KR950014697B1 - A process for producing of mgnesia-caisia clinker - Google Patents

Abstract

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Description

Magnesia calcia clinker and manufacturing method thereof

The present invention relates to a magnesia calcia clinker excellent in fire resistance and a manufacturing method thereof.

In recent years, along with the severity of the operating conditions such as the transition from the converter operation method, that is, the transition from the pure oxygen odor extraction to the pure oxygen erosion type to the complex blow type, etc., the refractory for interior use is also made from the magnesia carbon calcined bricks. It changed rapidly to the fluorine-based bricks.

However, in the case of furnace smelting in stainless steel smelting, AOD furnace, etc. by converters, magnesia and carbonaceous fluorine bricks have better solvent resistance than magnesia and carbonaceous fluorine bricks in consideration of these conditions. Magnesia-calcia-fired bricks are generally used without shifting.

Moreover, in Japan, blast furnaces and converter makers are performing refractory deformation in order to reduce the manufacturing cost of steel. Currently, about 50% of the refractory used is converted into irregular refractory materials.

In addition, in Japan as a refractory brick for embedding rotary kiruns for cement, calcined dolomite bricks have recently been replaced by conventional magclo or spinelene bricks.

CaO and MgO clinkers used in the production of MgO and CaO-based furnace materials include lime or lime oil in natural dolomite clinker prepared by calcining dolomite ore and magnesium hydroxide (Mg (OH) ₂ ) obtained by seawater and lime methods. Synthetic Magclaw clinkers produced by adjusting and firing are known. These naturally occurring dolomite clinkers and synthetic magclo clinkers both contain MgO, CaO or CaO, Fe ₂ O ₃ , A ₂ lO ₃ based low-melting minerals distributed in the matrix portion. Low-melting minerals are designed to improve the sinterability of clinkers, while flux sources such as SiO ₂ , Fe ₂ O _3, or Al ₂ O added in dolomite or mixtures of Mg (OH) ₂ and Ca (OH) ₂ before firing Produced by reaction. These low-melting minerals improve the sinterability of the clinker and at the same time improve the fire resistance, but have the disadvantage of deteriorating the other hot characteristics and the slack erosion resistance. Therefore, when the operating conditions of the converter are severe, MgO · CaO based ash produced using the natural dolomite clinker or the synthetic magdol clinker as described above can be used as the internal refractories of the converter. In this regard, the result is unsatisfactory.

In view of the above background, the production of high purity magnesia calcia clinker with low impurity content is noted. It has also been attempted to produce high purity magnesia calcia refractory materials by mixing. However, the high-purity magnesia-calcia refractory material obtained in this way has a defect which causes peeling etc. because MgO and CaO distribution is heterogeneous.

The present inventors first proposed a high-density magnesia calcia clinker containing iron in a content of up to 5% by weight in terms of Fe ₂ O _{3 in the} ferriclase crystals (Japanese Patent Application No. 58-21572). This application discloses a method of producing the above-mentioned high density magnesia calcia clinker by mixing magnesium hydroxide prepared in the presence of a water-soluble iron compound from seawater or the like with calcium hydroxide and calcining. The high density magnesia calcia clinker is improved in hot characteristics, slack erosion resistance and the like.

An object of the present invention is to provide a high density magnesia calcia clinker excellent in fire resistance.

Another object of the present invention is to provide a magnesia calcia clinker excellent in fire resistance and sporing resistance suitable for use as a raw material of amorphous refractory materials.

It is another object of the present invention to provide a magnesia calcia clinker having excellent fire resistance suitable for use as a refractory for cement kiln.

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

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

According to the present invention, the above objects and advantages of the present invention include MgO, CaO and Fe ₂ O ₃ as oxides (A), and are expressed in weight%.

96% or more of MgO and CaO

MgO 40-55%

CaO 44 ~ 58%

Fe ₂ O ₃ 2% or less

Chemical composition,

(B) the bulk density of 3.2g / cm ³ or more and

(C) Fire resistance 1.5% or less expressed by weight increase rate

It is achieved by the magnesia calcia clinker which is excellent in fire resistance, characterized by having a.

