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EP-4735401-A1 - REFRACTORY CERAMIC PRODUCT, USE OF HOLLOW SPHERES OF MAGNESIA SPINEL, BATCH FOR PRODUCING A REFRACTORY CERAMIC PRODUCT, METHOD FOR PRODUCING A REFRACTORY CERAMIC PRODUCT, KILN FOR PRODUCING CEMENT CLINKER OR LIME AND METHOD FOR PRODUCING CEMENT CLINKER OR LIME

EP4735401A1EP 4735401 A1EP4735401 A1EP 4735401A1EP-4735401-A1

Abstract

The invention relates to a refractory ceramic product, a use of hollow spheres of magnesia spinel, a batch for producing a refractory ceramic product, a method for producing a refractory ceramic product, a kiln for producing cement clinker or lime and a method for producing cement clinker or lime.

Inventors

  • SCHULZE-BERGKAMEN, HILMAR
  • DING, QIANG
  • SUN, XIAOTING
  • MA, YING

Assignees

  • Refractory Intellectual Property GmbH & Co. KG

Dates

Publication Date
20260506
Application Date
20240621

Claims (15)

  1. 1. A refractory ceramic product, comprising the following features: 1.1 a matrix of particles sintered together; 1.2 the particles sintered together comprise first particles and second particles; 1.3 the first particles are particles based on magnesia; 1.4 the second particles are hollow spheres of magnesia spinel; 1.5 the proportion of the second particles is in the range from 1 to below 10% by mass, based on the total mass of the matrix.
  2. 2. The refractory ceramic product according to claim 1 , wherein the hollow spheres have a diameter not above 3 mm.
  3. 3. The refractory ceramic product according to at least one of the preceding claims, wherein the hollow spheres have a diameter in the range from 100 pm to 3 mm.
  4. 4. The refractory ceramic product according to at least one of the preceding claims, wherein the hollow spheres have a chemical composition comprising the following oxides in the following mass proportions, each relative to the total mass of the hollow spheres: MgO: 25 to 34% by mass; AI2O3: 66 to 75% by mass.
  5. 5. The refractory ceramic product according to at least one of the preceding claims, wherein the hollow spheres have a bulk density in the range from 0.5 to 1.0 g/cm 3 , relative to the total mass of the hollow spheres.
  6. 6. The refractory ceramic product according to at least one of the preceding claims, wherein the particles sintered together comprise the first particles, the second particles and third particles, and wherein the third particles are particles based on at least one spinel-type material.
  7. 7. The refractory ceramic product according to claim 7, wherein the third particles are particles of at least one of the following spinel-type materials: magnesia spinel, magnesia spinel coated magnesia, herzynite or pleonaste.
  8. 8. The refractory ceramic product according to at least one of the preceding claims, having a proportion of the first particles that complements the proportion of the second particles and the third particles to 100% by mass, based on the total mass of the matrix.
  9. 9. The refractory ceramic product according to at least one of the preceding claims, wherein the matrix has a chemical composition comprising the following oxides in the following mass proportions, each relative to the total mass of the matrix: MgO: 82 to 94% by mass; AI2O3: 4 to 14% by mass; further oxides: 0 to 6% by mass.
  10. 10. The refractory ceramic product according to at least one of the preceding claims, having a thermal conductivity at 800°C of less than 5.0 W/m-K.
  11. 11 . Use of hollow spheres of magnesia spinel to reduce the thermal conductivity of a magnesia-based refractory ceramic product, wherein the hollow spheres of magnesia spinel are used with the proviso that the magnesia-based refractory ceramic product comprises a proportion of the hollow spheres of magnesia spinel in the range from 1 to below 10% by mass, based on the total mass of the magnesia-based refractory ceramic product. 12. A batch for producing a refractory ceramic product, comprising the following features: 12.1 a first component and a second component; 12.2 the first component is at least one raw material based on magnesia; 12.3 the second component are hollow spheres of magnesia spinel;
  12. 12.4 the proportion of the second component is in the range from 1 to below 10% by mass, based on the total mass of the first and second component.
  13. 13. A method for producing a refractory ceramic product, comprising the following steps: A. providing a batch according to claim 12; B. firing the batch. 14. A kiln for producing cement clinker or lime, comprising the following features: 14.1 the kiln comprises a lining of refractory products;
  14. 14.2 the refractory products comprise refractory ceramic products according to at least one of claims 1 to 10.
  15. 15. A method for producing cement clinker or lime, comprising the following steps: A. providing a kiln according to claim 14; B. providing raw materials from which cement clinker or lime can be produced through firing; C. firing the raw materials in the kiln.

