Alumina-zirconia-silica refractory products

Abstract

A fused and cast refractory product, the refractory product comprising, as a mass percentage based on oxides, ZrO 2+ The refractory product as defined above comprises HfO2: 39.0%-55.0%, SiO2: 10.5%-14.0%, Al2O3: balance up to 100%, Na2O+K2O: 0.80%-3.00%, Na2O: <0.60%, B2O3: <1.0%, Fe2O3+TiO2: <0.60%, other species: <1.0%, with the proviso that HfO2 <5%, and with the proviso that the ratio (K2O / 1.52) / (Na2O+K2O / 1.52) is greater than 0.30.

Description

[Technical Field]

[0001] The present invention relates to AZS (alumina-zirconia-silica) fused refractory products and to glass melting furnaces containing such products. [Background technology]

[0002] A glass melting furnace generally contains a large number of refractory products arranged in different locations according to their characteristics. For each part of the furnace, the product selected is one that is long-lasting enough to give the furnace a satisfactory service life without causing defects that would make the glass unusable (which would reduce production yields).

[0003] Among refractory blocks, a distinction is made between fused blocks and sintered blocks.

[0004] Unlike sintered blocks, fused blocks typically contain an intergranular vitreous phase that binds the crystal grains together. Thus, the problems encountered with sintered and fused blocks, and the technical solutions employed to solve them, are generally different. Therefore, compositions developed for producing sintered blocks cannot, in principle, be used directly to produce fused blocks, and vice versa.

[0005] Fused blocks, often referred to as "electrofused blocks" or "fused cast blocks," are obtained by melting a mixture of suitable starting materials in an electric arc furnace or via any other suitable technique. The molten material is then conventionally poured into a mold and then allowed to solidify. The resulting product is then generally cooled to ambient temperature without destruction; this operation is known to those skilled in the art as "annealing."

[0006] Alumina-zirconia-silica (AZS) fusion products are known and contain primarily alumina (Al2O3), zirconia (ZrO2), and silica (SiO2). In particular, AZS products conventionally contain less than 80% by weight of zirconia. AZS products also contain corundum (either free or in the form of a corundum / zirconia eutectic), typically in amounts greater than 10%, or even greater than 30%.

[0007] AZS products conventionally contain sodium oxide, Na2O, to impart suitable physical and chemical properties to the vitreous phase. Generally, K2O and Na2O are considered to be equally effective.

[0008] In response to feasibility issues regarding AZS products containing 9%-12% SiO2 and 0.4%-1.7% iron oxide, US2438552 recommends adding sodium oxide (1.0%-2.2%) and a total content of MgO+CaO of 0.2%-0.8%.

[0009] EP 939065 proposes to reduce the exudation of AZS products containing 20% ​​to 59% ZrO2 and 5% to 12% SiO2 by adding B2O3, P2O5 and at least one oxide from the group of SnO2, ZnO, CuO and MnO2.

[0010] WO 2011 / 161588 proposes an exudation-resistant AZS product that contains, in addition to Al 2 O 3 , 30% to 50% ZrO 2 , 8% to 16% SiO 2 , Y 2 O 3 , and more than 0.2% Na 2 O + K 2 O + B 2 O 3 .

[0011] Chinese Patent Application Publication No. CN107555971 proposes an AZS product containing 31%-45% ZrO2, 9%-14% SiO2, 44%-56% Al2O3, 0.6%-1.4% Na2O, and at least one oxide from the group of B2O3, Y2O3, Li2O, Ta2O5, Nb2O5, P2O5 and K2O.

[0012] With the increasing electrification of glass melting furnaces, the refractory blocks, especially those located near the electrodes, must have as high an electrical resistivity as possible to avoid the risk of electrical current deflection in the refractory.

