Fluidized bed incinerator

The fluidized bed incinerator is used for waste with a low density and it must be homogenic (ex. WWTP sludge). Also to clean paint from iron or steel, fluidized bed is a common used technology.

The combustion chamber has mostly a square chape and there is a lot of sand present. The start up and maintance burner is upstares the combustion chamber. At the bottom, the floor of the combustion chamber,  there is a mixere of gas and air injected. Every sand particale has now 2 forses:

• The graviation forse (Fg)  which pulls the sand particle down
• The pneumatic forse (Fp) which lift the sand particle up

The sand particles have now the next possibilities:

Fgrav. > Fpneu.	Fgrav. = Fpneu.	Fgrav. < Fpneu.
Gravitation The sand particles are falling down in the combustion chamber	Fluidized bed stage The sand particles are floating in the combustion chamber	Pneumatic transport The sand particles are flying up to the top of the combustion chamber

 So, the fluidized bed stage of the incinerator is the stage that the sand floats in the combustion chamber at a temperature of min. 350 degr.C. The most difficult is controlling the correct air-gas mixure and flow regulations at the bottom of the combustion chamber.  

If the combustion chamber is correct working, there is a blue flame tracking over the fluidized bed zone of the combustion chamber.

Medical waste in fluidized bed?

Medical waste contains hard metal materials, like needles, this is not homogenous and the waste falls through the fluidized bed zone. Sometimes a grid basket is set up in the fluidized bed combustion chamber to catch up the materials which fall through the fluidized bed zone. But the grid basked disturbs the sand floating process, which creates a bad combustion.

Flue gas treatement

Because of the high concentrations of sand in the combustion chamber, also the flue gas will contain a lot of sand. As a first flue gas treatement step, a cyclone is used.