Description

Refractory ceramic product, use of hollow spheres of magnesia spinel, batch for producing a refractory ceramic product, method for producing a refractory ceramic product, kiln for producing cement clinker or lime and method for producing cement clinker or lime D e s c r i p t i o n The invention relates to a refractory ceramic product, a use of hollow spheres of magnesia spinel, a batch for producing a refractory ceramic product, a method for producing a refractory ceramic product, a kiln for producing cement clinker or lime and a method for producing cement clinker or lime. Refractory ceramic products are products that can withstand high temperatures. The term “refractory product” in the sense of the invention refers in particular to refractory materials with an operating temperature above 600°C and preferably to refractory materials in accordance with DIN 51060:2000-06, i.e. , materials with a pyrometric cone equivalent >SK17. The pyrometric cone equivalent can be determined in particular in accordance with DIN EN 993-12:1997-06. As is well known in the art, the term “ceramic” refractory product refers to a refractory product that is comprised of ceramic material, i.e., particles which are sintered together. Further, as well known in the prior art, a “batch” for producing a refractory ceramic product is comprised of components from which a refractory ceramic product can be produced by firing. A typical field of application for refractory ceramic products is their use in kilns for the production or firing of cement clinker and lime. Such kilns may be rotary kilns or shaft kilns in particular. Such kilns are lined with refractory ceramic products that can withstand the high temperatures in such kilns. Typically, such refractory ceramic products by which such kilns for the production of cement clinker and lime are lined are based on magnesia, i.e. , a refractory material based on the oxide MgO. In principle, such refractory ceramic products based on magnesia have proven to be suitable for lining such kilns. However, it is a permanent task to improve such refractory ceramic products in terms of their insulating capacity and strength. Thus, it is a constant goal to give such refractory ceramic products a good insulating effect with a high strength at the same time. However, the increase of an insulating effect in prior art refractory ceramic products is usually accompanied by a reduction in strength. A main reason is that an improved insulating effect is associated with increased porosity, which leads to a reduction in strength. Furthermore, increased porosity, which in particular is also associated with increased open porosity, can lead to a deterioration in the corrosion resistance of the refractory ceramic product, since components can penetrate the open porosity, resulting in corrosion of the product. In rotary kilns and shaft kilns for burning cement clinker and lime, temperatures in the range of up to 1 ,400 to 1 ,500°C regularly prevail. However, this is regularly not the temperature to which the refractory ceramic products lining the kilns are subjected to. This is due to the fact that on the hot side of the refractory ceramic products, the fired material, i.e., clinker or lime, usually presents some barrier to the furnace atmosphere. Further, the temperature within the refractory ceramic products decreases from the hot side to the cold side. The average temperature within the refractory ceramic products is therefore well below the aforementioned temperatures and often in the range of about 800°C. It is therefore desirable that the refractory ceramic products have good strength and a good insulating effect at 800°C. It is an object of the invention to provide a refractory ceramic product that has a good insulating effect and a high strength. At the same time, the refractory ceramic product should preferably also have a high corrosion resistance. In particular, the refractory ceramic product should have a good insulating effect at about 800°C and further a good strength. It is a further object of the invention to provide a batch for producing such a refractory ceramic product, as well as a method for producing such a refractory ceramic product. To solve the problem, according to the invention there is provided a refractory ceramic product, comprising the following features: a matrix of particles sintered together; the particles sintered together comprise first particles and second particles; the first particles are particles based on magnesia; the second particles are hollow spheres of magnesia spinel; the proportion of the second particles is in the range from 1 to below 10% by mass, based on the total mass of the matrix. Surprisingly, it has been found in the context of the invention that a refractory ceramic product having the above features has at the same time both a good insulating capacity, i.e. , a low thermal conductivity, and a good strength, and in particular a low thermal conductivity at