[0013] In particular, electrical current deflection causes localized heating due to the Joule effect, which accelerates block corrosion. Corrosion can also be accelerated in and around electrode-bearing blocks by increased glass convection, which can destabilize the glass-refractory interface and allow hotter glass to contact the refractory product. Summary of the Invention [Problem to be solved by the invention]

[0014] There is a need for AZS refractory products with improved electrical resistivity. [Means for solving the problem]

[0015] The present invention relates to a fused and cast refractory product, the refractory product comprising: As mass percentages based on oxides, out of a total of 100%: ZrO2+HfO2: 39.0%~55.0%, but HfO2<5% SiO2: 10.5%~14.0% Al2O3: balance up to 100% Na2O+K2O: 0.80%~3.00%, but Na2O<0.60% B2O3: <1.0% Fe2O3+TiO2: <0.60% Other species: <1.0% Including, However, the ratio (K2O / 1.52) / (Na2O+K2O / 1.52) is greater than 0.30; The above fused cast refractory product is proposed.

[0016] As will be described in detail later in this specification, products according to the present invention have improved resistivity. The inventors have surprisingly discovered that Na2O and K2O have different effects on resistivity. In addition, the inventors have discovered that in a content range determined by several criteria, in particular by the ratio (K2O / 1.52) / (Na2O+K2O / 1.52) and by a total Na2O+K2O content of 0.80% to 3.00%, Na2O and K2O not only improve resistivity but also maintain feasibility.

[0017] Articles according to the present invention may include one or more of the following optional features, when in accordance with the specific embodiments described below, including when any of these optional features are incompatible with the specific embodiments: the total porosity of the product is less than 10%, or even less than 5%; Preferably, the oxide represents more than 90%, more than 95%, more than 99%, or even substantially 100% of the mass of the product; the mass content of ZrO2 + HfO2 is less than 54.0%, or even less than 53.0%, or even less than 52.5%, or even less than 52.0%, or even less than 51.0%, or even less than 50.5%, or even less than 50.0%, or even less than 49.5%, or even less than 49.0%, or even less than 48.5%, or even less than 48.0%, or even less than 47.0%, or even less than 46.0%, and / or more than 40.0%, or even more than 41.0%, or even more than 42.0%, or even more than 42.5%, or even more than 43.0%, or even more than 43.5%, or even more than 44.0%, or even more than 44.5%, or even more than 45.0%, or even more than 45.5%; a SiO2 mass content of less than 13.8%, or even less than 13.6%, or even less than 13.5%, or even less than 13.4%, or even less than 13.3%, or even less than 13.2%, or even less than 13.0%, or even less than 12.7%, or even less than 12.5% ​​and / or preferably more than 10.6%, or even more than 10.7%, or even more than 10.8%, or even more than 10.9%, or even more than 11.0%, or even more than 11.3%, or even more than 11.5%; an Al2O3 mass content of less than 46.0%, or even less than 45.5%, or even less than 45.0%, or even less than 44.0%, or even less than 43.5%, or even less than 43.0%, or even less than 42.0% and / or more than 29.0%, or even more than 30.0%, or even more than 32.0%, or even more than 34.0%, or even more than 36.0%; the sum of the mass contents of sodium oxide NaO and potassium oxide KO is preferably more than 0.85%, more than 0.90%, more than 0.95%, more than 1.00% and / or preferably less than 2.90%, preferably less than 2.80%, preferably less than 2.70%, preferably less than 2.60%, less than 2.50%, or even less than 2.30%, or even less than 2.20%, or even less than 2.10%, or even less than 2.00%, or even less than 1.90%; The NaO mass content is preferably less than 0.55%, or even less than 0.50%, or even less than 0.40%, less than 0.30%, less than 0.20%, or less than 0.10%; in one embodiment, NaO is present as an impurity; a KO mass content preferably less than 2.50%, or even less than 2.00%, or even less than 1.90%, or even less than 1.80%, or even less than 1.70%, or even less than 1.60%, or even less than 1.50%, and / or more than 0.60%, or even more than 0.65%, or even more than 0.70%, or even more than 0.75%, or even more than 0.80%, or even more than 1.00%; the ratio (K2O / 1.52) / (Na2O+K2O / 1.52) is greater than 0.40, or even greater than 0.45, or even greater than 0.50, or even greater than 0.60, or even greater than 0.65, or even greater than 0.70, or even greater than 0.75, or even greater than 0.80, and / or less than 0.95, or even less than 0.90; B2O3 is present as an impurity and / or the mass content of boron oxide B2O3 is less than 0.90%, preferably less than 0.80%, preferably less than 0.70%, preferably less than 0.60%, preferably less than 0.50%, less than 0.40%, or even less than 0.30%, or even less than 0.20%, or even less than 0.10%; a Y2O3 mass content of less than 0.80%, or even less than 0.60%, or even less than 0.50%, or even less than 0.40%, or even less than 0.30%, or even less than 0.20%; the sum of the mass contents of iron oxide and titanium oxide Fe2O3 + TiO2 is less than 0.40%, preferably less than 0.30%, more preferably less than 0.20%; the total mass content of "other species" is less than 0.9%, or even less than 0.8%, or even less than 0.6%, or even less than 0.5%, or even less than 0.4%; "Other species", i.e., other than ZrO2, HfO2, SiO2, Al2O3, Na2O, K2O, B2O3, Fe2O3 and TiO2, consist only of impurities; the mass content of any "other species", in particular Ta2O5 and / or Nb2O5, is less than 0.4%, or even less than 0.3%, or even less than 0.2%, or even less than 0.1%; the sum of the mass contents of calcium oxide, barium oxide BaO, strontium oxide SrO and magnesium oxide MgO is less than 0.6%, less than 0.5%, less than 0.4% or even less than 0.3%; a CaO mass content of less than 0.4% or even less than 0.3%; the BaO mass content is less than 0.4% or even less than 0.3%; the SrO mass content is less than 0.4% or even less than 0.3%; the MgO mass content is less than 0.4% or even less than 0.3%; The product is in the form of a block.

