JP7772026B2 - Refractory brick processing method - Google Patents

Description

The present invention relates to a method for treating refractory bricks.

In recent years, as part of efforts to improve recycling efficiency in steelmaking, it has been proposed to reuse refractory bricks used in the ironmaking process. Refractory bricks include torpedo bricks and converter bricks.

Generally, iron and slag adhere to the working surface of refractory bricks (the surface that comes into contact with molten steel and slag) through the pores in the refractory, and mortar may adhere to some other surfaces. When recycling such refractory bricks, if these deposits are mixed in, the durability of the recycled product as a refractory material will be significantly reduced, making it unsuitable for use. Therefore, when recycling refractory bricks, it is necessary to remove the above deposits, such as slag.

The current method for recycling refractory bricks involves manually striking each refractory brick to separate the slag adhering to its surface, and then crushing it. This method only allows for the reuse of a portion of the refractory bricks, and is not entirely satisfactory in terms of work efficiency and running costs. Therefore, in order to efficiently recycle refractory bricks, it is desirable to be able to automate the separation of slag and other adhering materials from the surface of refractory bricks on a large scale.

In response to this, for example, Patent Document 1 proposes a water jet type scraping device that performs scraping (a process to remove surface deposits) by spraying water from a jet nozzle onto the transported workpiece.

Japanese Patent Application Laid-Open No. 2001-009390

However, with the device described in Patent Document 1, the high-speed water spray not only cleans the surface but can also scrape the base material itself. In other words, the above device has the problem of reducing yield.

The present invention was developed in consideration of these circumstances, and aims to provide a method for treating refractory bricks that can effectively separate slag adhering to the surface of the refractory bricks while ensuring the yield of the refractory bricks.

As a result of extensive research into solving the above problems, the inventors discovered that by soaking refractory bricks in water and repeatedly freezing and thawing them multiple times, gaps are formed between the refractory bricks and the slag, making it easier for the slag to peel off, which led to the invention of the present invention.

The gist of the present invention is as follows:

[1] A method for treating refractory bricks having slag attached to their surfaces, comprising:
A method for treating refractory bricks, characterized in that water is taken up into the refractory bricks, and then freezing and thawing are repeated multiple times to remove slag from the refractory bricks.

[2] The method for treating refractory bricks described in [1], wherein the freezing temperature is -20°C or lower.

[3] The method for treating refractory bricks according to [1] or [2], wherein the total processing time for the repeated freezing and thawing is 1 hour or more.

[4] The method for treating refractory bricks according to any one of [1] to [3], wherein the freezing and thawing are repeated four or more times.

The refractory brick processing method of the present invention makes it possible to effectively separate slag adhering to the surface of the refractory brick while ensuring the yield of the refractory brick.

FIG. 1 is a schematic diagram of a processing flow according to an embodiment of the processing method of the present invention. 1 is a schematic diagram showing an effect of the processing method of the present invention. 1 is a graph plotting the crushing strength and slag content of slag remaining on the surface of refractory bricks after treatment in Examples against the treatment time (number of repetitions) of freezing and thawing.

The following describes a method for treating refractory bricks according to one embodiment of the present invention (sometimes referred to as the "treatment method of this embodiment"). Note that the following description illustrates one embodiment or preferred aspect of the present invention, and does not limit the present invention in any way.

The treatment method of this embodiment is a method for treating refractory bricks with slag adhering to their surfaces, characterized by introducing water into the refractory bricks and then repeatedly freezing and thawing them multiple times to separate the slag from the refractory bricks.

More specifically, the treatment method of this embodiment includes a step of taking in water into refractory bricks having slag adhered to their surfaces (hereinafter sometimes referred to as "refractory bricks with slag") (water taking in step), a step of freezing the refractory bricks (freezing step), and a step of thawing the refractory bricks (thawing step), and requires repeating the freezing and thawing steps multiple times.

Figure 1 is a schematic diagram of the processing flow according to this embodiment. Each step will be described in detail below based on Figure 1.

