The effect of riser termination geometry on close-coupled cyclone performance

An investigation was conducted to determine the effect of riser termination geometry on close-coupled cyclone performance at high solid loadings. The testing was conducted using air at ambient conditions with a 0.54-m-diameter cyclone attached to a 20-cm-diameter riser. FCC catalyst was used as the test material. Elbow and blind tee riser termination geometries were studied. Steady-state conditions were determined by measuring the exit losses from the test cyclone. The solids loading into the cyclone was varied over the loading range of approximately 3 to 32 kg/m(3). The solids loss from the first-stage cyclone was determined as a function of time. The overall efficiency of the cyclone was determined from the total loss rate and the rate of solids fed to the cyclone. Cyclone fractional efficiency curves were obtained from the particle size distributions taken from samples of the various solids streams. The results of the testing showed that cyclone efficiency decreased with loading when a blind tee was used as the riser termination device. When an elbow was used as the riser termination geometry, the cyclone efficiency increased with increasing loading. The difference in results appears to be due to the fact that the elbow concentrates the solids into a coherent strand of particles, whereas the blind tee causes the solids to enter the cyclone in a more dispersed fashion.