Simulation and Analysis of Hydrodynamic Behavior in Different Nozzles and Its Corresponding Fluidized Beds

Uniform air distribution is the basic condition for the stable operation of circulating fluidized beds and closely related to the hole layout of nozzles and the air outlet conditions. In this paper, CAD modeling software is used to establish different opening types for nozzles and the corresponding gasifier models, and Fluent simulation software for numerical simulations (k-ε model) is introduced to the hydrodynamic behavior of the upper opening, the side opening and the combined opening types of nozzles, as well as the corresponding single-nozzle fluidized bed gasifiers. The flow field distribution under the above opening modes is obtained, including the velocity distribution, static pressure distribution, and total pressure distribution, and the influence of the boundary conditions, including the inlet gas velocity and outlet pressure, on the flow field distribution inside the nozzle and in the single-nozzle fluidized bed gasifier is also investigated. The simulation results show that the suitable optimal operating conditions for the coal gasifier can be achieved with an inlet velocity of 30 m/s and an outlet pressure of 25 kPaG. Under the above conditions, the local fluidization dead zone at the elbow and top of the nozzle is narrower, the uniformity of the wind velocity can be improved, the pressure drop of the inner core tube of the nozzle is gentle, and the pressure distribution tends to be stable. Theoretically, the anti-slag performance of the nozzle is improved, which will enhance the stability and reliability of the operation of the gasification unit.