JPS5818335B2 - Processing method for blast furnace slag - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating blast furnace slag (pigment slag), and more specifically, to separate the sulfur content contained in blast furnace slag, and to create a form of resource that can effectively utilize blast furnace slag. Regarding new processing methods for

When producing pig iron, iron ore, coke, limestone or quicklime, and manganese ore or slag are charged into a blast furnace, and impurities other than iron contained in the iron ore are removed in the form of blast furnace slag.

It is said that the amount of blast furnace slag produced reaches approximately 25 million tons per year, and if we include that in storage or burial,
It is expected that the amount will reach a huge amount.

This blast furnace slag has been used for blast furnace cement, slag wool, fertilizer, aggregate for cement concrete, etc. since ancient times, but the amount of blast furnace slag used for these purposes is The amount is less than 10%, and most of the blast furnace slag is disposed of for industrial use or as landfill on the coast.
Alternatively, the current situation is that they are disposed of at ports.

However, blast furnace slag contains harmful components such as sulfur, making it extremely difficult to landfill or dispose of it due to environmental pollution.

Blast furnace slag is mainly composed of silica, calcia, and alumina, and if harmful components such as sulfur in blast furnace slag are effectively removed, it can be used in the various fields mentioned above without causing problems such as environmental pollution. It is expected that it will be highly applicable to

However, since blast furnace slag produces a huge amount of by-products, it is completely unsuitable for complex processing operations or processing operations that require expensive chemicals, and removal of sulfur content, etc. is simple and easy. It is required to be low cost.

On the other hand, the amount of sulfur contained in blast furnace slag is on the order of 1% at most, and it is extremely difficult to substantially remove the sulfur content by simple treatment.

Therefore, an object of the present invention is to provide a method for treating blast furnace slag that can remove the sulfur content contained in the blast furnace slag with a simple operation.

Another object of the present invention is to provide a method for treating blast furnace slag that can remove the sulfur content contained in the blast furnace slag and provide the blast furnace slag for various uses without causing environmental pollution problems. It is on offer.

Still another object of the present invention is to contain blast furnace slag without requiring complicated processes, without requiring expensive chemicals, and without using or consuming large amounts of thermal energy. An object of the present invention is to provide a method for treating blast furnace slag that can effectively remove sulfur content.

According to the present invention, blast furnace slag is wet-pulverized so that the maximum particle size is 50μ or less, and the resulting blast furnace slag fine particle slurry is
H10-13 in alkaline aqueous medium 60-95
℃ and for a period not exceeding 90 minutes, the sulfur content contained in the blast furnace slag is eluted without precipitation into the aqueous medium, and the sulfur content is substantially removed from the sulfur extract. There is provided a method for treating blast furnace slag, which is characterized in that the blast furnace slag is separated from the blast furnace slag, and then the sulfur content is separated from the sulfur content extract by means known per se.

The invention will be explained in detail below.

The present invention is widely applicable to any slag discharged from a blast furnace.

Blast furnace slag is broadly classified into so-called water slag and air-cooled slag depending on its treatment method, and the treatment method of the present invention is suitable for both of these types of blast furnace slag, especially nitrogen-cooled slag, which accounts for the majority of blast furnace slag. Applicable.

These blast furnace slags mainly contain calcia (CaO), silica, and alumina, although they differ depending on the steelworks.
It also contains small amounts of metal components such as manganese, magnesium, titanium, and iron, as well as sulfur.

An example of the composition of typical blast furnace slag is as follows:
It is as follows.

Component Weight% Ca0 38-43Si
n229-38 A120313-19.5 g03-8 Mn0 0.3-3T10
2 0 3Fe203
o, 5-1SO15-1,5 Loss on ignition 0-3 According to the present invention, first, the grinding of blast furnace slag into fine particles is important for effectively removing a small amount of sulfur content in blast furnace slag. be.

Generally speaking, the degree of pulverization of blast furnace slag has a maximum particle size of 5.
It is important that the sulfur content be 0μ or less, most preferably 20μ or less, in order to effectively remove the sulfur content.

