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CN-121974710-A - Method for producing refractory blocks

CN121974710ACN 121974710 ACN121974710 ACN 121974710ACN-121974710-A

Abstract

The present invention relates to a method for manufacturing refractory blocks. A method for manufacturing a refractory block comprising more than 80% zirconia, based on the weight of the oxide, the method comprising the steps of a) melting a feed comprising more than 50% zircon by weight under reducing conditions to reduce zircon and obtain a molten material, b) subjecting the molten material to oxidizing conditions, by a combined action of a medium length arc which does not produce reduction and stirring which favours reoxidation, c) casting the molten material, d) cooling until the molten material at least partially solidifies into the form of a block, the weight of the block being more than 10 kg, e) optionally heat treating the block, the feed comprising on the one hand alumina particles and on the other hand sodium source and/or boron source particles, the method parameters being such that the block obtained in step d) has more than 2.5% SiO 2 and more than 0.2% Na 2 O.

Inventors

  • Isabella Capodi
  • Pierre Rick vespa
  • Lao Lunte.batu
  • Olivier Siddy

Assignees

  • 法商圣高拜欧洲实验及研究中心

Dates

Publication Date
20260505
Application Date
20181009
Priority Date
20171011

Claims (15)

  1. 1. A method for manufacturing a refractory block comprising, in weight percent on an oxide basis, greater than 80% zirconia, the method comprising the steps of, in order: a) Melting a feed comprising greater than 50% zircon by weight under reducing conditions to reduce the zircon and obtain a molten material, B) Applying oxidizing conditions to said molten material, said oxidizing conditions being obtained by the combined action of an arc of moderate length which does not produce reduction and stirring which facilitates reoxidation, C) The molten material is cast and the molten material is cast, D) Cooling until the melted material solidifies at least partially into the form of a mass, the mass having a weight greater than 10 kg, E) Optionally, heat treating the block, The feed comprises particles of alumina on the one hand, particles of a sodium source and/or particles of a boron source on the other hand, The parameters of the process are such that the mass obtained in step d) has more than 2.5% SiO 2 and more than 0.2% Na 2 O.
  2. 2. The method of claim 1, wherein step a) is continued until the silica content in the molten material is less than 15%, and step b) is continued until the carbon content in the molten material is less than 500 ppm.
  3. 3. The method of any of the preceding claims, wherein the feed comprises greater than 80% zircon, based on the weight percent of the feed.
  4. 4. The process according to any of the preceding claims, wherein the feed has a composition of an amount of reducing agent, preferably an amount of carbon, of more than 2.0% and less than 10.0% in weight percent based on the feed.
  5. 5. The method according to the immediately preceding claim, wherein the amount of reducing agent is greater than 4.0% and less than 8.0%.
  6. 6. The method of any of the preceding claims, wherein the feed comprises an amount of alumina greater than 0.2% and less than 3.0% by weight based on the feed.
  7. 7. The method according to the immediately preceding claim, wherein the amount of alumina is greater than 0.5% and less than 2.5%.
  8. 8. The method of any one of the two immediately preceding claims, wherein the amount of alumina is less than 1.5%.
  9. 9. The method of any of the preceding claims, wherein the feed comprises an amount of sodium source, preferably an amount of sodium carbonate, of greater than 0.5% and less than 5.0% in weight percent based on the feed.
  10. 10. The method according to the immediately preceding claim, wherein the amount of sodium source is greater than 1.0% and less than 4.5%.
  11. 11. The method of any of the preceding claims, wherein the feed comprises a total amount of zirconia stabilizers greater than 1.0% and less than 10.0%.
  12. 12. The method according to the immediately preceding claim, wherein the feed comprises a total amount of zirconia stabilizer of greater than 4.0%.
  13. 13. The process according to any of the preceding claims, wherein the feed is modified such that the mass obtained in step d) has the following chemical composition, amounting to 100%: ZrO 2 is more than 82.0% and less than 97.0%, SiO 2 is more than 0.5% and less than 15.0%, Al 2 O 3 to more than 0.2%, Oxides other than ZrO 2 、SiO 2 、Al 2 O 3 and Na 2 O are less than 10.0%.
  14. 14. The process according to the immediately preceding claim, wherein the feed is modified such that the mass obtained in step d) has the following chemical composition, amounting to 100%: ZrO 2 is more than 86.0%, SiO 2 is more than 2.5 percent, Al 2 O 3 -1.0 wt%, Less than 0.5 percent of Na 2 O, Oxides other than ZrO 2 、SiO 2 、Al 2 O 3 and Na 2 O are less than 5.0%.
  15. 15. The method of any one of the preceding claims, configured such that at ambient temperature and in weight percent, greater than 80% of the zirconia of the block is monoclinic or greater than 25% of the zirconia is tetragonal.

