The ratio of zone lengths in high-temperature tunnel kilns

Shumilin, A. A.; Abbakumov, V. G.; Tarakanchikov, G. A.

doi:10.1007/bf01290070

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“…2 (see Table 4) which provides bricks of excellent properties when a fast firing rate is used, and also the recommended firing schedule for corundum articles of simple shape. Bearing in mind the slow heat exchange in the cooling zone of a tunnel kiln [8], the duration of cooling compared with the minimum value obtained in the experiments was increased by ~ 1.6 times --to 40-45% of the firing cycle [9,10].…”

Section: Ty 75~mentioning

confidence: 99%

Firing technology for refractories made of sintered corundum

et al. 1979

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The quality of corundum refractories for various purposes depends substantially on the firing conditions in which the processes of sintering and material recrystallization occur together with the formation of the macro-and microstructure of the articles, and their strengthening. The firing parameters should be economical and provide the required degree of heat-exchange and physicochemical processes; no destructive thermal stresses should develop during any period of the firing cycle.The minimum heating and cooling time for the articles in the various sections of the kiln may be limited by the temperature variations in the articles themselves, leading to the formation of cracks, which is connected with the heat-exchange rate in the heating and cooling zones. In the firing zone the decisive factor is the kinetics of thephysieochemical sintering processes, whose parameters serve as the starting data in planning the kiln' s heating system, and the development of measures for creating the sections of required maximum temperature of the necessary length.Theoretical calculation of the rational technology for firing corundum refractories is at present causing difficulties because of the complicated nature of the temperature field in the setting of the goods and the lack of study data on the kinetic equation constants, and shortcomings and inadequacies of known experimental data [1][2][3][4][5][6][7]o Therefore, studies were made of the development of a firing technology for corundum articles which is needed for planning industrial equipment.The starting material for making corundum chamotte was GA85 alumina, and alumina grade GK was used as the finely milled bond. Altllnina GA85 was vibromilled in the M-200 mill with a material : ball ratio of 1 : 9 in 6-7 h to obtain a predominance of particles measuring 4-8 ~m. The GK alumina was milled for 1.5 h to a predominant particle size of 4-20 ~m. The chemical composition of the alumina before and after milling hardly changed, During the milling of the GAS5 alumina there was no contamination, and for the GK alumina the Fe203 content rose by 0.2%.The milled GA85 was moistened in a mixer with Z-shaped blades with a solution of sulfite lye (SSB) calculated to give 1.5% on the dry residue; the blending time was 15 rain, and the water content of the compound 16-1870. The briquets measuring 236 x 116 x 70 mm were prepared on a hydraulic press w2th a force of 6.2 ICfN under a pressure of 50 MPa. After drying to a residual moisture content of 5% the briquets were fired in a periodic kiln at 1500 and 1700~ the water absorption of the chamotte was up to 12 and 3%, respectively.

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Section: Ty 75~mentioning

confidence: 99%