As shown in Comparative Example 2, which will be described later, in the case of coarse powder blast furnace slag with a particle size of about 100 to 80 microns, only about 05% of the sulfur content is removed at most.

On the other hand, according to the present invention, as shown in the following examples, the sulfur content in the blast furnace slag can be reduced by a simple operation of finely pulverizing the blast furnace slag and then contacting it with an alkaline aqueous medium. This makes it possible to easily remove a substantial amount of, for example, 60% by weight or more.

Grinding can be done using ball mills, ring roll mills, rod mills,
Impact crusher, disc crusher, jet crusher, Pichius,
The pulverization can be carried out wet or dry using a known pulverizer such as a colloid mill or an informal pulverizer.

Of course, if the diameter of the blast furnace slag to be used is large, before pulverizing it, use a coarse crusher such as a show crusher or gyrate recrusher, or an intermediate crusher such as a hammer mill or roll crusher. The powder can be made into a powder with a particle size suitable for use.

Blast furnace slag (air-cooled slag) is a brittle lump with many pores inside, and a fine powder of blast furnace slag suitable for the purpose of the present invention can be obtained by ball milling for a relatively short time, for example, 0.5 to 6 hours. It will be done.

In the treatment method of the present invention, it is particularly desirable to wet-mill the blast furnace slag in an aqueous medium.

In other words, when blast furnace slag is dry-pulverized, the sulfur content in the blast furnace slag may volatilize in the form of hydrogen sulfide, or dust may be scattered during grinding or transportation, causing secondary pollution. Special equipment is required to prevent this.

On the other hand, when blast furnace slag is wet-pulverized in an aqueous medium, the sulfur content contained in the blast furnace slag is effectively captured in the aqueous medium, and the problem of dust scattering is also solved.

As a liquid medium for wet grinding, non-hydraulic liquids such as methanol, toluene, xylene, trichlene, perchlorene, and various other organic liquids can of course be used, but water is the least expensive liquid available, and Since the blast furnace slag after pulverization is treated with an alkaline aqueous medium (extraction/ripening treatment), water is most suitable.

According to the present invention, blast furnace slag fine particles wet-milled to the above particle size are brought into contact with an alkaline aqueous medium having a pH of 10 to 13 at a temperature of 60 to 95° C. for a period not exceeding 90 minutes. The sulfur content in the blast furnace slag can be effectively removed by eluting the sulfur content in the aqueous medium in the form of a stable solution without re-precipitating as precipitate.

In other words, under conditions where the sulfur content eluted into the aqueous medium is precipitated, the precipitated sulfur content will be mixed into the blast furnace slag after treatment, and the sulfur content removal rate and filterability will be significantly reduced. .

From this point of view, it is necessary to quickly transfer the sulfur content in the blast furnace slag into an aqueous medium, and to stabilize the eluted sulfur content in the form of a solution during treatment.

First, wet grinding of blast furnace slag to a maximum particle size of 50μ or less is important in promoting the elution of sulfur content into the aqueous medium, and the pH of the aqueous medium is adjusted to 10 to 1.
Maintaining the sulfur content within the range of 3 also has an important meaning in increasing the elution rate of sulfur content and further stably maintaining the sulfur content dissolved in the aqueous medium without precipitating it.

Furthermore, setting the temperature at the time of contact to 60 to 95°C also improves the leaching rate of sulfur content, keeps the eluted sulfur content stable, and further improves the permeability of blast furnace slag particles after treatment. In order to suppress the formation of sulfur precipitates, this treatment must be completed within 90 minutes.

If the pH during contact treatment is outside the above range, the stability of the sulfur eluate tends to decrease, and if the temperature exceeds 95°C, sulfur content tends to precipitate.

In order to maintain the pH of the aqueous medium within the above range, alkali metal hydroxides and carbonates such as sodium hydroxide and soda carbonate; or alkaline earth metal hydroxides and carbonates such as calcium hydroxide, ammonia, etc. The alkaline agent is actively added into the aqueous medium.

