| Water-coal-slurry Fluidization-suspension combustion boiler combines water-coal-slurry and Circulating Fluidized Bed the two clean coal technology. The combustion technology is developed by the application of Circulating Fluidized Bed Boiler(CFBB). Circulating Fluidized Bed Boiler has been widely used in the whole world because of its high-efficiency and less pollution advantage. The gas-solid flow is very typical and complex in the CFBB. The research on the character of the gas-solid flow is greatly necessary and one of important aspect for the development of the CFB combustion technology. With the help of Fluent software and on the basis of the Euler two-fluid model, numerical simulation of the gas-solid flow character in the riser field and the bubbling bed was performed on the cold scale model of commercial CFBB.The simulated results show that the Euler two-fluid model can well provide the gas-solid flow pattern in the riser section of CFBB. The comparison of simulated pressure drop with the theoretical result approves the validation of numerical simulation. Moreover, it is analyzed that the particle concentration distribution shows a core–annular flow frame where the solid is denser in the annular region than core region and the particle axial velocity shows the internal circulation pattern that the particle movement is upward in the core zone and down in the annulus zone. In addition, under different operating condition, particle volume fraction distribution is affected prominently at the lower-middle zone along the axial direction and at the wall area along the radial direction. Furthermore, the effect of operating condition on the particle velocity reflects that the changing of upward particle velocity at the core area is more obvious than at the wall area. The gas-solid flow pattern at the wall area needs further investigation. The flow character of different size particle is diverse, and the larger the particle size, the more particle volume fraction at the lower zone in the furnace. The effect of different secondary air injecting design on the gas-solid flow character in the riser section of CFBB is also analyzed. Through the comparison, results indicate that when the angle between the injecting and axial direction is 60°(case B), the solids will mainly distribute in the upper-and-middle region of furnace, which is beneficial to the combustion and heat transfer efficiency and can increase the jet's length.The simulation of the effect of materials bed's density on the gas-solid fluidization character in the dense bubbling bed of CFBB was conducted. The result shows that the effect of the density of Geldart A and B particles on the gas-solid fluidization character is the same. The gas-solid mixing performance and bed stability of the small density particle are better.According to the application of differential density fluidized bed on water-coal-slurry Fluidization-suspension combustion technology, the research on the gas-solid fluidization character in the dense bubbling bed with changing the bed materials and operating the different condition is carried out. It is analyzed that when the air velocity is low, the gas-solid mixing performance and bed stability in the bed containing bed material 1 (the light density) is better than that of the bed material 2 (the small particle size) and the effect of density on the gas-solid flow is larger. With the high air velocity, the law is reverse and the effect of particle size on the gas-solid flow is larger. Bed material 1 (the light density) is beneficial to the practice of the character of differential density fluidized bed. The change of air velocity is not influenced the control of density to the character of differential density fluidized bed. All in all, the above results supply the reference basis on the chosen of bed material for the further industrial differential density fluidized bed.
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