Simulating the Process of Oxy-Fuel Combustion in the Sintering Zone of a Rotary Kiln to Predict Temperature, Burnout, Flame Parameters and the Yield of Nitrogen Oxides

Abstract

In this study, for predicting situations that may occur when using oxy-coal combustion technology in a cement rotary kiln, computational fluid dynamics (CFD) methodology was used to investigate the temperature distribution, burnout rates of coal, flame shape and release of NO x in conditions of oxy-coal combustion with different O2/N2 volume ratios ranging between 21% and 31% in the primary air in the sintering zone of a rotary kiln. Simulations were performed using ANSYS-CFX, a commercial CFD package. The results revealed a significant temperature increase in the rotary kiln, and the average temperature increase value was verified experimentally. Coal particles combust more rapidly near the burner, and the final degree of burnout increases simultaneously. Increased combustion efficiency reduces fuel consumption. However, shifting the ignition point toward the burner may reduce the service time of the burner, and the shortening of the flame kernel may lead to a decrease in the calcination time of cement. The content of oxygen in the kiln rises, but the change is slight and can be ignored for cement clinker formation. The amount of NO x, produced increases with increasing oxygen content in the primary air. The results of this study can be used to select the optimal sintering parameters for oxy-coal combustion in industrial production of cement.