Particularly desirable is a wood that causes the sulfur content to be leached out in this alkaline medium.

In addition, blast furnace slag has a strong basicity as shown by the fact that it contains 38 to 43% CaO, and slurry obtained by wet grinding blast furnace slag in an aqueous medium generally has a
Shows strong alkalinity of 1 to 12.

In the contact treatment of the present invention, the slurry obtained by this wet grinding may be directly subjected to a 5-stage aging treatment, but in this case, it is particularly preferable to carry out two or more stages of contact treatment. desirable.

During the contact treatment, the slurry concentration of the blast furnace slag can be varied over a wide range, but generally speaking, it is between 10 and 60% by weight;
In particular, a solid content concentration of 20 to 45% by weight is preferred.

That is, if the slurry concentration is higher than the above range, the extraction removal rate of sulfur content tends to decrease, and reducing the slurry concentration lower than the above range is important because it is necessary to avoid handling a large amount of liquid. This is disadvantageous for operation.

The above-mentioned contact time is the contact time between the blast furnace slag and a certain aqueous medium, and in a batch contact operation, contact for a longer time than 90 minutes in one batch should be avoided.

Of course, even in batch-type contact operations, when contact is carried out in multiple stages, there is no problem even if the total contact time is longer than 90 minutes. Contact over a long period of time is also possible when the two are brought into contact continuously or intermittently.

In the present invention, the details of the mechanism by which the sulfur content in the blast furnace slag is eluted into the aqueous medium by the grinding of the blast furnace slag and the contact treatment with the aqueous medium are still unknown.

However, considering that the extract separated after contact is a yellow transparent liquid and that this sulfur extract is formed in an alkaline medium, the sulfur content in blast furnace slag is in the form of polysulfides. It is believed that it is eluted into the aqueous medium.

To prevent sulfur precipitation during wet grinding, (1)
It is desirable to carry out wet pulverization in as short a time as possible, (11) to keep the temperature of wet pulverization as low as possible, and (1) to not make the pH of the aqueous medium during wet pulverization too high.

The milling and contacting steps can be carried out in batch or continuous operations.

For example, it is possible to supply coarsely crushed blast furnace slag and an aqueous medium to a tube mill or the like, and continuously take out an aqueous slurry of the finely crushed blast furnace slag to continuously crush the blast furnace slag.

Of course, at this time, the wet-pulverized slurry of blast furnace slag is passed through a classifier such as a hydrocyclone, and blast furnace slag other than a predetermined particle size is circulated to the pulverizer.

Further, the contact treatment of the blast furnace slag with the alkaline aqueous medium can be carried out in one stage or in multiple stages, and it is generally preferable to carry out the contact treatment in at least two stages, as shown in the examples below.

Furthermore, the blast furnace slag and the alkaline earth metal body can be brought into continuous contact in a countercurrent or cocurrent manner to effect aging.

Alternatively, extraction and aging may be performed by bringing the blast furnace slag into contact with an alkaline aqueous medium using a fluidized bed.

The sulfur extract formed by the above-mentioned contact treatment and the slag from which the sulfur content has been removed are separated by any solid-liquid separation operation such as filtration, centrifugation, or decantation.

At this time, the blast furnace slag fine particles subjected to the contact treatment of the present invention have a remarkable advantage that they are excellent in filterability, etc., and the solid-liquid separation operation can be carried out very easily.

The sulfur content from the separated sulfur extract can be easily recovered by means known per se.

For example, by adding an aqueous acid solution such as nitric acid to the sulfur extract to adjust the pH of the solution to a range of 3 to 4, the sulfur can be easily precipitated in solid form.

Furthermore, the sulfur content can be precipitated by adding, for example, a small amount of hydrogen peroxide to the sufficiently alkaline sulfur extract.

71)<L, the sulfur content can be recovered in the form of a highly pure solid by subjecting this precipitate to a solid-liquid separation operation such as filtration.

