JPH062608B2 - Slag treatment agent - Google Patents

Description

TECHNICAL FIELD The present invention relates to a slag treating agent for modifying iron-making slag and steel-making slag. More specifically, the present invention relates to a modified slag treating agent which is effective in preventing turbid water generated by pulverization or self-disintegration or contact with water in the cooling process of steelmaking slag such as blast furnace slag or steelmaking slag.

[Prior Art] Steelmaking slag, especially stainless steelmaking slag,
Slag with a basicity (CaO / SiO ₂ weight ratio) of about 1.5 or more,
In the cooling process, it has the property of transforming from α-type phase to α'type, and then to γ-type or β-type due to the phase transition of 2CaO · SiO ₂ , and in many cases, when it changes from α'to γ-type, about 14%
It is known that the slag itself self-disintegrates and powders due to the volume expansion of the.

This pulverization phenomenon deteriorates the working environment, and the problem that a large amount of dehydrated cake as a residue after recovery during metal recovery in slag is a major cause of increased burden on stainless steel manufacturers for slag treatment. ing.

Preventing the slag from pulverizing and solidifying it has been a long-standing problem for stainless steel manufacturers because the discharged slag can be effectively used as a secondary aggregate for civil engineering such as roads.

The following methods are mentioned as a method of suppressing slag pulverization.

Method for granulating vitrified glass when slag is discharged; 2CaO ・ SiO ₂ slag with SiO ₂ source added, with CaO ・ SiO ₂ as the main component having a basicity of 1.5 or less (substantially varying depending on the slag composition) A method of modifying into slag; a method of suppressing the α′-type to γ-type phase transition having a large density change and promoting the α′-type to β-type phase transition having a small density change.

In the method described above, the molten metal that accompanies the slag slag may cause a steam explosion during water granulation, and the granulated material may not have sufficient strength for use as an aggregate for civil engineering due to its softness. Although some have been experimentally tested, the current situation is that they have not been put to practical use.

Some of the methods are currently marketed as SiO ₂ -based modifiers, but a large amount of Si, about 20% of the molten slag, is used.
Since O ₂ is required, it is necessary to install charging equipment and stirring equipment, and further increase the viscosity of the slag due to the temperature decrease of the molten slag accompanying the addition, which is unsuitable in terms of workability and cost.

, That is, the phase transition from α'type to β type has been studied for a long time and various methods have been proposed. Among these methods, Si in slag is included.
^The method of substituting Si ⁴⁺ with B ³⁺ having a smaller radius than ⁴⁺ ion has been proposed as the most effective and reliable method at present [Japanese Patent Laid-Open No. 53-43690, Kawatetsu Technique Vol. 18,
No. 1 (1986) 20-24].

However, since such a conventional boron-based slag dusting inhibitor is in the form of fine powder, and is itself a water-containing substance, it is coupled with a dehydration vaporization reaction when it comes into contact with molten slag, and causes a blowing-up phenomenon of the slag dusting inhibitor. And the working environment is significantly deteriorated, and at the same time, it is dangerous, which makes the operation very difficult.

Further, the conventional boron-based slag dusting inhibitor, because the chemical composition and physical properties are significantly different from the slag, relative to the molten slag, viscosity, density is likely to cause a difference, so-called slag and slag dusting inhibitor However, it has a drawback in that it has a poor affinity and a small diffusive mixing ability, and despite the proposals so far, it cannot be used in actual operation.

Secondly, as a problem of steelmaking slag such as blast furnace slag or steelmaking slag, there is generation of so-called yellow turbid water generated when water and slag come into contact with each other, such as rainwater and drowning water.

As is well known, blast furnace slag and the like are widely used as various aggregates, especially roadbed materials. However, when the sulfur content in these slags is high, it has been confirmed that if the usage conditions and usage methods are incorrect, rainwater contacting the slag, turbid water, and the like, causing cloudy water of sulfur compounds and hydrogen sulfide odor, Particularly for road slag applications, in order to secure products that do not have such a risk of damage, the slag must be one that does not generate yellow turbid water or hydrogen sulfide odor as a standard for road slag, and the color determination test is It is adopted as a confirmation method, and it is stipulated that it should be passed (JIS A 5015: Announced on November 1, 1985).

The phenomenon of cloudy water generation is due to the elution of sulfur (S) contained in the form of calcium sulfide (CaS) mainly contained in slag, and the yellow polysulfide (for example, CaS
It is considered that x) is generated, and the following method, for example, is known to prevent the generation of turbid water.