(Water intake process)
In the water intake step, as shown in FIG. 1A, water 5 is taken into the refractory brick 1 with the slag 2 attached thereto. This water intake step is performed to facilitate peeling of the slag 2 in the subsequent freezing and drying steps. Furthermore, in this water intake step, it is preferable that moisture penetrate between the refractory brick 1 and the surface-adhered slag 2 in order to facilitate peeling of the slag 2 as described above. Specifically, as shown in FIG. 1A, the water intake step is preferably performed by immersing the refractory brick 1 with the slag 2 attached thereto in water 5 stored in a water tank 4. In this case, the immersion time is preferably 8 seconds or more to obtain the desired effect, and preferably 20 seconds or less from the viewpoint of processing efficiency.
In addition, the method of spraying water onto the surface of the refractory bricks, for example, by a sprayer, may result in the water not penetrating easily or not penetrating at all between the refractory bricks 1 and the surface-adhering slag 2 (i.e., the water may not be absorbed into the refractory bricks).

(Freezing process)
1B, in the freezing step, the refractory bricks 1 with the slag 2 after the water intake step are frozen in a freezer 6 or the like. In this freezing step, the water 5 that has penetrated between the refractory bricks 1 and the surface-adhered slag 2 freezes to form ice 5', which expands in volume. The freezing temperature is preferably −15° C. or lower, more preferably −20° C. or lower, and even more preferably −25° C. or lower, from the viewpoint of ultimately making the slag 2 more easily detachable from the refractory bricks 1. On the other hand, the freezing temperature is preferably −30° C. or higher, more preferably −28° C. or higher, from the viewpoint of sufficiently causing volume expansion of the water (avoiding rapid freezing).
The freezing time is not particularly limited, but can be about 10 to 30 minutes.

(Thawing process)
Next, in the thawing step, the refractory brick 1 with the slag 2 after the freezing step is thawed. The thawing is preferably performed by natural thawing, as shown in Fig. 1(C). In the case of natural thawing, the time required for thawing is about 5 to 15 minutes.

(Repeated freezing and thawing)
The treatment method of this embodiment requires the above-described freezing and thawing to be repeated multiple times. Repeating the freezing and thawing processes multiple times causes the water 5 that has penetrated between the refractory brick 1 and the surface-adhered slag 2 to turn into ice 5', resulting in repeated volume expansion (see FIG. 2). Furthermore, repeating the freezing and thawing processes multiple times reduces the strength of the slag 2 that has adhered to the surface of the refractory brick 1. As a result, the slag 2 becomes more easily peeled off from the refractory brick 1 (so-called freeze peeling). In this way, the slag 2 that has adhered to the surface of the refractory brick 1 can be effectively peeled off. Specifically, the treatment method of this embodiment can achieve a slag content of 2.7% by mass or less (a target value set based on the requirements of a specific recycling destination).

The timing for transitioning from the thawing process to the freezing process can be when the ice on the surface of the refractory brick 1 melts and turns back into water.

The total processing time for the repeated freezing and thawing is not particularly limited, but is preferably at least one hour. In this case, the slag adhering to the surface of the refractory bricks can be more effectively removed. From the same perspective, the total processing time for the repeated freezing and thawing is more preferably at least three hours, and even more preferably at least four hours. On the other hand, if the total processing time is too long, the amount of slag removed will saturate, so it is preferable that it be at most seven hours.

Repeating the freezing and thawing process multiple times (two or more times) produces a certain effect, but four or more times is particularly preferable. In this case, the slag adhering to the surface of the refractory brick can be more effectively removed. From the same perspective, the number of times the freezing and thawing process is repeated is more preferably six or more times, and even more preferably nine or more times. However, if the number of times is too high, the amount of slag removed will saturate, so it is preferable that the number of times is 14 or less.

(sieving process)
In the treatment method of this embodiment, after repeated freezing and thawing steps, the treated material (refractory bricks 1 and slag 2) can be passed through a sieve 8 and separated into a plurality of different fractions for recovery, as shown in Fig. 1(D). For example, by using a sieve 8 with a mesh size of 40 mm, refractory bricks 1 with a size of 40 mm or more remain on the sieve 8, which allows separation from other substances, including the flaked slag 2, that fall below the sieve 8, and ultimately recovery of the treated refractory bricks 1.

