JPS5934666B2 - Method for manufacturing blast furnace slag ballast - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing blast furnace slag ballast that does not elute so-called yellow water and does not reduce compressive strength when used for road bases and the like.

Generally, blast furnace slag u discharged from the blast furnace during pig iron production,
The main components are calcium, aluminum, aluminum, etc. other than iron, and when it is cooled under relatively gentle conditions, it becomes crystalline and hard, and at the same time has latent hydraulic properties.

The crushed material obtained by this slow cooling method has good compaction properties and exhibits high compressive strength, so it is suitable as a road base material.

As described above, blast furnace slag ballast has excellent physical properties as a roadbed material, but when used as a roadbed material, yellow water may be leached when it comes into contact with large amounts of rainwater or groundwater during the rainy season. Since this yellow water has a very bright color tone, it can cause visual discomfort to those who view it, so measures are being taken to prevent the elution of this yellow water.

Therefore, conventionally, a so-called aging treatment method has been used to prevent elution of yellow water from blast furnace slag ballast.

In other words, this aging treatment method is a method in which the slow cooling method is crushed into shipping size (usually particle size of 100 mm or less) and then piled up at a height of several meters to 10 meters and left to stand naturally for a long period of time. This is a method to prevent yellow water from eluting after being left for up to 4 months, or at most 4 to 5 months.

However, such aging treatment methods have the problem that the treatment requires a long period of time, and the compressive strength that can be imparted to the roadbed material is greatly reduced, making it unsuitable as a roadbed material.

Therefore, in order to solve the above-mentioned problems, the inventors of the present invention, (1) The cause of yellow water elution is said to be due to the sulfur component present in approximately 1 weight percent of blast furnace slag (slow cooling method). .

In other words, sulfur in the slow-cooling primeval exists mainly as calcium sulfide (CaS) and elemental sulfur (S), and the calcium sulfide in the slow-cooling primeval exudes and dissolves in the water existing on its surface. Calcium polysulfide is produced as a result of the reaction between simple sulfur fixed on the surface and CaS+S - "CaSx" as shown in the above formula. Since the substance is an unstable substance, when it comes into contact with oxygen in a solution (yellow water), it rapidly begins to decompose 1- and the yellow color disappears from the solution, usually by air aeration for 1 to 2 hours.

@ The above-mentioned calcium polysulfide production reaction is accelerated at a temperature that is somewhat higher than room temperature.

○ In the conventional aging treatment method, the internal temperature of the piles piled up in the slow cooling method reaches 40 to 80 ° C. 2 weeks to 1 month after they are piled up, and then gradually decreases. Often, the color changes to gray-green at the highest temperature, and turns gray-brown by the end of aging, and even if the product has been thoroughly aged, it will still remain even after being immersed in water. Even when boiling, the yellow water does not elute, but in order to advance the aging reaction, the heat released by its own hydraulic reaction must be applied, and therefore, it does not affect the development of compressive strength. A part of the necessary hydraulic properties are already lost when used as a roadbed material, and due to the hydraulic reaction, the powdery portions of the slow cooling agents stick to each other, and the particle size distribution tends to become coarser. As a result, the compressive strength of the balance after knee zinc treatment decreases.

(2) Since the hydraulic reaction rate of the slow cooling method in the aging method is very slow, it must be kept in the dark for a long period of time until the aging is completed.

■ On the other hand, JP-A-49-91.004, JP-A-5
As described in Publication No. 2-129730, by heating the blast furnace slag ballast to a temperature of 100°C or higher (the melting point of elemental sulfur (So) is 112.8°C) (therefore, in the absence of moisture), A method that attempts to prevent the generation of CaSx by sublimating or evaporating the S crystals present on the surface of the blast furnace slag ballast and removing only the so of CaS and soo, which causes the generation of yellow water. I don't know.

According to this method, the blast furnace slag ballast after the heat treatment is
Even if it comes into contact with water, it will not produce yellow water unless S is present.

However, if the blast furnace slag ballast obtained by this method is left in a humid atmosphere for a certain period of time, as shown by the black circle in Fig. occurred (-Mari.

,■ Therefore, when we investigated in detail the cause of yellow water generation in blast furnace slag ballast, we found that C.
It is thought that aS b and S react in the presence of moisture and oxygen as shown in FIG. 2.

For example, Ca, S 2 and S 2 react to form CaSx, and CaS and CaSx change to the final oxide CaSO4 via Ca5203.

Therefore, in the blast furnace slag ballast obtained by method (2), of the CaS L- and S that cause yellow water, only S has been removed, but CaS still exists in the blast furnace slag ballast. By leaving this in a humid atmosphere (i.e. in actual use conditions), it reacts with the CaS in the blast furnace slag, moisture, oxygen, etc., and passes through calcium thiosulfate and polythionate salts. , it is thought that it may chemically change to elemental sulfur (So), and therefore, if the So obtained in this way reacts with CaS remaining in the blast furnace slag ballast, yellow water will be generated again. I can't think.