A method of oxidizing and stabilizing slag with water and air by aging; a method of adding an oxidant to molten slag; a method of treating slag with CO ₂ to stabilize the slag surface; a method of increasing the cooling rate of slag .

Since the method of (1) requires a period of about 1 to 3 months for aging treatment, a vast storage space is required.

Examples of the method include a method of adding a high-order iron oxide into the molten slag and a method of introducing a gas containing oxygen, for example, air.
_{Since 2} occurs, it is not a safe method,
In addition, the current situation is that the generation of cloudy water has not been completely prevented.

In the method of, the slag surface is stabilized,
When used as a crow, if it is crushed during rolling, it has the drawback that sulfides will be re-eluted from the fracture surface.

The method of is a method of forming a glassy material by pulverizing and dispersing the molten slag and quenching it, and preventing the leaching of the contained sulfur content, but the deterioration of the strength is unavoidable, and in order to form the glassy material, There is a problem that it needs to be pulverized to have a specific viscosity or less, and that it can be used as a fine aggregate but is difficult to use as a coarse aggregate.

From the above, the actual situation is that slag aging is the only method currently available for preventing slag from becoming muddy water.

[Problems to be Solved by the Invention] As is clear from the above, the present invention is industrially inexpensive because of the pulverization phenomenon and the generation of turbid water, which have been problems of steelmaking / steelmaking slag for many years. At the same time, a simple slag treating agent is intended to be solved.

Therefore, the object of the present invention is to improve the conventional boron-based powdering inhibitors to more effectively promote the substitution reaction of S ⁴⁺ and B ³⁺ to reform the slag at once. The point is to solve the problem.

[Means for Solving the Problems] In view of the above problems, the present inventors have conducted earnest research on improvement of a boron-based slag dusting inhibitor, and completed the present invention.

That is, in the present invention, MeO (Me represents at least one or two kinds of alkaline earth metals selected from Mg, Ca, Ba or Sr): 5 to 40% by weight, B ₂ O ₃ 20 to 80% by weight %, SiO _2: 10 to 60 wt%, and others: 0-20 wt% (provided that Al ₂ O ₃ is less than 3 wt%, when CaO as MeO is present alone, and more than 15% by weight, Na ₂
O is less than 3% by weight).
A sandy glass powder mainly composed of an alkaline earth metal borosilicate represented by B ₂ O ₃ —SiO ₂ system, the powder having a fineness distribution of 0.1 to 5 mm is 90 % Or more of the slag treating agent.

[Operation] The present invention will be described below.

The slag treating agent according to the present invention is different from the conventional borate powder made of hydrous crystals as a powdering inhibitor for steelmaking slag, and is a glass powder of a substance mainly composed of alkaline earth metal borosilicate. It is characterized by being a sandy powder of.

The substance mainly composed of alkaline earth metal borosilicate is not particularly limited as long as it is in the composition range capable of forming glass,
As chemical composition, MeO: 5-40 wt% in terms of oxide
(Me represents one or more alkaline earth metal elements selected from Mg, Ca, Ba or Sr), B ₂ O ₃ : 20-
80% by weight, SiO ₂ : 10 to 60% by weight and other 0 to 2
0 wt% (however, Al ₂ O ₃ is less than 3 wt%, Me
When CaO alone is present as O and is present in an amount of 15 wt% or more, Na ₂ O is less than 3 wt%) and MeO
+ B ₂ O ₃ + SiO ₂ ≧ 80% by weight. Of these, those having a particularly high melting point or softening point are in the range of 1100 ° C., preferably 700 to 1050 ° C.

Further, in the above borosilicate glass, other components may be contained up to 20% by weight at most.
Other components that are inevitably mixed in due to the circumstances of the raw materials or the manufacturing method, or components that adjust the physical properties of the glass such as viscosity, softening point and surface tension, if necessary, such as Fe ₂ O ₃ , Al ₂ O ₃ and Na ₂
It means that one or more kinds of O ₃ , K ₂ O, F and the like or those containing them can be tolerated. Further, the glass means that a raw material mainly composed of borosilicate is melted and cooled to be in an amorphous state to the extent that it cannot be clearly identified by a specific diffraction line intensity on X-ray diffraction analysis.

Further, the slag treating agent according to the present invention is characterized in that it is a powder having a particle size distribution in the form of sand.

