DE3610586A1 - Binder for a refractory material and refractory product containing this binder - Google Patents

Abstract

A binder for a refractory material and also a refractory product containing this binder and a refractory material are provided. The main component of the binder is a calcium aluminate. This calcium aluminate is selected from the group consisting of the amorphous calcium aluminates of the composition CaO+Al2O3, CaO+2Al2O3, 3CaO+Al2O3, 3CaO+3Al2O3+CaF 2, 11CaO+7Al2O3+CaF2 and 12CaO+7Al2O3, the crystalline calcium aluminates of a composition 3CaO+3Al2O3+CaSO4, the amorphous calcium aluminates of the composition 3CaO+3Al2O3+CaSO4 and mixtures of these materials.

Description

The invention relates to a binder for a refractory Material, as well as a containing this binder fireproof product.

Refractory products for lining furnace walls were made often applied by spraying and the spray method is often been used to repair such furnace walls. Contain refractory products used for this purpose Binder made from phosphates, alumina cements and / or crystalline calcium aluminates in powder form in each case for themselves or a combination of these materials consist.

Although it was normally possible to spray the known refractory products onto the furnace wall when the temperature of the furnace was in the room temperature range, these materials could not be applied to form a satisfactory intact liner when the furnace was still at a high temperature found. When the usual refractory products are sprayed onto the furnace walls, which are still at an elevated temperature, the sprayed refractory products often peel off due to the abrupt evaporation of the water they contain, leaving stains and defects that are not caused by the fireproof lining are covered. To avoid this disadvantage, it is necessary to cool the furnace down for a long period of rest, for example three days or even more, until it is ready for repair. Nevertheless, the usual refractory products have the disadvantage that they have insufficient fire resistance and poor adhesiveness, so that they have to stand in situ for a long time after they have been applied to the furnace wall.

The invention is therefore based on the object Binder for a refractory material (high temperature resistant or meltable material) To provide, which to a large extent with rapid Setting capacity is equipped and therefore even then a refractory coating that adheres firmly to the furnace wall forms without peeling or peeling when using under high pressure temperature conditions takes place, and a refractory (connection) with To create help of such a binder.

It is also an object of the invention to provide a binder for to provide a refractory material which a refractory product with high temperature resistance leads, and a refractory bond or To create connection using this binder.

The invention also relates to a binder to provide for a refractory material which forms a fireproof product that quickly becomes high Has strength, so that satisfactory effectiveness can be achieved even if the share of the binder is relatively small, and it is also Object of the invention, a meltable connection with the help of such a binder.

Another object of the invention is a binder to provide for a refractory material which can be applied by a spray process, with only a small proportion bouncing off, so that a extremely high operational efficiency is achieved. It is further object of the invention, a refractory connection to produce with such a binder.

Another object of the invention is an economical Creating binders for a refractory material which is manufactured with high production efficiency  can be, and a refractory connection with a to create such binders.

The above and other objects of the invention by the subject matter described below solved.

The binder according to the invention for a refractory material contains as a main component a calcium aluminate, which from the group of amorphous calcium aluminates. each having a composition according to CaO + Al ₂ O ₃ , CaO + 2Al ₂ O ₃ , 3CaO + Al ₂ O ₃ , 3CaO + 3Al ₂ O ₃ + CaF ₂ , 11CaO + 7Al ₂ O ₃ + CaF ₂ and 12CaO + 7Al ₂ O ₃ , the crystalline calcium aluminate of a composition 3CaO + 3Al ₂ O ₃ + CaSO ₄ , the amorphous calcium aluminate of the composition 3CaO + 3Al ₂ O ₃ + CaSO ₄ and the mixtures of these materials is selected.

The invention also relates to a refractory product which comprises a refractory material and a binder for this refractory material, the binder as the main component being a calcium aluminate, which from the group of the amorphous calcium aluminates, each having a composition according to CaO + Al ₂ O ₃ , 3CaO + Al ₂ O ₃ , 3CaO + 3Al ₂ O ₃ + CaF ₂ , 11CaO + 7Al ₂ O ₃ + CaF ₂ and 12CaO + 7Al ₂ O ₃ , the crystalline calcium aluminates of a composition 3CaO + 3Al ₂ O ₃ + CaSO ₄ , the amorphous calcium aluminate of the composition 3CaO + 3Al ₂ O ₃ + CaSO ₄ and the mixtures of these materials is selected.

The invention is described in more detail below.

