Investigation On The Heat-Mass Transfer In Spin Flash Dryer

Spin flash drier (SFD), which combines drying and fluidization technology, was introduced into China in 1980s. This equipment precedes other traditional driers in many aspects and has been widely used in industries.The experimental studies on the drying characteristics in SFD are performed. The quick drying for wet emplastic material in SFD is achieved. The drying rates in a constant-rate period increase with the increase of the gas inlet velocity. The influence of the rotational speed of the whisk on the drying process in SFD is found un-remarkable. The heat and mass transfer coefficients obtained in the drying process can be correlated asNu_p=2.2148Re_p^0.5Pr^1/3Sh_p=2.2148Re_p0.5Sc^1/3These equations can be used for designing and operating SFD drier in engineering.A mathematical model for the gas solid two-phase flow in the fluidize-region of SFD is adopted. The k ?ε　turbulent model for gas flow and the particle-trajectory model for particle motion in the gas phase are used to describe the two phase flow in SFD's fluidized-region. The numerical simulations indicate that the gas flow in SFD's fluidized-region is the complex turbulent flow with region change and rotational motion. The prediction of the tangential component of the velocities agrees with the experimental results. Further, the influences of the various primary parameters on two phase flow in SFD's fluidized-region are calculated and analyzed.The numerical simulations for the particle's trajectories in SFD's fluidized-region clearly show that the particles ejected singly into the fluidized-region move not only toward in the tangential direction, but also in the radial direction because of the action upon by the drag force of the gas flow and the Coriolis force. When the gas inlet speed decreases, the out entrainment of particle from the drier is suppressed obviously. The influences of the various primary parameters on the particle motion characteristics are also calculated and analyzed.The numerical results can be used to design the SFD equipment.