The reason for this is that when added to the molten slag, depending on the mode of addition, it can be quickly added with fluidity, the generation of dust can be suppressed, and rapid and stable meltability can be provided.

In many cases, it is preferred that the particle size is in the range 0.1-5 mm, at least 90%.

The slag treating agent according to the present invention can be used in combination with an auxiliary agent, if necessary. That is, depending on the mode of addition to the molten slag, the smooth dissolution into the molten slag may be inferior, and sometimes an unmelted mass, so-called "mamako" may occur.

Therefore, after the addition of the slag treating agent, an auxiliary agent can be added to the slag treating agent, if necessary, in order to promote rapid dissolution, diffusion and mixing effects in the molten slag.

Such an auxiliary agent refers to a powder that causes a dehydration and / or decarboxylation reaction by heating, and examples of such a powder include clays, activated clay, aluminosilicates such as diatomaceous earth, bentonite, and aluminosilicates such as zeolites, At least one selected from pearlite, limestone, sodium bicarbonate, carbonate such as sodium, potassium, calcium, magnesium or barium, and borate such as borax, carnite, urexite and colemanite may be used, or two or more thereof may be mentioned.

The amount of these auxiliaries added is not uniform depending on the type, the addition method of the pulverization preventing agent, the physical properties and the state of the molten slag, but at most 30% by weight based on the pulverization preventing agent, preferably 5 Is in the range of up to 15% by weight.

In many cases, the particle size of this auxiliary agent is preferably smaller than that of the anti-dusting agent, and its average particle size is preferably below the lower limit value of the anti-dusting agent.

The slag treating agent according to the present invention is produced by blending raw materials containing one or more of borosilicon and an alkaline earth metal salt, then heating and melting the resulting formulation, followed by cooling and particle size adjustment. can do.

As a boron raw material, for example, boric acid as described above, a chemical product such as calcium borate, or colemanite.
_{e) (Cc 2 B 6 O} 11 · 5H 2 O), ulexite _{(ulexite) (NaCaB 5 O 9} ·
8H ₂ O), tincal (Na ₂ B ₄ O ₇・ 10H ₂ O), carnite
(Kernite) (Na ₂ B ₄ O ₇ · 4H ₂ O) such as borate minerals, and examples of the silicon raw material include silica rock, silica sand, silica flower, silicate, slag, glass. Such as scraps,
Examples of the alkaline earth metal raw material include hydroxides, oxides, carbonates and silicates of Atsuka earth metal, and slaked lime, limestone, calcium silicate, dolomite and the like are practical. Other desired raw materials include alkali compounds, clays, fluorides and the like.

These raw materials are appropriately selected and compounded so that the glass composition falls within the above range, and the mixture is put into a desired melting furnace and heated and melted. Next, the melt is cooled and then the particle size is adjusted to obtain a product.
In many cases, the most practical and preferable method of cooling the melt is to tap the melt and apply pressured water to the melt to granulate it and collect it as sandy glass. As another method, there is a method in which the melt to be tapped is placed on a belt conveyor, cooled with water or air, recovered as cullet, and crushed.

Next, the particle size is adjusted after drying to remove the adhered water.However, in the case of a water-damaged product, the particle size adjustment by crushing and sieving is not always necessary, and the dry product can be directly used as a product. It can be done as needed.

In this case, if desired, the above-mentioned auxiliary agents can be added.

The slag treating agent according to the present invention is a slag having a main composition of basic calcium silicate produced as a by-product in iron making, steel making, etc. rather than the compound or mineral of the hydrous crystalline borate which is the precursor thereof (hereinafter referred to as “slag”). The described) has a much better affinity for the melt and its modifying effect can be said to be more than expected.

For example, synthetic or natural products such as sodium borate or calcium borate containing water of crystallization are not only accompanied by dangerous phenomena such as explosion and dusting due to dehydration due to rapid thermal change with respect to molten slag. This is due to the local decrease in the slag temperature and the apparent specific gravity is small, so internal diffusion into the molten slag with a larger specific gravity is hardly performed and the slag remains on the surface or inside. However, it is not easily dissolved or diffused.

The steel slag to be modified in the present invention is one that causes a phenomenon of disintegrating or pulverizing upon cooling, or with time, or a so-called turbid water that is generated when contacted with water. A slag mainly composed of calcium silicate, which generally has a basicity CaO / SiO ₂ (weight ratio) of at least 1.3, and usually in the range of 1.5 to 3.5. For example, blast furnace slag, Examples of the steelmaking slag such as stainless steel or converter slag.