The binder for a refractory material provided according to the invention contains a calcium aluminate which is selected from amorphous calcium aluminate as defined above and in the claims, and a crystalline calcium aluminate which also corresponds to the definition given above and as claimed or mixtures of these materials. The amorphous calcium aluminates which can be present as the main constituent of the binder according to the invention include those of the compositions CaO + Al ₂ O ₃ , CaO + 2Al ₂ O ₃ , 3CaO + Al ₂ O ₃ , 3CaO + 3Al ₂ O ₃ + CaF ₂ , 11CaO + 7Al ₂ O ₃ + CaF ₂ , 12CaO + 7Al ₂ O ₃ around their mixtures, and an amorphous calcium aluminate of the composition 3CaO + 3Al ₂ O ₃ CaSO ₄ or its mixtures. The crystalline calcium aluminate, which is also suitable for the purposes of the invention, is a material of the composition 3CaO + 3Al ₂ O ₃ + CaSO ₄ .

Each of the calcium aluminates of the compositions correspond to CaO + Al ₂ O ₃ , CaO + 2Al ₂ O ₃ , 3CaO + Al ₂ O ₃ , 3CaO + 3Al ₂ O ₃ + CaF ₂ , 11CaO + 7Al ₂ O ₃ + CaF ₂ , 12CaO + 7Al ₂ O ₃ and 3CaO + 3Al ₂ O ₃ + CaSO ₄ can be prepared by melting the corresponding materials at a temperature of not less than 1000 ° C, preferably not less than 1400 ° C, and then melting the melted mass to a temperature below the crystallization temperature is quenched by contacting the molten mass with a cooling medium, such as compressed air or water, so that an amorphous calcium aluminate is formed. The degree of the amorphous structure can be increased if the raw material for the amorphous calcium aluminate is completely melted and if the quenching rate is increased. It is therefore desirable that rapid quenching be accomplished by contacting the molten mass with a large amount of a cooling medium within a quenching time of not more than 5 seconds, particularly not more than 1 second, so that the quenching occurs during this time a temperature of not higher than 500 ° C, preferably not higher than 100 ° C takes place. Although a small amount, e.g. 5 percent by weight or less, of a melting point depressant such as a halide (e.g. CaF ₂ ) or a boron compound such as borax may be added to obtain a perfectly melted mass and In order to accelerate the formation of an amorphous mass, it is preferred to keep the amount of the melting point depressant added as small as possible.

When producing an amorphous calcium aluminate having the composition 3CaO + 3Al ₂ O ₃ + CaSO ₄ , it is desirable that the starting material is melted at a temperature of 1300 to 1400 ° C, since the above-mentioned calcium aluminate decomposes at 1500 to 1600 ° C, and that quenching is carried out at extremely high speed, for example by blowing a large amount of a cooling medium into the system to increase the glass content.

It is desirable that the glass content of the amorphous Calcium aluminates in general not less than 50% by weight, preferably not less than 90 percent by weight, and in particular 100 percent by weight, is. The glass content of a certain amorphous calcium aluminate is determined by the height of the maxima in the X-ray diffraction spectrum obtained by X-ray diffraction Spectrometry of the amorphous to be produced Calcium aluminate, which was quickly quenched with the height of the maxima in the X-ray diffraction spectrum of a compared perfectly crystallized calcium aluminate which is achieved by cooling a molten mass at a cooling rate of no more than 10 ° C per minute until a temperature of the mass is reached of 500 ° C was obtained.

The glass content then becomes from the results obtained calculated according to the following equation

The crystalline calcium aluminate of the composition 3CaO + 3Al ₂ O ₃ + CaSO ₄ can be produced by melting the material at a temperature of not less than 1000 ° C, preferably at a temperature of 1300 to 1400 ° C, and then cooling it. The degree of crystallization can be checked by X-ray diffraction spectrometry.

To produce the amorphous and crystalline calcium aluminates of the compositions defined above, a CaO source, such as quicklime, an Al ₂ O ₃ source, such as bauxite or aluminum oxide, and a CaSO ₄ source, such as anhydrous calcium sulfate, are combined in one of those defined above Compositions determined molar ratio mixed together and the mixture is then melted by heating in an electric furnace, shaft furnace, hearth furnace or other conventional furnace and then either quenched or slowly cooled.

The calcium aluminate is used in powder form. The specific surface area (Blaine value) of the powdered calcium aluminate should generally not be less than 2000 cm ² / g and preferably in the range from 4000 to 7000 cm ² / g. Extremely fine particle size powdered calcium aluminate causes dusting difficulties, while excessively large particle size powdered calcium aluminate is disadvantageous because the reaction affinity is lowered, causing a decrease in initial strength and adhesiveness.