[0018] According to a particular embodiment, the fused cast refractory product according to the invention comprises, as mass percentages on an oxide basis: ZrO2+HfO2: 39.0% to 55.0%, or even 39.0% to 49.5%, or even 42.5% to 49.5% SiO2: 10.5%~14.0% Al2O3: balance up to 100% Na2O+K2O: 0.80% to 2.50%, or even 0.80% to 2.00% Na2O: <0.60% B2O3: <1.0%, or even <0.5% Fe2O3+TiO2: <0.60% Other species: <1.0% Including, However, the ratio (K2O / 1.52) / (Na2O+K2O / 1.52) is greater than 0.50, or even greater than 0.60, or even greater than 0.65.

[0019] According to a particularly advantageous embodiment, the fused cast refractory product according to the invention comprises, as percentages by mass on the basis of oxides: ZrO2+HfO2: 39.0% to 51.0%, preferably 39.0% to 49.5%, preferably 42.5% to 49.5%, SiO2: 10.5%~13.0% Al2O3: balance up to 100%, preferably <44.0% KO: 1.00% to 2.00%, preferably 1.10% to 1.80% Na2O: <0.30% B2O3: <1.0% Fe2O3+TiO2: <0.60% Other species: <1.0% Including, However, the ratio (K2O / 1.52) / (Na2O+K2O / 1.52) is greater than 0.65, or even greater than 0.70.

[0020] According to a particularly advantageous embodiment, the fused cast refractory product according to the invention comprises, as percentages by mass on the basis of oxides: ZrO2+HfO2: 42.5% to 49.5%, preferably 42.5% to 48.0% SiO2: 10.5% to 13.0%, preferably 11.0% to 13.0% Al2O3: balance up to 100% KO: 0.70% to 1.80%, preferably 0.80% to 1.60% Na2O: <0.60%, preferably <0.50%, preferably <0.40% B2O3: <1.0% Fe2O3+TiO2: <0.60% Other species: <1.0% Including, However, the ratio (K2O / 1.52) / (Na2O+K2O / 1.52) is greater than 0.62, preferably greater than 0.65, preferably greater than 0.70.

