METHOD FOR TREATING REFRACTORY CERAMIC PRODUCTS, USE OF THE TREATED PRODUCTS, AND A REFRACTORY CERAMIC PRODUCT

Abstract

A method for treating refractory ceramic products is described herein. The method includes providing a refractory ceramic product, comprising magnesia and at least one of the following salts: one or more alkali salts and one or more alkaline earth salts. The method also includes providing a water-based liquid, combining the refractory ceramic product with the liquid, and separating the refractory ceramic product and the liquid.

Claims

1. A method for treating refractory ceramic products, said method having the following features: providing a refractory ceramic product, comprising: magnesia and at least one of the following salts: one or more alkali salts and one or more alkaline earth salts; providing a water-based liquid; combining the refractory ceramic product with the liquid; separating the refractory ceramic product and the liquid.

2. The method according to claim 1 with a refractory ceramic product in the form of a used refractory ceramic lining of a rotary kiln for burning cement clinker.

3. The method according to claim 2, further comprising: prior to providing the refractory ceramic product, removing the refractory ceramic lining of a rotary kiln for burning cement clinker, said lining comprising magnesia and at least one of the following salts: one or more alkali salts and one or more alkaline earth salts.

4. The method according to claim 1, in which the refractory ceramic product is provided in the form of bulk material.

5. The method according to claim 1, wherein the refractory ceramic product is present to an extent of at least 90 mass %, in relation to the mass of the refractory ceramic product, with a grain size of less than 50 mm.

6. The method according to claim 1, wherein the refractory ceramic product is present to an extent of at least 90 mass %, in relation to the mass of the refractory ceramic products, with a grain size of more than 0.1 mm.

7. The method according to claim 3, further comprising: subsequent to removing the refractory ceramic lining of the rotary kiln for burning cement clinker and prior to providing the refractory ceramic product, comminuting the removed lining.

8. The method according to claim 7, in which the lining is comminuted to a grain size of at least one of: less than 50 mm, or more than 0.1 mm.

9. The method according to claim 1, in which the refractory ceramic product comprises a content of magnesia of at least 60 mass %, in relation to the total mass of the refractory ceramic product.

10. The method according to claim 1, in which the refractory ceramic product comprises a content of alkali or alkaline earth salts of at least 1 mass %, in relation to the total mass of the refractory ceramic product.

11. The method according to claim 1, in which water is provided as the liquid.

12. The method according to claim 1, further comprising: combining the refractory ceramic product separated from the liquid with at least one further magnesia-based refractory ceramic raw material; further processing the combined refractory ceramic product and the at least one further refractory ceramic raw material to provide a refractory ceramic product.

13. (canceled)

Description

[0063] A practical example of the invention will be explained in greater detail hereinafter.

[0064] The practical example relates to a method according to the invention for treating a refractory ceramic product in the form of a used refractory lining of a cement rotary kiln.

[0065] In a first method step the refractory lining of a cement rotary kiln which comprised magnesia and a number of alkali salts was removed from the rotary kiln. The refractory lining was formed of magnesia-based refractory ceramic bricks comprising further amounts of hercynite and magnesia spinel. These bricks contaminated by the alkali salts had the following composition, in each case in mass % and in relation to the total mass of the bricks: [0066] MgO: 78.01 mass % [0067] Al.sub.2O.sub.3: 6.56 mass % [0068] Fe.sub.2O.sub.3: 0.78 mass % [0069] alkali salts (Na.sub.2SO.sub.4, NaCl, K.sub.2SO.sub.4 and KCl): 7.85 mass % [0070] other: 6.80 mass %.

[0071] The removed material present in the form of large lumps following removal from the rotary kiln was crushed by a crusher to a desired grain size. In so doing, the removed material was crushed and processed in such a way that it was then present to an extent of 100 mass % with a mean grain size in the range from 0.5 to 10 mm.

