A secondary air flow biasing apparatus for a CFB combustion system includes a sorbent feed path configured to convey processed sorbent particles to a CFB furnace by utilizing a portion of secondary combustion air supplied to the furnace; a first air injection port disposed within a wall of a lower portion of the furnace, at a first elevation above a primary air distribution grate of the furnace; a second air injection port disposed within the wall of the lower portion of the furnace, at a second elevation above the first elevation; and an air/sorbent separation device in fluid communication with the sorbent feed path, the separation device configured to separate a substantial portion of the secondary combustion air from the processed sorbent particles such that a relatively lean sorbent-to-air mixture is introduced through the second air injection port and a relatively rich sorbent-to-air mixture is introduced through the first air injection port.