[0021] According to a particular embodiment, the fused cast refractory product according to the invention comprises, as mass percentages on an oxide basis: Al2O3: <44.0% ZrO2+HfO2: 45.5%~49.5% SiO2: 10.5%~13.5% Na2O+K2O: 1.00%~2.00% Na2O: <0.60% K2O: <2.00% Including, provided that the ratio (K2O / 1.52) / (Na2O+K2O / 1.52) is greater than 0.60, or even greater than 0.65, greater than 0.70 or greater than 0.75.

[0022] According to a particular embodiment, the fused cast refractory product according to the invention comprises, as mass percentages on an oxide basis: ZrO2+HfO2: 39.0%~52.5%, or even 42.5%~52.5% SiO2: 10.5%~14.0% Al2O3: balance up to 100%, preferably <44.0% Na2O+K2O: 0.90%~2.50% Na2O: <0.60% K2O: <2.00% B2O3: <0.5% Includes.

[0023] According to a particular embodiment, the fused cast refractory product according to the invention comprises, as mass percentages on an oxide basis: ZrO2+HfO2: 39.0%~49.0% SiO2: 10.5%~13.0% Na2O+K2O: 1.00%~2.00% Na2O: <0.60% K2O: <2.00% B2O3: <0.5% Includes.

[0024] According to a particular embodiment, the fused cast refractory product according to the invention comprises, as mass percentages on an oxide basis: ZrO2+HfO2: 39.0%~49.0% SiO2: 10.5%~13.0% Na2O+K2O: 0.85%~2.00% Na2O: <0.55% K2O: 0.80%~1.80% Includes.

[0025] To the extent that the above optional features are not technically inconsistent with each other, they may be combined.

[0026] The present invention also provides a method for producing a refractory product according to the present invention, comprising the steps of: a) mixing starting materials to form a feedstock; b) melting said feedstock until a molten material is obtained; c) casting the molten material and solidifying it by cooling to obtain a refractory product. The method includes the following consecutive steps: This method now relates to the above-described method, with the notable exception that the starting materials are selected so that the refractory product is in accordance with the invention.

[0027] Preferably, the oxides for which a minimum content is required, or precursors of these oxides, are added systematically and deliberately, preferably taking into account the content of these oxides in the raw materials of other oxides in which they are present as impurities.

[0028] The cooling is preferably controlled so that it occurs at a rate of less than 20°C per hour, preferably about 10°C per hour.

[0029] The present invention also relates to a glass melting furnace comprising a refractory product according to the invention or a refractory product produced or capable of being produced according to the method according to the invention, in particular in areas intended to come into contact with molten glass, in particular in a glass melting furnace vessel, in particular in areas intended to constitute electrode holder blocks, for example in the hearth of such a vessel.

[0030] The present invention therefore relates to a glass melting furnace comprising a vessel containing or intended to contain molten glass, said vessel comprising a block made of a product according to the invention.

[0031] definition

[0032] Conventionally, a product is said to be "molten" when it is obtained through a process in which a feedstock is melted until a molten material is obtained, and then this feedstock is solidified by cooling.

[0033] A block is an object the dimensions of which are all greater than 10 mm. All dimensions of a block according to the invention are preferably greater than 50 mm, more preferably greater than 100 mm. A block according to the invention may have, for example, a general parallelepiped shape or a specific shape suited to its application. Unlike layers, blocks made of fused cast refractory products are conventionally obtained through a process involving forming and demolding operations.

[0034] A block of product according to the invention may have one or even two or three overall dimensions (thickness, length or width) of at least 150 mm, preferably at least 250 mm, or even at least 400 mm, or even at least 500 mm, or even at least 600 mm, or even at least 800 mm or even at least 1000 mm, and / or less than 2000 mm, before or after cropping / machining.

[0035] Unless otherwise stated, all oxide contents in products according to the invention are percentages by mass on an oxide basis. The mass content of an oxide of a metal element refers to the total content of this element expressed in its most stable oxide form, in accordance with standard industry practice.