■ Therefore, if the blast furnace slag ballast is heated with steam instead of being heated to sublimate or evaporate only the S in the blast furnace slag ballast, it is possible to heat the blast furnace slag ballast with steam, which is necessary for the calcium polysulfide production reaction. Heat can be obtained without using the heat generated by the hydraulic reaction, and moreover, it can be obtained rapidly in a short period of time by the steam heating, so it is possible to suppress the hydraulic reaction as in the conventional aging method, and improve the compressive strength. In addition to being able to prevent deterioration, the heating temperature is almost 100% due to steam heating.
°C can accelerate the production of calcium polysulfide more than conventional aging methods, while the heat and moisture obtained by steam heating and the presence of oxygen in parallel with such calcium polysulfide production reactions As the blast furnace slag ballast is aged, calcium thiosulfate obtained in the reaction process shown in Figure 2 is coated on the surface of CaS and S in the blast furnace slag ballast, and this coated The surface of the material is coated with calcium sulfate, which is the final oxide of sulfur obtained in the same reaction process4, and as a result, CaS and S in the blast furnace slag ballast coated with these coatings are
The reaction is suppressed, the elution of CaS into water and contact with S, and the reaction of CaS as shown in Figure 2.
Since reactions such as the change of S into S are suppressed, the generation of calcium polysulfide can be effectively suppressed even if the product is left in actual use for a long period of time.

This invention has been made based on the knowledge shown in items 0 to 0 above, and is a blast furnace slag aging treatment method 1 in which blast furnace slag ballast crushed to a predetermined particle size or less (usually 100 myr+F or less) is piled up and aged. /C The method for aging blast furnace slag ballast is characterized in that the blast furnace slag ballast is heated with steam and exposed for 3 to 30 days in the atmosphere or an oxidizing atmosphere.

In addition, in this invention, as mentioned above, the joy time is 3 to 3.
On day 0 and less than 3 days, oxidation reactions as shown in Figure 2 and CaS as described above occur.

This is because the So coating is not done sufficiently.
On the other hand, this is because the progress of the oxidation reaction and coating cannot be observed even after 30 days.

As an example, FIG. 1 shows the absorbance of 12B obtained by the present invention after being left in a humid atmosphere for 21 days, as indicated by a white circle. It is clear that the outbreak is being steadily suppressed.

Next, examples will be explained.

50 toH blast furnace slag (particle size 35 mm or more) at a height of 2 m.
They were piled up in a conical shape, and steam (pressure 3 kq/cry) was spewed out in one direction from the center of the bottom of the pile.

About 1.5 tons of steam was jetted out, and after confirming that the internal temperature of the pile of blast furnace slag was 99 to 102° C., the steam jetting was stopped.

Then, after 120 hours from the stop of the steam jetting, ballasts were collected from inside the pile of blast furnace slag, and the collected ballasts of the present invention, the comparative balss collected from the pile of blast furnace slag before the steam jetting treatment, and the above. Similarly, absorbance, unconfined compressive strength, and Particle size distribution was measured.

The results are shown in Table 1. Note that the absorbance was measured for the filtrate after adding 300 CE of distilled water to Balas 1001 and boiling it for 1 hour.

From Table 1, the following is clear.

That is, the absorbance of the ballast of the present invention is reduced by 95φ compared to the comparative ballast, which indicates that the ballast of the present invention does not elute with yellow water.

The unconfined compressive strength of the ballast of the present invention is almost the same as that of the comparative ballast, which is the value required when used as a roadbed material (12k
It can be seen that the uniaxial compressive strength of the conventional ballast does not reach the above-mentioned required value.

-! In addition, in the ballast of the present invention, there is almost no difference in the particle size distribution corresponding to the change in the above-mentioned -axial compressive strength compared to the comparative ballast, whereas in the conventional ballast, the 0.074-lower value changes from 7th to 5th coefficient. , 0.4~0.074 body is 1 from 22
It can be seen that this result is reflected in the decrease in the unconfined compressive strength.

As explained above, in the present invention, a ballast suitable as a road base material that does not elute yellow water and maintains the necessary compressive strength can be produced in a short time.

[Brief explanation of the drawing]

Figure 1 shows the absorbance of blast furnace slag ballast when left in a humid atmosphere for 12 and 21 days, and Figure 2 shows the absorbance of CaS and So in blast furnace slag ballast in the presence of moisture and oxygen. It is a figure showing an example of reaction.

Claims (1)

[Claims] 1. A method for aging blast furnace slag ballast in which blast furnace slag ballast crushed to a predetermined particle size or less is piled up and subjected to aging treatment, in which the blast furnace slag ballast is heated with steam and placed in a dry air or oxidizing atmosphere for 3 to 30 minutes. A method for aging blast furnace slag ballast, characterized by exposing it for 30 days.