Question

1. Discuss the applications of fluidization along with examples and diagrams 2. What is expansion of fluidized beds and derive the equation for particulate fluidization to derive V, in terms of void fraction along with the charts 3. Derive Ergun equation, Kozney Karman equation and Burke Plummer equation and give their Reynolds number conditions 4. Solve Problem 7.16 : Air leaving a fluidized bed at 1500c contains a small amount of dust with particle sizes between 2 and 20 micro meter. The particle density is 3400 kg/m'. A) Calculate the terminal velocity for the smallest and largest particles. B) If the dust were allowed to settle in a large rectangular chamber with a depth of lm, what residence time would be needed to get complete dust removal 5. Solve problem 7.2: A catalyst tower 40 ft high and 18 ft in diameter is packed with 1-inch diameter spheres. Gas enters at the top of the bed at a temperature of 450°F and leaves at the same temperature. The pressure at the bottom of the catalyst bed is 30lb/inch' absolute. The bed porosity is 0.4. If the gas has average properties similar to propane and the time of contact (based on flow in the void space) between the gas and the catalyst is 8 sec, what is the inlet pressure.

Answer 1

Edliation. When a equid or gas is passed, at clow velocity to a bed of sould pastichs. the partech don't move and the promure drop is given by the apgem Eigun Egos of the fluted velocity ú steadily increased the premise dopp overno the diag on average on individual partides veicirea and the particles start to move and becomet suspended in the shed . This condition is known as fluedisallon. → The term Muldlsation and fuldsed bed au used to describe the condition of fully suspended particles sence the Siuspension gent behaves a dense Huid. - Condition a fluidieation 7.porousplate Air Consider a vestical tube , partially filled with granula material such as catalytic cracking Catalyst as Shown in fg. The Tube is open at the top and has a posans plate at bottom, to support the bed of a socatalysts and to distribute the geow uniformly CamScanner

as the entire croyection Air is admitted allow the Ariston utor plate at a low flow rate and passes through the bed without causing any partile motion. the particles are quite small flow in channels b/w . the particles will be laminar and pressure drop acron the bed will be proptional to the superficial velocity to froed udfofurstered Pressure drop and bed height · Sploche Superfpe&alvelówhy V, - A** B- st. Huidisation starts from B As we increase the relacity the pressure drop t but the portedly dont move and the bed hilght remains the same At a certain velailty the pressure drop across the bed counter balance the force of gravity on ca the particles or the weight of the bed and I any futhion Excrease in velocity cause the partice cs to more this point is represented by "A on the graph Салата

True feuidisation starti at point B. Once the ben Huidesed, the pressure drop across the bed stays co but the bed height continue to increase with the MIN whcrease in flow r Minimum fuul disation velocely: mini fluidisation velocity Can be obtained by Setting the Ap acron the bed equal to the weight of the bed per unât area of croesection, to or the buoyant force of the displaced fluid. Dp = g (1-2)(?p=) At escépient Huidisation, Enter the minimuem poraine * polla g1-6m) (g=s hoa G ropi colegun Son T = Lon(1-Em (1-6) Scanned with CamScanner

flow through. bed of solids :- can be partleles of a bed of The general structure Characterpsed by voidage] in the fractional ropdage of the bed surface area of the bed. Porosita i The Specefic voidage / Ponity /&r the traction of the volume of the bed not occupled by soled material. It is demension less and is given by & volume of bed- volume of the parte des volumnie of bed. in volume o poulidly Mrr volume of bed. scanned with

Specifee sunface area of the pastice: (aw) or (a). It is defined as the ratio of the surface area of the particle to its volume. wh. 4082 are- for a Spherical particle ce i The volume fraction heat partedes is bed is a = a, (1-2) Suoclona Vow pailde, vo Ta e lire Slowener voluntated for a packed bed reynoldi member can be defined as NR = Sop u GPp t Re (16)M (1-EM a is defined as the ratio of total surface area in the bed to the total volume of the bed. The most common method of calculating pressure drop through a bed of solids are based on estimate of total deag on the eolied, boundance, the tortomous channels through the bed Scanned with CamScanner

The actual channel are inregular in shapes have a variable croesedion and onentation and an highly inter connected To caluate an Equivalent channel diameter it is assumed that the bed has a set of uniform circular channels. The total surfall area is the surface area per paõlidle times the mo.ch particles : But It Is more convincent to bace the calculations on the volume fraction parties in the bed and the Surface wherne ratio for the particles. To determine the equie alent channd dia (Deq) The Surface area for n parallel channels of length 'L' is set ilqual to the surface volume ratio times the portfele volume. Sol(1- ) where So is the crossectional area of the bed. A MADA 5,4(1-4). Se in TDe qoso (1-2) pp. Om A The void volume in the bed as same .. as the total volume a m- channels CS Scanned with CamScanner

Sof&= 1 xnxx Part so = mt pea . 6-82 Op que (1-) The pressure drop depends on the aug, velocity in the channels. I, which is proportsonal to the superficial or empty tower relocity to and enversly proportional to the porosity. Qurowe Lonelt ortopedical - 32 pe ū (1-532 AP = 12MT (1-2) 12MVO (1-2) 2 D2ES. Scanried with popie CamScanner

paited kozeny - Carmani Equation - Com) at is applicable for flow through bede and pain Reynold numbu. Cet upto about 1. vescous loss part of the Cover Buske plummer &qm 8-com) t. The pressure drop in packed bed at high Reynolds number ( Rep> 10). is calculated by the following Egn. Ergun equation : ONN (1-) er 42