ES2273605B2 - MOLDED PIECE OF INDUSTRIAL CERAMICS, PROCEDURE FOR OBTAINING AND EMPLOYMENT. - Google Patents

Abstract

Industrial ceramic molded part, procedure for obtaining and using it.

The invention relates to a molded part of industrial ceramics, baked, alkaline, refractory, which It has at least one basic resistance component and a elastic component, wherein the elastic component is an aluminate of calcium of abbreviated formula CA6. The invention further relates to a procedure for the production of the molded part as well as to your employment

Description

Industrial ceramic molded part, procedure for its production and employment.

The invention relates to a molded part. elastified industrial ceramic, refractory, alkaline, cooked baked, based on at least one resistance component such as Magnesia and dolomite. The invention further relates to a procedure for the production of the molded part and its job.

Molded parts of general type are used as  refractory lining in particular in high processes temperatures with alkaline slag attack, p. e.g., in ovens, tanks or deposits of cement, lime, dolomite, magnesite, steel e non-ferrous metal industries, and also in the industry of glass.

A molded part based on a component of resistance (hereafter simply called resistor) as MgO or CaO / MgO (dolomite), effectively has a high power refractory and good chemical resistance, as a rule brittle, since it has an elastic modulus (module E) relatively high and an unfavorable shear module (module G). This acts negatively in particular on the dissipation of thermal stresses, stress resistance mechanical and temperature change stability (TWB). Is therefore desirable to adjust low modulus of elasticity put that these are responsible for thermomechanical stability.

To increase elasticity or respectively for the decrease of the modulus of elasticity, it is already known the  add a so-called elastification component (hereinafter simply called elastifier) to a mixture for production of a molded part or adding some first materials that in the ceramic baking oven generate the elastifier in the mixture.

For example, bricks are produced from magnesia-chromite or bricks of magnesia-spinel, which have G modules of useful shear, in the range of 8 to 12 GPa (gigapascals)

The refractory bricks that contain molten hercinite or molten zirconium oxide as elastifier, they have a small elasticity, on the contrary, they are ductile. G modules of approximately 15 to 20 GPa are relatively too high

These known molded, elasticized pieces, alkaline, refractory, are valued in particular with respect to their  elasticity, to the desired formation of a coating in a rotary cylindrical oven, resistance to reactions redox, to alkali stability, to stability to hydration and the ability to discard them, where each of These known molding parts have advantages and disadvantages with regarding these properties, which are summarized in the following table:

TABLE 1 Qualitative properties of molded parts known

one

Magnesia-spinel bricks and magnesia-zirconia bricks form a very difficult stable mixture in the rotating cylindrical furnace; consequently p. For example, they can only be used in the sintering zone. Magnesia-Hercinite bricks have a good mixture formation (see "Variation of Physical and Chemical Parameters as a Tool for the Development of Basis Refractory Bricks") as a tool for the development of refractory bricks alkalis "); Klischat, Hans-Jurgen, Dr .; Weibel, Guido -REFRATECHNIK GmbH, Germany, at the Unified International Technical Conference on Refractories (PROBEDINGS), 6th Biennial World -wide Congress, together with the 42 ^ nd International Colloquium on Refractories ("42nd International Colloquium on Refractories"), Refractories 2000, BERLIN - Germany 6-9 September 1999, 50 Years German Refractory Association; pages 204-207), but nevertheless, they present a bad redox stability as well as to the alkalis. The same happens in magnesia-chromite bricks which also create known problems when discarded. Dolomite bricks that do not contain any elastifier nevertheless guarantee a very good coating formation, although they are neither sufficiently alkaline nor sufficiently resistant to
hydration.

The invention aims at creating a molded, refractory, elastified, alkaline piece, which It presents with a high refractory power and good stability chemistry, in particular good elasticity and good capacity of coating formation, as well as good stability redox, alkalis and hydration, and can be discarded without problems.

This problem is solved by characteristics of claim 1. Different advantages versions of the invention are defined in the subclaims and the subordinate claims.

According to the invention, it is used as a resistor alkaline sintered magnesia and / or molten magnesia as well as sintered dolomite and / or molten dolomite, chosen from large number of known resistors. As elastifier, the Calcium aluminate with the CaO / Al 2 O 3 ratio between 0.14 and 0.2, in particular with the chemical composition CaAl 12 O 19 with the oxidic formula CaO.6 Al 2 O 3 or respectively the abbreviated formula CA_ {6}.

