JPS61256961A - Calcia clinker and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a calcia clinker with excellent digestion resistance and a method for producing the same.

[Prior art] In recent years, as steel manufacturing has become more sophisticated and operations have been streamlined, continuous casting, enhanced degassing, and ladle refining have been implemented, making it difficult to use furnaces under harsh conditions such as high-temperature tapping. Operations have begun. Therefore, the refractories used are now required to have better thermal shock, mechanical shock, and chemical stability than ever before.

Conventionally, MCI O has been used as the lining material for converters.

Basic refractories such as MGO-Cr2Os are used.

Furthermore, as mentioned above, the lining of the ladle has been changed from silicic acid and zirconate earth to basic refractory material by introducing the refining process.

As basic refractories, MqO-based materials have been mainly used.

On the other hand, CaO has excellent thermal shock resistance and slag corrosion resistance, and is superior to MgO in terms of its ability to remove AlzOa from molten steel. Due to its low fire resistance, it is difficult to handle, store, and manufacture bricks, and is hardly ever put to practical use as a large material for steelmaking furnaces. Therefore, in order to utilize CaO-based materials as refractories, prevention of their digestion is a major issue.

The following methods are mainly known as methods for improving the digestibility of refractories with a high CaO content.

(a) Coating CaO crystals with various additives.

(b) Carbonate the CaO particle surface.

(c) Apply oil to the surface of CaO particles.

Among these, various attempts have been made especially regarding method (a). For example, as described in JP-A-54-13) 612, CaO or cao-M (I
As described in JP-A No. 59-35060, there is a method of improving the digestion resistance by adding one or more of Fe2o3, CeO2, and TiQz to Q in a total amount of 10% or less. with CaO or CaO-MqO as the main component, Fe2OsO,4~t, 2wt%,
TiQzO1) ~ 0.5 wt%, 3 i Q 2 1.
5wt% or less, containing 1.0wt% or less of AI2O3, and containing the above-mentioned FezO3, Ti0z, 5iOz, AI2
A method in which the total amount of Os is limited to 0.5 to 3.0 wt% is known.

Regarding method (b), see document Amer.

Ceram, Soc, Bull, 49(5)
, 53) (1970) It has been reported that when a CaO sintered body is heat-treated in a CO2 atmosphere to form a CaCO5 layer on the surface, the digestion resistance is improved. Furthermore, although it is not a sintering method, it is already known from JP-A-56-88825 that CaO refractory particles produced by a melting method are heated and carbonated to improve their digestion resistance.

[Problems to be Solved by the Invention] However, although the digestion resistance of the calcia clinker improves in the method (a) by adding oxides other than CaO and MgO, it produces low melting point compounds and reduces the refractoriness. There are drawbacks such as loss of For example l”ezos and Al2
When O3 is added, 2CaO Fe, zos (melting point 1441°C), 2Ca 0-AI 2O3 (melting point 13
60℃).

In addition, in the method (b), carbonation treatment is performed on highly purified CaO as in the reagent in the cited literature.

However, when high-purity CaO is used, although the digestion resistance is certainly improved by carbonation, mechanical shocks such as friction are likely to occur, and hydration starts rapidly from the peeled part.

Therefore, in this method, in order to obtain sufficient digestion resistance, the carbonation rate must be increased and the CaCO3Ji must be thickened. However, when obtaining a sintered body of CaO, C
It is already known that calcined aCO5 has poor sinterability and does not increase the density of the sintered body, but if the carbonation rate is increased to improve the digestion resistance of CaO,
When making refractory bricks using this, the sinterability deteriorates, resulting in a significant decrease in hot bending strength. Alternatively, if the carbonation rate is high, CaCO5 decomposes at high temperatures in the case of unfired bricks, resulting in disadvantages such as large voids being formed in the bricks.

[Means for Solving the Problems] The object of the present invention is to provide a calcia clinker with excellent digestion resistance consisting essentially of Ca0-MllIO without adding any other oxide as a third component, and its The purpose is to provide a manufacturing method.

As a result of researching the properties (composition and physical properties) of calcia clinker and carbonation conditions, the present inventors found that the above problems can be solved by selecting the properties of calcia clinker and selecting appropriate carbonation conditions. Ta.

