Research On Solid Hydrodynamics Of Gas-Solid In A Cfb Riser

Research about solid particle characters in circulating fluidized bed is very important to study the principle of gas-solid two phase flow. High speed photography system technology applies widely in studying the gas-solid flow pattern in the cold Circulating Fluidized Bed (CFB) riser because it is visual and no interference to flow.Experiments about particle motion in circulating fluidized bed gas-solid two phase using high speed photography camera with high frames combining with laser sheet technique were carried out. In this paper, a series of key problems were reported, mainly including three sections: cluster motion, particle rotation and particle collision in cold CFB riser.Above all, behavior of particle aggregate in gas-solid two phase flow was reported, c oncluding s hape, s ize a nd e xistence t ime o f c lusters h ad little d ifference under different operating conditions in different sections. The various shape of cluster can be observed and the maximal size of cluster had been obtained. Analyzing the pictures, the velocity of single cluster had been calculated by border analysis method. And, it was concluded that the existence time of clusters were from 10ms to 200ms. Observing cluster motion process, formation theory and decaying cause were understood. Tentative research on the cluster interior was reported.Afterwards, some particle image characteristics points produced by irregular shape or surface of the particles were regarded as the main references in particle rotation velocity determination. To eliminate misjudgment of rotational velocity, a dual-frequency imaging method was presented, which was deduced in theory and verified in experiment. Analyzing particle images in section of dilute phase with Matlab, PhotoShop and ACDsee software, a series of results were obtained. The fastest particle rotation velocity attained 2000r/s and average particle rotation velocity was about 300r/s. In CFB riser, average particle rotation velocity was higher on the wall than in the core of CFB riser. There were more opportunities that small particles rotated faster than large particles. It was more obvious that average rotation velocity of irregular particles was faster than spherical particles. Increasing the superficial gas velocity or the solid volume concentration, average rotation velocity tended to increase.In the end, the motion velocity and rotation velocity of particle were not the same before and after collision. Calculated value of particle rotational velocity was close to real value to the spherical particle after particle-wall collision, however, the...