JP2015189602A - Method of modifying steel slag and steel slag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To modify steel slag at low costs in a short time, without transfer, as it is at high temperatures.SOLUTION: Steel slag in a molten state is kept in high-temperature water of 50°C or higher for a specified time to modify it, and the steel slag of grain sizes of 30 mm or smaller is recovered. Preferably, the steel slag in a molten state is reduced in grain sizes, poured into the high-temperature water and kept in the high-temperature water for a specified time to modify it. The grain sizes may be reduced to 10 mm or smaller by causing water to collide with the steel slag in a molten state, or the grain sizes may be reduced to 5 mm or smaller by causing a gas to collide with the steel slag in a molten state. The procedure allows modification of the steel slag at low costs in a short time, without transfer, as it is at high temperatures.

Description

  The present invention relates to a steelmaking slag reforming method and steelmaking slag in water.

  Since lime is used as an auxiliary material in the steelmaking process, free lime (hereinafter referred to as f-CaO) in which part of the lime remains is present in the steelmaking slag. Since this f-CaO expands when it reacts with water, the volume stability of the steelmaking slag is lowered to prevent its use as a roadbed material.

  In order to suppress the expansion of such steelmaking slag, a technique is known in which faging is performed by aging and reacting f-CaO with moisture in advance to convert it into slaked lime, thereby modifying the steelmaking slag. There are two types of aging: atmospheric aging that is piled up in a yard and performed by the atmosphere, and vapor aging that uses steam. Patent Document 1 describes a technique of steam aging that uses steam obtained by watering high-temperature steelmaking slag.

JP 2009-227490 A

  However, atmospheric aging requires a long period of time for f-CaO in steelmaking slag to stabilize. Steam aging uses a large amount of steam and increases processing costs. The technique described in Patent Document 1 includes a process A for obtaining steam by water spraying and a process B for aging by steam. Since the process A and the process B are performed at different places, the steelmaking slag must be transported between the process A and the process B. And in process B, in order to make steelmaking slag contact with a steam in high temperature, you have to convey high temperature steelmaking slag.

  The present invention has been made in view of the above, and provides a steelmaking slag reforming method and a steelmaking slag that can be reformed in a short time at a low cost without transporting the steelmaking slag at a high temperature. With the goal.

In order to solve the above-described problems and achieve the object, the steelmaking slag reforming method according to the present invention includes a reforming step in which molten steelmaking slag is reformed by holding it in high-temperature water at 50 ° C. or higher for a predetermined time. And a recovery step of recovering steelmaking slag having a particle size of 30 mm or less.

  Further, the steelmaking slag reforming method according to the present invention includes, in the above invention, a refinement step for reducing the particle size of the molten steelmaking slag, wherein the reforming step is performed by the refinement step. Steelmaking slag having a reduced size is poured into high-temperature water at 50 ° C. or higher, and is reformed by holding it in high-temperature water at 50 ° C. or higher for a predetermined time.

  Moreover, the steelmaking slag reforming method according to the present invention is characterized in that, in the above-mentioned invention, the finely pulverizing step makes the particle diameter 10 mm or less by causing water to collide with the molten steelmaking slag.

  Moreover, the steelmaking slag reforming method according to the present invention is characterized in that, in the above-mentioned invention, the fine graining step makes the particle size 5 mm or less by causing a gas to collide with the molten steelmaking slag.

  The steelmaking slag according to the present invention is a steelmaking slag modified by the above invention.

  According to the present invention, steelmaking slag can be reformed in a short time at a low cost without being transported at a high temperature.

  Hereinafter, an embodiment of the present invention will be described in detail. In addition, this invention is not limited by this embodiment.

  The present inventors have found that the expansion of steelmaking slag by f-CaO can be suppressed by discharging the molten slag into high-temperature water and modifying it as it is.

  Therefore, in the present embodiment, first, the molten slag discharged from the converter and put in the slag pan is discharged from the slag pan and dropped into a water tank installed below. The amount of water in the water tank when the slag is charged should be at least 100 times the mass of the slag. After introducing the slag, the slag is reformed by holding it in high temperature water at 50 ° C. or higher for a certain period of time.

  Further, even if the particles are kept in a high temperature water of 50 ° C. or higher with a large particle size, the progress of reforming is slow. Therefore, after being discharged and held in high-temperature water at 50 ° C. or higher, only those having a particle size of 30 mm or less are sieved and collected. Alternatively, a refinement step is performed to reduce the particle size of the molten steelmaking slag. For example, a slag having a particle size of 10 mm or less is obtained by colliding with high-speed water in a molten state. Alternatively, a slag having a particle size of 5 mm or less is obtained by colliding with a high-speed gas in a molten state.

  Specifically, the slag is reformed by any one of the following methods [1] to [3].

