JP2660221B2 - Magnesia calcia clinker and its production method - Google Patents

Description

The present invention relates to a magnesia-calcia clinker excellent in digestion resistance and a method for producing the same.

<Conventional technology> In recent years, refractory for lining has also been changed due to the change in converter operation method, that is, the shift from pure oxygen top-blowing type to pure oxygen bottom-blowing type or combined blowing type and other severe operating conditions. Magnesia
There was a rapid change from calcia-based fired bricks to magnesia-carbon-based unfired bricks.

However, in the case of stainless steel smelting using a converter and out-of-pile smelting in an AOD furnace, etc., considering the operating conditions, the magnesia-calcia fired bricks are more resistant to melting than the magnesia-carbon fired bricks. Magnesia-calcia-based fired bricks are generally used without shifting to magnesia-carbon-based unfired bricks because of their excellent properties.

In addition, blast furnace and electric furnace manufacturers in Japan are making refractories irregular in order to reduce the cost of steel production. At present, about 50% of refractories used have been changed to irregular refractories. Is the actual situation.

Furthermore, in Japan, fired dolomite bricks have recently started to be used as refractory bricks for lining of rotary kilns for cement in place of conventional magcro or spinel bricks.

Examples of CaO and MgO clinker used for manufacturing MgO and CaO-based furnace materials include naturally occurring dolomite clinker produced by calcining dolomite ore and magnesium hydroxide (Mg (OH) ₂ ) obtained by a seawater / lime method. There is known a synthetic mud clinker manufactured by adding lime or milk of lime thereto, adjusting the temperature, and firing. These naturally occurring dolomite clinker and synthetic mug black clinker distributed in both the matrix section MgO, CaO, SiO ₂ system or Ca
O, Fe ₂ O ₃ · Al ₂ O ₃ contains low melting minerals. The low-density mineral is SiO ₂ , Fe ₂ O ₃ or Al ₂ O ₃ added to dolomite or a mixture of Mg (OH) ₂ and Ca (OH) ₂ before firing in order to improve the sinterability of the clinker. A flux source such as is generated during the firing. These low-melting minerals improve digestion resistance at the same time as improving clinker sinterability, but have the disadvantage of reducing hot properties and slag erosion resistance. Therefore, in recent years when the converter operating conditions have become severe, MgO / CaO manufactured using the above-mentioned natural dolomite clinker or synthetic magdro-clinker has been used.
If the system furnace material is used as a refractory lining of a converter, the results are actually unsatisfactory in terms of hot properties, slag erosion resistance and the like.

From the above background, attention has been focused on the production of high-purity magnesia-calcia clinker with a low impurity content, using high-purity, high-density magnesia or electro-fused magnesia as a magnesia source, and using high-purity electro-fused calcia as a calcia source. Attempts have also been made to produce a high-purity magnesia-calcia refractory by mixing these under appropriate particle size mixing. However, it is said that the high-purity magnesia-calcia refractory obtained in this manner has a defect that peeling or the like occurs due to the inhomogeneous distribution of MgO and CaO.

The present inventors have previously proposed a high-density magnesia, calcia clinker, which contains iron as a solid solution in a periclase crystal at a content of up to 5% by weight in terms of Fe ₂ O ₃ (Japanese Patent Application 58-219572). This application discloses a method of mixing magnesium hydroxide produced from seawater or the like in the presence of a water-soluble iron compound with calcium hydroxide and calcining to produce the high-density magnesia calcia clinker. The high-density magnesia / calcia clinker has improved hot properties and slag erosion resistance.

<Problems to be solved by the invention> It is an object of the present invention to provide a high-density magnesia-calcia clinker excellent in digestion resistance.

Another object of the present invention is to provide a magnesia-calcia clinker which is suitable for use as a raw material of an amorphous refractory and has excellent digestion resistance.

Still another object of the present invention is to provide a magnesia-calcia clinker excellent in digestion resistance and spalling resistance suitable for use as a refractory for cement kilns.

Still another object of the present invention is to provide a novel method for producing the high-density magnesia and calcia clinker of the present invention.