Furthermore, by adding lime, barium carbonate, etc. to the sulfur extract, sulfur content can be recovered in the form of calcium sulfide, barium sulfide, etc.

In the present invention, the method for recovering sulfur from the sulfur extract is not limited to the method exemplified above.

There are many known methods for recovering sulfur in various forms from an aqueous sulfide solution, and any of these known methods can be applied to the present invention.

In the present invention, the mother liquor obtained by recovering the sulfur content is a clear and colorless liquid, and it can be used directly or after adjusting the PU to an appropriate range as desired, and then used as an aqueous medium in the wet grinding process or the contact treatment process described above. can be used repeatedly as
This eliminates the hassle of wastewater treatment.

The blast furnace slag from which the sulfur content has been substantially removed can be washed with water, dried, or subjected to other post-treatments, if necessary.

For example, this blast furnace slag can be fired at a high temperature of 300° C. or higher or sintered into particles to stabilize its morphology and properties.

By treating this blast furnace slag with an acid such as sulfuric acid, nitric acid, or hydrochloric acid, the basicity of the blast furnace slag can be adjusted to be neutral or close to it.

Since the blast furnace slag treated according to the present invention has substantially removed harmful sulfur content, it can be used as landfill material, roadbed material for roads, railways, airports, etc., as well as as raw material for slag wool, slag wool, etc.
It can be advantageously used for other ceramic raw materials, various fillers, fertilizers, soil improvement materials, etc.

The invention is illustrated by the following example.

Example 1 The following composition components Weight % Ca0 40.9AI2
0314.6 S io 2 35-4Mg0
5.8Ti020.6 Fe6Fe2O 3060,7 S O,83
10 kg of crushed material from an air-cooled source having a loss on ignition of 0.6 was mixed with 151 kg of water,
Charged into a ball mill with an internal volume of 301, the water-based blast furnace slag powder was charged into a ball mill with an internal volume of 301, and wet-milled for 6 hours while maintaining the temperature at 30°C or lower to obtain a 300-mesh (Tyler standard) grain size (particle size of 44μ or less). Slurry 131 (solid concentration 40% by weight) was obtained.

The pH of this aqueous slurry was 12.

The obtained aqueous slurry was placed in a 100 A' container equipped with a stirrer, and heated and contacted at a temperature of 85° C. for 1 hour.

The slurry after contact is supplied to a vacuum PJ machine (i.e., 50 crrL in diameter) equipped with a filter paper (Separate 3),
It was filtered under reduced pressure of mH, V differential pressure.

The filtration rate is expressed as the amount of P liquid per unit time (ll/ml), and is 3.211/min.

The obtained P liquid was a transparent yellow liquid.

On the other hand, the obtained cake was washed with N by slowly flowing water 61 at 25° C. from the top using the above-mentioned filtration method, and the blast furnace slag from which the sulfur content had been removed was recovered.

Next, the filtrate and washing liquid were collected, 3N nitric acid was added under stirring to adjust the pH of the liquid to 3.5, and the dissolved sulfur content was precipitated as solid sulfur. The sulfur was separated by filtration.

Based on the analysis results of the blast furnace slag powder after treatment, the sulfur content removal rate was 6.
It was 2.1% by weight.

Furthermore, the recovery rate of sulfur contained in the blast furnace slag was calculated from the solid sulfur recovered from the filtrate and was found to be 59.5%.

Comparative Example 1 The aqueous slurry of blast furnace slag powder with a pH of 12 recovered by wet pulverization in Example 1 was treated without heating and contact treatment.
When filtration was performed under the same conditions using the Nutsche with a diameter of 40 cIrt, the filtration rate was 1,117 m1.
It was n.

Furthermore, from the analysis results of the blast furnace slag after PJ, the removal rate of sulfur content was 24.8%, and the recovery rate of sulfur content recovered from P liquid was 19.7%.

Example 2 This example shows that the mother liquor after separation of the sulfur content can be used repeatedly in the process of the present invention.

