact surface is raised to 900 ° C. or higher. It is essential to hold for more than a minute. This can be performed without using a new heating source by setting the average temperature in the slag thickness direction of the solidified slag discharged from the mold to be over 900 ° C. and laminating the solidified slag in the pit 19 or the solidified slag holding container. I confirmed that there was.

<Temperature by slag lamination>
Increasing the surface temperature of the slag to 900 ° C or higher due to the heat content of the solidified slag itself means that the solidified thickness of the solidified slag, the cooling time of the slag until the solidified slag is dropped after inverting the mold, and the solidified slag holding container This is realized by appropriately selecting conditions such as the holding time at. This point will be specifically described below.

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

Using infrared thermography, measure the temperature of the solidified slag from the top of the solidified slag holding container, and measure the solidified slag below the solidified slag of the surface layer (hereinafter referred to as the solidified slag of the surface layer, not the solidified slag of the surface layer) The surface temperature of “sometimes referred to as subsurface solidified slag” is plotted in FIG. The surface temperature of the solidified slag having an average thickness of 22 mm or more existing under this surface layer was over 900 ° C. in all measured values. The slag thickness on the horizontal axis in FIG. 7 is an average value of values measured after cooling the slag thickness near the surface layer.

On the other hand, the solid line shows the calculated value of the temperature of the solidified slag at the mold contact surface, and the temperature immediately after discharge from the mold and the solidified slag under the surface layer in the solidified slag holding container for 3 minutes (180 seconds) It is the temperature after holding. As shown in FIG. 7, the calculated temperature at the mold contact surface of the solidified slag after being held for 3 minutes exceeds 900 ° C. if the average thickness is 20 mm or more, and the mold contact increases as the average thickness increases. It was found that the temperature at the surface was high.

The measured value of the surface temperature of the solidified slag under the surface layer laminated in the holding container tends to be higher as the slag thickness is larger as in the calculation result, and all the solidified slag having an average thickness of 22 mm or more tested After 3 minutes, it was 900 ° C or higher. That is, the surface temperature measurement value of the solidified slag under the surface layer is in good agreement with the calculation result. From the calculation result and the actual measurement value, the solidified slag having an average thickness of 20 mm or more is laminated, and the solidified slag after 3 minutes. It was confirmed that the surface temperature of can be made 900 ° C. or higher.

When the heat source for raising the surface temperature of the solidified slag is limited to the heat content of the solidified slag itself, it is stored in a solidified slag holding container in order to reduce the influence of heat radiation to the outside. It is necessary to secure a certain amount of solidified slag. Specifically, it is preferable that the solidified slag of 5 tons or more, more desirably 10 tons or more is stacked and accommodated with a thickness of 1 m or more.

Plate-shaped solidified slag cast with a metal mold has a larger average solidification rate than slow-cooled slag, and therefore tends to have smaller crystal grains. By relieving and eliminating the residual stress, a material superior in strength characteristics to that of slowly cooled slag can be obtained.

In addition, the solidified slag produced by the method for producing solidified slag according to the present invention has a drop strength (Shatter Index) defined later which is 70% or more, and the method for producing solidified slag according to the present invention provides a drop strength (Shatter A high-strength plate-like solidified slag having an index of 70% or more is obtained. In addition, by using plate-shaped solidified slag cast with a metal mold having a drop strength of 70% or more, this is crushed and classified to produce slag products such as coarse aggregate for concrete. The yield is improved.

Furthermore, in the coarse aggregate obtained by crushing and classifying the solidified slag produced by the method for producing solidified slag according to the present invention, the coarse aggregate for concrete having an average compressive strength measured by the method described later of 100 N / mm ² or more. And is suitable as a raw material for coarse aggregate when producing high-strength concrete.

The function and effect of the present invention will be described based on specific examples.

In this example, solidified slag was manufactured using the apparatus shown in FIG. The mold 5 is made of cast steel having a trapezoidal shape in plan view, the thickness thereof is 45 mm, the outer dimension of the mold corresponding to the upper base of the trapezoid is 0.7 m, and the outer method of the mold corresponding to the lower base of the trapezoid. The dimension was 1.0 m, and the outer dimension of the mold corresponding to the height of the trapezoid was 2.7 m. Moreover, the depth of the recessed part 5a of the casting_mold | template 5 which pours molten slag was 100 mm. The mold 5 was circulated and conveyed by the circulatory movement mechanism 7, and the conveying speed of the circulatory conveyance was 14 m / min at the mold center.

At the slag inflow site, molten blast furnace slag of 1360 ° C. or higher and 1410 ° C. or lower was flowed into the mold 5 at about 2 ton / min. The mold 5 into which the molten slag 3 has been poured conveys the air-cooled moving part 9 for about 120 seconds {the length of the air-cooled moving part is 2/3 (240 degrees) of the entire circumference}. did.