Still other objects and advantages of the present invention will be apparent from the following description.

<Means and Actions for Solving the Problems> The above objects and advantages of the present invention are as follows. According to the present invention, (A) MgO, CaO and Fe ₂ O ₃ are contained as oxides, and expressed as% by weight. , the sum of MgO and CaO 96% or more, MgO 40~55%, CaO 44~58% , Fe 2 O 3 2% or less of the chemical composition, (B) bulk density 3.2 g / cm ³ or more and (C) weight gain This is achieved by a magnesia-calcia clinker having excellent digestion resistance, characterized in that it has a digestion resistance expressed as a percentage of not more than 1.5%.

As far as the inventor knows, what is conventionally known as magnesia-calcia clinker excellent in digestion resistance is as follows according to the analysis of the inventor. MgO39.04
_{%, CaO58.66%, SiO 2 0.70} %, Fe 2 O 3 0.41%, Al 2 O 3 0.41
_{%, B 2 O 3 0.018%} ; porosity 2.3%; digestion resistant weight increase of 1.
25% and powdering rate 6.43%.

The magnesia calcia clinker of the present invention contains MgO, CaO and Fe ₂ O ₃ as oxides. And with MgO
The total of CaO is 96% by weight or more, preferably 98% by weight.
That is all. MgO is contained at 40 to 55% by weight, preferably 45 to 50% by weight. In addition, CaO is 44
5858% by weight, preferably 48-55% by weight. Fe ₂ O ₃ is contained in an amount of 2% by weight or less, preferably 1% by weight or less. Further, the magnesia-calcia clinker of the present invention contains at least a part of the iron component as a solid solution in periclase crystal, which is a magnesia crystal, and its amount preferably reaches at least 30% of the iron content. .

The magnesia-calcia clinker of the present invention further comprises, for example, as an oxide, 1.0% by weight or less of SiO ₂ and 0.1% by weight of Al ₂ O ₃ .
It may contain up to 5% by weight and up to 0.05% by weight of B ₂ O ₃ .

The magnesia-calcia clinker of the present invention has a bulk density of 3.
2 g / cm ³ or more, preferably a 3.25~3.35g / cm ^3.

One of the features of the magnesia-calcia clinker of the present invention is that it has a digestion resistance of 1.
It is at most 5% by weight, preferably at most 1% by weight. Also,
The magnesia-calcia clinker of the present invention further has a digestion resistance represented by a powdering rate of 4% by weight or less, preferably 2% by weight or less.

According to the present invention, the magnesia calcia clinker of the present invention comprises: (1) a seawater, bitter or brackish water, (a) a water-soluble iron compound, and (b) dolomite porcelain, lime or a hydrate thereof. Adding simultaneously or in the above order to form a precipitate mainly composed of magnesium hydroxide, (2) mixing the magnesium hydroxide with natural dolomite, and (3) calcining the obtained mixture. It can be produced by the method of the present invention.

The aqueous magnesium-containing solution used in the method of the present invention is seawater, bitter or brackish water, preferably a decarbonated aqueous solution thereof. The decarbonated aqueous solution can be obtained by adding an alkaline compound such as lime or calcium hydroxide or a strong acid such as sulfuric acid to seawater, bitter or brackish water according to a known method.

It is widely known that an alkaline compound such as calcium hydroxide is added to such a decarbonated aqueous solution to precipitate magnesium hydroxide.However, in the method of the present invention, an alkaline compound such as lime is added to a magnesium-containing aqueous solution using a water-soluble iron. It is important to add the water-soluble iron compound before adding the compound or the alkaline compound such as lime. When the water-soluble iron compound is added after the addition of an alkaline compound such as lime, it is at least very difficult to produce the magnesia-calcia clinker aimed at in the present invention.