Furthermore, the cake with a sulfur removal rate of 62.1% by weight obtained in Example 1 was mixed with the mother liquor 15A from which sulfur was recovered obtained in Example 1 to form a slurry, and the slurry was mixed in the same manner as in Example 1. The mixture was placed in a container equipped with a stirrer, heated to about 90° C. while stirring, and subjected to contact treatment for about 1 hour.

The pH of the slurry was 12, and the filterability under the same reduced pressure conditions was slightly improved (filtration rate: 3.61/ml).

The cake that was sent from door to door was washed with about 51 degrees of water and then heated to 110 degrees Celsius.
The blast furnace slag powder was dried at a temperature of 93.5% (by weight) with a sulfur removal rate of 93.5% (by weight).

Further, 3N nitric acid was added to the sulfur-containing liquid to adjust the pH to about 35 to precipitate sulfur.

Including the sulfur content obtained in Example 1, the overall sulfur content recovery rate was 85.6%.

Example 3 This example describes a case where lime is added to a wet milled slurry and contact treatment is performed.

200 g of the blast furnace air-cooled slag used in Example 1 was added to 500 ml of water, and the mixture was ball-milled for about 6 hours to obtain a
A slurry consisting of finely powdered blast furnace slag of 0 mesh or less was obtained.

The pH of this slurry was about 12.

Add 12g of lime to this slurry and heat it to about 80℃,
The contact treatment was carried out for 1 hour under stirring conditions.

Immediately, the mixture was filtered under reduced pressure, and several drops of 30% hydrogen peroxide were added to the r solution, followed by thorough stirring.

The pH of the liquid decreased to about 9.7, and fine sulfur particles were precipitated.

The sulfur content is removed from this liquid, washed with about 20rrLl of water, and the washing liquid is combined with the mother liquor to make 1 bottle.

The liquid from which the sulfur content had been removed was mixed with the above-mentioned cake, and extracted again.

The treatment conditions were as follows: the slurry was kept at a temperature of about 80° C. and the contact treatment was carried out for about 1 hour while stirring.

The pH of the slurry was approximately 12.5.

This slurry was immediately filtered and
The cake was washed with water in m and e, and the cake was dried in a constant temperature bath at 105°C.

A few drops of concentrated hydrogen peroxide solution are added dropwise to the P solution containing the cleaning solution while stirring, and the precipitated sulfur content is separated by P over-separation.

Analysis of the treated blast furnace slag obtained by drying the cake showed that the sulfur content removal rate was 99.7%, confirming that the sulfur content was completely removed1.

Comparative Example 2 This example shows that the particle size of blast furnace slag powder has an important effect on the extraction of sulfur content.

The air-cooled slag of Example 1 was dry-pulverized and adjusted to various particle sizes, which were then subjected to desulfurization treatment.

The treatment conditions were as follows: 200 g of the sample dregs was suspended in 500 ml of water and treated under stirring to elute the sulfur content.

Table 2 below summarizes the sulfur removal rate (%) when contact treatment was performed on particles in various particle size ranges by changing the temperature and time during this extraction.

From Table 2 above, the particle size that does not pass through a 150 mesh sieve (
It is clear that a substantial amount of sulfur cannot be extracted from blast furnace slag with a maximum particle size of 80 μm or more.

Furthermore, it was confirmed from the discoloration of the lead acetate coated test paper that a considerable amount of hydrogen sulfide was generated during dry grinding.

Example 4 This example describes cases in which the type of aqueous medium and time during wet grinding are varied.

200 g of the blast furnace slag used in Example 1 was charged into a ball mill having an internal volume of 1.51 ml together with 250 ml of the aqueous medium shown in Table 3 below, and wet-pulverized for the time shown in Table 3.

Water was added to the wet-pulverized slurry that had passed through 300 meshes to make 500ml, and this was heated at 85°C for 30 minutes,
It was filtered under reduced pressure and the residue was dried without washing.

Based on the analysis results of the residue, the sulfur content removal rate was determined and shown in Table 3.

The results in Table 3 above show that long-term wet milling results in a decrease in the sulfur content removal rate, and that wet milling within 6 hours is desirable.

