Gas-solid flow behavior in a horizontal pipe after a 90 degrees vertical-to-horizontal elbow

The characteristics of the particle flow in a horizontal pipe following a 9 0 degrees vertical-to-horizontal elbow were investigated both numerically a nd experimentally. Laboratory experiments were conducted in a 0.154 m LD te st section. The effects of air velocity, the ratio of air-to-solids mass fl ow rate, geometry of the elbow and inlet conditions on gas-solid flow patte rns were investigated experimentally. Pulverized coal with a mean particle diameter of 50 mum was used as the solid material. Experiments were perform ed with conveying air velocities ranging from 15 to 30 m/s and air-to-solid s mass flow rate ratios of 1 and 3, with elbows having bend radius to pipe diameter ratios of 1.5 and 3. Measurements of particle concentration and particle velocity were performed at various locations along the horizontal pipe using a fiber-optic probe w hich was traversed over the pipe cross-section of the pipe. It was observed that the strong rope created by the elbow disintegrates within an axial di stance of 10 pipe diameters. Fully developed concentration and velocity pro files were obtained within approximately 30 pipe diameters from the elbow e xit plane. The rope behavior was different for the two elbows studied (R/D = 1.5 and 3). The shapes of the fully developed profiles were found to be i ndependent of inlet conditions. CFD simulations of gas-solid flow through 90 degrees circular elbows were p erformed using the Lagrangian approach. The simulations were used to predic t the location of the rope and its dispersion rate along the horizontal pip e after the elbow exit plane. (C) 2001 Elsevier Science B.V. All rights res erved.