Experimental investigation of the effects of particle properties on solids holdup in an LSCFB riser

The effects of particle properties (density and size) on solids holdup (ɛs) in the riser of a Liquid–Solid Circulating Fluidized Bed (LSCFB) were investigated experimentally based on three parameters: the superficial liquid velocity (Ul), the normalized superficial liquid velocity (Ul/Ut) and the excess superficial liquid velocity (Ul − Ut). The results showed that the excess superficial liquid velocity (Ul − Ut) among those three parameters is a more appropriate parameter to evaluate the effects of the particle properties on the solids holdup (ɛs), 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 (Ul − Ut  ) is approximately equivalent to the average particle velocity (V¯P) when the solids holdup (ɛs) is less than 0.1. Also the solids holdup (ɛs) is a function of superficial solids velocity (Us) and particle velocity (Vp  ), expressed quantitatively in terms of average value as ε¯s=Us/V¯P=Us/(Ul-Ut) when ε¯s<0.1.

► Solids holdups were compared based on three types of superficial liquid velocity. ► Effects of the particle properties rely on type of the superficial liquid velocity. ► Excess superficial liquid velocity is better to evaluate particle property effects. ► Terminal velocity is better to represent particle properties. ► Solids holdup was predicted directly by operating conditions and particle properties.