Experimental Studies And Numerical Simulation Of Pneumatic Conveying Of High Concentration Powdered Solid

Problems as low combustion efficiency, bad part-load operating performance, too much pollutants emission, and high temperature corrosion and slugging on water wall surface occurred in many domestic coal fired boilers. Recent studies show that high concentration combustion is an efficient method to solve these problems. High concentration combustion has a series of advantages as strengthening ignition, stabilizing combustion and decreasing NOx emission. According to this point, by considering the results of previous studies, the new scheme of high concentration conveying and combustion of pulverized coal (PC) is put forward in this article, the feasibility of the scheme and the problems to be settled are discussed as well.In the dissertation, after the argumentation of the feasibility and advantages of high concentration conveying of PC, by comparing capabilities of various high concentration feeder, the fluidized silo was confirmed to be the best device used in high concentration conveying. The feeding characteristics of fluidized silo were experimentally studied on the self-made high concentration pneumatic conveying system using coal and sand as the material. To the problems of two-phase mixing appeared in high concentration pneumatic conveyance, a double-nozzle blender was designed, and the structural parameters and operating conditions were optimized through orthogonal test.The resistance characteristics of high concentration pneumatic conveying of powder in horizontal and vertical pipes were experimentally studied in the dissertation. Within the scope of the concentration presented in the experiment, the correlation formulas were regressed according the data got from experiments in horizontal and vertical pipes. The formulas are usable for the two materials used in the experiment under certain conditions and can be used in the engineering designing.The interacting force among gas and solid phase and pipe surface in the horizontal pipe is analyzed in detail, then the theoretical model of fully developed gas-solid stratified flow in horizontal pipe was brought forward. Using this model, the pressure loss of the high concentration pneumatic conveying of powder in horizontal pipe was calculated under the experimental conditions, the numerical results were compared with the experimental data. The simulation of mass distribution and velocity field of gas-solid phase fluid in vertical pipe has been performed using the Euler two-fluid-trajectory model, the numerical results were also analyzed by comparing with the experimental data.