Calcium hexaluminate has the formula chemical CaAl_ {12} O_ {19} or respectively the mineral name of "hibonite" and the oxidic formula CaO.6Al_ {O2} or respectively the abbreviated formula CA_ {6}.

Obviously, the Al_ {2} O_ {3} of the CA_ {6} does not reacts with alkali metal and calcium compounds, e.g. eg in the cement rotary cylindrical furnace, since it is already saturated with CaO. This results in a very good stability to the corrosion. Probably the CaO of CA_ {6}, which is like main component in the cement klinker material, care of the formation of a very effective coating in the oven cylindrical rotation, which cannot be achieved even with molded forming parts, elasticized, already known refractories, such as the bricks of magnesia-hercinite or magnesia-chromite.

CA_ {6} is no stranger among refractory materials A molded part is known refractory, from the patent DE 199 36 292 C2 whose mineral oxidic component is formed by a number of phases of α-Al 2 O 3 minerals, β-Al 2 O 3, CA 6 and CA 2. The amount of mineral phases should increase the stability to the corrosion of the molded part. CA_ {6} does not play this respect no elastifying paper.

The invention is clarified below with more detail view of the example of a version:

Magnesia was mixed with a maximum grain of 4 mm and a grain distribution corresponding to a typical curve of Fuller, and the mineral calcium hexaaluminate with a fraction of grain from 0.5 to 4 mm, with a necessary amount of sulphonate of lignin as a binder, they were molded in the form of bricks and they were pressed with a specific pressure of 130 MPa. After a dried at 110 ° C. the bricks were cooked in a tunnel oven at a sintering temperature of 1600 ° C.

The achieved properties of the bricks cooked as a function of the added amount of hexaaluminate of  Calcium are summarized in the following table 2. For comparison a brick of cooked magnesia of the same was used way.

TABLE 2 Properties of the molded part according to the invention compared to the properties of a brick of magnesia

2

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From table 2 it follows that the bricks according to the invention for use in a rotary cylindrical oven of cement with its dynamic temperature conditions are sufficiently elasticized. The elastic modules are within A very good margin. Temperature change stability (TWE) it's excellent.

The mechanism that leads to a very good elastification of the bricks has not been clearly determined so far. It is probably the formation of microscopic cracks between the matrix of magnesia and calcium hexaaluminate when the bricks are baked, caused by the difference in thermal expansion between the two
materials.

From the following table 3 you can see the important individual properties of the known pieces molded according to table 1 and molded parts according to the invention.

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TABLE 3 Qualitative properties of molded parts known, compared to a molded part according to the invention

3

Table 3 shows that all kinds of Bricks known so far show important properties of Clearly disadvantageous application. On the contrary, the magnesia-CA6 bricks according to the invention they have exceptional good properties, as they were not known in the set of important applications.

The molded parts according to the invention can be used advantageously in all applications where they have  place strong temperature differences and where they are generated mechanical and thermomechanical stresses. These are for example the sintering zones and transition zones of the cylindrical furnace Rotary of the brick and earth industries, in particularly the cement, lime, dolomite and magnesite industry, ferrous and non-ferrous metal industry as well as deposits of foundry and iron industry treatments or respectively steel and non-ferrous metals. Molded parts according to the invention show excellent behavior in the application with respect to hydration stability, to alkalis, redox and corrosion along with simultaneous tendency to a good coating formation. They are also superior to known products due to the possibilities of Discard them without problems after being used.

Elasticization of molded parts alkalines according to the invention can be achieved not only with pure calcium hexaaluminate but in calcium hexaaluminate secondary phases may also be present with a content up to 10% by mass, p. e.g., SiO_ {2} and / or TiO_ {2} and / or Fe 2 O 3 and / or MgO. In addition, calcium hexaaluminate acts also as described, when 58% by mass of Al_ {2} O_ {3} is replaced by Fe_ {2} O_ {3} or when the Ca 2+ is partially replaced by Ba 2+ or Sr 2+, as described in "Trojer, F .: Die oxydischen Kristallphasen der anorganischen Industrie-produkte "(" Phases crystalline oxides of the inorganic products of the industry "), E. Schweitzerbart'sche Verlagsbuchhandlung ("Schweitzerbart Publishing Library"), Stuttgart 1963, page 272.

