JP6996453B2 - A method for suppressing boron elution of a boron-containing substance and a method for producing a material for suppressing boron elution. - Google Patents

Description

The present invention relates to a method for suppressing boron elution of a boron-containing substance and a method for producing a material for suppressing boron elution.

With the development of industry, the industrial by-products produced in various industries are increasing.
Recently, industrial by-products have been effectively used from the viewpoint of global environmental conservation. For example, blast furnace slag generated from steelworks, steel slag such as steelmaking slag (converter slag, electric furnace slag), coal ash generated from thermal power plants, incineration ash of waste and sewage sludge, etc. are melted at high temperature. Industrial by-products such as the obtained molten slag; are cooled and solidified, and after appropriate particle size adjustment, they are reused as civil engineering and building materials such as roadbed materials and ground materials.

By the way, heavy metals such as cadmium, mercury, chromium and lead can be typically exemplified as components having an adverse effect on the surrounding environment. In addition to these heavy metals, fluorine, selenium, arsenic, boron, etc. are also strictly regulated as components that have an adverse effect on the environment. For example, in the case of boron, the amount of elution from civil engineering and building materials constituting the soil (the amount of elution by the elution test specified in Notification No. 46 of the Environment Agency) is regulated to be 1 mg / L or less.

Various methods for suppressing the elution of components that adversely affect the environment have been proposed.
For example, Patent Document 1 discloses a technique of "containing ... boron in soil or incinerated ash by adding and mixing magnesium oxide ... to soil containing boron or incinerated ash and performing a solidification insolubilization treatment". ([0006]). According to this technology, "... boron is fixed and does not elute, and ... the environmental load can be reduced" ([0023]).

Patent Document 2 discloses a technique of "humidifying and curing coal ash for a predetermined period" for coal ash discharged from a thermal power plant or the like ([Claim 1]). As a result, it is stated that "the elution of boron from the landfill can be significantly suppressed as compared with the case where the coal ash is disposed of in the landfill as it is" ([0012]).

Patent Document 3 describes a harmful substance containing steelmaking slag, "the content of Al ₂ O ₃ is 3% or more, and the total content of Fe ₂ O ₃ and Al ₂ O ₃ is 15% or more." The reducing material is disclosed ([Claim 1]). Regarding the brain specific surface area of this steelmaking slag, it is described that "the effect of reducing harmful substances is not sufficient if it is less than 3,000 cm ² / g" ([0027]).

In Patent Document 4, as a method for suppressing boron elution of a boron-containing substance, "... a mixture of steelmaking slag with a boron-containing substance is mixed with water, and the mixture is air-dried and / or cured for a predetermined period". It has been disclosed ([Claim 1]). For this steelmaking slag, it is desirable that the index calculated from the contents of calcium oxide (CaO), silicon oxide (SiO ₂ ), etc. satisfies specific conditions from the viewpoint of "improving the effect of suppressing boron elution". ([0028], [0029]).

Japanese Unexamined Patent Publication No. 2004-298741 Japanese Unexamined Patent Publication No. 2007-90155 Japanese Unexamined Patent Publication No. 2005-36159 Japanese Unexamined Patent Publication No. 2015-178098

The technique described in Patent Document 1 is a technique for adding expensive magnesium oxide as a boron elution inhibitor to a boron-containing substance, so that the cost is high and the addition work is complicated. The boron-containing substance to which magnesium oxide is added may be hardened and agglomerated, and there is also a problem that it is difficult to reuse.
The technique described in Patent Document 2 requires humidification and curing of a boron-containing substance for a predetermined period of time, and a long-term humidification and curing of a boron-containing substance having a large amount of boron elution is required. It is complicated and inferior in productivity.
The techniques described in Patent Documents 3 and 4 are complicated because they are techniques in which a predetermined steelmaking slag is added and mixed with a boron-containing substance as a boron elution inhibitor, and then cured. Further, the obtained mixture has a problem that it is difficult to reuse because the mass and volume of the obtained mixture are significantly increased as compared with the boron-containing substance used.
In the technique described in Patent Document 3, crushing work may be required to increase the specific surface area of the steelmaking slag, which is more complicated.

The present invention has been made in view of the above points, and an object of the present invention is to suppress boron elution of a boron-containing substance by a simple method.