[1] Discharge molten slag from a slag pan to a water tank and hold at 50 ° C. or higher for a predetermined time. Thereafter, the slag is taken out from the water tank and dried, and then a slag having a particle size of 30 mm or less is separated and collected using a sieve having a mesh size of 30 mm.

[2] The molten slag being discharged (slag flow) is collided with high-speed water from the rear so that the particle size is 10 mm or less, and is dropped into the water tank as it is. Thereafter, the slag is held in high-temperature water at 50 ° C. or higher for a predetermined time. In addition, the water made to collide with the slag flow may be ejected from the nozzle or may be made to flow from the ridge.

[3] A high-speed gas is collided with the molten slag being discharged from the rear to make the particle size 5 mm or less, and is dropped into the water tank as it is. Thereafter, the slag is held in high-temperature water at 50 ° C. or higher for a predetermined time.

  As described above, molten steelmaking slag is discharged into water at a high temperature, and only those having a particle size of 30 mm or less are recovered after a predetermined time, and the molten slag being discharged is crushed by collision with high-speed water. The diameter is set to 10 mm or less, dropped into the water tank and held for a predetermined time, the particle diameter is set to 5 mm or less by collision with gas, and dropped into the water tank and held for a predetermined time, so that the steelmaking slag can be shortened without being transported at high temperature Steelmaking slag can be reformed at low cost in time. Moreover, about the steelmaking slag after modification | reformation, the amount of f-CaO and an expansion coefficient can be made low.

  The modification time may be appropriately selected depending on the particle size and water temperature. For example, when the particle size is 30 mm or less and the water temperature is 50 ° C. or more, the modification time may be 8 hours or more. When the particle size is 10 mm or less and the water temperature is 50 ° C. or more, the modification time is 4 hours or more. That's fine. The reforming time can be shortened as the particle size is reduced, the reforming time can be shortened as the water temperature is increased, and the temperature of water in the water tank during reforming is preferably 80 ° C. or higher. Moreover, the particle diameter of slag is preferably 20 mm or less from the viewpoint of the amount of f-CaO after modification and the expansion coefficient.

  In the case of screening only those having a particle size of 30 mm or less after being kept in high temperature water for a certain time, the time required for reforming is 8 hours or more. In addition, when colliding with high-speed water or gas, the particle size can be further reduced, so the time required for reforming may be 4 hours or more. The optimum time required for reforming differs depending on the underwater temperature at the time of reforming and the particle size of the steelmaking slag.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited to these embodiments. Various modifications according to specifications and the like are within the scope of the present invention. It is obvious from the above description that various other embodiments are possible within the scope of the above.

[Example]
In Examples and Comparative Examples described below, slag (converter decarburization slag) generated by decarburization processing in a converter was used as the steelmaking slag. Table 1 shows the composition of the converter decarburization slag used in the examples and comparative examples. As shown in Table 1, f-CaO content in the slag is about 4 to 5 wt%, basicity (CaO mass% / SiO ₂ mass%) is about 3.4. In Table 1, the total Fe concentration in the slag is expressed as T.P. It was described as Fe. Moreover, the total CaO density | concentration in slag was described as T-CaO.

[1] Table 2 shows the conditions and results when the molten slag is discharged directly into the water tank and kept at a constant temperature and time in the water tank and then sorted by sieving. The molten slag having the composition shown in Table 1 discharged from the converter and placed in the slag pan was discharged from the slag pan and dropped as it was into a water tank installed below. The amount of water in the water tank when the slag was charged was 100 times or more the mass of the slag, and after the slag was charged, the temperature and time conditions shown in Table 2 were maintained and reformed. The slag retained under the conditions in Table 2 was dried and then separated by sieving into 30 mm or less and other than that, and only the slag of 30 mm or less was regarded as modified and recovered. When the amount of f-CaO in the slag before reforming was about 4 to 5% by mass, the amount of f-CaO in the slag after reforming was 1.8% by mass or less as shown in Table 2. It was confirmed that it was reduced. Moreover, the water immersion expansion test of JIS was implemented using the modified slag. As a result of the water immersion expansion test, the expansion rate was 1.1% or less.

  As a comparative example, the molten slag having the composition shown in Table 1 discharged from the converter and placed in the slag pot was discharged from the slag pot and dropped into a water tank installed below. In Comparative Examples 1-1 and 1-2, the slag having a maximum particle size of 50 mm or 40 mm was retained in a water bath at 80 ° C. for 10 hours or more for modification. In Comparative Example 1-3, the slag having a maximum particle size of 20 mm was modified by being held in a water bath at 40 ° C. for 8 hours. In Comparative Example 1-4, the slag having a maximum particle size of 20 mm was modified by holding it in high-temperature water in a water bath at 80 ° C. for 5 hours. As a result of evaluating the slag of these comparative examples, the amount of f-CaO was 3% by mass or more, and the expansion coefficient was 3.2% or more.

