Component which is intended for a facility for producing or preparing glass melts

Abstract

The present invention relates to a method of treating a component which is intended for a facility for producing or preparing glass melts and has surfaces which are made of noble metal and come into contact with glass melts during operation.

Description

[0001] The present invention relates to the field of production or preparation of glass melts.

[0002] Glass melts are produced from inorganic compounds, particularly from glass shards or glass batches.

[0003] Numerous devices have become known, using which the materials cited may be melted or refined. For example, see German Patent 33 16 546 C1. This refers to a skull crucible.

[0004] The melting process must typically be followed by a refining process. In this case, the refining has the task of freeing the molten glass from physically and chemically bonded gases.

[0005] In this case, every effort is made to perform the degassing as completely as possible. Therefore, refining agents are used during the refining process and particularly high temperatures of up to 2000° C. are applied.

[0006] In practice, it has been shown that in spite of great efforts in the refining stage, bubbles arise in the glass melt. As is known, this originates from localized temperature gradients existing in the melt, which lead to the formation of local elements and therefore to the occurrence of further gas bubbles, which are referred to as “secondary bubbles”. See European Patent Application 1 050 513 A3.

[0007] Further publications which deal with the phenomenon of bubble formation are the following:

[0008] Cowan J. H, Platinum Glass Reactions, Ceramic Proceedings 1982, pp. 218-228

[0009] Cowan J. H., An Electrochemical Theory for Oxygen Reboil, Journal of the American Ceramic Society 1966, pp. 559-562

[0010] Onishi, Reboil Phenomenon at the borosilicate-glass-platinum-interface, 10. Int. Congress on Glass, Kyoto 1974, pp. 63-70

[0011] Shinji, Kawachi; Yoshio, Iwatsubo, Diagnosis and Treatment of Bubbles, Glass 2000, pp. 122-129

[0012] German Patent Application 198 56 797 A1

[0013] Japanese Patent 2982959

[0014] U.S. Pat. No. 3,387,961

[0015] U.S. Pat. No. 5,385,595

[0016] U.S. Pat. No. 4,123,263

[0017] WO 0818731

[0018] European Patent 559330

[0019] Japanese Patent 56129618

[0020] European Patent 967179

[0021] European Patent 908417

[0022] Japanese Patent 02221129

[0023] It is known that bubble formation occurs at the surface of platinum in contact with borosilicate glass (Onishi, Fujij 1974). Furthermore, it is known that the process is based on electrochemical mechanisms (U.S. Pat. No. 427,934 [sic] and Cowan, Buehl, et al. 1966).

[0024] NH Technoglass describes the use of platinum having slight osmium impurities to avoid bubbles, aging is not shown (German Patent 198 56 797 and/or Japanese Patent 2,982,959). Criticisms of the related art: the theories and embodiments described, however, only show the phenomenon; a solution through suitable selection of alloy is not indicated. In this case, bubble formation is not acceptable in those melts from which optical glasses, LCD glasses, and technical glasses are to be produced. The necessary quality criteria are not achieved in this way.

[0025] The present invention is based on the object of treating components of the type described in such a way that bubble formation is avoided or suppressed so that the necessary quality requirements are fulfilled.

[0026] This object is achieved by the features of claim 1. According to this, the component is subjected for a certain period of time to an elevated temperature, i.e., a temperature above room temperature, possibly also over the operating temperature, in an oxidizing atmosphere, before it is put into operation in the facility cited for producing or preparing glass melts.

[0027] The inventors have recognized the following: organic impurities are decomposed through the treatment cited. Oxidic impurities vaporize through the high decomposition pressure or form stable layers. These layers have a low diffusion tendency in relation to hydrogen, compared to pure metals. However, if no hydrogen can diffuse into the layer, then also no oxygen, which leads to the formation of the secondary bubbles cited, is left behind. This means that the formation of bubbles in the glass melt is strongly reduced through the application of the present invention and that high-quality glasses may be produced.

[0028] The concept of “component” includes those components which could be a part of a facility for producing or preparing glass melts. Therefore, pipes, pipe elbows, containers, stirrers, and other things are in consideration. In this case, the entire component does not have to be made of noble metal, there are numerous cases in which the relevant component is only partially coated using noble metal, the noble metal surfaces being in contact with glass melts during operation.