As a result of diligent studies, the present inventors have found that the amount of boron elution of the boron-containing substance can be reduced by controlling the cooling rate of the boron-containing substance, and completed the present invention.

That is, the present invention provides the following [1] to [4].
[1] A method for suppressing the elution of boron from a boron-containing substance, which is a method for suppressing boron elution of a boron-containing substance, in which the boron-containing substance in a temperature state having a liquid phase is cooled and the boron-containing substance is cooled. After cooling at Z, the cooling rate (unit: ° C./min) in the range of 0.1 ° C./min or more and 20 ° C./min or less is A, and the above-mentioned cooling rate A. A method for suppressing boron elution of a boron-containing substance, which satisfies the following formula (1), where B is the boron elution amount (unit: mg / L) of the above-mentioned boron-containing substance.
Z ≧ A × B ³ ... (1)
However, the cooling rates Z and A represent the time ratio of the temperature change when the boron-containing substance is cooled from the temperature having the liquid phase to 900 ° C.
[2] The method for suppressing boron elution of a boron-containing substance according to the above [1], wherein the boron-containing substance is slag generated in a steel process.
[3] A method for producing a boron elution-suppressing material, which comprises treating a boron-containing substance by the method according to the above [1] or [2] to obtain a boron elution-suppressing material in which boron elution is suppressed.
[4] The method for producing a boron elution inhibitor according to the above [3], wherein the boron elution inhibitor is a civil engineering and building material.

According to the present invention, boron elution of a boron-containing substance can be suppressed by a simple method.

It is the graph which plotted the test result of the boron elution suppression.

[Method for suppressing boron elution of boron-containing substances]
The method for suppressing boron elution of a boron-containing substance of the present invention (hereinafter, also simply referred to as “the method for suppressing boron of the present invention”) generally suppresses the elution of boron from a boron-containing substance containing boron as an elution component. This is a method for suppressing boron elution of a boron-containing substance.

More specifically, the suppression method of the present invention cools a boron-containing substance in a temperature state having a liquid phase.
Then, the cooling rate (unit: ° C./min) when cooling the boron-containing substance is Z, the cooling rate in the range of 0.1 ° C./min or more and 20 ° C./min or less (unit: ° C./min) is A, and cooling is performed. When the amount of boron elution (unit: mg / L) of the boron-containing substance after cooling at the rate A is B, the following formula (1) is satisfied.
Z ≧ A × B ³ ... (1)
However, the cooling rate Z and the cooling rate A both represent the time ratio of the temperature change when the boron-containing substance is cooled from the temperature having the liquid phase to 900 ° C.

As demonstrated in [Example] below, by satisfying the above formula (1), the amount of boron elution of the boron-containing substance is reduced.
As a result of diligent investigation by the present inventors, it was clarified that boron is mainly concentrated in the glass phase region in the boron-containing substance. It was also found that by increasing the cooling rate of the boron-containing substance, the ratio of the glass phase in the structure is increased, and the boron concentration in the glass phase is relatively decreased, so that the amount of boron elution is suppressed. ..
In this way, the boron elution of the boron-containing substance can be suppressed and the environmental standard can be satisfied by a simple method of only adjusting the cooling rate.
The amount of boron elution is measured by the elution test specified in Notification No. 46 of the Environment Agency.

The boron-containing substance is not particularly limited, and examples thereof include slag generated in a steel process.
Regarding the boron-containing substance which is such a slag, the content of each component is not particularly limited, but for example, SiO ₂ : 22.0 to 40.0% by mass and Al ₂ O ₃ : 2.0 to 20.0% by mass. %, CaO: 25.0 to 45.0% by mass, MgO: 2.0 to 18.0% by mass, Fe: 3.0% by mass or less, MnO: 1.0 to 18.0% by mass are preferable.

Such slag has a substantially constant composition for each of the ironmaking process, the various refining processes of the steelmaking process, and the smelting process of various ferroalloys.
The slag that is discharged in a molten state at the operating temperature of each process and then cooled and solidified becomes a slag product through processes such as crushing and classification.
Each slag product may have environmental standards that must be met according to its application. In that case, each slag product is subjected to various elution tests using representative samples collected as needed, and the amount of elution of each component is controlled.
As mentioned above, the composition of the slag generated from each process is generally constant. Therefore, the elution amount of each component in the slag product produced from the slag generated from each process or the raw material thereof is also a substantially constant value.
Therefore, the boron elution amount B may be measured for a sample collected by cooling at a cooling side degree A in the range of 0.1 ° C./min or more and 20 ° C./min or less at a predetermined frequency such as every month.

