Here are the some of advantages:

a) Even temperature distribution eliminates hot spots.

b) Catalyst is easily replaced or regenerated.

c) Allows for continuous, automatically controlled operations.

d) More efficient contacting of gas and solid than in other catalytic reactors.

Thanks for the reply Dr. Kiran. I doubt that these advantages may be also with circulating type FBCs.

In bubbling bed particle size used are larger than circulating fluidized bed so power requirement for sizing is less.

Sensible heat loss will be less inbubbling fluidized as air to solid is less in bubbling fluidized bed than in a circulating fluidized bed.

The biggest disadvantage of BFB's is that you run the risk of ash fusion. This means that you have to either remove heat from the bed to keep the bed temperatures down or you have to run at "very" high excess air conditions. Heat removal is again challenged by abrasion of the heat transfer surface. You can use SiC coatings to give your pipes/tubes longer life. 

As you may know, high excess air simply results in the venting of hot air to atmosphere. This reduces your energy efficiency vs say chain grate or PF combustors.

Dear Kiran,

      Compared with CFB, I think the advantages of BFB are: (a) more uniform temperature distribution, especially smaller axial temperature gradient than in CFB; (b) the longer solids residence time due to its high particle concentration, which is especially suitable to low-rate reaction systems and is difficult to achieve in CFB, as the height of CFB can not be too long; (c) the reactor is much simple as solids circulation system is avoided; (4) the requirement for solids separation in BFB is often lower and the  separation system is simpler.  FYI.

Dear sir,

in the fluidized bed heat exchanger the bubbling is vary important things,

1st it help the particles beds to move up stream

2nd when particle moving up takes away the heat from heat exchanger which embedder in it.