In the reverse discharge unit 11, the mold 5 was inverted and the solidified slag 18 peeled off from the mold was dropped into the solidified slag holding container 22 arranged in the pit 19. The casting mold 5 from which the solidified slag 18 was discharged was moved while the inversion moving unit 13 was in the inverted state, and was rapidly cooled by injecting cooling water from the upper and lower surfaces at the site where the cooling device 21 was installed.

Subsequently, the mold 5 in the inverted state was re-inverted by the re-inversion part 15 and returned to the state in which the original recessed part 5a was directed upward again. Thereafter, molten slag was poured again into the returned mold. The above process was repeated 5 times for one slag pan, and 30 tons of molten slag was continuously processed in 15 minutes.

After all the solidified slag dropped from the mold, the solidified slag was held in the solidified slag holding container for a predetermined time, and then the solidified slag was discharged from the solidified slag holding container to the slag cooling bed and spread and cooled in the atmosphere.

In the example of the present invention, the molten slag temperature is 1385 ° C., the holding time after completion of slag storage in the solidified slag holding container is 10 minutes, the average thickness of the solidified slag is 25 mm, and the solidified slag is held immediately after a predetermined holding time. The solidified slag was discharged from the container to the slag cooling bed, spread and cooled in the atmosphere.

In the comparative example, the molten slag temperature is 1380 ° C., the average thickness of the solidified slag is 23 mm, the solidified slag is dropped from the mold into the pit, and after all the solidified slag has fallen from the mold, the solidified slag is immediately removed with a shovel car. It was taken out from the pit and cooled in the slag cooling bed, and prepared for the treatment of the molten slag in the next slag pan. In the comparative example, when the solidification thickness of the solidified slag was measured after cooling, it was 20 to 26 mm, and the average thickness was 23 mm. The influence of the solidification thickness on the glassy abundance ratio on the mold contact surface was not in the range of 20 to 26 mm.

In the solidified slag after cooling, the ratio of the vitreous portion of the mold contact surface during solidification was evaluated, and the drop strength of the slag was evaluated.

First, from the solidified slag produced according to the example of the present invention, the glass contact surface (crystalline) is visually selected from the solidified slag, and on the other hand, the solidified slag produced according to the comparative example is contacted with the mold. A drop test was performed by visually selecting glassy surfaces.

8 and 9 are photographs showing the test results. FIG. 8A shows the state before the test of the example of the present invention, and FIG. 8B shows the state after the drop test of the example of the present invention. ) Shows a state before the test of the comparative example, and FIG. 9B shows a state after the drop test of the comparative example.

In the solidified slag of the comparative example in which the mold contact surface portion of the solidified slag is glassy, as shown in FIG. 9B, the whole was finely broken by dropping. This is because a large residual stress is generated in the vicinity of the surface having a large temperature gradient during solidification, so that even a relatively small impact of about 1 m is easily 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. It became solidified slag. This is because the residual stress in the vicinity of the surface is relaxed or eliminated when the glassy portion of the mold contact surface is crystallized.

The drop strength (Shatter Index) was measured by the method described below. As the apparatus for the drop strength test, the apparatus described in JIS M8711 Iron Ore Sinter-Drop Strength Test Method was used. Using a sample of plate-like solidified slag of 40 to 100 mm (a sample of plate-like solidified slag whose sieve opening passes through a 100-mm sieve and does not pass through a sieve of 40 mm; about 3 kg) Then, a drop test was performed in which the sample was dropped four times. After the drop test, a ratio that was not crushed to 40 mm or less (mass ratio of the sample that does not pass through a sieve having an opening of 40 mm) was obtained, and this ratio was defined as drop strength (Shatter index). Other test conditions were in accordance with the JIS M8711 iron ore sinter ore drop strength measurement method, which is a test method for sintered ore.

The drop strength (Shatter Index) of the plate slag was calculated by the following equation (4).
S (%) = A / B × 100 (4)
S: Drop strength (Shatter Index) of plate-like slag judged at 40 mm or more
A: Mass (kg) of 40 mm or more after the test
B: Mass of sample of 40 to 100 mm before test (kg)
FIG. 10 shows the result of comparing the relationship between the ratio of the vitreous portion on the mold contact surface and the drop strength S between the inventive example and the comparative example. In the inventive example, the ratio of the vitreous portion was reduced from 52 area% in the comparative example to 9 area%, and the drop strength S was improved from 46% in the comparative example to 89%.

From the above results, in order to effectively improve the strength of the solidified slag by crystallization of the vitreous portion, 80% by area or more of the mold contact surface during solidification, more desirably 90%, of the surface of the solidified slag. About area% or more, it can be said that it is suitable to hold | maintain slag surface temperature at 900 degreeC or more for 5 minutes or more. That is, 80% by area or more, more desirably 90% by area or more of the mold contact surface at the time of solidification of the solidified slag is made crystalline, in other words, the area ratio of the vitreous portion of the mold contact surface of the solidified slag is It is preferable that the content be less than 20 area%, more desirably less than 10 area%.