Amount added for slag Surak treatment agent according to the present invention is not uniform depending on the composition and physical properties, or slag composition, etc., at least about as B ₂ O ₃ in any of the purposes of the powdering prevention and yellow cloudy inhibiting water slug Although it is 0.15% by weight, considering the durability of the modified slag, it is preferably 0.3% by weight or more.

The reason for this is that if it is less than about 0.15% by weight, it is insufficient to prevent turbid water and pulverization. On the other hand, although the upper limit need not be particularly limited, it is mostly for economic reasons or for hot metal. It is of a nature that is naturally limited in consideration of its influence. Therefore, 0.3 to 1.5% by weight as B ₂ O ₃ is a practically preferable range.

When modifying the slag using the slag treating agent according to the present invention, without changing the operating conditions of the conventional blast furnace or steelmaking furnace, in the conventional operating process, the presence or absence of hot metal into the molten slag Add slag treating agent.

Therefore, for example, when tapping from a blast furnace through a gutter, an input port is provided at a desired position of the gutter, and when adding from this, when the molten slag is removed by a slag wheel etc. by a weir provided in the gutter, Alternatively, it is added to the slag treating agent when tapped together with the molten slag in a torpedo car or the like.

Further, the same applies to the case of making steel such as stainless steel, and when removing molten stainless steel pig from the melting electric furnace to the ladle or when removing molten slag from the ladle to the slag pot, a slag treatment agent. Is added.

In this case, the mode of addition of the slag treating agent to the molten slag is not particularly limited as long as it adopts a method in which the slag treating agent is quickly dissolved and diffused in the slag.

For example, the molten slag in the presence or absence of hot metal, the slag treating agent, the method of adding as it is, the method of adding together with air pressure, the method of adding by adding as a packaging bag, or the slag hot water in the presence of the slag treating agent in advance. And the like.

Even if the slag treating agent is added in the presence of hot metal, the influence of boron mixed in the hot metal is so small that it is practically negligible in many cases.

Therefore, addition of slag treated is performed when slag pot etc. are removed, only when the above influence is considered,
In other cases, since the viscosity of the slag melt is smaller if it is carried out in the slag in the presence of hot metal held at a high temperature, the slag treating agent is dissolved and diffused quickly, so that the slag is uniformly modified. It is rational and preferable.

When added to the slag pot or the like, if the viscosity of the slag melt becomes high and the dissolution / diffusion of the slag treating agent may become insufficient, reheating or diffusion of the slag is promoted as necessary. The above-mentioned auxiliary agents can be used in combination.

However, after adding the slag treating agent to the molten slag, it is substantially unnecessary to provide a special diffusion means for prompt dissolution and diffusion.

Therefore, after the addition, the modified slag can be obtained by slow cooling or rapid cooling by a conventional method.

[Examples] The present invention will be further described with reference to Examples.

Example 1 Preparation of slag treating agent sample: Raw material blends having the following blending ratios (parts by weight) were melted in an electric furnace.

Next, the obtained melt was water-granulated and then dried to prepare a slag treating agent of glass sandy powder.

Note: boric acid is an anhydride, magnesium hydroxide, barium carbonate is an industrial chemical, and colemanite is B ₂ O ₃ 45%, CaO 25
%, SiO ₂ 4%, Ig loss 24%, balance 2% Borax is Na ₂ O
21.43%, B ₂ O ₃ 48.21%, Ig Ioss 29.96
% Of all are from Turkey and silica is 98% pure SiO ₂
I used a dried African one.

The composition (% by weight) of the slag treating agent obtained by the above formulation is generally as follows.

Slag dusting prevention test: When removing the slag basicity (CaO / SiO ₂ = 2.10) after the first tapping produced from the electric furnace for stainless steel (30 t capacity) from the ladle to the slag pot, 40 kg of the plastic bag containing 10 kg of the test sample of each of the slag treating agents obtained above was simultaneously put into the slag, and the slag was left to cool and solidify, and then the state of the temperature was observed.

The conditions during the test are as follows.

When adding each sample, no dust generation or gas generation was observed in any of the experiments, the addition operation was safe, and good diffusion mixing was obtained when pouring slag into the slag pot.

When the slags tested were allowed to cool to room temperature and then observed, the slags of Test Nos. 1 to 5 showed no disintegration powdering phenomenon.