[0029] For lining materials made of platinum and its alloys, four types of bubbles in the glass may be differentiated in principle:

Bubble type I:   organic impurities of the surface (CO, CO2)
                 observation time period: several days
Bubble type II:  leakage of the lining (noble gases, O2, . . . )
                 observation time period: continuous
Bubble type III: impurities (oxides) in the noble metal (O2)
                 observation time period: several days to weeks
Bubble type IV:  bonded hydroxyl groups in the glass (O2)
                 observation time period: continuous

[0030] The treatment of components, semifinished products, or coatings made of platinum and its alloys represents a possibility for avoiding bubble types I and III in a glass melting furnace.

[0031] In this case, the components, the semifinished product, or the coatings are treated, at a temperature which lies around 100 K above the application temperature, for 400 hours in a forced-air furnace.

[0032] The advantages achieved using the present invention are particularly that the production with reduced bubbles may be begun immediately after the installation of the components.

[0033] Furthermore, the present invention contributes to increasing the quality of high-quality glasses.

EXEMPLARY EMBODIMENTS

Example 1

[0034] Laboratory crucibles (size 106) were produced from the alloys Pt(3N), PtRh10, FGS [fine-grain stabilized] 16Pt, FGS 16PtRh10 und FGS 16PtAu5 in laboratory scale.

[0035] Each crucible was treated for 400 hours at 1200° C. and at 1450° C. in a standard forced-air furnace.

[0036] The crucibles were filled in the cold state with borosilicate glass shards. The glass test was performed by heating to operating temperature, a holding time of 24 hours, and cooling in the heat of the furnace.

[0037] While the samples treated at 1200° C. had definite bubbles, no bubble formation could be detected in the samples annealed at 1450° C.

Example 2

[0038] Zircon mullite rod samples were coated with a layer thickness of 200 μm to 1500 μm through thermal spraying.

[0039] One sample of each layer thickness was treated for 400 hours at 1200° C. and at 1450° C. in a standard forced-air furnace.

[0040] The rod samples were introduced at operating temperature into a crucible filled with borosilicate glass shards. The glass test was performed by introducing the samples into the glass melt at the operating temperature, a holding time of 24 hours, and the cooling in the furnace heat.

[0041] While the samples treated at 1200° C. had definite bubbles, no bubble formation could be detected in the samples annealed at 1450° C.

[0042] Further variants of the method according to the present invention are conceivable. Thus, the temperature may be changed during the treatment.

[0043] For example, it may be very high during a starting phase of the treatment period and then be reduced, or, vice versa, be low during a starting phase and increase in the course of the treatment period.

[0044] It is also possible to apply a flow of oxidizing gas to the component during treatment. This gas flow may be directed in a targeted way onto specific parts, which come into contact with glass melts during operation.

[0045] In accordance with the method according to the present invention, the inventors suggest a device according to the present invention. This includes a chamber which is intended for receiving the components to be treated. The chamber may be appropriately heated. In addition, the chamber has a connection for introducing an oxidizing gas.

Claims

1. A method of treating a component, which is intended for a facility for producing or preparing glass melts and has surfaces which are made of noble metal and come into contact with glass melts during operation, characterized by the following feature: 1.1 the component is subjected to an oxidizing atmosphere for a certain period of time before being put into operation.

2. The method according to claim 1, characterized in that the component is subjected to an elevated temperature during the time period cited.

3. The method according to claim 2, characterized in that the temperature lies above the operating temperature of the component.

4. The method according to claim 3, characterized in that the temperature lies between 1000° C. and 2000° C.

5. The method according to claim 4, characterized in that the temperature lies between 1100° C. and 1500° C.

6. The method according to one of claims 1 to 5, characterized in that the time span lies between 1 and 500 hours.

7. The method according to claim 6, characterized in that the time span lies between 100 and 500 hours.

8. The method according to one of claims 1 to 7, characterized in that the temperature is changed during the treatment of the component.

9. The method according to claim 8, characterized in that the temperature is high during a first treatment phase and is low during a second treatment phase, or the temperature is low during a first treatment phase and is high during a second treatment phase.

10. The method according to one of claims 1 to 9, characterized in that an oxidizing gas is applied to the component during at least a part of the treatment period.

11. A device for treating a component, which is intended for a facility for producing or preparing glass melts and has surfaces which are made of noble metal and come into contact with glass melts during operation, characterized by a treatment chamber which receives the component and in which an elevated temperature may be set.

12. The device according to claim 11, characterized in that the temperature in the chamber may be set to a value which lies above room temperature or above the operating temperature.

13. The device according to claim 11 or 12, characterized in that the chamber has an inlet for applying an oxidizing gas.