Question

What is a fluidized bed reactor? Explain the working of fluidized bed reactor in

refineries with a neat diagram? Mention the advantages and disadvantage of

fluidized bed reactor.

Answer 1

A fluidized bed reactor or a FBR is a type of reactor that is used in industries to carry out a number of multiphase chemical reactions. In this type of reactor, reactants are passes through solid particles which is generally catalyst and the reactants have enough velocity to suspended solid and make it behave a fluid. That is why this type of reactor is known as fluidized reactor.

Fluidized bed reactor in refinery is known as fluidized catalytic cracking (FCC) unit.

As you can see in the diagram, a FCC unit in a refinery consists of a reactor and a regenerator. Petroleum reactant which is preheated to a high temperature is ejected from the bottom of the reactor into the reactor. The reactant rises into the reactor where it is being vaporized and cracked into smaller fraction by contacting with a very hot powered type substance which is the catalyst. The catalyst rises with the reactant into the reactor while cracking. The cracking takes place within 2-4 seconds into the reactor. Further it is being sent to the reactor part where the catalyst and vapors separates. The catalyst is being sent to a regenerator where the coke deposited on the catalyst is burned off at a very high temperature while the vapors are sent for distillation and separation. The regenerated catalyst again enters the reactor for cracking.

Advantages of fluidized bed reactor

- Uniform mixing takes place because of fluid nature,.

- Because of uniform mixing, there is no hot spot generation, results in uniform temperature gradient within the reactor.

- This type of reactor has the ability to operate in continuous mode.

Disadvantages of fluidized bed reactor

- Since the expansion of particles takes place and solid particle suspends in air, large reactor size is required.

- For suspending the solo catalyst particles, higher velocity is required thus pumping requirements is very high which increases cost.

- Particle entrainment can happen for very fine particles because of high velocity.