Gas flow in a gassolid fluidized bed is characterized by the predominance of bubbles. When gas flow is more than the minimum fluidization velocity, the top of the fluidized bed may fluctuate vigorously leading to unstable operation. Bed fluctuation and fluidization quality are interrelated. The quality of fluidization can largely be improved by introducing baffles in bubbling and turbulent fluidized beds. In the present work three baffle geometries, i.e., circular, triangular and square are used to determine different hydrodynamic parameters such as minimum fluidization velocity, bed expansion, pressure drop across the bed, fluctuation ratio, expansion ratio, etc. in a bubbling fluidized bed. A new parameter blockage ratio is introduced to analyze the behaviour of baffled fluidized beds. It is found from the current experimental studies that the blockage ratio mainly influences the hydrodynamics of the bed rather than the shape of the baffle.
Low-rank coal gasification using a bubbling fluidized bed reactor at low operating temperature