Fluidized Bed Reactor

FLU ID IZ E D B E D R E A C T O R

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A fluidized bed reactor (FBR) is a type of reactor device that can be used to carry out a variety of multiphase chemical reactions 

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In this type of reactor, a fluid (gas or liquid) is passed through a granular solid material (usually a catalyst ) at high enough velocities to suspend the solid and cause it to behave as it were a liquid. 

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Basic Principles 

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T h e so lid su b stra te is su p p o rte d b y a d istrib u to r. T h e flu id is fo rce d th ro u g h th e d istrib u to r u p th ro u g h th e so lid m a te ria l A t lo w e r flu id ve lo citie s, th e so lid s re m a in in p la ce a s th e flu id p a sse s th ro u g h th e vo id s in th e m a te ria l T h is is kn o w n a s a p a cke d b e d re a cto r A s th e flu id ve lo city is in cre a se d , th e re a cto r w ill re a ch a sta g e w h e re th e fo rce o f th e flu id o n th e so lid s is e n o u g h to b a la n ce th e w e ig h t o f th e so lid

Basic Principles 

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T h is sta g e is kn o w n a s flu id iza tio n a n d o ccu rs at th is m in im u m flu id iza tio n ve lo city A s th e flu id ve lo city is in cre a se d , th e re a cto r w ill re a ch a sta g e w h e re th e fo rce o f th e flu id o n th e so lid s is e n o u g h to b a la n ce th e w e ig h t o f th e so lid m a te ria l T h is sta g e is kn o w n a s flu id iza tio n a n d o ccu rs at th is m in im u m flu id iza tio n ve lo city O n ce th is m in im u m ve lo city is su rp a sse d , th e co n te n ts o f th e re a cto r b e d b e g in to exp a n d a n d sw irl

Basic Principles • • • • 

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The reactor is now a fluidized bed. Depending on the operating conditions and properties of solid phase various flow regimes can be observed in this reactor.

Uses

s a re stillu se d to p ro d u ce g a so lin e a n d o th e r fu e ls, a lo n g w ith m a n y o th e r ch e m

 p o lym e rs a re m a d e u sin g FB R te ch n o lo g y , su ch a s 

R ’ s . T h e se in clu d e

t se ttin g s.

flu id ize d b e d re a cto rs a llo w fo r a cle a n e r, m o re e fficie n t p ro ce ss th a n p re vio u s s

Catalytic Cracking of Petroleum

ro u g h o f flu id iza tio n in 1 9 4 2 w a s a sso cia te d w ith ca ta lytic cra ckin g o f g a so ilin to

ca ta lytic cra ckin g h a d b e e n ca rrie d o u t in fixe d b e d re a cto rs.

ckin g d e p o sits ca rb o n a ce o u s p ro d u cts o n th e ca ta lyst, ca u sin g ra p id d e a ctiva tio a in ta in th e p ro d u ctio n ca p a city , th e ca rb o n h a d to b e b u rn e d o ff.

a tio n re q u ire d sw itch in g th e re a cto r o u t o f p ro d u ctio n .

Catalytic Cracking of Petroleum

h e n fo u n d th a t th e d e n se m ixtu re o f so lid s a n d g a s b e h a ve d in m a n y a sp e cts lik

a ke s th e co n tro l o f stre a m s m u ch m o re co n ve n ie n t.

h e n flu id ize d b e d s h a ve b e e n u se d in o th e r fie ld s w h e re so lid s h a ve to b e h a n d le

Advantages Uniform Particle Mixing Due to the intrinsic fluid-like behavior of the solid material, fluidized beds do not experience poor mixing as in packed beds. This complete mixing allows for a uniform product that can often be hard to achieve in other reactor designs. 

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Uniform Temperature Gradients Many chemical reactions require the addition or removal of heat. Local hot or cold spots within the reaction bed, often a problem in packed beds, are avoided in a fluidized situation such as an FBR. I n other reactor types, these local temperature differences, especially hotspots, can result in product degradation. Thus FBRs are well suited to exothermic reactions. 

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Advantages Ability to Operate Reactor in Continuous State The fluidized bed nature of these reactors allows for the ability to continuously withdraw product and introduce new reactants into the reaction vessel. Operating at a continuous process state allows manufacturers to produce their various products more efficiently due to the removal of startup conditions in batch processes. 

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Disadvantages • • • • •

Increased Reactor Vessel Size Pumping Requirements and Pressure Drop Particle Entrainment Lack of Current Understanding Erosion of Internal Component