JPH0611657B2 - Method for recovering lime from dephosphorized slag - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to hot metal flowing out of a blast furnace to a hot metal ladle (including torpedo and other containers; the same applies hereinafter) or during tapping gutter or in a hot metal ladle. In order to recover the lime content contained in the slag as slag and / or gypsum from the slag generated when the phosphorus contained in the hot metal is removed using a coal-based flux. The present invention relates to a method for recovering lime content from slag.

[Prior art and its problems]

Recently, in the middle of or in the hot metal ladle for guiding the hot metal flowing out of the blast furnace to the hot metal ladle, in the hot metal ladle, a lime-based flux is supplied to the hot metal in the hot metal ladle or the hot metal ladle, and by the said flux. Phosphorus in hot metal is removed.

The molten slag produced during the removal of phosphorus contained in such hot metal contains metal and a large amount of lime. Although this metal has been conventionally collected by magnetic separation or the like, the slag after collecting the metal has been discarded without recovering a large amount of lime contained in the slag.

[Object of the Invention]

Therefore, the object of the present invention is to efficiently recover the ingots from the slag produced when the phosphorus in the hot metal is removed by using the lime-based flux, and after recovering the ingots. It is to provide a method for recovering lime content from slag for recovering lime content contained in the slag as slaked lime and / or gypsum.

[Outline of Invention]

This invention is to crush the slag produced when performing dephosphorization of the hot metal using a lime-based flux, and then contact the crushed slag with water to produce CaO in the slag.
To form Ca (OH) _2, and the slag is pulverized by such a grading reaction, and then the metal in the pulverized slag is adsorbed on a magnet to be separated and recovered. It is characterized by separating the finely ground slag after recovering the metal by physical means, and Ca (OH) ₂ in the finely ground slag as it is, or by applying sulfuric acid to this to recover it as gypsum. I have.

[Structure of Invention]

Table 1 is an example of the component composition of the slag produced when phosphorus in the hot metal is removed using a lime-based flux. As can be seen from Table 1, since slag contains free lime as a main component, it is so active (unstable) that it expands and collapses even if left in the atmosphere.

As a result of microscopic observation, the above slag is a constituent mineral β-2CaO ・ SiO ₂ , Ca ₅ OF (PO ₄ ) ₃ , C in the matrix of free lime.
It has a structure in which aF ₂ is dispersed, and iron components are contained in the slag in a state of being incorporated, from fine particles having a size of about 20 μm to flat particles having a size of several cm.

The slag having the above-described composition is used, for example, by using a jaw crusher, and the particle size is about 50 mm or less (preferably 15 mm or less).
mm or less). Then, the slag thus roughly crushed is put into a water tank containing hot water of 60 to 100 ° C. and stirred.

As a result, CaO in the slag is dissolved in the aquarium and C
It becomes a (OH) ₂ and the slag expands, collapses itself, and is pulverized.

The following is an example of conditions for favorably performing fine pulverization due to expansion and collapse of slag.

Water temperature: 60 to 100 ° C (preferably 80 to 100 ° C) Slag amount: 100 to 500 kg (preferably 1) per ton of water
50 to 300 kg) Treatment time: 1 to 3 hours In the coarsely crushed slag, for example, 50 × 100 mm
It contains a large amount of flat metal ingot to a fine metal ingot of about 20 μm. Therefore, if the large metal is removed after the coarse crushing, the workability of the subsequent slaking and fine crushing steps can be improved.

That is, the slag is about 50 mm or less (preferably 15 mm or less)
After crushing to a particle size of, the metal is separated and collected in the slag by a magnet, and then the slag after collecting the metal is placed in a water tank and stirred to dissolve. As a result, most of the metal in the slag in the aquarium has been removed, so the amount of slag settling at the bottom of the aquarium is small, and the slag can be finely pulverized efficiently with good stirring. Then, the metal in the pulverized slag can be completely recovered by magnetic separation.

Furthermore, some of the ingots magnetically selected and recovered in the crushing stage have insufficient slag separation due to slag biting. Therefore, by pouring and stirring such a metal in water to dissolve it, and separate the slag from the metal, the quality of the recovered metal can be further improved.

In addition, metal is also mixed in the slag separated by magnetic separation in the coarse crushing stage. Therefore, if such a slag is soaked in water and then magnetically selected in the same manner as described above, it is possible to recover the bullion mixed in the slag.

Table 2 shows the components of the fine slag and the specific gravity thereof after recovering the metal as described above.

