Experimental And Numberical Studies On Gas-particle Two-phase Flows In Swirl Burner

With the rapid development of economic and increasing industrialization process, energy and environmental problems have become increasingly evident. In a certain long time, it is apparent that coal will still be the major energy source. However, a large number of pollutants will be generated in the coal combustion processes. In recent years, the emission control of SOx has been focused and desulfurizations have been equipped in many plants as a mature technique, while another main pollution-NOx, has not been controlled in plants. Therefore, it has very significant meaning to investigate how to lower down the emission of NOx in the manner of high-efficiency.This paper aims at finding the best structure and running parameters for the swirl burner in order to reduce NOx emission. Both the numerical simulation and the cold gas-particle flows experiments have been carried out, including an extensive parametric study that mainly focuses on the central air expanding angle, the primary air fraction, the primary velocity, the once-through secondary air velocity, the swirling number of inner secondary air, and the outer secondary air, etc.In the cold gas-particle flows experiments, the temperature trace method is adopted to study the mixture between the primary air and the secondary air, meanwhile the NaCl particle method is applied to study the distribution of solid particles. With the analysis on the "cold pulverized coal concentration" and the distribution of solid particles, it is concluded that, the smaller the central air expanding angle or the later the secondary air interfused, the larger the area of high concentration zone and the more particles fall on the cold pulverized coal zone. When the primary air fraction is 0.2 with a velocity of 15 m/s, and the once-through secondary air velocity is 25 m/s, the high concentration zone is relatively larger, and the number of particles all on the cold pulverized coal zone is higher; all of which will be in favor of NOx reduction. The swirling number of inner secondary air is found to play a more important role, compared with that of the outer secondary air for NOx reduction. Based on the above, an optimal conduction condition is suggested:the swirling number of inner secondary air is 1.35, and the swirling number of outer secondary air is 1.56.In addition, the FLUENT numerical simulation is conducted to construct a three-dimensional (3D) model, using the Realizable k-εtwo-equation model to simulate the distribution of aerodynamic field at the exit of the burner. Based on the numerical simulation results, various parameters that have impact on the burner velocity field distribution and the recirculation velocity are analyzed. According to the comparison between the simulation results and the obtained experimental datas, it is found that, the simulation results fit well with the obtained experimental data, regardless of the shape of data distribution or data distribution of a special section, which not only validates of the model calculation, but also demonstrate the accuracy of the test methods. This reliable method is useful for the following heat numerical simulation of the swirl burner.