No change was observed even after these slag blocks were left outdoors for 3 months. On the other hand, test number 6
The ordinary slag containing no slag treatment agent self-disintegrated and pulverized when cooled.

Example 2 For the samples A and B of the slag treating agent used in Example 1, activated clay (particle size 1-2 mmφ) or limestone (particle size 1-2 mmφ) or sodium hydrogen carbonate (powder) is shown in the table below. Auxiliary agents were added and mixed in the proportions shown and sealed in a 10 kg vinyl bag to give a test sample. A slag treatment test was performed on this sample by the same method as in Example 1.

The conditions during the test are shown in the table below.

The slag composition analysis value (wt%) at the time of the test is generally as follows.

Test No. CaO SiO ₂ MgO Al ₂ O ₃ 1-6 49-5521-269-1111-15 In all experiments, no dusting phenomenon due to sample injection was seen at all on molten slag due to dehydration and decarbonation reactions. The sample scattered and flowed in an instant, and rapidly melted and diffused into the slag. When the slag at the time of the test was allowed to cool to room temperature and the condition was observed, no phenomenon of disintegration pulverization was observed, and the amount of the pulverization inhibitor used was 0.31 to 0.37B.
It has been found that can increase the sufficient effect ₂ O ₃ wt%.

Example 3 The same slag treating agents A, D and E as those used in Example 1 for the molten slag in tap iron produced from an electric furnace were removed from the ladle into a slag pot B in a plastic bag as B. ₂ O ₃
A 0.40% by weight equivalent was added. The molten slag that had been subjected to this treatment was subjected to normal standing cooling and then adjusted to a particle size range equivalent to MS-25 to obtain a ballast.

The ballasts obtained by treatment with the respective treatment agents were tested for cloudy water as described below, and no cloudy water was observed in any of the balls.

Evaluation method of turbid water 500 g of the obtained sample ball was weighed and put in 1500 ml of pure water and boiled for 45 minutes in accordance with the color determination test of JIS A 5015. Visually compare the colors with a coloring standard solution made of potassium chromate to judge whether the color is present or not.

EFFECTS OF THE INVENTION Since the slag treating agent according to the present invention is a vitrified sandy powder, it does not cause a degassing reaction such as carbon dioxide and water vapor when dissolved in a slag melt, and works by blowing up and scattering. It does not make the environment worse.

In addition, for the same reason, there is substantially no heat absorption amount due to melting such as heat of vaporization and vaporization, heat of transition, and the like, and the sandy powder is quickly dissolved in the slag.

Diffusion after dissolution in slag can be adjusted as necessary by using an auxiliary agent together.

The slag treating agent according to the present invention can prevent powdering of slag produced as a by-product during iron making and steel making, and at the same time substantially prevent cloudy water.

According to the method of the present invention, such as a vinyl chloride resin bag containing a slag treating agent, a so-called poly bag or a paper bag can be simply charged into the molten slag without changing the conventional process, which is industrially very difficult. Is advantageous to.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takashi Fukuzawa 2-25 Matsuki-cho, Koriyama-shi, Fukushima Prefecture Koriyama Plant Co., Ltd. (72) Kosuke Takeuchi 2-25 Matsuki-cho, Koriyama-shi, Fukushima Nippon Chemical Industry Co., Ltd. Koriyama Plant (72) Inventor Tatsushi Tabata 2-25 Matsuki-cho, Koriyama-shi, Fukushima Nippon Chemical Industry Co., Ltd. Koriyama Plant

Claims (2)

[Claims] 1. MeO (Me is Mg, Ca, Ba or S)
represents at least one or more alkaline earth metal selected from r): 5 to 40 wt%, B ₂ O ₃ 20 to 80 wt%, SiO _2: 10 to 60 wt% and others: 0 20% by weight (however, Al ₂ O ₃ is less than 3% by weight, and when CaO alone as MeO is present and 15% by weight or more is present, Na ₂
O is less than 3% by weight).
A sandy glass powder mainly composed of an alkaline earth metal borosilicate represented by B ₂ O ₃ —SiO ₂ system, the powder having a particle size distribution of 0.1 to 5 mm is 90%. The slag processing agent characterized by the above. 2. The slag treating agent according to claim 1, wherein the slag treating agent has the functions of preventing ironing and steelmaking slag from pulverizing and preventing turbidity at the same time.