The clinker that achieves the above purpose contains CaO-Mgo as a main component, contains more than 1% by weight of MaO, and contains FezO
5. One or two of Al zo3, BzOs, TiQz
The total content of seeds or more is 2% by weight or less, and the relative density is 9
6% or more, the open porosity is 2% or less, and the thickness of the CaCO3 layer formed by carbonation of CaO on the surface is 0.
．． It is characterized by having a thickness of 0.05 to 4 μm. This method for producing calcia clinker is based on CaO-Ma
Contains O as the main component and MgO in an amount of more than 1% by weight,
1 of Fe2O3, Al2O3, B2Os, Ti02
A gas containing calcia clinker with a total content of 2% by weight or less of one species or two or more species, a relative density of 96% or more and an open porosity of 2% or less, and a partial pressure of 15% or more of COz. CaO
It is characterized by carbonating a part of it.

In addition, the above CO2-containing gas further produces water vapor at a partial pressure of 0.
Carbonation may be carried out using a gas containing 5 to 10%. Here, the relative density refers to the theoretical density of CaO of 3.37
, MQ When the theoretical density of O is 3°65 (Kagaku Handbook, Maruzen), the content of CaO is 8% by weight, and the content of MaO is 5% by weight, the value is expressed by the following formula. .

BD 337 Xa 3,65 xb X 100 (%
)' + − In the formula, BD is the value of the apparent specific gravity of the calcia clinker measured based on the method specified by the 124th Committee of the Japan Society for the Promotion of Science. Further, the open porosity is the apparent porosity measured based on the method specified by the same committee.

The properties and shape of the calcia clinker used in the present invention are as follows: The composition is Ca O-M (mainly composed of O and 1% MaO).
1: e zos, Al
The combined content of one or more of 2O3, BzOs, and Ti02 is 1% or less. In terms of physical properties, the relative density is 96% or more, and the open porosity is 2.
% or less. In this way, by suppressing the amount of impurities that form low melting point compounds with CaO and increasing the relative density, the properties of CaO, such as hot bending strength, can be fully exhibited. Furthermore, by containing more than 1% by weight of MaO and having an open porosity of 2% or less, even if a thin 08003 layer is formed on the surface, the digestion resistance is significantly improved compared to the conventional carbonation method. can be improved.

In order to form a CaCO5 layer on the surface of the calcia clinker, it is necessary to perform heat treatment in a CO2 atmosphere. The temperature range required for carbonation is 380 to 830°C, preferably 600 to 100°C. At temperatures lower than 380°C and temperatures higher than 830°C, the carbonation rate is slow and it is difficult to obtain a sufficiently thick CaCO5 layer. The treatment temperature has an appropriate range depending on the components of the target calcia clinker, that is, the proportion of MaO contained, and conditions that provide the desired digestion resistance may be selected within that range.

For example, in the case of a clinker containing 90% by weight of CaO, the carbonation concentration is 380°C or higher, but in the case of a clinker containing 30% by weight of MaO, it is desirable to process at a temperature of 500°C or higher.

The CaCO5 layer can be formed to a desired thickness depending on the processing time and temperature. For example, in the case of clinker containing 97% by weight of CaO, carbonation treatment at 500°C results in approximately 0.08 μm in 10 minutes and approximately 0.2 μm in 60 minutes.
When treated at 650° C., a CaCO3 layer with a thickness of about 0.2 μm can be formed in 10 minutes and about 0.6 μm in 60 minutes.

Furthermore, when carbonating, the presence of water vapor in the CO2-containing gas increases the rate of carbonation, and the thickness of the CaCO3 layer when carbonated for the same amount of time is approximately twice as thick as when no water vapor is present. Therefore, by including water vapor in the Co2-containing gas, the carbonation treatment time can be shortened, and there is an advantage that the violet for treatment can be made smaller. A small amount of water vapor may be contained in the gas for carbonation treatment, but the partial pressure should be 0.
5-10% is required. If it is less than 0.5%, there is almost no effect of water vapor, and even if it is more than 10%, the effect remains unchanged.

The digestion resistance of carbonated calcia clinker varies depending on the thickness of the CaCO3 layer produced, but is 0.05~
A thickness of 4 μm is required.

In particular, it is desirable that the mist be 0.1 to 2 μm.

If the thickness of the CaCO3 layer is thinner than 0.05 μm, ■Difficult to obtain sufficient digestive resistance.

■CaCOsMI has low strength and is easily broken by friction between clinker grains, impact, etc.

