CFD studies on mass transfer of gas-to-particle cluster in a circulating fluidized bed

Mass transfer of air to naphthalene particle cluster in a circulating fluidized bed (CFB) is investigated via computational fluid dynamic (CFD) approach. Distributions of naphthalene vapor concentration and velocity in the spherical cluster are numerically predicted. The computed results indicate that the mass transfer of air to particles in the cluster is reduced due to the particle clustering and increments of particle size and temperature. Influences of the porosity of the cluster, inlet gas velocity and temperature on mass transfer of air to the cluster are analyzed. The mass transfer coefficients of gas to cluster increase with the increase of porosity of the cluster and inlet air velocity, but decrease with the particle diameter. The down-moving cluster gives higher mass transfer than that of the upward moving cluster. The computed Sherwood numbers are compared with the estimated values from empirical equations reported in literature.