It is preferred that the amount of calcium aluminate that in the binder according to the invention for a refractory Material is as high as possible, the preferred content generally not less than 50 Percent by weight, especially not less than 70 percent by weight, is.

Examples of materials for binders that go together used with the calcium aluminates to to bind the refractory material include alumina cements, various phosphates, such as aluminum phosphate, Alkali silicates such as sodium silicate and various Cements such as Portland cements. This from calcium aluminate different materials can be used in the manufacture a refractory product with the invention Binder to be mixed. The proportion of the binder for the refractory material can generally range from 2 to 40 percent by weight, preferably from 5 to 20 percent by weight, being a refractory product with satisfactory High temperature resistance is formed. If the share the binder is less than 2 percent by weight, the bond strength is deteriorated if on the other hand the binder content more than 40 percent by weight is the high pressure temperature resistance of the refractory product formed.

With regard to refractory materials in combination used with the binder of the invention there is no particular limitation. So materials based on aluminum oxide are particularly suitable, Silicon dioxide based materials, materials based on aluminum oxide-silicon dioxide, materials based on magnesium oxide, materials based of zirconium oxide and materials based on silicon carbide. The special type of refractory and  whose particle size can take into account the practical implementation of the spraying process and Strength can be chosen to apply the refractory Product at the expected application temperature necessary is.

The following is an exemplary method for spray coating with the refractory according to the invention Material described.

The binder according to the invention for a refractory Material comes with the refractory material to be used mixed. The mixture is pneumatically sprayed fed immediately before spraying with water spiked and that of binder, refractory and Water existing mixture is on the furnace wall or a other surface sprayed with a refractory Coating to be coated. If an excessively large Amount of water added can form the Strength after spraying in an unexpected way Evaporation of water can be reduced, resulting in a deteriorated adhesiveness and, as a result, peeling or the coating applied by spraying falls off leads. In contrast, if the amount of added Water is too low, the amount of rebounding Material undesirably increased. It will therefore preferred that the amount of water added at this stage is kept as small as possible and preferably in Range is about 5 to 20 weight percent. At this stage it is preferable to use a water reducing agent, like a compound of the lignin sulfonate system, to add the amount of water added at this stage to diminish. A particularly preferred connection works as a plasticizer, such as one by condensation polymerization obtained from naphthalenesulfonic acid and formaldehyde Product.  

Other additives commonly used for similar applications added to certain compositions can also be used for the refractory according to the invention Materials are used. Examples of such Common additives include retarders, such as organic ones Acids, including hydroxycarboxylic acids, and Alkali carbonates, such as sodium carbonate or sodium bicarbonate.

It is also advantageous to contain finely powdered silica or alumina-containing material, such as powdered silica powder or alumina powder add to the high temperature strength of the formed Increase or to increase the amount of in the coating Spray level to reduce bouncing material.

In addition, together with the binder according to the invention additionally conventional binders for refractories Materials are used, such as aluminum oxide cements, Phosphates and silicates.

The binder according to the invention for a refractory Material and the refractory containing this binder Product can not only by spray coating, but also applied by casting processes and stamping processes will. A delay agent can optionally be added to the materials be added, if necessary takes place during these processing processes.

The invention will be described in more detail below with reference described in the examples below.

In the following examples and comparative examples, C is CaO, A is Al ₂ O ₃ and SO ₃ , while A-CA is an amorphous calcium aluminate.

example 1

From a mixture of slaked lime (98% purity) and aluminum oxide (97% purity), a CA composition characterized by the formula C ₁₂ A _{7 was} melted in an electric furnace at 1700 ° C. and the melted mixture was then blown off by blowing in compressed air 5 kg / cm ² rapidly cooled to a temperature below 500 ° C within one second, whereby A-CA was obtained. The A-CA thus formed was pulverized until a Blaine of 5700 cm ² / g was reached, and 7 parts by weight of the pulverized A-CA was mixed with 3 parts by weight of alumina powder, 7 parts by weight of silica flour and 100 parts by weight of one to a particle size of less mixed as 5 mm powdered magnesia clinker. The mixture was pneumatically fed over a distance of 50 m to a sprayer with the trade designation "Model 260" from Aliva Co. and mixed with water at a point 5 m in front of the spray nozzle at a rate such that 100 parts by weight of the mixture with 12 parts by weight of water were transferred. The mixture mixed with water was sprayed onto a surface of a wall made of refractory bricks, which had an area of 30 m ² and was kept at an average temperature of 327 ° C.

The refractory composition of this example solidified immediately after spraying on the wall, without significant peeling or peeling and when spraying, the rebounding portion was very much low and was 8 percent by weight.

