JP2002173348A - Method of manufacturing blast furnace granulated slag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing granulated slag which has a high coarse grain rate and is dense. SOLUTION: The method of manufacturing the granulated slag comprising adding an iron oxide-containing material at <=2 mass% of the mass of molten slag flowing out of a blast furnace in terms of the weight of the iron oxide to the molten slag, than granulating the slag with water above 60 deg.C. At this time, the slag is granulated with the water at a water flow rate/slag flow rate of >=5 to <30 for an added effect. The iron oxide-containing material is preferably <=5 mass% in content as water of crystallization.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing blast furnace slag fine aggregate for concrete by water granulation, and more particularly to a method for producing dense granulated blast furnace slag having a high coarse grain ratio.

[0002]

2. Description of the Related Art Blast furnace slag is used as a raw material for cement, roadbed material,
It is effectively used as aggregate for concrete. The method of treating slag is selected in accordance with these applications. Directly, pressurized water is sprayed on the molten slag to granulate it and then crushed to adjust it to the required particle size. After cooling and solidifying, there is a method of adjusting to a required particle size by crushing. The former granulation method is used in the production of cement raw materials and fine aggregate for concrete.

[0003] For fine aggregate for concrete, dense granulated slag that satisfies the JIS standard for density is required. However, there is a problem that blast furnace slag is easily foamed and lightened during granulation. As a technique to solve this, for example,
Japanese Patent Application Laid-Open No. 4-56627 describes hard as having almost the same meaning as dense. However, Japanese Patent Application Laid-Open No. 55-136151 discloses a technique for lowering and adjusting the slag temperature to 1300 ° C. to 850 ° C. A technique for injecting pressurized water having a water flow rate / slag flow rate ratio of 8 to 12 at a temperature of not more than 0 ° C is disclosed in Japanese Patent Application Laid-Open No. 62-113338. Each is disclosed.
In addition, Japanese Patent Publication No. 60-37066 discloses a method of adding an iron oxide-containing substance to molten slag.

Further, in order to use granulated blast furnace slag as fine aggregate for concrete, an appropriate particle size distribution similar to natural sand is required. However, granulated blast furnace slag is rarely used alone as fine aggregate for concrete, and is often used in the form of a mixture with natural sand. Fine particle sizes are often desired.

[0005] In order to improve the particle size distribution and particle shape of the granulated blast furnace slag, crushing after granulation is often performed. However, if the particle size of the slag after the water granulation is already small, the slag becomes finer when crushed, the sand that can be mixed is limited, and the range of use as fine aggregate is narrowed. Therefore, it is preferable that the particle size of the slag after water granulation is appropriately large in order to improve the particle shape and particle size. This is because fine aggregate having a high coarse particle ratio can be used by lowering the coarse particle ratio by further crushing when the sand to be mixed is coarse, and is highly useful. As a method for producing coarse granulated hard granulated slag, for example, Japanese Patent Application Laid-Open No.
There is disclosed a method of performing water granulation at a temperature of ° C., and further setting the ratio of water flow rate to slag flow rate (hereinafter referred to as water flow rate / slag flow rate ratio) to 30 or more.

[0006]

In the prior art, no method relating to a method of coarsening fine granulated slag could be found other than the above-mentioned Japanese Patent Application Laid-Open No. 11-236255. The present inventors have experimentally examined the publication technology in the pre-furnace method, and confirmed that the higher the cooling water temperature, the higher the coarse particle ratio, but the lower the density. Therefore, in order to improve the density in the pre-furnace method in this publication,
The water flow rate / slag flow rate ratio is set to 30 or more, and the present inventors also confirmed that the density was increased by performing the same test, but on the other hand, the coarse particle ratio was reduced. The publication states that the coarse particle ratio did not have a clear relationship with items other than the cooling water temperature. However, the present inventors have conducted extensive studies and found that the water flow rate / slag flow rate ratio was as described above. It has been found that the higher the density, the higher the density but the lower the coarse particle ratio.
That is, such a technique cannot obtain a dense granulated slag having a high coarse particle ratio.