As far as this inventor knows, what is known as the magnesia calcia clinker excellent in the fire resistance conventionally is as follows according to the analysis of this inventors. MgO 39.04%, CaO 58.66%, SiO ₂ 0.70%, Fe ₂ O ₃ 0.41%, Al ₂ O ₃ 0.41%, B ₂ O ₃ 0.0018%; Porosity 2.3%; Fire resistance weight increase rate 1.25% and eruption rate 6.43%.

Magnesia, calcia clinker of the present invention, containing MgO, CaO and Fe ₂ O ₃ as an oxide. Therefore, the sum total of MgO and CaO is 96 weight% or more, Preferably it is 98 weight% or more. In addition, MgO is contained in 40 to 55% by weight, preferably 45 to 50% by weight. In addition, CaO is contained in 44 to 58% by weight, preferably 48 to 55% by weight. Fe ₂ O ₃ is contained at 2 wt% or less, preferably at 1 wt% or less. In addition, the magnesia calcia clinker of the present invention contains at least a part of the iron component dissolved in a perclyde crystal which is a crystal of magnesia, and the amount thereof is preferably at least 30% of the iron content.

Magnesia, calcia clinker of the present invention, other, for example in the form of oxide can be containing SiO ₂ of 1.0 wt% or less, Al ₂ O ₃ less than 0.5% by weight of wool and B ₂ O ₃ less than 0.05% by weight.

The magnesia calcia clinker of this invention has a bulk density of 3.2 g / cm <3> or more, Preferably it is 3.25-3.35 g / cm <3>.

Moreover, the magnesia calcia clinker of this invention is 1.5 weight% or less, Preferably it is 1 weight% or less as shown in the weight increase rate as one of the characteristics. Moreover, the magnesia calcia clinker of this invention is 4 weight% or less, Preferably it is 2 weight% or less in fire resistance shown by the differentiation rate.

According to the present invention, the magnesia calcia clinker of the present invention comprises (a) water-soluble iron compounds and (b) dolomite calcined products, limestone or hydrates thereof in seawater, juice or brine. Simultaneously or in this order to produce a precipitate consisting predominantly of magnesium hydroxide, wherein (2) this magnesium hydroxide is mixed with natural dolomite and then (3) the resulting mixture is calcined by the process of the invention. There is a number.

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

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

It is particularly preferable to add a water-soluble iron compound to an aqueous solution containing magnesium before adding an alkaline compound such as lime. According to the method of the present invention, the reason for obtaining a magnesia calcia clinker having a higher density than 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 present invention, when lime or the like is added to a magnesium-containing aqueous solution containing a water-soluble iron compound, dominant fine iron hydroxide particles are formed, and then magnesium hydroxide is formed as a nucleus, so that the water-soluble iron compound works advantageously when generating magnesium hydroxide. However, it is thought that there is little opportunity to produce a low melt compound in other baking.

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 water-soluble iron compounds include inorganic acid salts such as iron chloride, iron sulfate, iron nitrate, and iron phosphate, acetates, iron benzoate, and p-toluene sulfonate. The water-soluble iron compound is mainly magnesium hydroxide and can be added in an amount of up to 2% by weight on a burning basis during precipitation.

The addition of an alkaline compound, such as lime, to the magnesium-containing aqueous solution containing a water-soluble iron compound is carried out so that the pH of the aqueous solution is about 10.8 or more to form magnesium hydroxide, preferably pH 11 or more, for example pH 11-12. It is done to become. When the pH of the aqueous solution exceeds 10.8, the alkaline compound is slightly added, thereby producing magnesium hydroxide having a low boron content, and consequently, a magnesia calcia clinker having a low boron content can be produced. When the pH is set to 11 to 12, alkaline compounds such as lime in the reaction solution are slightly excessive as described above, and the reaction solution is separated from the reaction solution prior to separating the precipitate mainly composed of magnesium hydroxide from the reaction solution. It is preferable to dissolve an alkaline compound, such as excess lime, by making it react with hydrous decarbonated aqueous solution. In this way, precipitates of magnesium hydroxide having a reduced calcium content as well as boron content can be obtained.

Examples of the alkaline compound used in the above step include dolomite calcined products or hydrates thereof in addition to lime.