[0036] HfO2 does not chemically dissociate from ZrO2. However, according to the present invention, HfO2 is not intentionally added to the feedstock. Therefore, HfO2 represents only traces of hafnium oxide, which is always naturally present in zirconium oxide sources at a content generally less than 5%, more generally less than 2%. In the blocks according to the present invention, the mass content of HfO2 is less than 5%, preferably less than 3%, more preferably less than 2%. For clarity, the total content of zirconium oxide and traces of hafnium oxide can be expressed either by "ZrO2" or by "ZrO2 + HfO2". HfO2 is therefore not included in "other species".

[0037] The term "impurities" refers to unavoidable components introduced with the starting materials or resulting from reactions with these components. The impurities are not necessary components, but only tolerated components. For example, oxides, nitrides, oxynitrides, carbides, oxycarbides, carbonitrides, and compounds that belong to the group of metallic species of iron, titanium, vanadium, and chromium are impurities.

[0038] Total porosity, as a percentage, is conventionally equal to 100 x (1 - the ratio of geometric density divided by absolute density).

[0039] The geometric density is measured according to standard ISO 5016:1997 or EN 1094-4 and is expressed in g / cm 3 It is conventionally equal to the ratio of the mass of the sample divided by its bulk volume.

[0040] The absolute density value is g / cm 3 It is expressed as ρ = ρ ⁢ ... and can be measured by dividing the mass of a sample by the volume of the sample that has been comminuted to substantially remove porosity. DETAILED DESCRIPTION OF THE INVENTION

[0041] In the fused cast products according to the invention, the ZrO2 + HfO2 content allows for high corrosion resistance requirements, while an excessively high content is detrimental to the industrial feasibility of the block.

[0042] The hafnium oxide HfO2 present in the product according to the invention is preferably the hafnium oxide naturally occurring in the ZrO2 source, and therefore its content in the product according to the invention is less than 4%, generally less than 2% or even less than 1%.

[0043] The presence of SiO contributes to the feasibility of the product, in particular by allowing the formation of a grain boundary glass phase, which can thereby efficiently respond to temperature deformation. The mass content of SiO is preferably limited in order to limit the amount of glass phase.

[0044] The presence of Na2O+K2O contributes to the feasibility of the product. The mass content of Na2O+K2O is preferably limited in order to limit the amount of glass phase and, in particular, to maintain good corrosion resistance by the molten glass and also good electrical resistivity.

[0045] The presence of K2O is necessary to have the ratio (K2O / 1.52) / (Na2O+K2O / 1.52) greater than 0.30, or even greater than 0.40, or even greater than 0.50, or even greater than 0.60, or even greater than 0.62, or even greater than 0.65, and to improve the electrical resistivity.

[0046] Na2O has a negative effect on electrical resistivity, therefore the mass content of sodium oxide Na2O must be limited.

[0047] B2O3 can have a negative effect on feasibility, therefore the mass content of boron oxide B2O3 must remain limited.

[0048] Y2O3 can have a negative effect on feasibility and electrical resistivity, therefore the mass content of Y2O3 must remain limited.

[0049] According to the invention, the mass content of Fe2O3 + TiO2 is less than 0.60%, preferably less than 0.50%, more preferably less than 0.30%. Preferably, the mass content of P2O5 is less than 0.05%. In particular, these oxides are detrimental, inter alia, to the bleeding of refractory products or to the coloring of glass, and their content must be limited to trace amounts introduced as impurities with the starting materials.

[0050] "Other species" are oxide species not listed above, i.e., species other than ZrO, HfO, SiO, AlO, NaO, KO, BO, YO, TiO, and FeO. In one embodiment, the "other species" are limited to species whose presence is not particularly desired and which are commonly present as impurities in the starting materials.

[0051] Preferably, the product according to the invention is in the form of a block, preferably a block with at least one, preferably at least two, or even all, of its overall dimensions being greater than 150 mm.

[0052] The total porosity of products according to the invention is less than 15%, or even less than 10%, or even less than 5%, or even less than 2%, or even less than 1%.

[0053] The product according to the present invention can be conventionally produced according to the steps a) to c) described below: a) mixing starting materials to form a feedstock; b) melting said feedstock until a molten material is obtained; c) solidifying the molten material by cooling to obtain a refractory product according to the invention.

