Experimental And CFD Simulation Studies On Hydrodynamic Characteristic In A Pressurized Fluidized Bed

Gas-solid fluidized bed is widely used in many industrial processes such as catalytic cracking, S-zorb desulfurization process, etc. Understanding and improving the flow behavior is helpful to operate the fluidized bed smoothly and increase the yield of target products. It is necessary to find out the flow behaviors in the reactor by analysis the pressure fluctuation in the gas-solid fluidized bed, especially the gas-solid pressurized fluidized bed. In order to investigate the relationship between the pressure fluctuation and the flow behavior in the pressured gas-solid fluidized bed. Experiments were conducted in pressurized fluidized bed of 300mm-i.d.×3800mm in high(with an expanded top section of 600mm-i.d.×800mm in high) with FCC materials. FCC catalyst volume fraction distribution at different axial positions under diffeerent air velocity and pressure were measured. Statistical analysis, fast Fourier transform (FFT), and wavelet analysis were also used to investigate the pressure fluctuations in the fluidized bed.With the increase of pressure, gas density increase, the drag force on the FCC particles increased, Making more uniform particle distribution in fluidized bed, a "smooth" the fluidization were found. The fluidization at different pressure and gas velocity can be characterized by a dimensionless parameters Frp. So, the same fluidization can be obtained at higher gas velocity,lower pressure or lower gas velocity,higher pressure.Through statistical analysis,flow regime transition velocity uc was determined, Axial position had no significant effect on uc. By analysis of power spectrum, characteristic frequency of bubbles(0.5Hz～1.75Hz) was obtained. By wavelet analysis, characteristic frequency of bubbles(D5-D7) was found.uc can be determined by analysising the energy distribution of this band changed with superficial gas velocity. The influence of pressure on uc was also discussed. The results showed that:power energy mainly concentrated in the low-frequency, With the increase of gas velocity, energy eigenvalue of the pressure fluctuation increased first and then decreased, When pressure increased uc decreased.By computational fluid dynamics (CFD) software, two-dimensional and three-dimensional fluidized bed were simulated. Two-fluid model was adopted to simulate FCC catalyst particle distribution under different pressure in the fluidizedbed. Through simulation:With the pressure increased, more uniform axial distribution was found.Pressure can change the force between gas-particles and particles- articles, inhibit the growth of the bubble, resulting in a more uniform fluidization...