According to the method of the present invention, the precipitate, which is mainly composed of magnesium hydroxide, is separated by, for example, a thickening agent or the like, washed with necessity, then mixed with natural dolomite, and also pressure molded and fired.

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

In order to facilitate understanding of the method of the present invention, a preferred embodiment leading to the generation of magnesium hydroxide precipitation in the present invention is described as follows.

For example, an aqueous solution of iron sulfate is added to an aqueous solution of decarbonated water of seawater, followed by lime to produce a reaction solution having a pH of 11.2 to 11.8, and the weight ratios as oxides are CaO / MgO about 24 and SiO ₂ / MgO about 0.05 to 0.2 and Fe ₂ O ₃ / MgO A precipitate consisting mainly of magnesium hydroxide of about 0.2 to 3 is produced. Before separating the precipitate from the reaction solution, for example, an aqueous decarbonate solution of seawater is added to bring the pH to 9.8 to 10.8. To produce a precipitate consisting mainly of CaO / MgO of about 1.8 to 3.0, SiO ₂ / MgO of about 0.05 to 0.25 and Fe ₂ O / MgO of 0.2 to 3, followed by washing with necessity and weight ratio CaO / MgO as oxide Produces a precipitate consisting mainly of magnesium hydroxide, about 1.4-1.8, SiO ₂ / MgO about 0.05-0.30 and Fe ₂ O ₃ / MgO about 0.2-3.

Thus, according to the method of the present invention, the magnesium hydroxide obtained by mixing the magnesium hydroxide obtained by the above method in natural dolomite can be produced in the magnesia calcia clinker having excellent sintering and fire resistance.

The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention.

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

[Chemical Composition]

The measurements were made in accordance with the "School Method 1 Magnesia Clinker and Chemical Analysis Method" (refer to the 1981 edition of the Refractories Handbook), which was determined at the Japanese Society of Science Promotion Association 124 Committee Test Method.

In particular, the analysis of B ₂ O ₃ was carried out by the Krkmin method (absorbance spectroscopy method) adopted as a school-based method as a result of review by the Committee.

[Volume density (volume specific gravity)]

In accordance with the "Method for Measuring the Appearance Porosity, Appearance Specific Gravity, and Volume Specific Gravity of the Hakjin Method 2 Magnesia Clinker" determined by the Test Method Subcommittee of the 124th Committee of the Japan Academic Promotion Association, the following formula was obtained.

W ₁ : dry weight of the clinker (g)

W ₂ : Weight (g) in white kerosene of a sample saturated with white kerosene

W ₃ : Weight of sample saturated with white kerosene (g)

S: Specific gravity of white kerosene at the measurement temperature (g / cm 3)

[Digestibility (weight increase rate and differentiation rate)]

It is measured according to the method of Digestibility Test of the School Engineering Method 7, Dolomite Clinker and (II) Autoclave.

EXAMPLES 1-4

Dolomite ore was sintered to 7 mm / m or less and pulverized so as to have a particle diameter of 90% or more for passing 100 mesh (150 µm) or 90% or more for passing 200 mesh (74 µm) as a main MgO source.

On the other hand, FeSO ₄ solution was added to the decarbonated seawater so that the ratio of Mg ions and Fe ions became 0.4 / 100 in terms of Fe ₂ O ₃ / MgO weight, and purified Ca (OH) ₂ oil was added to the seawater. A slurry was produced based on Mg (OH) ₂ . PH of the reaction liquid at this time was 11.7. The slurry thus produced was washed with fresh water to produce an Mg (OH) ₂ slurry containing Fe to be a secondary MgO source.

The secondary MgO source is in the form of a cake and 5%, 10 in terms of MgO weight based on 100 parts by weight of solids of the main MgO source (MgO, CaO, SiO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ , B ₂ O ₃ ) %, 20% was added and mixed homogeneously in the form of pate. The paste-shaped cake was adjusted to moisture to have 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.

Further, the molded body was then calcined with oxygen propane at 1850 ° C. for 30 minutes to produce magnesia calcia clinker.

The sinterability, fire resistance, and chemical composition of the obtained clinker are shown in Table-1.

TABLE 1

Example 5

Dolomite ore was grained at 7 m / m or less, which was ground with a tube mill so as to have a particle size of 100 mesh (150 µm) and 90% or more, and was used as a main MgO source.

