For the lining of thermal equipment with a hydrogen-containing medium and a working temperature up to 1800~ corundum refractories, which are characterized by the optimum combination of physicochemical and thermomechanical properties, responsible for the technical and economic desirability of their use, are most promising.The life of corundum refractories at 1800~ in reducing media is determined by their purity and the thermal insulation properties primarily by the structure.To obtain corundum thermal insulation parts with more than 99 wt.% A1203 a mixture of G-00 and GK (85-95% a-A1203)aluminas and foam ~olystyrene was used [i]. After firing the parts had an apparent density of 1.05-i.08 g/cm , a compressive strength of 7.5-20 N/mm 2, and an additional volumetric shrinkage at 1750~ of less than 1%. However, the significant volumetric shrinkage of the parts in firing makes it difficult to produce large parts of complex configurationby this method.For the purpose of obtaining shrinkage-free thermal insulation corundum parts with not less than 99 wt.% A1203 it is desirable to use a porous filler of aluminum oxide distinguished by a constant volume in heating to 1800~C. Hollow corundum granules (spherical corundum) produced by inflation of molten corundum meet these requirements [2].
Vessels of platinum alloys are used for forming of glass fiber of high-modulus glass Cl].One of the directions in reducing the consumption of platinum alloys is increasing the life of vessels' linings, which at present are made of type ShL-0.4 lightweight parts (GOST 5040-78) for the outer layer, type KL-I.3 lightweight corundum parts (GOST 5040-78) for the intermediate layer, and an aluminosilicate composition ramming compound prepared from alumina and kaolin for the working layer. In service the lightweight corundum parts and the compound sinter, as the result of which the lining cracks.In this work hollow corundum spheres, which were obtained by inflation of molten aluminum oxide, were used as the lining working layer material. The constant volume at high service temperatures, insignificant impurity content, and presence of voids make it possible to use corundum spheres at temperatures up to 1800~ and provide linings of them with high thermal insulation properties [2]. Type MKRVG mu!lite-silica thermal insulation plates to Technical Specification 14-8-440-83 of kaolin wool were used as the lining intermediate layer, and the outer layer was made of ShL-0.4 parts.In [3] the choice of the optimum variation of the lining based on the condition of the refractory life in the specified temperature range and minimization of a certain cost function was considered.The high requirements imposed on materials for lining of glass melting equipment limit the choice of refractories of those produced by industry at present.With the use of new materials determination of their cost is difficult. According to preliminary data taking into consideration the insignificant consumption of refractories for a single lining (0.02 m 3) and the similar expenditures for installation of a furnace lining in comparison with the existing variation, we neglected calculation of the cost function.We have calculated the variations of multilayer linings of steel melting equipment providing minimization of the thermal losses on the outer surface of the lining with limitations on the thickness and temperature of the layers.The original data were: temperature on theworkingsurface of the lining t: = 1600~ thickness of the type MKRVG plates 0.047 m, and total lining thickness 0.185 m (the thickness of the present lining). The plans of different variations of the glass melting equipment linings are shown in Fig. i. In variation I, the thickness of a single layer lining of hollow corundum spheres with a ceramic binder in relation to the temperature on the outer surface of the lining was calculated.The thermal calculations of each variation of the lining were made considering it as a unidimensional plate with a temperature field T = T(X). The calculations were made on a Mir-i computer.The basis of the calculation was the known relationships [4]:
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