• fluidization;
  • circulating fluidized beds;
  • internals;
  • particles distribution;
  • counter-current fluidized bed

The redistribution of solids in a counter-current circulating fluidized bed (CFB) by effect of ring-type internals was investigated in a downscaled cold-flow model. The system consists of two interconnected CFB reactors, in which the primary reactor operates like a common riser while the secondary reactor operates in counter-current. The unit works without circulation rate control devices and the inventory splits inherently between the two reactors by pressure balance and depending on the fluidization velocities. Previous studies showed an increment in the total pressure drop in the secondary reactor as result of the internals installation. With the purpose of obtaining comparable inventory in the secondary reactor with and without rings, a device for adjustment of total inventory was designed and installed. Effects of the aperture ratio, number of rings, fluidization velocity, and particles circulation rate were studied. The results obtained approach a guideline for the detailed design of similar configurations. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3612–3623, 2013