It is particularly preferred to add the water-soluble iron compound to the magnesium-containing aqueous solution before adding the alkaline compound such as lime. According to the method of the present invention, the reason why a magnesia-calcia clinker having a higher density than that obtained by the conventional method of adding a water-soluble iron compound after adding an alkaline compound such as lime is not necessarily clear,
According to the method of the present invention, when lime or the like is added to a magnesium-containing aqueous solution containing a water-soluble iron compound, fine iron hydroxide particles are first formed, and then magnesium hydroxide is formed using the particles as nuclei. This is thought to be because magnesium has an advantageous effect in forming a precipitate of magnesium hydroxide, but has less chance of forming a low-melting compound in firing.

The water-soluble iron compound may be either an inorganic acid salt or an organic acid salt of divalent iron or trivalent iron. Inorganic acid salts, especially mineral salts, are preferred iron compounds. Examples of such a water-soluble iron compound include inorganic acid salts or acetates such as iron chloride, iron sulfate, iron nitrate and iron phosphate, acetates, iron benzoate and p-toluenesulfonate. The water-soluble iron compound can be added to the precipitate consisting mainly of magnesium hydroxide in an amount of 2% by weight or less on a burning basis.

Addition of an alkaline compound such as lime to a magnesium-containing aqueous solution containing a water-soluble iron compound is performed so that the pH of the aqueous solution is about 10.8 or more that generates magnesium hydroxide, and is preferably pH 11 or more, for example, pH 11 to 12. It is done to become. When the pH of the aqueous solution is above about 10.8, a slight excess of the alkaline compound can be added, thereby producing magnesium hydroxide with a low boron content, and thus also a boron content. Magnesia-calcia clinker with a small amount can be manufactured. When the pH is adjusted to 11 to 12, since the alkaline compound such as lime in the reaction solution is somewhat excessive as described above, the separated precipitate mainly composed of magnesium hydroxide is separated from the reaction solution before the separation. Preferably, this reaction solution is reacted with a decarbonated aqueous solution of sea water, bitter water or brackish water to dissolve excess alkaline compounds such as lime. In this case, a precipitate of magnesium hydroxide having a reduced calcium content as well as a boron content can be obtained.

Examples of the alkaline compound used in the above step include lime, dolomite, and hydrates thereof in addition to lime.

According to the method of the present invention, the formed precipitate mainly composed of magnesium hydroxide is separated with, for example, a sickener or the like, washed with water if necessary, then mixed with natural dolomite, further molded under pressure, and then calcined.

The calcination is usually performed at a temperature of 1800 to 2100 ° C. for about 15 minutes to 1 hour. The compaction is preferably carried out under a pressure of 0.2 to 2 ton / cm ² to give a compact with a density of about 1.7 to 2.5 g / cm ³ . According to the present invention, before firing, it can be added to the magnesium hydroxide precipitate in an amount of 1.0% by weight or less in terms of SiO _{2 based on} magnesia and calcia clinker.

In order to facilitate understanding of the method of the present invention, preferred embodiments leading to the formation of magnesium hydroxide precipitate in the present invention are described as follows.

For example, an aqueous solution of iron sulfate is added to an aqueous solution of decarbonated seawater, and then lime is added to produce a reaction solution having a pH of 11.2 to 11.8, and a weight ratio of CaO / MgO as an oxide of about 2 to 4, SiO ₂ / MgO
A precipitate consisting essentially of magnesium hydroxide of about 0.05 to 0.2 and Fe ₂ O ₃ / MgO of about 0.2 to 3 is formed, and before the precipitate is separated from the reaction solution, for example, an aqueous solution of decarbonated seawater is added to the reaction system. Te and pH9.8~10.8 weight as an oxide ratio CaO / MgO about 1.8~3.0, SiO ₂ / MgO about 0.05-0.25 and Fe ₂
A precipitate mainly composed of magnesium hydroxide of about 0.2 to _{3 of} O ₃ / MgO is formed, and then, if necessary, washed with water, and a weight ratio of oxide as CaO / MgO of about 1.4 to 1.8, SiO ₂ / MgO of about 0.05 to
A precipitate consisting mainly of magnesium hydroxide of 0.30 and about 0.2 to ₃ Fe ₂ O ₃ / MgO is formed.

Thus, according to the method of the present invention, as described above, the magnesium hydroxide obtained by the above method is mixed with natural dolomite to produce the magnesia-calcia clinker of the present invention having excellent sinterability and digestion resistance. can do.