On the other hand, Japanese Patent Publication No. 60-37066 does not disclose the coarse particle ratio of the obtained granulated slag, but in order to obtain the densified granulated slag of the publication, the cooling water temperature is usually lowered. A method is used. The present inventors have experimentally studied the technology of the publication and found that when the cooling water temperature was low, the coarse particle ratio was reduced. Also, depending on the iron oxide-containing substance used, sufficient denseness was not obtained in some cases.

[0008] In view of the above, an object of the present invention is to provide a method for producing dense granulated slag having a high coarse particle ratio.

[0009]

Means for Solving the Problems The inventors of the present invention conducted a study for the purpose of obtaining coarse granulated blast furnace slag, and it became clear that when the granulated water temperature at the end of slagging is high, the coarse particle ratio increases. However, the density of the granulated slag decreased. Therefore, it was found that a fine granulated slag having a high coarse-grain ratio and a dense granulated slag can be obtained in the final stage of the slag when the iron oxide-containing substance is added and granulated experimentally. In view of the above, the present invention has been completed by earnestly studying conditions for stably producing dense granulated slag having a high coarse particle ratio.

That is, according to the present invention, an iron oxide-containing substance is added to a molten slag flowing out of a blast furnace in an amount of iron oxide of 2% by mass or less based on the mass of the molten slag, and then granulated with water having a water temperature of 60 ° C. or higher. A method for producing granulated slag, characterized in that:

At this time, the water flow rate / slag flow rate is 5 or more and 3
It is effective to granulate at less than 0.

It is preferable to use an iron oxide-containing substance having a water content of 5% by mass or less.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is characterized in that an iron oxide-containing substance is added to molten slag flowing out of a blast furnace at a content of iron oxide of 2% by mass or less, and then granulated with water having a water temperature of 60 ° C or more. This is a method for producing granulated slag.

Various tests of iron oxide-containing substances having different iron oxide contents clearly showed a correlation between the net addition amount of iron oxide and the density. That is, the density was improved while the amount of iron oxide was added to the molten slag. The amount of iron oxide added was improved except for 0% by mass, that is, not added at all, and sufficiently dense granulated slag was obtained when 2% by mass was added. Even if more than 2% by mass was added, there was almost no further improvement in density. In the present invention, iron oxide is iron (II)
And the total of oxides containing iron (III) and the content is J
It can be measured according to IS M8212, M8213 and the like. The iron oxide-containing substance is preferably added while the slag temperature is as high as possible, but a sufficient effect can be obtained if the iron oxide-containing substance is dissolved. As described above, the density of the granulated slag could be increased by adding the iron oxide-containing substance, and the influence of the granulated conditions on the slag density was small.

As described above, the effect of the present invention can be obtained by adding 2% by mass or less of iron oxide to the molten slag. However, in order to minimize the addition amount of the iron oxide-containing substance, The iron-containing substance preferably contains at least 40% by mass of iron oxide, and the higher the content, the more preferable. In order to prevent a decrease in the slag temperature by adding a large amount of iron oxide-containing substance to the molten slag,
This is because it is difficult to add a large amount of the iron oxide-containing substance due to the high viscosity of the molten slag. A particle size of about 1 mm or less is sufficient for the iron oxide-containing substance, but the finer the particle size, the shorter the mixing time with the molten slag and the more uniform the dispersion.

On the other hand, the coarse particle ratio greatly varies depending on the granulation conditions, particularly the water temperature. Therefore, in the present invention, it is preferable to granulate with water having a water temperature of 60 ° C. or higher after adding the iron oxide-containing substance. If the water temperature is lower than 60 ° C., although the density is high, the coarse particle ratio may be reduced. Also, the higher the water temperature, the higher the coarse particle ratio, but since it is water-granulated with liquid water, it will be granulated below the boiling point of water at most. If the temperature is too high, an undesirable phenomenon may occur from the viewpoint of circulating water operation cost such as intense evaporation of water. Considering this point, the temperature of the water used for granulation is preferably 60 to 85 ° C. In the present invention, when the water temperature fluctuates during granulation, the water temperature means an average value of the water temperature.

When the water temperature was low, the effect of the addition of the iron oxide-containing substance on the coarse particle ratio was not remarkable, but when the water temperature was high, the addition of the iron oxide-containing substance There is a synergistic effect of coarsening by the addition. Hereinafter, this point will be described in detail.