[0054] In step a), the starting materials are selected so as to ensure the oxide content in the final product obtained at the end of step c), and those skilled in the art are well aware how to select said starting materials for this purpose.

[0055] In step b), the melting is preferably carried out by the combined action of a fairly long electric arc, which does not cause any reduction, and stirring, which promotes reoxidation of the product.

[0056] For the intended application, it is preferred to carry out the melting under oxidizing conditions.

[0057] Preferably, the long arc melting process described in French patents no. 1208577 and additionally nos. 75893 and 82310 is used.

[0058] The process comprises using an electric arc furnace, the arc being struck between the feedstock and at least one electrode spaced from the feedstock, and adjusting the length of the arc to minimize its reducing effect while maintaining an oxidizing atmosphere above the molten bath and stirring the bath, e.g., by the action of the arc itself.

[0059] In step c), cooling is preferably carried out at a rate of less than 20° C. per hour, preferably about 10° C. per hour, preferably in a mold of the desired dimensions, taking into account the feeding and possible machining after step c).

[0060] Any conventional process for producing products based on fused zirconia intended for use in glass melting furnaces can be used, provided that the composition of the starting feedstock makes it possible to obtain a product having a composition that corresponds to that of the product according to the present invention.

[0061] Example

[0062] The following non-limiting examples are presented for the purpose of illustrating the present invention.

[0063] In these examples, the following starting materials were used: Zirconia Q1 contains an average of 99% ZrO2+HfO2; "Sable BE01 Bedouin" contains an average of 99% SiO2; AC34 alumina containing an average of 99% Al2O3, Sodium carbonate containing an average of 99.5% Na2CO3 as a source of Na2O, Potassium carbonate containing an average of 99.5% K2CO3 as the K2O source.

[0064] The products were prepared via a conventional arc furnace process and then cast in a mould to obtain blocks with a minimum size of 150mm x 250mm x 500mm after cropping.

[0065] chemical analysis

[0066] The average chemical analysis of the resulting product is given in Table 1. This is the chemical analysis of the liquid feedstock poured into the mold and is given as a mass percentage.

[0067] Example 5 contains 0.68% Ta2O5.

[0068] Species other than ZrO2, HfO2, SiO2, Al2O3, B2O3, Na2O and K2O and Ta2O5 in Example 5, particularly Fe2O3, TiO2 and Y2O3 (which may be present), are impurities, with Y2O3<0.2% and Fe2O3+TiO2<0.3%.

[0069] In Table 1, the HfO2 content is always less than 4%. The ratio (K2O / 1.52) / (Na2O+K2O / 1.52) is referred to as the "ratio."

[0070] Feasibility

[0071] The outer appearance of the obtained product was observed. Its size was such that three sides were greater than 150 mm and at least one side was at least 400 mm, which allowed estimation of industrial feasibility. If there was a through slit, the feasibility was judged to be unsatisfactory. Next, the product was cut in half and the filling state was observed. If it was not properly filled, the feasibility was judged to be unsatisfactory. Otherwise, the feasibility was judged to be satisfactory. All examples in the present invention have satisfactory feasibility.

[0072] Electrical resistivity measurement

[0073] In various examples of the produced blocks, measurements of electrical resistivity R were carried out by applying a potential difference of 1 volt at a frequency of 60 Hz at 1400°C to cylindrical product bars of 30 mm diameter and 30 mm height.

[0074] [Table 1]

[0075] It can be seen that when the NaO content is less than 0.60%, a higher electrical resistivity value than the reference electrical resistivity value is achieved when the ratio is greater than 0.3. When the ratio is greater than 0.60, or even greater than 0.62 or even greater than 0.65, the electrical resistivity value is significantly improved.

[0076] As can be clearly seen, the present invention provides a product that has outstanding performance in the environment of a glass melting furnace vessel, particularly the hearth.

[0077] Of course, the present invention is not limited to the described and illustrated embodiments, which are provided for illustrative purposes only.