On the other hand, FeSO ₄ solution was added to the decarbonated seawater so that the ratio of Mg ion and Fe ion became 0.4 / 100 in terms of Fe ₂ O ₃ / MgO weight, and further purified Ca (OH) ₂ oil was added to the seawater. It added and produced the slurry which has Mg (OH) ₂ as a main component. PH of the reaction liquid at this time was 11.7.

The slurry thus produced was washed with fresh water and further dried with a rotary dryer to produce Fe-containing Mg (OH) ₂ to be a secondary MgO source.

Fe content Mg (OH) equivalent to 10% in terms of MgO weight based on 100 parts by weight of solids (MgO, CaO, SiO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ , B ₂ O ₃ ) of the main MgO source _{After 2} was added and mixed, a molded body was produced by a rotary continuous molding machine.

In addition, it was calcined at a boiling point of 1900 ° C. with rotary kiln to produce magnesia calcia clinker.

The sinterability, fire resistance, and chemical composition of the obtained clinker are shown in Table-2.

TABLE 2

Comparative Example 1

Dolomite ore was stipulated to be 7 m / m or less, which was ground to a 90% or more pass through 100 mesh with a mill. The crushed powder was granulated at a molding pressure of 500 kg / cm 2 to form a molded product, and then the molded product was calcined in an oxygen propane under a condition of 1850 ° C. for 30 minutes to produce magnesia calcia clinker.

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

Comparative Example 2

Dolomite ore was grained at 7 m / m or less, and pulverized with a vibrating ball mill so as to have a particle size of 90% or more through 100 mesh passages, to obtain a main MgO source.

On the other hand, Ca (OH) ₂ oil refine | purified with the decarbonated seawater was added, and the slurry which made Mg (OH) _{2 the} main component was produced. PH of the reaction liquid at this time was 11.7. The slurry thus produced was washed with fresh water as a secondary MgO source.

The secondary MgO source was added and mixed homogeneously so that the main MgO source was 10% in terms of MgO weight based on 100 parts by weight of the solid content.

After adjusting so that a moisture content might be 9 to 10 weight%, it granulated at 500 kg / cm <2> of molding pressure, and it was set as the molded object.

Further, the molded body was then calcined under oxygen propane at 1850 ° C. for 30 minutes to produce magnesia calcia clinker.

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

Comparative Example 3

A solution of FeSO ₄ was added to the decarbonated seawater so that the ratio of Mg ions and Fe ions was 0.4 / 100 in terms of Fe ₂ O ₃ / MgO weight, and purified Ca (OH) ₂ oil was added to the seawater, and MgO A slurry containing (OH) ₂ as a main component was produced. After washing with fresh water, the Ca (OH) ₂ oil was added as a CaO source to adjust to a chemical composition of 40/60 in terms of MgO / CaO weight, and after filtration, drying and molding, it was calcined at 1900 ° C. for 30 minutes. . Table 3 shows the sintering properties, fire resistance and chemical composition of the obtained magnesia calcia clinker.

TABLE 3

Claims (2)

(a) MgO, CaO and Fe ₂ O ₃ as oxides, expressed in weight percent, total 96% or more of MgO and CaO, mgO 40-55%, CaO 44-58%, Fe ₂ O ₃ 2% or less A magnesia calcia clinker having excellent fire resistance, which has a chemical composition, (b) a bulk density of 3.2 g / cm 3 or more, and (c) a fire resistance of 1.5% or less. (1) To the seawater, juice or water, (a) dolomite calcination, lime or their hydrates are added to produce a precipitate consisting primarily of magnesium hydroxide, and (2) the magnesium hydroxide is mixed with natural dolomite And then (3) the resulting mixture is calcined to produce magnesia calcia clinker, wherein (b) iron chloride is added before or simultaneously with addition of the dolomite calcined product, lime or their hydrate in step (1). Inorganic salts selected from iron sulfate, iron nitrate, and iron phosphate, or organic acid salts selected from acetate, iron benzoate, and p-toluene sulfonate add water-soluble iron compounds to produce precipitates consisting mainly of Fe-ion-containing magnesium hydroxide. How to.