FIG. 2 is a conceptual comparison diagram of the granulated slag quality of the present invention and the prior art. In order to increase the density in a normal water granulation method, a method of lowering the water temperature and quenching is performed, and the quality range 1 of the granulated slag obtained by this method (the quality range of the normal water granulation technology at low water temperature) As shown in FIG. However, as shown in the figure, the density is high but the coarse grain ratio is low. Therefore, a method of increasing the water temperature in order to improve the coarse particle ratio has been disclosed. FIG. 2 shows the quality range 2 of the granulated slag obtained by this method (the quality range of the prior art for coarsening at high water temperature). However, as shown in the figure, although the coarse grain ratio increased, the density decreased. Therefore, a method of increasing the water flow rate / slag flow rate ratio has been applied to improve the density. FIG. 2 shows the quality range 3 of the granulated slag obtained by this method (the quality range of the prior art in which the granulated particles are coarsened at a high water temperature and densified at a high water flow rate / slag flow ratio).
However, although the density could be increased, the percentage of coarse particles decreased. On the other hand, there is a conventional technique for densification by adding an iron oxide-containing substance. However, as described above, the water temperature is lowered for densification by ordinary water granulation. 4 (quality range of the prior art in which densification is performed with an oxide-containing substance), and although a slight densification is possible, the coarse particle ratio hardly changes.

The inventors of the present invention combined the conventional technique of densification by adding an iron oxide-containing substance and the conventional technique of coarsening by increasing the water temperature to obtain a region 5 (oxide-containing substance). It is estimated that the quality of the quality range expected by the combination of the conventional technology of densification and the conventional technology of coarsening at high water temperature can be obtained. The estimated area is the maximum effect obtained by adding the iron oxide-containing substance of the prior art (the absolute dry density in the area 4), and the maximum effect obtained by increasing the water temperature in the prior art (the coarse area of the area 2). (Grain ratio) is simply added. However, when the present inventors tested,
The obtained granulated slag shows the quality of the region 6, and it has been newly found that there is an effect that the coarse particle ratio when both techniques are combined is higher than estimated.

The water granulation method includes a method in front of a furnace in which pressurized water is directly injected into molten slag flowing down from a slag gutter to granulate the water, and a method in which molten slag is once received from a slag gutter into a slag pot and then transported out of a blast furnace. Similarly, an out-of-furnace method for water granulation is implemented, but the present invention is applicable to any method. However, compared with the out-of-furnace method, the pre-furnace method has a higher coarse-grain ratio and makes it easier to obtain dense granulated slag. Therefore, when the present invention is applied to the before-furnace method, a more remarkable effect is obtained.

In the present invention, the ratio of water flow rate / slag flow rate is 5
It is preferable to carry out water granulation at a number not less than 30. Here, the water flow rate means the mass flow rate of the water, and the slag flow rate means the mass flow rate of the slag, and usually, the mass per minute (ton / ton)
min). As a result of intensive experiments, the inventors have found that the coarse particle ratio varies depending on the water flow rate / slag flow rate ratio in addition to the water temperature, and that the lower the water flow rate / slag flow rate ratio, the higher the coarse particle rate. From this viewpoint, the water flow rate / slag flow rate ratio is preferably less than 30. On the other hand, if the ratio of water flow rate / slag flow rate is less than 5, the amount of slag that falls without passing through the water flow without being granulated increases, so that the water flow rate / slag flow rate ratio is preferably 5 or more. In the present invention, when the water flow rate / slag flow rate fluctuates during granulation, the water flow rate / slag flow rate ratio means the average value of the water flow rate / slag flow rate ratio.

The iron oxide-containing substance used in the present invention preferably has a crystallization water content of 5% by mass or less. In the present invention, the crystallization water is water that is not removed even when dried at 100 ° C., and is water present in the iron oxide-containing substance in the form of a hydroxide or the like. The water content of crystallization is based on JIS
It can be measured in accordance with K0067. The present inventors have conducted various studies on iron oxide-containing substances, and found that even if the iron oxide content is substantially the same, the density may not be as high as expected, which was caused by the contained crystallization water. . When a substance containing water of crystallization was calcined (equivalent to ignition) and a substance from which water of crystallization was removed was used, a densification effect commensurate with the iron oxide content was obtained. Therefore, in the present invention, it is recommended to use an iron oxide-containing substance having a crystallization water content as small as possible. However, if the crystallization water content is 5% by mass or less, a sufficiently dense slag can be obtained. Further, even a substance having a high iron oxide content but a high crystalline content can be used in the present invention if the crystallization water content is reduced to 5% by mass or less by calcination or the like.

