Fluidized Bed Reactor Design: Diagram, Parameters, Applications, Advantages and Disadvantages

In this article, the topic named “Fluidized bed reactor design” and fluidized bed reactor design related facts such as, Design, Diagram, Parameters and Applications, will be summarize.

The fluidized bed reactor is a classification of reactor device which is mainly carry out a wide range of multiphase chemical reactions. In the fluidized bed reactor a fluid substance which can be stay at liquid or gaseous state is go through at a high speed by a solid granular material. The procedure terms as fluidization.

In various applications of industrial fields fluidized bed reactor is used.

Fluidized bed reactor diagram:

Fluidized-bed reactors are the most popular reactor configurations employed for reactions involving solid reactants. In the FBR, a fluidization medium (gas or liquid) is passed through the bed of solid reactants at high enough velocities to suspend the solid and cause it to behave like a fluid.

The diagram of the Fluidized bed reactor is given below,

• The fluidized bed reactor is a classification of reactor device which is mainly carry out a wide range of multi phase chemical reactions.
• In the fluidized bed reactor a fluid substance which can be stay at liquid or gaseous state is go through at a high speed by a solid granular material.
• The procedure terms as fluidization, notify principally important favor to the fluidized bed reactor.
•  In various applications of industrial fields Fluidized bed reactor is used.
• Fluidized bed reactor is widely used in the commercial scale to laboratory.
• Inside the fluidized bed reactor when the velocity of the fluid on the substance of the solid is increases the bed reactor go up to a period where the fluid force is suitable to adjust balancing the weight of the solid substance. The period of the process is identified as incipient fluidization and happened at the lowest velocity of the fluidization.
• In the coal gasification the fluidized bed reactor is used first.

Fluidized bed reactor design parameters:

The parameters which are depend upon the Fluidized bed reactor are listed below,

• Rate of reaction
• Mass transport rate
• Bubble residence time

Mechanical design of fluidized bed reactor:

With the help of Navier – Stroke equation the behaviour of the fluidization of a solid particle can be deriving. Fluidization is appear in the case of the fluid is flow in upward direction and used to mobilized and eliminate solid particle.

Three key equations used in fluidization prior of building and designing the project which is included to the terminal velocity of spherical particle as well as fluidization velocity based off of the particle’s Reynolds number.

The terminal velocity of a spherical particle can be expressed by this equation,

v_max = (πr²)* d² x (ρ_solid – ρ_fluid) *g / 18*μ_fluid

The fluidization velocity of a particle with a Reynolds number less than 20 can be expressed by this equation,

V_min = (πr²)* d² x (ρ_solid – ρ_fluid) *g*∈³*φ/150*μ_fluid*(1-∈)

The fluidization velocity of a particle with a Reynolds number more than 1000 can be expressed by this equation,

Where,

is denoted the Flow rate of the fluid

r = is denoted the radius of the particle which is flowing in the fluid and value is 10 millimetre

d = is denoted the diameter of the particle which is flowing in the fluid and value is 0.15 millimetre

ρ_solid = is denoted the density of the particle which are flowing in the fluid and value is 1.5 kilogram per cubic meter

ρ_fluid is denoted the density of the flowing fluid and value is 1.2 kilogram per cubic meter

g is denoted the Gravity and value is 9.81 meter per square second.

μ is denoted the viscosity of the flowing fluid and value is 1.8 Pascal second.

φ is denoted the sphericity which is flowing in the fluid of the particle and value is 1.0.

Fluidized bed reactor applications:

In the waste water preparation Fluidized bed reactor widely used.

Waste water preparation:-

• In the waste water preparation the fluidized bed reactor is used for this reason the cost can be minimize and represent as cost effective preparation for the waste water which containing recalcitrant pollutants (The mixture which is bio gradable or non biodegradable in a slow process which identified as, recalcitrant mixture and group from facile halogenated hydrocarbons to complicated polymers.)
• The fluidized bed reactor is widely used in the waste water preparation although in the large scale industrial field the fluidized bed reactor is used for the advanced oxidation method and also in the laboratory.
• In the fluidized catalytic cracking fluidized bed reactor is used which is introduced in the 1940s.
• Anaerobic fluidized bed reactor in modern generation used as anaerobic platform to achieve high strength and also for the high solid waste streams like corn ethanol thin stillage and sludge of the municipalities.

