Types of Reboiler for Distillation Column

 

TYPES OF REBOILER FOR DISTILLATION COLUMN

●  REQUIREMENT OF REBOILER FOR DISTILLATION COLUMN

As we all know that distillation column is used to separate component from mixture. Distillation column is used to contact vapor and liquid due to that mass transfer occurs. Liquid is coming from tray above to tray below and vapor is going to tray above to tray below. Generally, vapor is generated by vaporizing bottom liquid.

Required heat in reboiler is provided by the high-pressure steam or heat transfer oils or some hot fluid available in the plant. For the liquid having high boiling point, generally fuel-fired furnace is used.

·         DIFFERENT TYPES OF REBOILERS USED WITH DISTILLATION COLUMN

Different types of reboilers are used to generate vapours in distillation column are described below:

1.      Jacketed Kettle Reboiler:

      Small Fractionating columns used for the pilot plant; these types of jacketed kettle type reboiler are used. Vapor generated by jacketed kettle is very low.

Construction: Jacket is provided around the distillation column sump to provide sufficient heat to the liquid. Steam or heat transfer oil is supplied in the jacket to provide heat to the liquid. Refer Fig 1.

 

 

 

Fig. 1: Jacketed Kettle Reboiler

 

 

2.      Internal Reboiler:

Internal reboiler provides large heat transfer area compared to the jacket kettle reboiler. We can use floating head type rear head for the tube bundle which will take care of thermal expansion of tubes. But when scaling occurs on the outer surface of the tubes, we need to remove entire tube bundle from the column for the maintenance purpose. Vapour issuing column from jacket kettle and internal reboiler is equilibrium with the residue product. We can consider one stage of distillation column so the required stage will decrease by one. Sometimes these types of reboilers are known as bundle in column reboiler.

Construction: Tube bundle is constructed in the column itself. Inside the tube heating medium is supplied to provide heat to the liquid. Refer Fig 2.

 

 

 

 

Fig. 2: Internal Reboiler

 

3.      Kettle Type Reboiler:

Like jacket kettle and internal reboiler, vapor generated in kettle type reboiler is always in equilibrium with residue product so e can consider kettle type reboiler as one stage.

Construction: this type of reboiler receives liquid from column by gravity and heating medium is circulated inside the tubes. Vapor generated in reboiler is fed back to the column. Liquid coming out from the overflow wear is taken out as residue product. This type of reboiler is generally used with the vacuum distillation column because it provides low pressure drop. Refer Fig 3.

 

 

 

Fig. 3: Kettle Type Reboiler

 

 

4.      Thermosyphon Reboiler:

Vapor generated in this reboiler has the same composition as the liquid entering the reboiler. It is safe to not to consider the thermosyphon reboiler as one stage, instead of that it is safe to provide extra stage in the distillation column itself.

Construction: In vertical thermosyphon reboiler heating medium is fed in shell side and the liquid which is to be vaporised is fed inside the tubes. Refer Fig 4.

 

 

Fig. 4: Vertical Thermosyphon Reboiler

  

External reboilers are used with large distillation columns with the spares for cleaning and maintenance purpose.