Claims (28)

1. Baked, ceramic molded part industrial, refractory, alkaline, which has at least one alkaline resistor component and an elastifying component, characterized because The elastifying component is an aluminate of calcium with a CaO / Al 2 O 3 ratio between 0.14 and 0.2, in particular with the formula CaAl_ {12} O_ {19}. 2. Molded part according to claim one, characterized because the elastifying component has the formula oxidic CaO.6 Al 2 O 3 or respectively the abbreviated formula CA_ {6}. 3. Molded part according to claim 1 and / or 2, characterized because the elastifying component has up to 10% in mass of secondary phases. 4. Molded part according to claim 3, characterized because the elastic component has as phases Secondary SiO 2 and / or TiO 2 and / or Fe 2 O 3 and / or MgO 5. Molded part according to one or more of the claims 1 to 4, characterized because in the elastifying component can substitute up to 58% by mass of Al 2 O 3, by Fe_ {O} {3}. 6. Molded part according to one or more of the claims 1 to 5, characterized because in the elastifying component can partially replace the Ca 2+ with Ba 2+ and / or Sr 2+. 7. Molded part according to one or more of the claims 1 to 6, characterized because the resistor component is the sintered MgO and / or molten magnesia, and / or sintered dolomite and / or dolomite cast. 8. Molded part according to one or more of the claims 1 to 7, characterized because the molded part has 60 to 99.5% by mass of the resistor component and 0.5 to 40% by weight of the component elastifier 9. Molded part according to one or more of the claims 1 to 8, characterized because at least there is another elastifier in itself already known 10. Molded part according to one or more of the claims 1 to 9, characterized by a crude density between 2.5 and 3.2 g / cm3.

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11. Molded part according to one or more of the claims 1 to 10, characterized by a porosity between 12 and 25, particularly between 14 and 23% by volume. 12. Molded part according to one or more of the claims 1 to 11, characterized by a cold pressure resistance above 35 MPa, in particular above 45 MPa, and a resistance to cold flexing above 2 MPa. 13. Molded part according to one or more of the claims 1 to 12, characterized by an E module between 14 and 35, particularly between 15 and 32 GPa, as well as a G module between 6 and 15, particularly between 7 and 14 GPa. 14. Molded part according to one or more of the claims 1 to 13, characterized by a temperature change stability of > 80. 15. Procedure for the production of a molded part according to one or more of claims 1 to 14, where at least one component is mixed resistor, with at least one elastic component CA6, and the mixture is combined with a binder and mixed forming a moldable composition, then the dough is molded into a piece and the molded part is dried and then cooked to high sintering temperature. 16. Method according to claim fifteen, characterized because as a binder the sulphonate of lignin 17. Method according to claim 15 and / or 16, characterized because the resistor component is used with a grain maximum of 4 mm and a grain distribution corresponding to a Fuller's curve 18. Procedure according to one or more of the claims 15 to 17, characterized because the elastifying component is used in a grain fraction of 0.5 to 4 mm. 19. Procedure according to one or more of the claims 15 to 18, characterized because It is dried at temperatures between 100 and 120 ° C. 20. Procedure according to one or more of the claims 15 to 19, characterized because it is sintered at temperatures between 1400 and 1700 ° C, in particular between 1550 and 1650 ° C. 21. Procedure according to one or more of the claims 15 to 20, characterized because 60 to 99.5% by mass of component is used resistor and 0.5 to 40% by mass of elastifying component. 22. Procedure according to one or more of the claims 15 to 21, characterized because at least one component is used previously synthesized elastifier. 23. Procedure according to one or more of the claims 15 to 22, characterized because a granulated mixture based on corresponding raw materials for the elastic component, mixes with the resistor component, and the component is generated Elasticizer during cooking time. 24. Procedure according to one or more of the claims 15 to 23, characterized because cooking is carried out in such a way that produces the formation of microcracks between the resistor matrix and the elastifying component. 25. Use of molded parts according to one or several of claims 1 to 14, manufactured according to one or several of claims 15 to 24, in a coating of rotary cylindrical kiln masonry. 26. Use according to claim 25, characterized because the molded parts are placed in the area of sintering of the rotary cylindrical furnace. 27. Use according to claim 25 and / or 26, characterized because the molded parts are placed in the area bottom of rotary cylindrical furnace transition. 28. Employment according to one or more of the claims 25 to 27, characterized because the molded parts are placed in an oven rotary cylindrical cement.