Experimental and computational study of T- and L-outlet effects in dilute riser flow

Riser outlet effects induced by an L-outlet and by abrupt T-outlets with different extension heights and outlet surface areas are studied experimentally and computationally.Experiments are carried out in a cold flow riser. The cold flow riser has a diameter of 0.1 m and a height of 8.765 m and is operated in the dilute flow regime with a superficial gas velocity of 2.48–7.43 m/s and a solids flux of 3.0 kg/m2/s. Particle velocities are measured using Laser Doppler Anemometry (LDA).Vortex formation in the extension part of the riser is observed. The vortex circulates the solids along the wall opposite to the outlet, thus inducing a solids reflux. The flow pattern upstream the outlet is, however, hardly affected in the small diameter riser. The vortex position and length are affected by the extension height, but hardly by the outlet surface area and the superficial gas velocity. The use of an L-outlet significantly reduces the vortex formation.The experimental measurements are used to validate a 3D Eulerian–Eulerian and Kinetic Theory of Granular Flow (KTGF) based gas–solid flow model. In general, the calculated trends are qualitatively in agreement with the experimentally observed phenomena. The exact shape of the vortex is not always accurately predicted.

Graphical AbstractRiser outlet configurations.Figure optionsDownload full-size imageDownload high-quality image (36 K)Download as PowerPoint slideHighlights► Riser outlet effects induced by an L-outlet and by abrupt T-outlets are studied experimentally and computationally. ► Vortex formation in the extension part of the riser is observed.► Mean (and fluctuating) particle velocities are measured with a one probe Laser Doppler Anemometer.► The in-house developed gas–solid flow model FLOW-MER is validated using the experimental data.