Solid concentration and particle velocity distributions in the transition section of a φ 200 mm turbulent fluidized bed(TFB) and a φ 200 mm annulus turbulent fluidized bed(A-TFB) with a φ 50 mm central standpipe we...Solid concentration and particle velocity distributions in the transition section of a φ 200 mm turbulent fluidized bed(TFB) and a φ 200 mm annulus turbulent fluidized bed(A-TFB) with a φ 50 mm central standpipe were measured using a PV6 D optical probe. It is concluded that in turbulent regime, the axial distribution of solid concentration in A-TFB was similar to that in TFB, but the former had a shorter transition section. The axial solid concentration distribution, probability density, and power spectral distributions revealed that the standpipe hindered the turbulence of gas–solid two-phase flow at a low super ficial gas velocity. Consequently, the bottom flow of A-TFB approached the bubbling fluidization pattern. By contrast, the standpipe facilitated the turbulence at a high super ficial gas velocity, thus making the bottom flow of A-TFB approach the fast fluidization pattern. Both the particle velocity and solid concentration distribution presented a unimodal distribution in A-TFB and TFB.However, the standpipe at a high gas velocity and in the transition or dilute phase section signi ficantly affected the radial distribution of flow parameters, presenting a bimodal distribution with particle concentration higher near the internal and external walls and in downward flow. Conversely, particle concentration in the middle annulus area was lower, and particles flowed upward. This result indicated that the standpipe destroyed the coreannular structure of TFB in the transition and dilute phase sections at a high gas velocity and also improved the particle distribution of TFB. In conclusion, the standpipe improved the fluidization quality and flow homogeneity at high gas velocity and in the transition or dilute phase section, but caused opposite phenomena at low gas velocity and in the dense-phase section.展开更多
基金Supported by the National Natural Science Foundation of China(U1361112,U1162125)
文摘Solid concentration and particle velocity distributions in the transition section of a φ 200 mm turbulent fluidized bed(TFB) and a φ 200 mm annulus turbulent fluidized bed(A-TFB) with a φ 50 mm central standpipe were measured using a PV6 D optical probe. It is concluded that in turbulent regime, the axial distribution of solid concentration in A-TFB was similar to that in TFB, but the former had a shorter transition section. The axial solid concentration distribution, probability density, and power spectral distributions revealed that the standpipe hindered the turbulence of gas–solid two-phase flow at a low super ficial gas velocity. Consequently, the bottom flow of A-TFB approached the bubbling fluidization pattern. By contrast, the standpipe facilitated the turbulence at a high super ficial gas velocity, thus making the bottom flow of A-TFB approach the fast fluidization pattern. Both the particle velocity and solid concentration distribution presented a unimodal distribution in A-TFB and TFB.However, the standpipe at a high gas velocity and in the transition or dilute phase section signi ficantly affected the radial distribution of flow parameters, presenting a bimodal distribution with particle concentration higher near the internal and external walls and in downward flow. Conversely, particle concentration in the middle annulus area was lower, and particles flowed upward. This result indicated that the standpipe destroyed the coreannular structure of TFB in the transition and dilute phase sections at a high gas velocity and also improved the particle distribution of TFB. In conclusion, the standpipe improved the fluidization quality and flow homogeneity at high gas velocity and in the transition or dilute phase section, but caused opposite phenomena at low gas velocity and in the dense-phase section.
