Particle rotation characteristics in CFB riser
By using an advanced measurement system composed of a high-speed digital video camera and a high-power laser sheet, an experimental research was carried out on the particle rotation characteristics in a cold Circ ulating Fluidized Bed (CFB) riser with square cross-sectional area of 200 mm×2 00 mm and height of 4 m.Particle movement images were analyzed with Matlab, Phot oShop and ACDSee software, captured at 13 measurement points in a quarter of a c ross-section in the upper dilute phase area of the CFB riser.Particle rotation speed was observed and checked by the dual-frequency method. The results showe d that the particle rotated when moving along the riser in gas-solid two-phase flow of the CFB riser, and the average particle rotational speed in the wall ar ea was higher than that in the center area in the testing cross-section. Those particles, with either relatively smaller diameter or higher radial component o f velocity,were inclined to have a higher rotational speed. The average rotatio nal velocity of irregular particles was obviously higher than that of regular on es.Average particle rotational velocity in the CFB riser was 300 r·s-1 and maximum rotational velocity was 2000 r·s-1 at superficial gas velo city V_g=5 m·s-1,recycling solids mass flux G_s=1.5 kg·m- 2·s-1 and particle average diameter d_p=0.5 mm.