[0072] The accordingly processed removed material or refractory ceramic product was then combined in a mixing drum with a liquid in the form of water. The mass ratio of water to refractory ceramic product was approximately 1.5. The refractory ceramic product and the water were then left combined in the mixing drum for a period of approximately 10 minutes. During this period, the refractory ceramic product and the water were thoroughly mixed with one another by rotation of the mixing drum. During this period, significant amounts of the alkali salts of the refractory ceramic product dissolved in the water, so that the content of the alkali salts and the refractory ceramic product could be reduced from initially 7.85 mass %, in relation to the total mass of the refractory ceramic product, to approximately 2.70 mass %, and therefore on the whole by approximately 66%.

[0073] In a next method step the refractory ceramic product and the water were separated from one another. For this purpose, the water with the alkali salts dissolved therein was firstly removed from the mixing drum and fed to an environmentally friendly disposal system. The refractory ceramic product was also fully dried in a drying apparatus.

[0074] The resultant refractory ceramic product treated by the method according to the invention was used as raw material for the production of refractory ceramic products in the form of bricks for lining cement rotary kilns. For this purpose, the treated, recycled refractory ceramic product was combined with further raw materials in the form of sintered magnesia and magnesia spinel, compacted, and sintered to provide refractory ceramic bricks.

[0075] Refractory ceramic products denoted by A to H are specified in Table I below. The proportions of the components of the batches from which the products A to H were produced are provided in the upper part of Table I in mass %, more specifically in each case in relation to the total mass of the batch. Physical properties of the products A to H are specified in the lower parts of the Table I.

[0076] The used sintered magnesia had a proportion of MgO, in relation to the sintered magnesia, of 96.0 mass %.

[0077] CRK treated removed material denotes the refractory lining of a cement rotary kiln treated in accordance with the invention according to the above practical example. CRK untreated removed material denotes the refractory lining of a cement rotary kiln forming the basis of the above practical example, but not treated in accordance with the invention.

[0078] The physical properties were determined in accordance with the following standards: raw density and open porosity according to DIN EN 993-1:1995-04

[0079] cold compressive strength according to DIN EN 993-5:1998-12

[0080] hot strength according to DIN EN ISO 1893:2008-09

TABLE-US-00001 TABLE I Component A B C D E F G H sintered magnesia >0.1-5 mm 55 30 30 30 30 30 30 sintered magnesia >0-0.1 mm 29 29 29 29 29 29 29 29 MA spinel (magnesia aluminate spinel) 16 11 11 11 11 11 11 11 CRK treated removed material 0.1-5 mm 30 60 30 30 CRK untreated removed material 0.1-5 mm 30 30 30 raw density [g/cm.sup.3) 2.96 2.94 2.87 2.91 2.91 2.89 2.94 2.91 open porosity [vol. %] 16.1 16.3 18.4 17.0 17.4 17.8 16.9 17.7 cold compressive strength [MPa] 65 59 44 46 59 49 55 48 hot strength t.sub.0 [ C.] 1464 1441 1460 1338 1444 1267 1424 1410 hot strength t.sub.0.5 [ C.] 1697 1679 1662 1605 1696 1569 1642 1648

[0081] Product A is a conventional refractory ceramic product based on the raw materials sintered magnesia and MA spinel.

[0082] In products B to H some of the sintered magnesia and the MA spinel was replaced by a raw material in the form of a used refractory lining of a cement rotary kiln, more specifically in products B, C, E and G by the raw material CRK treated removed material and in products D, F and H by the raw material CRK untreated removed material. Since the raw materials CRK treated removed material and CRK untreated removed material contained amounts of Al.sub.2O.sub.3, the amount of oxides MgO and Al.sub.2O.sub.3 in all products A to H was approximately the same.

[0083] It can be clearly seen in Table I that the values of the cold compressive strength and hot strength of the products B, C, E and G correspond approximately to the values of product A, whereas these values are significantly lower in products D, F and H.

[0084] Furthermore, in products B, C, E and G, the values for the raw density are below, and the values for porosity are above the corresponding values of product A. This results in a low thermal conductivity of products B, C, E and G compared to product A, and therefore products B, C, E and G have a good thermal insulation capability.

[0085] At the same time, products B, C, E and G can be provided more economically than product A, since significant amounts of economical, recycled raw material in the form of a used refractory lining of a cement rotary kiln can be used for the production of products B, C, E and G.