[2] Table 3 shows conditions and results when the particle size of the slag was modified to 10 mm or less by colliding with high-speed water. The molten slag having the composition shown in Table 1 discharged from the converter and placed in the slag pan is discharged from the slag pan, and water is collided with the slag flow at a rate of 5 to 30 m / sec from the rear to the front. The slag was scattered and dropped into the water tank installed below. In that case, the speed | rate and quantity of the water made to collide with molten slag were adjusted so that a particle size might be 10 mm or less by collision with molten slag and water. The amount of water in the water tank when the slag was charged was set to 100 times or more of the mass of the slag, and after the slag was charged, the temperature and time conditions shown in Table 3 were maintained and reformed. When the amount of f-CaO in the slag before reforming was about 4 to 5% by mass, the amount of f-CaO in the slag after reforming was 1.5% by mass or less as shown in Table 3. It was confirmed that it was reduced. Moreover, the water immersion expansion test of JIS was implemented using the modified slag. As a result of the water immersion expansion test, the expansion rate was 1.0% or less.

  As a comparative example, the molten slag having the composition shown in Table 1 in a state of being discharged from the converter and placed in the slag pot is discharged from the slag pot, and water is collided with the slag flow at a high speed from the rear to the front. The slag was scattered and dropped into the water tank installed below. In Comparative Examples 2-1 and 2-2, water is collided with the slag flow that is being discharged from the rear at a speed of 3 m / second or less, the maximum particle size is 20 mm or 15 mm, and after the slag is charged, the water tank is kept at 80 ° C. Retained and modified. Moreover, in Comparative Example 2-3, the particle diameter was 7 mm, and after the slag was charged, the inside of the water tank was maintained at 40 ° C. for modification. In Comparative Example 2-4, the particle size was set to 7 mm, and after the slag was charged, it was modified by being held in high-temperature water at 80 ° C. for 2 hours. As a result of evaluating the slags of these comparative examples, the amount of f-CaO was 3% by mass or more, and the expansion coefficient was 4.8% or more.

[3] Table 4 shows the conditions and results when the particle size of the slag was modified to 5 mm or less by colliding with high-speed gas (air). The molten slag having the composition shown in Table 1 discharged from the converter and placed in the slag pan is discharged from the slag pan, and air is collided with the slag flow at a rate of 60 to 100 m / sec from the rear to the front. The slag was scattered and dropped into the water tank installed below. At that time, the velocity and amount of the gas colliding with the molten slag were adjusted so that the particle size became 5 mm or less due to the collision between the molten slag and air. The amount of water in the water tank when the slag was charged was 100 times or more the mass of the slag, and after the slag was charged, it was maintained and reformed under the conditions of temperature and time shown in Table 4. When the amount of f-CaO in the slag before reforming was about 4 to 5% by mass, the amount of f-CaO in the slag after reforming was 0.6% by mass or less as shown in Table 4. It was confirmed that it was reduced. Moreover, the water immersion expansion test of JIS was implemented using the modified slag. As a result of the water immersion expansion test, the expansion rate was 1.0% or less.

  As a comparative example, the molten slag having the composition shown in Table 1 in a state of being discharged from the converter and placed in the slag pan is discharged from the slag pan, and air is collided with the slag flow at a high speed from the rear to the front. The slag was scattered and dropped into the water tank installed below. In Comparative Examples 3-1 and 3-2, air was collided from the rear at a speed of 60 m / sec to set the maximum particle size to 7 mm, and kept in an 80 ° C. water tank for 6 hours or more for reforming. In Comparative Example 3-3, the particle size was 3 mm, and the sample was modified by being held in a water bath at 40 ° C. for 6 hours. As a result of evaluating the slag of these comparative examples, the amount of f-CaO was 2.7% by mass or more, and the expansion coefficient was 3.1% or more.

Claims (5)

A reforming step of reforming the molten steelmaking slag by holding it in high-temperature water at 50 ° C. or higher for a predetermined time;
A recovery step of recovering steelmaking slag having a particle size of 30 mm or less;
A method for reforming steelmaking slag, comprising: Including a refinement step to reduce the particle size of the molten steelmaking slag,
The reforming step is characterized in that the steelmaking slag whose particle size has been reduced in the fine graining step is poured into high-temperature water at 50 ° C. or higher, and is reformed by holding it in high-temperature water at 50 ° C. or higher for a predetermined time. The method for reforming steelmaking slag according to claim 1.   The method for reforming steelmaking slag according to claim 2, wherein in the fine graining step, the particle diameter is reduced to 10 mm or less by causing water to collide with molten steelmaking slag.   The method for reforming steelmaking slag according to claim 2, wherein the particle size is reduced to 5 mm or less by causing gas to collide with the molten steelmaking slag in the fine graining step.   A steelmaking slag modified by the steelmaking slag reforming method according to any one of claims 1 to 4.