The industrially discharged slag is left in a cooling yard and naturally cooled, and then treated appropriately. When such a process is performed, the cooling is performed within the range of the cooling rate A.
For example, thermocouples are installed in several places in the cooling yard in advance, or the surface of the discharged slag is measured with a thermoviewer or the like. This makes it possible to measure the cooling rate A of the boron-containing substance, which is industrially discharged slag.
Then, using a boron-containing substance having a cooling rate A in the range of 0.1 ° C./min or more and 20 ° C./min or less, the amount of boron elution of the boron-containing substance after cooling at the cooling rate A can be measured. can.

In the suppression method of the present invention, the boron-containing substance in a temperature state having a liquid phase (for example, 1200 ° C. or higher) is cooled so as to satisfy the above formula (1), whereby the amount of boron elution of the boron-containing substance is satisfied. To reduce.
The boron-containing substance in a temperature state having a liquid phase is, for example, steel slag discharged from a blast furnace, a converter or an electric furnace, and molten slag discharged from a melting furnace.

The method for cooling a boron-containing substance having a liquid phase and in a temperature state (simply referred to as “boron-containing substance” in this paragraph) is not particularly limited, and for example, the boron-containing substance is discharged onto an iron plate to a predetermined thickness. There are an iron plate cooling method for cooling the boron-containing substance, a water crushing method for rapidly cooling the boron-containing substance using a water stream, a wind crushing method for rapidly cooling the boron-containing substance using an air stream, and the like, which can be appropriately selected according to a desired cooling rate.

[Boron elution suppression treatment material and its manufacturing method]
Boron elution is suppressed by treating the boron-containing substance by the above-mentioned suppression method of the present invention (that is, cooling the boron-containing substance in a temperature state having a liquid phase so as to satisfy the above formula (1)). The resulting boron elution inhibitor is obtained.
The obtained boron elution suppressing treated material is suitably used as a civil engineering and building material such as a roadbed material and a ground material after the particle size is adjusted as necessary.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these.

Three types of slag generated in the steel process were used as boron-containing substances α, β and γ, respectively. Both are usually discharged at a high temperature of 1500 ° C. The composition of each boron-containing substance is shown in Table 1 below. However, each boron-containing substance also contains components other than those shown in Table 1 below. Therefore, in each boron-containing substance, the total content of the component compositions shown in Table 1 below is not 100% by mass.

100 g of each of the boron-containing substances α, β and γ were placed in a graphite crucible and held in an electric furnace to bring the temperature to a temperature state (1200 ° C.) having a liquid phase. Then, it was cooled from 1200 ° C. to 900 ° C. at a predetermined cooling rate A. Then, the graphite crucible was taken out from the electric furnace and cooled with water. Each boron-containing substance was taken out from the graphite crucible, pulverized to 2 mm or less, and the boron elution amount B was measured by the elution test specified in Notification No. 46 of the Environment Agency.
As shown in Table 1 below, the boron-containing substance α had a boron elution amount B of 11.7 mg / L after cooling at a cooling rate A of 3 ° C./min.
The boron-containing substance β had a boron elution amount B of 9.1 mg / L after being cooled at a cooling rate A of 0.1 ° C./min.
The boron-containing substance γ had a boron elution amount B of 1.2 mg / L after being cooled at a cooling rate A of 20 ° C./min.

Next, 10 kg of each boron-containing substance was placed in a crucible, redissolved using a small melting furnace, and then cooled at a cooling rate Z (unit: ° C./min) shown in Table 2 below. The cooling rate Z is the time ratio of the temperature change when each boron-containing substance is cooled from the temperature having the liquid phase (the temperature at which it is redissolved) to 900 ° C.
Cooling methods include a method of slowly cooling each boron-containing substance by controlling the cooling rate in the pot (inside the pot), and each redissolved boron-containing substance is discharged onto a 20 mm-thick iron plate for cooling. A method (iron plate) or a method of cooling each redissolved boron-containing substance by a water crushing method using a water stream (water crushing) was used. In each cooling method, the cooling rate Z was determined by measuring the temperature as follows.