Comparative example 3 This example shows the influence of pH during the extraction process of blast furnace slag powder.

200 m of wet milled slurry obtained in Example 1
Add nitric acid to A, maintain the pH at 8.0, and heat at 85°C for 1
After humidifying for a period of time, perform FJ under reduced pressure to separate the residue.
child.

This operation was performed three times, and the results obtained are shown in Table 4 in comparison with the results of Examples 1 and 2.

From the results in Table 4 above, it is understood that increasing the pH during extraction to a value higher than 8 is important for removing sulfur content.

Example 5 This example describes a case where the type and amount of the alkaline agent added to the aqueous medium are changed.

Aqueous solution 3 containing the type and amount of alkali agent shown in Table 5-A below was added to 200 ml of the wet-pulverized slurry obtained in Example 1.
00ml was added and treated in the same manner as in Example 4.

The results obtained are shown in Table 5-A. According to Table 5-A above, no matter which alkali agent is used, the sulfur removal rate can be improved by 1.

The numbers within 0 in the Na2CO3 column in Table 5-A are NaO.
Shows the number of grams converted into H.

For Experiments Nos. 1 to 3 and 7 to 9, it was confirmed by quantifying the Na content of the furnace liquid that the alkaline content added to the aqueous medium could be repeatedly reused for extracting sulfur content.

Table 5-B below shows the transfer rate (%) of alkaline content contained in the aqueous extraction medium to the filtrate.

Example 6 This example shows the effect of extraction time in aqueous media.

To 200 ml of wet pulverized slurry 'J-obtained in Example 1, (a
) reagent primary CaO1 and (b) 300 ml of water each containing 3y of 7jCaO obtained by thermal decomposition of calcium nitrate! and changing the time to 30 minutes, 60 minutes and 120 minutes,
Extraction and ripening treatments were performed in the same manner as in Example 4.

The results are shown in Table 6.

Table 6 above shows that contact treatment for up to about 60 minutes is desirable for improving the sulfur rate.

In addition, the residue of Experiment No. 5 was subjected to contact treatment for 30 minutes at 85°C for 30 minutes after removing sulfur from the p liquid as in Example 3, and then subjected to Oki separation. The residue is 938
% sulfur removal rate.

Example 7 This example shows the influence of the liquid volume ratio when bringing blast furnace slag and alkaline medium into contact.

To 200 ml of wet pulverized slurry 'J obtained in Example 1, 3
g of calcium hydroxide and water were added in the form of a suspension, making the total liquid volume as shown in Table 7 below.

It was then treated in the same manner as in Example 4.

The results are shown in Table 7.

Example 8 This example shows an example of two-stage contact processing.

To 200 ml of the wet pulverized slurry obtained in Example 1, (a)
Reagent 1st class CaO2,5,i7 and (b) reagent 1st class Ca
Add water each containing 23 g of (OH) and
The liquid volume is shown in the table as a slurry.

This slurry was treated in the same manner as in Example 4 for 1 hour, and filtered and separated.

The sulfur content was removed from this R liquid by the method of Example 3, the amount of this furnace liquid shown in Table 8 was added to the cake, and this slurry was further treated for 30 minutes in the same manner as in Example 4. Excessive fluid removal occurred.

The results are shown in Table 8.

Claims (1)

[Claims] 1. Blast furnace slag is wet-pulverized so that the maximum particle size is 50μ or less, and the resulting blast furnace slag fine particle slurry has a pH of 10 to 1.
The sulfur contained in the blast furnace slag is eluted without precipitating in the aqueous medium by contacting the blast furnace slag in an alkaline aqueous medium at 60 to 95°C for a period not exceeding 90 minutes. A method for treating blast furnace slag, which comprises separating the blast furnace slag from which the sulfur content has been substantially removed from the extract, and then separating the sulfur content from the sulfur-containing extract by means known per se. 2. The treatment method according to claim 1, wherein the contact between the blast furnace slag powder and the alkaline aqueous medium is carried out in at least two stages.