Method and apparatus for removing foreign objects from fluid bed systems

Apparatus for separating foreign objects from fluid bed particles of a fluid bed combustion chamber wherein foreign objects are moved to one side of the fluid bed comprising:

• a substantially vertical column, through which fluid can flow,
• means for withdrawing a quantity of mixed inert fluid bed particles and foreign objects from the fluid bed and filling said substantially vertical column with said mixed fluid bed particles and foreign objects,
• said withdrawing means including a material flow control plenum chamber having a first end and a second end and
• a substantially vertical passageway connected to said first end of said plenum chamber and connected to the one side of the fluid bed such that said passageway receives said withdrawn quantity of mixed particles and objects from said fluid bed and feeds them to said plenum chamber,
• means for fluidizing the bottom portion of said passageway of mixed fluid bed particles and foreign objects with an air stream which air stream is directed laterally to said column,
• said fluidizing means including means at a plurality of locations in the bottom of said plenum chamber for introducing fluidizing air with a directional component in a direction from said first end to said second end of said plenum chamber such that said mixed particles and foreign objects are directed into said vertical column,
• means for subjecting the laterally directed stream of mixed fluid bed particles and foreign objects to a substantially upwardly vertically directed stream of classifying air whereby the heavy foreign objects drop downwardly through said column for collection and the lighter fluid bed particles rise through said column and are elevated above said column, and
• means for separating said fluid bed particles from said classifying air and returning said fluid bed particles to the fluid bed combustion chamber.