The wall was back in within two hours be brought into a usable condition.  

Comparative Example 1

A composition was made in the same manner as in Example 1 produced, with the modification that a Cement with the trade name High Alumina Cement der Denki Kagaku Kogyo K. K. was used instead of the A-CA the 2 parts by weight of a commercially available calcium hydroxide when rapid setting agents had been added. The mixture was on the same wall surface as in Example 1 following the general procedure outlined in Example 1 sprayed on.

It was found that the composition of this comparative example not for practical purposes was suitable because frequent peeling or peeling of the sprayed coating was caused as soon as the temperature the wall was above 100 ° C.

Example 2

The procedure described in Example 1 was repeated, with the modification that molten masses were formed from such mixtures, the composition being characterized by one of the following formulas: CA ₂ , C ₃ A, C ₃ A ₃ + CaF ₂ and C ₁₁ A ₇ + CaF ₂ , the masses being melted by heating to 1800 ° C and the molten masses being quenched to less than 500 ° C within one second.

The results are shown in Table 1.

Table 1

Example 3

Using the same materials as in Example 1 were compositions with those shown in Table 2 Glass held manufactured by the pressure of the Cooling used compressed air and thus the cooling rate were varied. The further conditions and procedural steps were the same as in Example 1.

The results are shown in Table 2.

Table 2

Example 4

The same procedure as in Example 1 was repeated, with the modification that the A-CA according to Example 1 were modified in the manner shown in Table 3.

The results are shown in Table 3.

Table 3

Example 5

The same procedure as in Example 1 was followed repeated, with the modification that the mixing proportion of the A-CA produced in Example 1 on 4, 6, 12 or 27 parts by weight was changed, as in Table 4 is shown. The results are also shown in Table 4.

Table 4

Example 6

An alumina cement was melted in an electric furnace at 1800 ° C and compressed air under 5 kg / cm ² was blown into the molten mass to cool it rapidly to 500 ° C in one second. In this way an A-CA is manufactured. The A-CA was pulverized to a Blaine of 5500 cm ² / g and 7 parts by weight of the powdered A-CA, 3 parts by weight of powdered alumina, 7 parts by weight of silica flour and 100 parts by weight of a particle size less than 5 mm crushed magnesium oxide clinker was mixed together. During the process, a portion of the molten mass was removed and checked by X-ray diffraction spectrometry to ensure that the molten mass contained 90 percent by weight of the amorphous CA.

The mixture was fed pneumatically over a distance of 50 m to a "Model 260" sprayer from Aliva Co. and mixed with water 5 m in front of the nozzle in such a mixing ratio that 12 parts by weight of water were added to 100 parts by weight of the mixture. The water-added mixture was sprayed onto the 15 m ² surface of a refractory brick wall kept at an average temperature of 315 ° C.

The refractory composition of this example solidified immediately after spraying on the wall without essentially peeling or peeling occurred. Furthermore could spray on with an extremely small proportion performed on rebound material of 9 percent by weight will.

The wall was able to do so within two hours back in the ready to use for a fireproof material Condition.

Example 7

The same procedure as in Example 6 was repeated, with the modification that that produced in Example 6 A-CA was pulverized so that the in Example 5 specified values for the amount of rebounded Material were obtained.

The results are shown in Table 5.

Table 5

Example 8

The same procedure as in Example 6 was repeated, with the modification that the mixing proportion of the A-CA made in Example 6 to 4, 6, 12 or 27 parts by weight was changed, as in Table 6 is shown. The results are also in Table 6 shown.

Table 6

Example 9

Mixtures were made using slaked lime as the CaO source, bauxite as the Al ₂ O ₃ source, and anhydrous calcium sulfate as the CaSO ₄ source. Each of the starting materials used had been pulverized before mixing.

The results of the quantitative analysis of each Raw or starting materials are shown in Table 7.

26.3 kg of slaked lime, 52.9 kg of bauxite and 20.8 kg of anhydrous calcium sulfate were mixed and pulverized, and pellets were produced from the resulting mixture by compression molding. The pellets thus produced were calcined in a siliconite electric furnace at 1300 ° C. for one hour, a crystalline clinker characterized by the formula C ₄ A ₃ having the composition shown in Table 8 being obtained.

The calcined clinker was pulverized into a fine powder with a Blaine value of 4500 cm ² / g. 8% by weight of the calcined and pulverized clinker was mixed with 4% by weight of an alumina powder (product of Sumitomo Chemical Co., Ltd.), 8% by weight of an iron dust alloyed silicon dioxide flour and 80% by weight of a magnesium oxide clinker which had a particle size of less than 5 mm had been crushed, mixed.

