TYPES OF CHOKING IN VERTICAL PNEUMATIC SYSTEMS

Choking is examined in terms of its definitions. Three choking initiat ion mechanisms are identified: type A (accumulative) choking occurs wh en solids start to accumulate at the bottom of the conveyor as the sat uration gas carrying capacity is reached; type B (blower-/standpipe-in duced) choking results from instabilities due to gas blower-conveyor o r solids feeder-conveyor interactions where there is insufficient pres sure or too limited solids feed capacity to provide the needed solids flow; and type C (classical) choking corresponds to a transition to se vere slugging. Approaches for predicting the onset of each of these ty pe of choking are recommended. Implications for regime transitions in fast fluidization are also identified.