There are drawbacks such as: Furthermore, when the CaCO3 layer is made thicker than 4 .mu.m, (1) the rate of carbonation becomes slower as the CaCO.sub.5 layer becomes thicker, and several hours of treatment are required to make the CaCO 5 layer thicker than 4 .mu.m. Further, even if the thickness is 4 μm or more, the water resistance reaches a ceiling, so it is not economical to unnecessarily increase the thickness of the CaCO5 layer.

(2) If the thickness of CaCO3 is 4 μm or more, the proportion of CaCO3 as an impurity will increase, and the sinterability will decrease when producing refractory bricks.

■Unfired refractory bricks made using calcia clinker,
For example, when carbon bricks are manufactured, when used at high temperatures, CaCO3 on the surface of the calcia clinker decomposes and carbon
O2 is generated. At this time, if the CaCo3 layer is thicker than 4 μm, the gap between the clinker and carbon formed by the decomposition of CaCO5 becomes large, the clinker becomes liberated, and the strength of the brick decreases.

There are drawbacks such as:

The thickness of the CaCO3 layer was confirmed using a scanning electron microscope, model MSM-4, manufactured by Hitachi-Akashi.

Figure 1 shows Ca before carbonation treatment, Figure 2 shows Ca after carbonation treatment.
91% by weight of O and 1.0% by weight of MgO. An electron micrograph of a clinker containing γIiI% is shown. It can be seen that the surface of the carbonated clinker is uniformly covered with CaCO5 polycrystals, there are no cracks, and the formed CaCO5 layer is dense. It was confirmed by X-ray diffraction that this layer was CaCO5. Figure 3 also shows C after carbonation treatment.
An electron micrograph of the surface of a clinker containing 6 g of aO, 3% by weight, and 30.1% by weight of M (JO) is shown. The arrow ■ is the carbonated CaO part, and the arrow ■ is the MoO part. The thickness of the CaCO3 layer can be further determined by quantifying CO2 by thermal analysis or chemical analysis.

FIG. 4 shows the relationship between particle size (radius) and carbonation rate when clinker with a total Cao content of 91% by weight was carbonated. Here, the particle size refers to the arithmetic mean diameter of the three wheels of the clinker (arithmetic mean II of the minor axis diameter, major axis diameter, and height [thickness]),
Furthermore, the carbonation rate indicates the proportion of the original CaO that has changed to CaCO3.

To actually produce carbonated calcia clinker, for example, after being fired in a rotary kiln, the clinker that is in the middle of cooling is stored in a tank, and COz-containing gas is supplied into the tank to carbonate the surface of the clinker as it cools. There are possible ways.

[Example] Next, actual salary 91 of the present invention and a comparative example will be shown. In addition, in the digestion resistance test in Examples and Comparative Examples, the particle size was 2.00 to 2.00.
4.76g+1 clinker at 25℃ and 70% humidity
The weight increase rate (weight %) at that time was measured and the digestion resistance was evaluated.

Example 1 and Comparative Example 1 Calcia clinker was obtained using Ca(OH)z and MO(OH)2 as raw materials. Using a part of this, CO2
Carbonation treatment was performed at 700° C. for 60 minutes in a gas having a partial pressure of 95%. Digestion resistance was evaluated for the carbonated sample and the untreated sample. Table 1 shows the chemical composition, relative density, open porosity, and digestion resistance evaluation results of the samples. In addition, C8003 of the carbonated sample
The thickness of the layer is 0.6μ for sample N006 and 0.2μ for sample N01) from electron microscopy and 1m observation of the fractured surface of the clinker.
It was a request.

It can be seen from Table 1 that the clinker of the present invention has excellent digestion resistance.

Example 2 Samples N003 and N094 shown in Table 1 had a particle size of 2.0.
The clinker of θ ~ 4.76 rg- has a partial pressure of COz of 95
% COz-containing gas at 100°C. The relative density and open porosity values of the treated clinker did not change compared to the untreated sample even after 3 hours of treatment. FIG. 5 shows the relationship between the processing time and the thickness of the produced CaCO5 layer. This shows that the CaCOs layer becomes thicker as the treatment time increases, that the carbonation rate slows down as the thickness increases, and that the carbonation rate differs depending on the M(JO) content.

Next, samples N003 and N09 were carbonated as described above.
A low digestibility test was conducted on the clinker of No. 4.

