Hello Everybody,
I am writing to seek some inputs with reference to the above question, elaborated below.
In the context of gas-solid fluidization, relationship between bed heights and the corresponding voidages is written as follows:
L/L_mf = (1 - e_mf)/(1 - e) ...........(1)
(L, e) and (L_mf, e_mf) are the (bed height, voidage) at the incipient conditions and after expansion, respectively.
This formula is valid for both homogeneous/particulate (voidage is uniform throughout the bed) and inhomogeneous fluidization (voidage is non-uniform); in a non-reactive system, one can arrive at Eq. (1) by simply writing down mass balance over solids. Agreed?
How about a reactive system wherein solids are consumed by the fluidizing gas?; does Eq. (1) remain valid? if not, how does one evaluate the relationship?
Inputs are greatly appreciated!
Regards,
KD
Equation 1 is simply a statement that L.(1-€)=constant for constant quantity of material. If the quantity of solids varies or their shape or size change this equation is not valid.
I used to be involved with fluidised beds many years ago. I published a paper with J.Kubie in the Int.J.H&M TransferVol18,pages 289-299 in 1975 that may be of use. We considered the voidage variation near a surface, but the method could be extended to allow for varying particle size.
I forgot to mention a follow-up paper by Krishna Pillai on voidage near walls in packed beds. Ref: Chem.Eng.Sci, 19,7,page 59 ,1976.
Thanks very much, Sir; I shall go through the recommended article. I think one could still apply L*(1-e) = constant provided that the amount (volume fraction of solids) of shape/size changing solid particles is less; this is the case, I believe, in most of the bubbling fluidized beds wherein a large quantity of bed material is used. Please add in your views at your convenience.
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