<Examples> Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited in any way by the examples.

In addition, various physical property values in this specification are measured by the following methods.

Chemical composition The chemical composition was measured in accordance with the "Science and Technology Method 1 Chemical Analysis Method for Magnesia Clinker" (Refer to the 1981 edition refractory handbook) determined by the Society for the Promotion of Science, 124th Committee, Test Methods Subcommittee.

In particular, analysis of B ₂ O ₃ was carried out by the curcumin method (absorbance method) adopted as the Gakushin method after examination by the committee.

Bulk Density (Bulk Specific Gravity) “Study Method 2: Measurement method of apparent porosity, apparent specific gravity and bulk specific gravity of magnesia clinker” determined by JSPS 124th Committee Test Method Subcommittee (1981 Refractory Handbook) Refer to the following formula.

W ₁ : Dry weight of clinker (g) W ₂ : Weight of white kerosene-saturated sample in white kerosene (g) W ₃ : Weight of white kerosene-saturated sample (g) S: White kerosene at measurement temperature (G / cm ³ ) Digestion resistance (weight increase rate and pulverization rate) Gakushin method 7, Dolomite clinker digestibility test method,
(II) Measured according to a method using an autoclave [Refractory Handbook (Refractory Technical Association, 1981), pp. 347-349].

Sample sieved to a particle size of 3.36 to 2.00 mm (clinker)
Is dried in a 105-120 ° C air bath until a constant weight is obtained, and about 50 g thereof (weighed accurately to 0.01 g) is taken (the weight is W
₁ (g) to) which after two hour hold at 134 ° C. in an autoclave (3 atm), a sample taken from the autoclave was dried to constant weight at 105 to 120 ° C. in air bath, the sample at that time The weight is precisely weighed to 0.01 g (the weight is defined as W ₂ (g)). The dried sample is sieved using a 1.00 mm sieve for 10 minutes, and the weight of the sample remaining on the sieve is precisely weighed to 0.01 g (the weight is W ₃ (g)).
And).

 The rate of weight increase and the rate of powdering were determined by the following equations.

The measurement was performed three times, and the average value of both the weight increase rate and the powdering rate was rounded to the first decimal place.

Examples 1 to 4 Dolomite ore was sized to 7 m / m or less, and crushed by a vibrating ball mill so that the particle size became 90% or more for 100 mesh (150 μm) or 90% or more for 200 mesh (74 μm). And the main MgO source.

On the other hand, a FeSO ₄ solution was added to the decarbonated seawater such that the ratio of Mg ions to Fe ions was 0.4 / 100 in terms of Fe ₂ O ₃ / MgO weight, and further purified Ca (OH) ₂ was added to the seawater. Milk was added to produce a slurry based on Mg (OH) ₂ .
At this time, the pH of the reaction solution was 11.7. The slurry thus generated is washed with fresh water, and the Fe-containing Mg (OH) ₂
A slurry was generated and used as a secondary MgO source.

The secondary MgO source is cake-like and the solid content of the primary MgO source (MgO, C
aO, SiO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ , B ₂ O ₃ )
It was added so as to be 5%, 10%, and 20% in terms of gO weight, and was homogeneously mixed into a paste. This paste-like cake was adjusted to a moisture content of 9 to 10% by weight, and then granulated at a molding pressure of 500 kg / cm ² to obtain a molded body.

After that, the molded body was heated at 1850 ° C. in an oxygen propane furnace.
Baking was performed for 30 minutes to produce magnesia-calcia clinker.

Table 1 shows the sinterability, digestion resistance and chemical composition of the obtained clinker.

Example 5 A dolomite ore was sized to 7 m / m or less, and the dolomite ore was pulverized by a tube mill so as to have a particle size of 100 mesh (150 μm) passing 90% or more to obtain a main MgO source.

On the other hand, a FeSO ₄ solution was added to the decarbonated seawater so that the ratio of Mg ions to Fe ions was 0.4 / 100 in terms of Fe ₂ O ₃ / MgO weight, and further purified Ca (OH) ₂ milk was added to the seawater. Was added to produce a slurry containing Mg (OH) ₂ as a main component. At this time, the pH of the reaction solution was 11.7.