The processing method of this embodiment does not require crushing or grinding the refractory bricks, which saves the labor of crushing; it also makes it easy to separate the refractory bricks 1 from the flaked slag 2; and it ensures a high yield of refractory bricks 1 during sieving. Specifically, the processing method of this embodiment makes it possible to achieve a refractory brick yield of 90% or more.

Next, the present invention will be explained in more detail using examples. Note that the present invention is not limited to the following examples.

Below, we compared the ability to remove slag adhering to the surface of refractory bricks by changing the freezing and thawing processing time (number of repetitions) and the freezing temperature.

(1) Evaluation of Freezing and Thawing Processing Time (Number of Repetitions) Refractory bricks with slag (slag content: approximately 16% by mass) were prepared and immersed in water for approximately 10 seconds. Next, freezing (freezing temperature: -20°C, freezing time: 20 minutes) and thawing (natural thawing, thawing time: 10 minutes) were combined into one set (total of 30 minutes), and freezing and thawing (repeated) were performed in sets ranging from 0 sets (no freezing) to 14 sets (total of 7 hours) (15 cases in total).
For each example of refractory brick after repeated freezing and thawing, the crushing strength (MPa) of the slag remaining on the surface was measured using a rebound hammer. Also, for each example of refractory brick after repeated freezing and thawing, the slag content (mass%) was measured using a rebound hammer. A graph plotting these results is shown in Figure 3. In all examples, the yield of the refractory brick was nearly 100%.

Figure 3 shows that the strength of the surface slag decreases the more times the freezing and thawing is repeated, and that by repeating the freezing and thawing process sufficiently, the slag adhering to the surface undergoes freezing and peeling, and can eventually be completely peeled off from the refractory brick.

(2) Evaluation of Freezing Temperature: Refractory bricks with slag (slag content: approximately 16% by mass) were prepared and immersed in water for approximately 10 seconds. The freezing temperature was then varied between −5°C, −10°C, −15°C, −20°C, −25°C, and −30°C. Each set consisted of a combination of freezing (freezing time: 20 minutes) and thawing (natural thawing, thawing time: 10 minutes), totaling 30 minutes. A maximum of 20 sets (total of 10 hours) of freezing and thawing were performed (six examples in total).
In each example, the time when the slag content of the refractory bricks reached 2.7% by mass or less (a target value established based on the requirements of a specific recycling destination) was considered to be the completion of freeze stripping. This time is shown in Table 1. In each example, the yield of the refractory bricks was nearly 100%.

Table 1 shows that when the freezing temperature was -25°C, the slag content of the refractory bricks was reduced to the target value in the shortest time. When the freezing temperature was -30°C, the time to complete freezing and peeling was slightly longer. This is thought to be because the temperature was lowered too much, causing rapid freezing and making it difficult for the volumetric expansion of the water to proceed.

As described above, the refractory brick processing method of the present invention makes it possible to effectively separate slag adhering to the surface of the refractory brick while ensuring the yield of the refractory brick. In particular, the present invention is expected to achieve a slag content remaining in the refractory brick of 2.7 mass% or less and a refractory brick yield of 90% or more, which was not possible with conventional methods.

1: Refractory bricks 2: Slag 4: Water tank 5: Water 5': Ice 6: Freezer 8: Sieve

Claims (4)

A method for treating refractory bricks having slag attached to their surfaces, comprising:
A method for treating refractory bricks, characterized in that water is taken up into the refractory bricks, and then freezing and thawing are repeated multiple times to remove slag from the refractory bricks. The method for treating refractory bricks according to claim 1, wherein the freezing temperature is -20°C or lower. The refractory brick treatment method according to claim 1 or 2, wherein the total treatment time for the repeated freezing and thawing is 1 hour or more. 3. The method for treating refractory bricks according to claim 1, wherein the number of times the freezing and thawing is repeated is four or more.