Experimental research on particle rotation characteristics in CFB riser

By using a high-speed digital video camera measurement system, an experimental study of particle rotation characteristics in gas-solid two-phase flow in a cold pilot-scale Circulating Fluidized Bed (CFB) riser was performed. Particle movement images captured at 13 testing points in a cross-section in upper dilute-phase zone of the CFB riser were analyzed with Matlab, PhotoShop and ACDSee software. Particle rotational speed was determined manually and checked by a dual-frequency method. The result,; show that the average particle rotational speed is as high as 300 r (.) s(-1) with the top speed of 2000 r (.) s(-1), in condition with superficial gas velocity V-g = 5 m (.) s(-1), external solids mass flux G(s) = 1.5 kg/(m(2) (.) s) and particle average diameter d(p) = 0.5mm Furthermore, the average particle rotational speed in wall area is higher than that in center area in the testing cross-section. Those particles, with either relative small diameter or high radial component of velocity, may be inclined to higher rotational speed. The average rotational speed of irregular particles is apparently higher than that of regular ones.