1986 Volume 12 Issue 4 Pages 427-432
Room-temperature data on particle residence time in a swirling flow, entrained bed gasifier were obtained by use of a tracer response technique. Orifice plates (constriction) of various diameters were installed at the exit to the gasifier. Particle-laden air was injected through two sets of four burners, spaced at 90° intervals around the bed circumference at two locations along the bed axis. The radial and tangential components of injection velocity, as well as the axial location of the upper set of burners closest to the exit, were varied.
It was determined that particle residence times increased as the constriction diameter, or rotational circle diameter of the low burners (determined by the direction of injection), decreased. Increasing the height of the upper set of burners also increased particle residence times. This change can be related to variations in the tangential gas velocity profiles in the gasifier.
Particle trajectories were affected principally by the centrifugal acceleration associated with the tangential injection configuration. This factor is incorporated into a dimensionless empirical expression for residence time :
T=0.122×Z0.501
where T is the ratio of particle residence time in swirling flow to the residence time in plug flow and Z is the ratio of the centrifugal acceleration to the gravitational acceleration.