The slurry thus formed is washed with fresh water, and further dried with a rotary drier. Then, Fe-containing Mg (OH)
₂ was produced and used as a secondary MgO source.

Solids (MgO main MgO _{source, CaO, SiO 2, Fe 2} O 3, Al 2 O 3, B
Against ₂ O ₃₎ 100 weight fraction, after adding and mixing the Fe-containing Mg (OH) ₂ which corresponds to 10% by MgO weight basis, to produce a molded body by a rotary type continuous molding machine.

This was further fired in a rotary kiln at a burning temperature of 1900 ° C. to produce magnesia-calcia clinker.

Table 2 shows the sinterability, digestion resistance and chemical composition of the obtained clinker.

Comparative Example 1 Dolomite ore was sized to 7 m / m or less, and pulverized by a grinder so as to obtain 90% or more of a 100 mesh passing amount. This milled material is granulated at a molding pressure of 500 kg / cm ² ,
After forming into a compact, the compact was placed in an oxygen propane furnace for 18 hours.
It was calcined at 50 ° C. for 30 minutes to produce magnesia-calcia clinker.

Table 3 shows the sinterability, digestion resistance and chemical composition of the obtained clinker.

Comparative Example 2 Dolomite ore was sized to 7 m / m or less, and pulverized by a vibrating ball mill so that the particle size became 90% or more for 100 mesh passing, and used as a main MgO source.

On the other hand, purified Ca (OH) ₂ milk was added to the decarbonated seawater to produce a slurry containing Mg (OH) ₂ as a main component. At this time, the pH of the reaction solution was 11.7. The slurry thus formed, which was washed with fresh water, was used as a secondary MgO source.

10 in terms of MgO weight per 100 weight parts of solid content of main MgO source
%, And the above-mentioned secondary MgO source was added thereto and mixed homogeneously.

After adjusting the water content to be 9 to 10% by weight, the mixture was granulated at a molding pressure of 500 kg / cm ² to obtain a molded body.

Thereafter, the molded body was placed in an oxygen propane furnace for 1850 hours.
Calcination was performed at 30 ° C. for 30 minutes to produce magnesia-calcia clinker.

Table 3 shows the sinterability, digestion resistance and chemical composition of the obtained clinker.

Comparative Example 3 The ratio of Mg ions to Fe ions in the decarbonated seawater was Fe.
_A FeSO ₄ solution was added so that it would be 0.4 / 100 in terms of ₂ O ₃ / MgO weight conversion, and purified Ca (OH) ₂ milk was added to this seawater, and Mg (OH) was added.
A slurry containing ₂ as a main component was produced. After washing with fresh water, refined Ca (OH) ₂ milk was added as a CaO source in terms of MgO / CaO weight.
It was added and adjusted to have a chemical composition of 40/60, filtered, dried and molded, and then baked at 1900 ° C. for 30 minutes. Table 3 shows the sinterability, digestion resistance and chemical composition of the obtained magnesia calcia clinker.

Claims (2)

(57) [Claims] (A) MgO, CaO and Fe ₂ O ₃ as oxides
Containing, in terms of% by weight, a chemical composition of a total of 96% or more of MgO and CaO, 40 to 55% of MgO, 44 to 58% of CaO, and 2% or less of Fe ₂ O ₃ , and (B) a bulk density of 3.2 g / having a digestion resistance of 1.5% or less and a weight increase rate of not less than ³ cm ³ and (C) Gakushin method 7 [Drug digestibility test method for dolomite clinker, (II) autoclave method]. Excellent magnesia and calcia clinker. 2. A method of adding (a) a water-soluble iron compound, and (b) dolomite porcelain, lime or a hydrate thereof to seawater, bittern or brackish water, simultaneously or in the above-mentioned order, to mainly add hydroxylic acid. (2) mixing the magnesium hydroxide with natural dolomite, and then (3) calcining the resulting mixture. Manufacturing method.