Problem 2: Sizing of a Fluidized Bed (30 minutes) (25 Marks It is desired to fluidize spherical particles having size of

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Problem 2 Sizing Of A Fluidized Bed 30 Minutes 25 Marks It Is Desired To Fluidize Spherical Particles Having Size Of 1 (59.06 KiB) Viewed 40 times

Problem 2: Sizing of a Fluidized Bed (30 minutes) (25 Marks It is desired to fluidize spherical particles having size of D₁-3mm, and a density pp-2750 kg/m³ using a viscous fluid (p= 1050 kg/m³ and µ-0.95 Pa.s). The void fraction at minimum fluidizing conditions has been found to be &0.4. The bed has a diameter of 0.5m and a maximum height of 0.75m. It has been found that height of the particles at rest is Lo=0.095m and the bulk density of the particles+fluid at rest is about pm -2525 kg/m³. Assume that the mass of particles+fluid at rest is approximately that of the particles. (a) What is in this case, the void fraction at rest &? (hint: estimate the volume of particles per m³) (b) Then, using the cross section of the bed compute the mass of particles to be used? (c) Calculate (L) the minimum height of the fluidized bed ? (hint: use similarity!) (d) Calculate the pressure drop at these minimum fluidizing conditions? (e) Solve for the Reynolds number NRemy from a (Nem)+b- Ney+c=0! (compute a, b, and c ! then obtain the positive root!) (f) Use the value for NRe.my to calculate the minimum velocity for fluidization ? (g) At a bed expansion of y'=20 Vf, estimate the porosity of the bed ? (hint: from expansion formulas solve for & !) (h) What is in this case the height of fluidization ? does the used bed allow this fluidization?