Modeling and simulation of an industrial combustion reactor using computational fluid dynamics

For almost a century, the process of pulverized coal combustion is one of the dominant technologies for generating power in industrial reactors and utility boilers. The industrial reactors have mostly been designed prior to the actual application of computational fluid dynamics techniques. In the present study, the process of coal combustion in an entrained flow reactor is studied by means of computational fluid dynamics analysis. The model is validated with experimental data and similar published work. The average relative error between the experimental and numerical data is less than 4.8%. The validated model is utilized to study the influence of pulverized coal particle size on the combustion behavior and to understand which devolatilization model is more accurate to simulate the processes that take place within the reactor. Four devolatilization models are analyzed, and the ignition characteristics under the actual air-coal conditions are compared. The results have proven that there is an identical trend for the four studied cases. However, the single rate model has a maximum temperature of 1330 K at the reactor exit, while the chemical percolation devolatilization model predicts the lowest temperature of 1295 K. As the size of the coal particle is decreased from 120 to 30 µm in four steps, the temperature and CO2 species mole concentration increased along the reactor radial distance and the combustion process takes place closer to the injection burner.