Next, 10 tons of plate-like solidified slag was crushed using an impact crusher in order to make the solidified slag of the present invention and the comparative example produced as described above into a coarse concrete aggregate. And the crushed slag was classified with a 20 mm and 5 mm sieve. Thereby, a coarse aggregate for concrete having a thickness of 20 to 5 mm was produced.

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

The water absorption rate of the coarse aggregate of the example of the present invention is 0.9%, which is significantly smaller than the water absorption rate of 3 to 4% of the conventional blast furnace slow-cooled slag coarse aggregate, which is equivalent to that of natural aggregate. Things were obtained.

Also, the compressive strengths of the slag coarse aggregates of the present invention and the comparative examples were compared. Samples for compressive strength measurement were cut from large coarse aggregate particles including a flat surface to a size of 10 mm × 10 mm × 10 mm using a diamond cutter with the flat surface as the bottom, and an Amsler compression testing machine (universal testing machine) Compressive strength was measured for each of the six samples.

The compressive strength of the sample collected from the coarse aggregate of the comparative example has an average value of 50 N / mm ² and a minimum value of 10 N / mm ^2. did. In contrast, the compressive strength of the samples taken from the coarse aggregate of the present invention example, the average value of 167N / mm ^2, a minimum value is 80 N / mm ^2, a high compressive strength stably is obtained .

The concrete was compounded using the slag coarse aggregates of the present invention example and the comparative example, and the characteristics were evaluated. The amount of breathing was compared between the fresh concrete blended with the coarse aggregate of the present invention and the fresh concrete blended with the coarse aggregate of the comparative example. The survey results are shown in FIG. In the present invention example having a small glassy surface, the amount of breathing was smaller than in the comparative example having a large glassy surface.

Next, using each coarse aggregate, concrete was kneaded with a water-cement ratio of 35% for high strength, and a specimen for compressive strength measurement was prepared on the 28th. The strength was compared. For comparison, a specimen using commercially available natural limestone as a coarse aggregate was also produced and evaluated in the same manner.

In the concrete using the coarse aggregate of the comparative example, the 28-day strength was 53 N / mm ² , whereas in the concrete using the coarse aggregate of the present invention example, it was 75 N / mm ² . The 28-day strength of the concrete using natural limestone coarse aggregate is 72 N / mm ² , and the concrete using the coarse aggregate of the example of the present invention is compressed higher than the concrete using the natural limestone coarse aggregate. Strength was obtained. 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.

DESCRIPTION OF SYMBOLS 1 Solidification slag manufacturing apparatus 3 Molten slag 5 Mold 5a Concave part 7 Circumferential movement mechanism 9 Air-cooling movement part 11 Reverse discharge part 13 Reverse movement part 15 Reinversion part 17 Reinversion movement part 18 Solidification slag 19 Pit 20 樋 21 Cooling device 22 Solidification Slag holding container 23 Slag pot 24 Slag cooling floor

Claims

The molten blast furnace slag is poured into a moving metal mold and cooled to solidify it into a plate shape in the mold, and the slag solidified to the inside in the mold is used as the mold. A method for producing a solidified slag comprising: a slag dropping step of inverting and dropping from a mold; and a slag temperature holding step of holding the surface temperature of a part or the whole surface of the dropped slag at 900 ° C. or more for 5 minutes or more.
The method for producing a solidified slag according to claim 1, wherein the thickness of the blast furnace slag solidified so as to form a plate in the mold is 20 mm or more and 30 mm or less.
In the slag temperature holding step, the slag surface temperature is maintained at 900 ° C. or more for 5 minutes or more for 80 area% or more of the mold contact surface during solidification among the surfaces of the solidified slag dropped from the mold. The manufacturing method of the solidification slag of Claim 1 or Claim 2 to do.
4. The solidification according to claim 1, wherein in the slag temperature maintaining step, the solidified slag dropped from the mold is laminated with an average temperature in the slag thickness direction exceeding 900 ° C. 5. A method for producing slag.
The said slag temperature holding process laminates | stacks the solidification slag dropped from the said casting_mold | template in the holding | maintenance container which can be taken out from this dropping position, The one of Claim 1 thru | or 4 characterized by the above-mentioned. A method for producing solidified slag.
A solidified slag produced by the method for producing a solidified slag according to any one of claims 1 to 5, wherein a slag sample that passes through a sieve having an opening of 100 mm and does not pass through a sieve having an opening of 40 mm, A solidified slag having a drop strength (Shatter） Index) of 70% or more evaluated by a mass ratio of a sample that does not pass through a sieve having an opening of 40 mm after a drop test that is dropped four times from a height of 2 m to the sample before the drop test.
A solidified slag production process including the method for producing a solidified slag according to any one of claims 1 to 5, a solidified slag crushing process for crushing the produced solidified slag, and a classification process for classifying the crushed solidified slag. A method for producing a coarse aggregate for concrete comprising:
The coarse aggregate for concrete manufactured with the manufacturing method of the coarse aggregate for concrete of Claim 7, Comprising: The coarse aggregate for concrete whose average compressive strength is 100 N / mm < 2 > or more.