As can be seen from Table ₂ , the specific gravity of Ca (OH) ₂ contained in the fine powder slag after collecting the metal is smaller than that of the other components. This Ca (OH) ₂ is 10μ when observed under a microscope.
On the other hand, other fine particles of β-2CaO.SiO ₂ , apatite, CaF _{2 and the} like are relatively large and have a size of 10 μm or more, and in particular, apatite may have a size exceeding 100 μm. Therefore, if the slag is finely pulverized to 0.1 mm or less by the above treatment, the minerals shown in Table 2 can be separated as a simple substance.

That is, the slag finely pulverized to 0.1 mm or less is passed through a cyclone, whereby light and fine Ca (O
H) ₂ is separated from other heavy and large particles. The separated Ca (OH) ₂ is in the form of slurry and can be used, for example, for neutralizing the pickling solution. In addition, after the centrifugal dehydration of Ca (OH) ₂ in the form of slurry, it can be recovered in the form of gypsum dihydrate CaSO ₄ , 2H ₂ O by applying H ₂ SO ₄ for various uses for building materials. Can be used for.

The pulverization of the slag described above may be performed as follows. That is, water is sprayed so that sufficient water is spread over the crushed slag, and steam is blown into the slag if necessary in order to accelerate the hydration reaction of free lime in the slag. As a result, CaO in the slag is pre-sorted into Ca (OH) ₂ and expands and is easily destroyed. The preliminary slaking can also be performed by only blowing in steam.

The slag finely pulverized by crushing the slag thus preliminarily soaked by, for example, an impact crusher rotating at a high speed.

Example of Invention

Dephosphorized slag coarsely crushed to a particle size of 25 mm or less (metal content 2
5.6%) in warm water at a temperature of 100 ° C, 2 per 1 ton of warm water.
It was added at a rate of 00 kg and stirred for 3 hours. During this period, steam was blown from the bottom of the container in order to strengthen the stirring and maintain the temperature. As a result, as shown in Table 3, the slag has a particle size of 0.1 mm or more and 21.1 wt.%, And a particle size of less than 0.1 mm 78.9 wt.% (Particularly
Less than 0.044mm 56.4wt.%) And pulverized to 5
0.4Kg of metal (equivalent to 252Kg per ton of slag) could be recovered. In addition, in the recovered metal,
The slag having a particle size of 0.1 mm or more was wet pulverized with a ball mill for about 30 minutes to obtain a metal particle having a particle size of less than 0.1 mm, which was also collected.

Next, the slag finely pulverized as described above was sieved with a 0.1 mm mesh sieve, and slag having a diameter of less than 0.1 mm was taken out to prepare a slurry having a mineral liquid concentration of 17%. Then, this slurry was passed through a cyclone under the conditions shown in Table 4.

The overflow was stored in the tank and the underflow was passed through the cyclone again. The overflow is stored in the tank, and the underflow is stored in another tank. The overflow in the tank was allowed to stand for about 1 hour, the supernatant was discarded, and the mixture was centrifuged and dehydrated at 100 ° C. Table 5 shows the analytical values of the slag obtained as described above, and it was possible to recover 270 kg of Ca (OH) ₂ per ton of slag.

Next, take 2.0 kg of the Ca (OH) ₂ cake (water content of about 50%) recovered as above, make sulfuric acid to form gypsum, and spin-dry after drying 2.1 g of gypsum (5 g / ton of slag).
67 kg) was obtained. Table 6 shows the analytical values of the gypsum thus obtained.

[Effect of the Invention] As described above, according to the present invention, by using the lime-based flux, from the slag generated when removing phosphorus in the hot metal, while efficiently recovering the metal, The lime content contained in the slag after collecting the metal is recovered as slaked lime and / or gypsum, and this can be effectively used, which brings about an excellent industrial effect.

Claims (2)

[Claims] 1. A slag produced during dephosphorization of hot metal using a lime-based flux is crushed, and then the crushed slag is brought into contact with water to cause CaO in slag.
To form Ca (OH) ₂ , slag by such a slag reaction is finely pulverized, and then the metal in the finely pulverized slag is adsorbed on a magnet to be separated and recovered. Separate the fine slag after collecting the metal by physical means,
Characterized by recovering Ca (OH) ₂ in fine powder slag,
A method for recovering lime from dephosphorized slag. 2. A lime component from the dephosphorization slag according to claim (1), characterized in that the recovered Ca (OH) ₂ is reacted with sulfuric acid to recover as gypsum. Recovery method.