Optimization of parameters of the cupola melting by the criterion of the maximum cast iron temperature

The object of the study was the temperature of cast iron discharged from the cupola furnace. The problem under study is the complexity of predicting the temperature of cast iron as a function of the control parameters of the melting. In the study, the control parameters were selected as the temperature of the air heated into the lances and the amount of coke. Using orthogonal experimental design, a mathematical model was constructed in the form of a second-order polynomial, which allowed us to identify the patterns of influence of each control factor on the resulting value – the temperature of cast iron on the cupola furnace trough. The resulting mathematical model allowed to find out that both input variables are approximately equally significant. The accuracy of the model turned out to be satisfactory, because all experimental data fell within the confidence intervals. This allows us to state the possibility of using the constructed model to predict the temperature of cast iron within the planning area. Based on the canonical transformation of the response surface, it was found that the shape of the curves of different levels is hyperbola, and therefore the stationary point is the saddle point, at which the value of the cast iron temperature of 1392 °C is reached. Based on the comb analysis, it was determined that the theoretical maximum of the cast iron temperature is about 1530 °C and is reached at the upper limit of the values of the input variables: the air heating temperature of about 480 °C and the amount of coke 13 %. These data allow to make adjustments to the melting process, including being used for further searching for optimal control of the melting. Such control can be performed by optimizing the coke dosing system in combination with metal filling during the melting process and controlling the operation of heaters that increase the temperature of the air blown into the cupola lances. The obtained solutions can be used in cast iron foundry shops of industrial enterprises equipped with cupolas