Abstract
In the study, a numerical model is developed on the basis of the suggested physical and mathematical models to research the thermoelectric power state of the Castner furnace in the process of graphitizing electrode blanks. A distinctive feature of this study is an opportunity to take into account the impact of factors such as thermal effects of the chemical reactions of gasification, evaporation, condensation, sublimation of graphite, and thermoelectric power contact interaction between the elements of the furnace design. The verification of the numerical model of graphitizing electrode blanks has showed that the relative deviation between the calculated values of the average temperature of the candle blank after the start of the carbonaceous material gasification process is about 4 % in the temperature range of 600-1,600 °C in comparison with the physical experiment. The analysis of the numerical simulation results has revealed overstated average temperature values of candle blanks in the case of excluding the impact of thermal effects of chemical gasification reactions, heat and mass transfer of moisture, and conversion of the carbon monoxide and the hydrogen in the insulating charge of the furnace. Under the circumstances, the relative deviation in the average temperature of the candle workpieces in the examined points exceeds 10 % in comparison with the experimental data.
Highlights
Electrode blanks under production-line conditions are graphitized mainly in electric furnaces of resistance by the Castner method or the Acheson method
To determine the thermoelectric state of the workspace in graphitization furnaces, it has become common to apply methods that are based on the rational use of numerical modelling in conjunction with selective physical experiments [4, 5]
The developed mathematical model of the thermoelectric power state of the Castner furnace is based on a physical model of the graphitization process
Summary
Electrode blanks under production-line conditions are graphitized mainly in electric furnaces of resistance by the Castner method (direct heating) or the Acheson method (indirect heating). Large-diameter electrodes (of 600 mm or more) are graphitized in direct heating furnaces that operate by the Castner method. Numerous studies show that the main factor that determines the degree of graphitizing the carbonaceous material of electrode blanks is the top temperature: to obtain artificial graphite of sufficient quality, the temperature should be at least 2,200–2,800 °C [3]. Experimental research on such high-temperature processes in a highly aggressive environment of the furnace is extremely complex and labour-intensive [3]. To determine the thermoelectric state of the workspace in graphitization furnaces, it has become common to apply methods that are based on the rational use of numerical modelling in conjunction with selective (separate) physical experiments [4, 5]
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