The relationship between the thickness of the CaCO5ll produced at this time and the weight increase rate is shown in FIGS. 6 and 7. In addition, Ca CO3
The weight increase rate values when the layer thickness is 0 are those of Sample No. 003 and No. 4 of Comparative Example 1 which were not subjected to carbonation treatment. According to the present invention, by forming a CaCO5 layer of about 0.05μ, the weight increase rate is about one-tenth that of the untreated sample, and for 0.4μ, it is about 100%.
It was found that the digestion resistance of calcia clinker was significantly improved.

Example 3 and Comparative Example 2 Sample N003 shown in Table 1 had a particle size of 2.0θ to 4.1
6-- Clinker with CO2 partial pressure of 95%
In the containing gas, 380℃ (above, Example 3), 2O0℃
, 350° C., and 870° C. (Comparative Example 2) for 60 minutes, and a digestion resistance test was conducted on each sample. The results of Example 3 and Comparative Example 2 are shown in FIG. 8 together.

From this, the effective temperature range for carbonation treatment is 380 to 830.
It can be seen that the temperature is ℃.

Example 4 Sample No. 3 shown in Table 1 had a particle size of 2.00 to 4, γ
6- The clinker of 6C02 has a CO2 partial pressure of 95%.
Containing waste content, 400℃, 500℃, 600℃, 100
Carbonation treatment was performed for 60 minutes at each temperature of .degree.

The results are shown in Table 2. From this, the processing temperature is 60
It turns out that 0 to 700°C is particularly effective.

Example 5 and Comparative Example 3 Sample N003 shown in Table 1 has a particle size of 2.00 to 4.7.
6+e- clinker with CO2 partial pressure of 2%, 15%,
A digestion resistance test was carried out by carbonation treatment at 600° C. for 60 minutes in a gas containing 50% and 95% CO2. The CO2-containing gas used here was a mixture of welding carbon dioxide gas with a COz partial pressure of 99.95% and air, and the CO2 partial pressure was analyzed using an Orsat gas analyzer. The results are shown in Table 3. From this, when the CO2 partial pressure is 15% or more,
It has a carbonation treatment effect and improves digestion resistance.

Example 6 and Comparative Example 4 Samples N003 and N004 shown in Table 1 had a particle size of 2.0.
0 to 4.76 gue of clinker was carbonated at 700° C. for 60 minutes in a gas containing CO2 and water vapor. Table 4 shows the results of the COz partial pressure and water vapor partial pressure of the gas used in the treatment and the thickness of the CaCOs layer after the treatment. The presence of water vapor in the CO2-containing gas makes CaCO5ll thicker, and a CaCO5 layer of the required thickness can be obtained in a short time. However, increasing the amount of water vapor does not necessarily increase the effect.

Example 7 and Comparative Example 5 Samples No. 2, No. 3, No. 4 shown in Table 1
The clinker with a particle size of 2.00 to 4,76 WAs was added to the fifth
Carbonation treatment was performed under the conditions shown in the table. Ca at that time
The thickness of the C03 layer is also shown in Table 5. These carbonated samples N008~NO,1) were heated to a diameter of 9CII.
Approximately 200g of the sample was placed in a cylindrical plastic container with a height of 13c+g, and photographed using a sieving machine for 30 minutes. The capacity of the shaker is 50 ffl in amplitude and 240 vibrations per minute. A digestion resistance test was conducted on the sample after shaking.

The results are shown in Table 6.

If the CaC03 layer is thinner than this, it will be weaker against mechanical impact.

However, even with a thickness of about 0.1 μm, the weight increase rate is about 1/10 of that of a sample not subjected to carbonation treatment, and the strength is sufficient for practical use.

Furthermore, even if CaC03Ml is peeled off, clinker with a high MaO content has excellent digestion resistance.

Example 8 and Comparative Example 6 A clinker having the same chemical composition as Sample N083 shown in Table 1 was blended with the following particle size.

3.36~2,00aua 5oa 2.00~1,0Onn 50g 1,OO~0.25mm 50g The sample with particle size blended in this way was carbonated at 700°C in a CO2-containing gas with a partial pressure of CO2 of 91%. . At this time, samples with the same particle size distribution and different thicknesses of the CaCO3 layer were obtained by changing the treatment time. Table 7 shows the thickness of the CaCO3 layer obtained by electron microscopic observation at this time.