(Inside the crucible)
When cooled in the crucible, the temperature at the middle position in the height direction and the center position in the horizontal direction of the crucible in the boron-containing substance in the crucible was measured with a thermocouple. The temperature change in the time from the temperature at which the boron-containing substance was redissolved to the temperature at 900 ° C. was determined. This is because the transformation between the crystal and the glass occurs at about 900 ° C. or higher, so it is important how to secure the cooling rate from the temperature state having the liquid phase to 900 ° C.

(Iron plate)
When cooled on the iron plate, thermocouples were installed in advance with respect to the iron plate at various height directions, and the temperature of the boron-containing substance discharged onto the iron plate was measured. The temperature change in the time from the temperature at which the boron-containing substance was redissolved to the temperature at which it dropped to 900 ° C. was determined at each height position, and the cooling rate Z was determined from the average value.

(Water crushing)
When cooled by the water crushing method, first, the time from pouring the redissolved boron-containing substance into the water stream to flowing into the water tank was measured. Next, a thermocouple was placed in the granulation of the boron-containing substance deposited in the water tank, and the temperature was measured. The cooling rate Z was determined from the difference between the redissolved temperature and the temperature during granulation in the water tank, and the time from when the boron-containing substance was poured into the water stream until it flowed into the water tank.

After cooling at the cooling rate Z, each boron-containing substance was pulverized to 2 mm or less, and the amount of boron elution was measured by the elution test specified in Notification No. 46 of the Environment Agency. The results are shown in Table 2 below. When the amount of boron elution was 1.0 mg / L or less, it was evaluated that the elution of boron from the boron-containing substance could be suppressed, and "○" was described in the "Boron elution suppression" column of Table 2 below. .. On the other hand, when the amount of boron elution was more than 1.0 mg / L, "x" was described in the "Boron elution suppression" column of Table 2 below.

Based on the results shown in Tables 1 and 2 above, the test results for suppressing boron elution were plotted in FIG.
FIG. 1 is a graph plotting the test results of boron elution suppression. In the graph of FIG. 1, the horizontal axis shows the cooling rate Z, and the vertical axis shows the amount of boron elution after cooling at the cooling rate Z.
The graph of FIG. 1 plots the test results (“◯” or “×”) for suppressing boron elution. However, "○" of the boron-containing substance β is replaced with "◇", and "○" of the boron-containing substance γ is replaced with “Δ” for plotting.
Further, in the graph of FIG. ¹ , a line segment represented by the formula Z = A × B3 is described for the boron-containing substances α, β and γ.
As shown in the graph of FIG. 1, the line segment represented by the equation Z = A × B ³ is arranged at the boundary between “×” and “◯” (“◇”, “Δ”).

From the graphs of Tables 1 and 2 and FIG. 1, it was found that when the following formula (1) was satisfied, the amount of boron elution was 1.0 mg / L or less, and the elution of boron could be suppressed.
On the other hand, when the following formula (1) was not satisfied, the amount of boron elution was more than 1.0 mg / L, and the suppression of boron elution was insufficient.
Z ≧ A × B ³ ... (1)
In this way, the boron elution of the boron-containing substance could be suppressed by a simple method.

Claims (3)

A method for suppressing boron elution of a boron-containing substance, which suppresses the elution of boron from a boron-containing substance.
The boron-containing substance is slag generated in the steel process.
The boron-containing substance having a temperature of 1200 ° C. or higher is cooled, and the substance is cooled.
The cooling rate (unit: ° C./min) when cooling the boron-containing substance is Z, the cooling rate in the range of 0.1 ° C./min or more and 20 ° C./min or less (unit: ° C./min) is A, and the cooling. A method for suppressing boron elution of a boron-containing substance, which satisfies the following formula (1), where B is the boron elution amount (unit: mg / L) of the boron-containing substance after cooling at a rate A.
Z ≧ A × B ³ ... (1)
However, the cooling rates Z and A represent the time ratio of the temperature change when the boron-containing substance is cooled from the temperature of 1200 ° C. or higher to 900 ° C. A method for producing a boron elution inhibitor, which comprises treating a boron-containing substance by the method according to claim 1 to obtain a boron elution inhibitor treated material in which boron elution is suppressed. The method for producing a boron elution inhibitor according to claim 2 , wherein the boron elution inhibitor is a civil engineering building material.

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