Abstract
A specially designed high-density downward gas–solids flow fluidized bed, consisting of a solids reservoir tank, a solid distributor, an acrylic downer (3.0 m high), a gas–solid separator and a solid receiver tank, has been developed to study the fundamentals of high-density downward gas–solids flow characteristics in the downer reactor. Experiments have been carried out using two types of sand particles (ρp=2600 kg/m3, dp=80 and 320 µm) as bed materials with superficial downward gas velocities (Ugd) ranging from 0 to 5 m/s. Particle diameter has a great effect on the solids mass flux (Gs) and solids hold-up (εs) in the downer. It is found that Gs in a 50 mm diameter downer reached up to 1876 and 815 kg/m2·s, with average εs up to 0.16 and 0.07 in the developed region, for 80 and 320 µm sand, respectively. The solids hold-up decreased with increasing Ugd at a fixed solids mass flux in the developed region. By considering the effects of downer diameters, operating conditions, and solids properties, a correlation for the prediction of dense solids hold-up (εs*>0.07) in the developed region of the downer is proposed based on experimental data from the literature and this study.