Description

Method for producing refractory blocks The present application is a divisional application of chinese patent application having application date 2018, 10-09, 201880066447.5, entitled "method for manufacturing fused mass with high zirconia content". Technical Field The present invention relates to a method for manufacturing a fused refractory block having a high zirconia content, to a block obtained by the method, and to a glass melting furnace comprising such a block. Background Among the refractory blocks, there are distinct fused blocks (well known for use in building glass melting furnaces) and sintered blocks. Unlike the sintered cake, the fused mass most often contains an intergranular vitreous phase incorporating crystalline grains. Thus, the problems caused by the sintered and fused masses are often different in the solutions adopted to solve these problems. Thus, the compositions developed for the manufacture of sintered cakes cannot be used on their own for the manufacture of melt cakes on a priori, and vice versa. The fused mass, commonly referred to as an "electric frit", is obtained by melting a mixture of suitable raw materials in an electric arc furnace or by any other suitable technique. The molten material is then typically cast in a mold and then solidified. Typically, the product obtained is then subjected to a controlled cooling cycle to bring it to ambient temperature without breaking. This operation is known to those skilled in the art as "annealing". In the fused mass, those having a Very High Zirconia Content (VHZC), generally comprising more than 80% by weight, or even more than 85% by weight, of zirconia, are well known for their very high quality of corrosion resistance and their ability to not stain the glass produced and to not create defects in the glass produced. FR1191665 describes a method for manufacturing refractory products comprising zirconia, alumina and silica using zircon. Under strong reducing conditions, the process results in a product with a high residual carbon content. This creates a risk of oozing and/or blistering, thereby creating defects in the glass. Furthermore, since almost all phases are crystalline, these products do not adapt well to thermal variations, especially for large-sized blocks. The product also exhibits a porosity that is incompatible with use in the form of large-sized pieces. Thus, these products are used only as a source of raw materials (in particulate form) for the manufacture of other refractory products. EP403387 describes a fused cast product with a high zirconia content comprising, in weight percent, 4% to 5% of silica SiO 2, about 1% of alumina Al 2O3, 0.3% of sodium oxide and less than 0.05% of P 2O5. FR2701022 describes a fused cast product with a high zirconia content, comprising, in weight percent, from 0.05% to 1.0% of P 2O5 and from 0.05% to 1.0% of boron oxide B 2O3. FR2723583 describes a fused cast product with a high zirconia content comprising, in weight percent, 3% to 8% of silica SiO 2, 0.1% to 2.0% of alumina Al 2O3, 0.05% to 3.0% of boron oxide B 2O3, 0.05% to 3% of bao+sro+mgo, 0.05% to 0.6% of Na 2O + K2 O and less than 0.3% of Fe 2O3 + TiO2. Fused blocks with very high zirconia content (e.g., ER 1195 manufactured and sold by SEFPRO corporation) are typically made under oxidizing conditions. They are now widely used in glass making furnaces. But its high cost can limit its use, particularly its use in the superstructure of a glass making furnace. Thus, there is a need for a method for manufacturing a fused mass having a very high zirconia content that is less costly than current methods. The object of the present invention is to meet this need. Disclosure of Invention The invention relates to a method for producing a refractory block comprising, in weight percentages based on oxides, more than 80%, preferably more than 85% zirconia, comprising the following steps carried out in succession: a) Melting a feed material comprising greater than 50% zircon by weight under reducing conditions to reduce the zircon and obtain a molten material, B) Oxidizing conditions are applied to the melted material and, C) The molten material is cast and the molten material is cast, D) Cooling until the melted material solidifies at least partially into a block form, E) Optionally, the block is subjected to a heat treatment, in particular an annealing heat treatment. As will be observed in more detail in the subsequent parts of the description, the method according to the invention advantageously enables refractory blocks usable in glass-making furnaces to be obtained rapidly at reduced costs by melting a feed containing all the oxides of the block to be produced. In particular, zircon is introduced directly into the feed with other raw materials without intermediate treatment. The method according to the invention may further comprise one or more of the following optional features: -continuing step a) until the silica content in the melte