Fluidized bed reactor advantages:

The advantages of the fluidized bed reactor is listed below,

• Mixing of the particles is uniformly
• Uniform Temperature gradient
• Ability to perform the reactor even in the continuous state

Mixing of the particles is uniformly:-

For behave like intrinsic fluid in the solid material the fluidized bed could not getting bad experience for the mixing in the packed beds. The complete and fine mixing in the fluidized bed is allow to make a uniform product that is not easy to achieve so easily in the other designs of the reactor. The deduction of the axial and radial concentration gradients even accommodate for better fluid solid contact, which is needed for the quality and reaction efficiency.

Uniform Temperature gradient:-

A lot of range of chemical reaction needed addition of heat or removal of heat. Local hot spot or cold spot beneath the reaction bed, at every turn a difficulty is packed beds, are avoided in a fluidized bed like as fluidized bed reactor.

In another classification of reactor, the difference of the local temperature mainly in the hotspot can make as a result of product degradation.

For this particular reason the fluidized bed reactor is appropriate for exothermic reaction. Observers are also observed that the bed to surface heat transfer coefficient for the fluidized bed reactor is higher.

Ability to perform the reactor even in the continuous state:-

The fluidized bed character of these reactors is to accommodate for the efficiency to continuously pick off product and establish new reactants into the reaction vessel.

Actions of a continuous method situation give away manufacturers to produce several of products more efficiently due to the elimination of startup situations in batch methods.

Fluidized bed reactor disadvantages:

The disadvantages of the fluidized bed reactor is listed below,

• The size of the reactor vessel is increases
• Pressure drop and pumping is needed
• Particle entrainment
• Pressure loss scenarios

The size of the reactor vessel is increases:-

In the fluidized bed reactor the materials are expand in the reactor for this reason a large size reactor vessel is needed than for a packed bed reactor. The size of the reactor vessel large means need to spend more initial cost. The fluidized bed reactor became very expensive.

Pressure drop and pumping is needed:-

The necessity for the fluid to break the material which stays at solid state requires that a higher fluid velocity is present in the reactor of the fluidized bed reactor.

For this particular reason, more pumping power is required and also higher energy costs needed. In addition, the pressure drop is attached with the deep beds thus also requires additional power of the pumping.

Particle entrainment:-

The high gas velocities present in this style of reactor often result in fine particles becoming entrained in the fluid. These captured particles are then carried out of the reactor with the fluid, where they must be separated.

This can be a very difficult and expensive problem to address depending on the design and function of the reactor. This may often continue to be a problem even with other entrainment reducing technologies.

Pressure loss scenarios:-

If fluidization pressure is suddenly lost, because the area of the bed surface may be suddenly start to reduced. This can either be an inconvenience like making bed restart difficult, or may have more serious implications, such as runaway reactions.

The other disadvantages of the fluidized bed reactor are,

• Lack of current understanding
• Erosion of internal components

Fluidized bed reactor working principle:

The purpose of the fluidization is to keep the solid particles floating in a direction of upward in a flow of liquid or gas. In freezing, the process of fluidization is occur when the same size and shape of particles are subjected to an upward stream of low temperature air.

The working principle of fluidized bed reactor is describe below,

• The fluidized bed reactor is mainly working in the flow of co – current.
• In general the Fluidized bed reactor three different types of particles are used,
• a. Inert core in which the biomass is created by the help of the cell attachment.
• b. Cell aggregates.
• c. Porous particles, in which generally the bio catalyst is soaked.
• The solid layers refer to the catalytic material in which the chemical reactors are reacted in the fluidized bed reactor adopted by the porous plate which term identified as distributor.
• In the next step the fluid is forced by the distributor thus the solid catalytic material can goes up.
• Inside the fluidized bed reactor when the velocity of the fluid on the substance of the solid is increases the bed reactor go up to a period where the fluid force is suitable to adjust balancing the weight of the solid substance. The period of the process is identified as incipient fluidization and happened at the lowest velocity of the fluidization.
• When the lowest velocity is passed away the volume of the reactor bed is spread and twisted more than like a boiling bowl of water or an agitated tank. The reactor is now placed in the fluidized bed.
• A bed which is filled with the immobilized enzymes is fluidized with the quick flow of the secondary fluid steam or upward direction flow of layer or mixing with a liquid.
• Depend on the condition of the operation and the characteristics of the solid phase a wide range of flow regimes can be noticed in the fluidized bed reactor.

Conclusion:

The fluidized bed reactor is used in a wide range of the material processing industrial fields where a good amount of heat and mass transfer is needed in between the particles and mass. The energy is provided in the fluidized bed reactor from the warm gas which one also fluidizes the bed.