The obtained granulated slag can be processed by appropriately using a method effective for improving the absolute dry density and various known methods effective for improving the grain shape. For example, it is possible to obtain a slag having a suitable coarse particle ratio using a normal crusher such as an impact crusher or a cone crusher.

[0024]

Embodiments of the present invention will be described below.
The influence on the quality of the granulated slag was investigated by changing the added iron oxide-containing substance and the granulation conditions.

The iron oxide-containing substance was dispersed and added onto the flowing molten slag in the slag trough after separating the molten slag from the hot metal flowing out of the blast furnace. Since the flow rate of the molten slag fluctuates, the amount of addition was determined in advance, and the addition rate was adjusted to add the amount. After the added iron oxide-containing substance was sufficiently dissolved, ordinary water granulation was performed. The granulated water temperature shown in Table 1 is an average value of the water temperature fluctuating during granulation. When the amount of water of crystallization exceeds 5% by mass, the iron oxide-containing material was calcined to 5% by mass or less, and the current material was added as it was. In addition, all the granulation methods were tested by the furnace front type.

In order to use granulated blast furnace slag as fine aggregate for concrete, it is desirable to satisfy the JIS standard. However, as described above, the particle size distribution should be such that it can correspond to the particle size of sand to be mixed. It is preferred to have various particle sizes from coarse to fine. For this reason, in the present embodiment, the target value was a coarse grain ratio of 3 or more.

Processing after granulation is performed until the absolute dry density is less than 2.5 of the JIS standard, and becomes 2.5 or more.
When the absolute dry density is already 2.5 or more, it is only necessary to improve the grain shape, and to obtain a fine aggregate having as high a coarse grain ratio as possible. The processing method was performed by combining and using a method effective for improving the absolute dry density and a method effective for improving the grain shape, for example, using a normal crusher such as an impact crusher or a cone crusher.

The absolute dry density and the coarse particle ratio after granulation and processing were measured according to JIS standards, and were used as a guide for evaluating slag quality.

Table 1 shows the conditions and results of the examples and comparative examples. FIG. 1 shows a change in quality of the slag according to the example and the comparative example between after granulation and after crushing.

[0030]

[Table 1]

In Example 1, the iron ore 2 (lobe river) having an iron oxide content of 80% by mass and a crystallization water content of 8% by mass was calcined (heated in an electric furnace at 900 ° C. for 1 hour) to form a crystal water. The calcined iron ore 2 having a content of less than 0.5% by mass and an iron oxide content of 87% by mass was, on average, 0.5% by mass with respect to the molten slag.
After the addition, that is, about 0.44% by mass in terms of the amount of iron oxide, the water temperature was 70 ° C. on average, and the water flow rate / slag flow rate ratio was 1 on average.
This is an example in which granulation was performed in Step 2. Since the obtained granulated slag had already exceeded the target values in both the absolutely dry density and the coarse particle ratio, processing was performed to the extent of improving the grain shape, and a dense slag fine aggregate having a high coarse particle ratio was obtained.

Example 2 is an example in which 2% by mass of calcined iron ore 2 and about 1.7% by mass of iron oxide were added in the same manner as in Example 1. A slag fine aggregate having both a high absolute dry density and a high coarse particle ratio was obtained from Example 1.

In Example 3, iron ore 1 (Carroll Lake) having an iron oxide content of 88% by mass and a crystallization water content of 2% by mass was prepared.
Since the water content of crystallization is small, an average of 1% by mass is added as it is, that is, about 0.88% by mass of iron oxide is added. Although the absolute dry density was slightly low, a slag fine aggregate satisfying the target values in both the absolute dry density and the coarse particle ratio was obtained.

In Example 4, an average of 1% by mass of a sintered ore having an iron oxide content of 75% by mass and a crystallization water content of less than 0.5% by mass was added because the crystallization water content was small. In this example, about 0.75% by mass was added. A slag fine aggregate satisfying the target values in both the absolute dry density and the coarse particle ratio was obtained.

