Browsing by Author "Dunkl, Michael"
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- ItemCorrosion tests - A very important investigation method for the selection of refractories for glass tanks(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Dunkl, MichaelFor determining and comparing the corrosion behavior of refractories against glass melts, a good reproducibility of the corrosion tests is needed. In the present paper the reproducibility of the various most common corrosion tests, the respective procedures and the applied evaluations are discussed. The investigation was carried out with fused-cast AZS material because it has an inhomogeneous microstructure, so that the reproducibility with this material is not as good as that of the corrosion tests with refractories which have a homogeneous microstructure. The investigated corrosion tests are: dynamic finger test, rotating cylinder face method, small rotating furnace test, crucible test, static finger test and static plate corrosion test. Among these methods the static plate corrosion test combines a good reproducibility with many advantages (disadvantages were not observed). An international round-robin investigation within the Technical Committee 11 of the International Commission on Glass confirmed the good reproducibility of the static plate corrosion test, and the TC 11 recommended it as standard corrosion test. In the present paper, moreover, the influence of the most important parameters on the static plate corrosion test is discussed. Besides the additional bubble drilling in the fluxline area, which can be eliminated directly by the evaluation, a possible influence of saturation, of evaporation or of initial processes must be considered and eliminated if necessary. For this reason the knowledge of the corrosion behavior for the various most common combinations refractory/glass melt is important, which will be determined within a round-robin investigation by TC 11 in the near future.
- ItemRecycling of refractories from the glass manufacturing industry(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1995) Dunkl, MichaelRefractories present at the end of campaigns of glass melting furnaces are to a large part corroded, infiltrated by glass and/or have reacted to its components. In addition to the refractories heavily contaminated by melted glass and its vaporized or condensated by-products, other refractories are retrieved, often in large quantities, which are only Hghtly contaminated or not at all. Up to now the larger amount of refractories remaining after furnace campaigns have been disposed of and only a relatively small amount re used in the refractory industry (approximately 10%). Recycling of this material is, however, legally imperative, and various lightly contaminated refractories are now being recycled by some companies for re-use as refractories as well as for other applications. This paper will discuss the present situation of recycling refractories retrieved from glass melting furnaces by the glass and refractories industries with the aim of initiating the problem solving process. Based on a recent inventory it will be shown which quantities of which types of refractory materials occur in the German glass industry and with which impurities the refractories can be contaminated. Using a qualitative presentation of the impurities present in the refractories retrieved from different parts of the furnace and different types of glasses, various possibilities for recycling will be discussed. Not yet existant, basic requirements and the necessity of corresponding research will be indicated. Successful and far-reaching solutions of these problems must be the common goal of the glass and refractory industries.
- ItemSpinel bricks for highly stressed roofs in glass melting furnaces(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2000) Boymanns, Gerda; Gebhardt, Franz; Dunkl, Michael; Schlacht, Hans DieterNew challenges are raised to the refractory materials in the crown and superstructure of oxy-fuel fired glass melting furnaces in comparison to air-fuel fired glass melting furnaces. In glass melting furnaces which are oxy-fuel fired the water steam partial pressure above the melt increases very strongly. In the case of soda-lime-silica glass melts together with the water steam partial pressure the alkaline hydroxide partial pressure increases with a factor of three in comparison to an air-fuel firing system. This leads to an aggressive action on the refractory lining in the crown and superstructure. After extensive thermodynamic calculations and laboratory tests a pure spinel refractory material (MgO ∙ AI2O3) was developed for the application in the crown and superstructure of oxy-fuel fired glass melting furnaces. The chemical and physical properties as well as the results of corrosion tests under oxy-fuel conditions of this direct-bonded fused spinel material will be discussed. Because of the high corrosion resistance to alkaline attack and the excellent behaviour of the creeping under load even at a temperature of 1650 °C, this spinel material can be proposed for the successful application as crown and superstructure refractory for oxy-fuel fired glass melting furnaces.