For each of these sample Nos. 12 to 16, the particle size was 0.
251) 1) Add 100 grams of the following MgO fine powder, further add ethyl silicate as a binder and knead it, put the sample in a rectangular mold of 25 x 125 a + m,
Pressure molding was performed at 1 tOn/C1. This molded body is 170
The bricks were fired at 0°C for 2 hours, and the hot bending strength of the resulting bricks at 12O0°C was measured using the apparatus shown in FIG. The relationship between the thickness of the caCO3 layer and the hot bending strength of the brick at this time is shown in FIG.

The scale on the vertical axis of the figure is a relative value when the value of the hot bending strength of sample No. 12, that is, the brick made using CaO not subjected to carbonation treatment, is 1.0. From this Ca
It can be seen that when the thickness of the Coa1 layer exceeds 4 μm, the strength of the brick decreases rapidly.

[Effects of the Invention] According to the present invention, a calcia clinker having excellent digestion resistance can be obtained. Furthermore, firebricks made using the clinker have excellent hot bending strength.

[Brief explanation of drawings]

Figures 1 and 2 are electron micrographs showing the crystal structure of the clinker before and after carbonation treatment, Figure 3 is an electron micrograph showing the crystal structure of the clinker surface after carbonation treatment, and Figure 4 is an electron micrograph showing the crystal structure of the clinker surface after carbonation treatment. The figure is a graph showing the relationship between clinker particle size and carbonation rate, Figure 5 is a graph showing the relationship between treatment time and the thickness of the CaCO3 layer, and Figures 6 and 7 are the thickness and weight of the CaCO3 layer. Graph showing the relationship between carbonation temperature and weight increase rate, Figure 8 is a graph showing the relationship between carbonation treatment temperature and weight increase rate, Figure 9 is an explanatory diagram of the hot bending strength measuring device, and Figure 10 is Ca C
3 is a graph showing the relationship between the thickness of layer 03 and hot bending strength. Patent Applicant Shin Nippon Chemical Industry Co., Ltd. Agent Patent Attorney Hide Komatsu Agent Patent Attorney Hirohei Asahi, Keiyuki Hiyu (Me) 1) 1Il@g! Ingredients (me) llIII@9? Cumulative! (Me) Figure 8 Carbonation treatment temperature (℃)
J nest position double m- Oki 0 country CaCO5 layer thickness (μm) Procedural amendment import) June 12, 1985 Manabu Shiga, Commissioner of the Patent Office 1, Patent Application No. 1988-95226 2. Name of the invention Calcia clinker and its manufacturing method Name Shin Nippon Chemical Co., Ltd. 4. Agent 5. Date of amendment order (voluntary) 6. Detailed description of the invention in the specification subject to amendment ( 1) In the specification, on page 6, line 7, "...is susceptible to impact..." is corrected to "When subjected to impact, carbonated parts are likely to peel off..." . (2) "Carbonation treatment" on page 17, lines 4-5 is corrected to "carbonation treatment." S) "...380°C (Example 3)" on page 18, line 9 of the same page was changed to [...380°C, 500°C, 600°C,
700°C, 830°C (Example 3)”.

Claims (5)

[Claims] (1) Main component is CaO-MgO and 1% by weight of MgO
The total content of one or more of Fe_2O_3, Al_2O_3, B_2O_3, and TiO_2 is 2% by weight or less, the relative density is 96% or more, and the open porosity is 2% or less, and A calcia clinker characterized in that a CaCO_3 layer formed by carbonating CaO on the surface has a thickness of 0.05 to 4 μm. (2) CaCO formed by carbonation of CaO on the surface
The calcia clinker according to claim (1), wherein the thickness of the _3 layer is 0.1 to 2 μm. (3) Main component is CaO-MgO and 1% by weight of MgO
Calcia containing a larger amount of one or more of Fe_2O_3, Al_2O_3, B_2O_3, TiO_2 in a total content of 2% by weight or less, a relative density of 96% or more and an open porosity of 2% or less A method for producing calcia clinker, which comprises heating clinker at 380 to 830°C for 5 minutes or more in a gas containing 15% or more of CO_2 at a partial pressure to carbonate a portion of CaO. (4) In a gas containing 15% or more of CO_2 in partial pressure,
The method for producing calcia clinker according to claim (3), which comprises heating at 600 to 700°C for at least 1 minute. (5) The calcia substance according to claim (3) or (4), wherein the gas containing 15% or more of CO_2 in partial pressure is a gas further containing 0.5 to 10% of water vapor in partial pressure. Method of manufacturing clinker.