The effects of particle properties (density and size) on solids holdup (epsilon(s)) in the riser of a Liquid-Solid Circulating Fluidized Bed (LSCFB) were investigated experimentally based on three parameters: the superficial liquid velocity (U-l), the normalized superficial liquid velocity (U-l/U-t)and the excess superficial liquid velocity (U-l-U-t). The results showed that the excess superficial liquid velocity (U-l-U-t) among those three parameters is a more appropriate parameter to evaluate the effects of the particle properties on the solids holdup facilitating general and direct comparisons for different types of particles. A discussion on the force balance of the particles revealed that the excess superficial liquid velocity (U-l-U-t) is approximately equivalent to the average particle velocity ((V) over bar (p)) when the solids holdup (epsilon(s)) is less than 0.1. Also the solids holdup (epsilon(s)) is a function of superficial solids velocity (U-s) and particle velocity (V-p), expressed quantitatively in terms of average value as (epsilon) over bar (s) = U-s/(V) over barp = U-s/(U-l-U-t) when (epsilon) over bar (s) < 0.1. (C) 2012 Elsevier B.V. All rights reserved.