Example 5 is an example using converter dust, and Example 6 is an example using rolled sludge. Those having a high iron oxide content were selected and used. In each case, what was generated in the iron-making process was recovered. However, although the water of crystallization in the solid content was low, it was used after drying because of the high water content. In each of the examples, fine slag aggregates satisfying the target values in both the absolute dry density and the coarse particle ratio were obtained.

Example 7 is an example in which iron ore 2 having a water content of crystallization higher than 5% by mass was used without calcining. Processing was performed because the absolute dry density of the granulated slag was slightly low,
When the absolute dry density was set to 2.50 g / cm ³ , the coarse particle ratio was able to secure the target value of 3 or more.

Comparative Examples 8 and 9 are ordinary granulations without addition of an iron oxide-containing substance, but were conducted at a high average water temperature of 80 ° C. and a low average water temperature of 50 ° C., respectively. When the water temperature was high, granulated slag having a low density but a relatively high coarse particle ratio was obtained. When this was processed to an absolutely dry density of 2.5, the coarse particle ratio was reduced, and only fine aggregate was obtained. Conversely, if the water temperature was low, granulated slag with an absolutely dry density of 2.5 or more was obtained, so we stopped the processing to the degree of improving the grain shape, but because the coarse grain ratio was already low, we could only obtain finer fine aggregate. I couldn't.

Comparative Example 10 was an example in which the water temperature was 60 ° C. or higher, the average was 80 ° C., the water flow rate / slag flow ratio was 30 or higher, and the average was 35 without adding the iron oxide-containing substance. Comparative Example 8 This is an example in which the water flow rate / slag flow rate ratio is increased. The absolute dry density of the granulated slag was 2.5 or more, but the coarse particle ratio was reduced. Then, when processing was performed to the extent that the grain shape was improved, the fine aggregate had a coarse grain ratio lower than the target. Comparing Comparative Example 10 with Comparative Example 8, it was found that by increasing the water flow rate / slag flow rate ratio, although the absolute dry density was improved, the coarse particle ratio was reduced.

In Comparative Example 11, iron ore 1
Was added and water was granulated at an average water temperature of 50 ° C. The granulated slag was dense but had a low coarse grain ratio, and after being processed to the extent that the grain shape was improved, the fine aggregate had a coarse grain ratio lower than the target.

As described above, the granulated slag according to the present invention to which the iron oxide-containing substance was added and the water temperature was adjusted was excellent in both the absolute dry density and the coarse particle ratio.

[0041]

According to the present invention, it is possible to produce dense granulated slag having a high coarse particle ratio. Granulated slag according to the present invention can be adjusted to various particle sizes from coarse to fine by crushing because of a high coarse particle ratio,
Since it has a good absolute dry density even after the crushing process, it can be properly used according to the particle size of the sand mixed with the fine aggregate. That is, the range of use as fine aggregate is greatly expanded.

[Brief description of the drawings]

FIG. 1 is a view showing the absolute dry density and the coarse particle ratio of slag after granulation and slag after crushing.

FIG. 2 is a conceptual comparison diagram of the granulated slag quality of the present invention and the prior art.

[Explanation of symbols]

1 Quality range of ordinary water granulation technology at low water temperature 2 Quality range of conventional technology for coarsening at high water temperature 3 Quality range of conventional technology for coarsening at high water temperature and densification at high water flow / slag flow ratio 4 Quality range of conventional technology for densification with oxide-containing material 5 Quality range expected by combination of conventional technology for densification with oxide-containing material and conventional technology for coarsening at high water temperature 6 Quality range of the present invention

Claims (3)

[Claims] 1. The molten slag flowing out of a blast furnace is provided with an iron oxide-containing substance in an amount of iron oxide of 2% based on the mass of the molten slag.
A method for producing granulated slag, wherein the granulated slag is granulated with water having a water temperature of 60 ° C. or higher after addition of not more than mass%. 2. The water flow rate / slag flow rate during granulation is 5
The method for producing granulated slag according to claim 1, wherein the slag is not less than 30. 3. The method for producing granulated slag according to claim 1, wherein the water content of crystallization in the iron oxide-containing substance is 5% by mass or less.