Claims

1. A fused and cast refractory product, the refractory product comprising: As mass percentages based on oxides, relative to a total of 100%, ZrO 2 +HfO 2 : 39.0% to 55.0%, except HfO 2 <5% Not. 2 : 10.5%~14.0% Al 2 O 3 : Remaining portion up to 100% In 2 OK 2 O: 0.80% ~3.00% So 2 O: <0.60% B 2 O 3 : <1.0% Faith 2 THE 3 +TiO 2 : <0.60% Other species: <1.0% Including, However, the ratio (K 2 O / 1.52) / (Na 2 O+K 2 O / 1.52) is greater than 0.30, The fused and cast refractory product.

2. The ratio (K 2 O / 1.52) / (Na 2 O+K 2 10. The fire-resistant product of claim 1, wherein the refractory strength is greater than 0.

50.

3. The ratio (K 2 O / 1.52) / (Na 2 O+K 2 3. The fire-resistant product of claim 2, wherein the refractory strength is greater than 0.

60.

4. The ratio (K 2 O / 1.52) / (Na 2 O+K 2 4. The fire-resistant product of claim 3, wherein the refractory strength is greater than 0.

62.

5. The ratio (K 2 O / 1.52) / (Na 2 O+K 2 5. The fire-resistant product of claim 4, wherein the refractory strength is greater than 0.

65.

6. The SiO 2 6. The fire-resistant product according to claim 1, wherein the mass content is less than 13.5%.

7. The SiO 2 7. The fire-resistant product of claim 6, wherein the mass content is less than 13.0%.

8. The SiO 2 The fire-resistant product according to any one of claims 1 to 7, wherein the mass content is greater than 11.0%.

9. The above K 2 9. The fire-resistant product according to any one of claims 1 to 8, wherein the O mass content is greater than 0.60% and less than 2.00%.

10. The above K 2 10. The fire-resistant product according to any one of claims 1 to 9, wherein the O mass content is greater than 0.70%.

11. The above K 2 11. The refractory product of claim 10, wherein the O mass content is greater than 0.80%.

12. The above K 2 12. The refractory product of claim 11, wherein the O mass content is greater than 1.00%.

13. The above K 2 13. The refractory product of claim 12, having an O mass content of less than 1.80%.

14. ZrO 2 +HfO 2 14. The fire-resistant product according to any one of claims 1 to 13, wherein the mass content is greater than 42.5% and less than 52.5%.

15. ZrO 2 +HfO 2 15. The fire-resistant product according to any one of claims 1 to 14, wherein the mass content is greater than 43.5%.

16. ZrO 2 +HfO 2 16. The fire-resistant product according to any one of claims 1 to 15, wherein the mass content is less than 51.0%.

17. ZrO 2 +HfO 2 17. The fire-resistant product of claim 16, wherein the mass content is less than 49.5%.

18. ZrO 2 +HfO 2 18. The fire-resistant product of claim 17, wherein the mass content is less than 48.0%.

19. The Al 2 O 3 19. The fire-resistant product according to any one of claims 1 to 18, wherein the mass content is less than 44.0% and more than 30.0%.

20. The Al 2 O 3 20. The fire-resistant product of claim 19, wherein the mass content is less than 42.0% and greater than 34.0%.

21. The above Na 2 21. The fire-resistant product according to any one of claims 1 to 20, wherein the O mass content is less than 0.55%.

22. The above Na 2 22. The fire-resistant product of claim 21, having an O mass content of less than 0.50%.

23. The above Na 2 O+K 2 23. The fire-resistant product according to any one of claims 1 to 22, wherein the O mass content is less than 2.50%.

24. The above Na 2 O+K 2 24. The refractory product of claim 23, having an O mass content of less than 2.00%.

25. 25. A glass melting furnace comprising a vessel intended to contain or which does contain molten glass, said vessel comprising a block made from a refractory product according to any one of claims 1 to 24.

26. A glass melting furnace according to claim 25, wherein the vessel comprises a hearth comprising a block made from the refractory product according to any one of claims 1 to 24.

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