Experimental study of inlet phenomena of 35∘35∘ inclined non-aerated and aerated Y-inlets in a dilute cold-flow riser

Inlet phenomena in a 0.1 m diameter cold-flow riser with a 35∘35∘ inclined side inlet are studied experimentally using 3D-Laser Doppler Anemometry for solids fluxes of 0.5–4.5kg/m2/s and gas velocities of 5.3–7.4 m/s. In the vicinity of the solids inlet, radial gas-solids mixing is hindered and bypassing of the solids jet occurs, resulting in steep velocity gradients and off-centre maxima in the velocity field. The feeding conditions and the type of the solids affect the bottom operation and gas–solids mixing to a large extent: compared to FCC particles, silica particles extend the acceleration zone in the riser. Low gas flow rates and/or high solids feeding rates result in an increased penetration depth of the solids jet and in explicit bypass zones in the plane facing the inlet. High root mean square fluctuating particle velocities are observed at the solids jet boundaries. A non-aerated Y-inlet configuration causes vortex formation, inducing a small reflux into the upper dilute part of the standpipe. The influence of dilution of the inlet solids jet is also investigated using an “aerated” inlet configuration. Aerated inlets lead to better entrainment, improved radial mixing, less pronounced broader bypass zones and a firm reduction of the penetration depth. In the 0.1 m diameter riser, radial mixing quickly dissipates the non-uniformities introduced by the solids inlet. Reflection phenomena can, however, occur in the case of a non-aerated solids inlet.