The mixture was conveyed pneumatically in a "Model 260" sprayer from Aliva Co. over a distance of 50 m and injected water was added 5 m in front of the nozzle at a rate such that 100 parts by weight of the mixture were mixed with 12 parts by weight of water. The mixture obtained by blowing water was sprayed on the surface of a wall made of refractory bricks with an area of 30 m ² , which was kept at an average temperature of 327 ° C.

The refractory composition of this example solidified immediately after spraying on the wall, without substantially peeling or peeling and when spraying, only an extremely small one bounced Amount of 7 percent by weight.

The wall was ready within about 2.5 hours Spray coating with the refractory composition be brought back into a usable condition.  

Table 7

Quantitative analysis (weight percent)

Table 8

Quantitative analysis of a calcined C ₄ A ₃ (weight percent)

Example 10

In the manner described in Example 9, the materials shown in Table 9 were mixed with one another to give the compositions (Experiments 2 to 9) which are shown in Table 9. Each of the compositions thus prepared was sprayed onto the surface of a brick wall which was maintained at an average temperature of 330 ° C and had a surface area of 10 m ² .

The results are shown in Table 9.

Comparative Example 2

The same procedure as in Example 10 was repeated, with the modification that the binder used for the refractory material only from an aluminum oxide cement consisted, as can be seen from experiment 1 in table 9 is. The result is shown in Table 9.

The results of the quantitative analysis of the previous Examples of calcium aluminates used are listed in Table 10 below.  

Table 9

The chemical analyzes of those in the previous examples Calcium aluminates used are in Table 10 shown.

Table 10

Claims (10)

1. Binder for a refractory material, characterized in that it is a calcium aluminate as the main component, which from the group of amorphous calcium aluminates of the composition CaO + Al ₂ O ₃ , CaO + 2Al ₂ O ₃ , 3CaO + Al ₂ O ₃ , 3 CaO + 3Al ₂ O ₃ + CaF ₂ , 11CaO + 7Al ₂ O ₃ + CaF ₂ and 12CaO + 7Al ₂ O ₃ , the crystalline calcium aluminates with the composition 3CaO + 3Al ₂ O ₃ + CaSO ₄ , the amorphous calcium aluminates with the composition 3CaO + 3Al ₂ O ₃ + CaSO ₄ or mixtures of such compounds is selected. 2. Binder according to claim 1, characterized in that that the calcium aluminate does not have a glass content has less than 50 percent by weight.   3. Binder according to claim 1 or 2, characterized in that the calcium aluminate has a specific surface area (Blaine value) of not less than 2000 cm ² / g. 4. Binder according to one of claims 1 to 3, characterized in that the calcium aluminate in a Amount not more than 50 percent by weight is. 5. Binder according to one of claims 1 to 4, characterized in that it is also a material contains, which from the group of alumina cements, Phosphates, alkali silicates, Portland cements and mixtures such materials is selected. 6. Refractory product containing a refractory material and a binder for this refractory material, characterized in that the binder as the main component is a calcium aluminate, which is selected from the group of the amorphous calcium aluminates of the composition CaO + Al ₂ O ₃ , CaO + 2Al ₂ O ₃ , 3CaO + Al ₂ O ₃ , 3CaO + 3Al ₂ O ₃ + CaF ₂ , 11CaO + 7Al ₂ O ₃ + CaF ₂ and 12CaO + 7Al ₂ O ₃ , the crystalline calcium aluminates with the composition 3CaO + 3Al ₂ O ₃ + CaSO ₄ , which is selected from amorphous calcium aluminates with the composition 3CaO + 3Al ₂ O ₃ + CaSO ₄ or mixtures of such compounds. 7. Refractory product according to claim 6, characterized characterized in that the refractory material from the Group of materials based on aluminum oxide Silicon dioxide base, aluminum oxide silicon dioxide Base, magnesium oxide base, zirconium oxide base, Silicon carbide base and mixtures of such materials is selected.   8. Refractory product according to claim 6 or 7, characterized characterized in that it contains the binder in an amount contains from 2 to 40 percent by weight. 9. Refractory product according to one of claims 1 to 8, characterized in that there are additionally 5 to 20 Weight percent water contains. 10. Refractory product according to one of claims 6 to 9, characterized in that it is additionally a Material from the group of water reducing agents (Water reducing agent), retardant, the finely divided materials containing silicon dioxide, the finely divided materials or mixtures containing aluminum oxide contains such materials.