Effects of particle size on the particle distribution of a two-pass circulating fluidized bed evaporator with a baffle

A two-pass circulating fluidized bed evaporator with a baffle is designed and built to enhance heat transfer, as well as prevent and remove fouling. The effects of particle size on particle distribution under various operating parameters are systematically investigated using the CCD image measurement and acquisition system. The particles used in the experiment are polyoxymethylene particles with diameters of 2.0, 3.15, 4.0, and 5.5mm. The height of the baffle is 0.1m. In this study, the particle distribution in the up-flow bed is uniform, whereas that in the down-flow bed is uneven, especially for large particles. In the down-flow bed, the particle distribution becomes uniform, and large particles have a fast reduction in non-uniform degree as the circulation flow rate increases. When the circulation flow rate is low, the distribution of large particles becomes uneven as the amount of particles added is increased, whereas that of small particles remains uniform. However, when the circulation flow rate is high, the amount of particles added and particle size only slightly affect particle distribution. Finally, four phase diagrams are established to show the optimal range of the operating parameters. [Display omitted] •The particle distribution in the up-flow bed is uniform.•The particles unevenly distribute in the down-flow bed especially for the big ones.•A high flow rate greatly enhances the uniformity of the big-particle distribution.•The distribution of particle POM-2.0 is the best among the four sizes of particles.•Results can serve as references for the industrial application of such equipment.