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Types of Reboilers

Reboilers are heat exchangers that provide heat to the bottom of distillation towers. There are three main types of reboilers: kettle reboilers, which have a pool of boiling liquid on a tube bundle; thermosyphon reboilers, which use density differences to circulate liquid either vertically or horizontally; and forced circulation reboilers, where the fluid is pumped through the exchanger. Kettle reboilers are the simplest design but thermosyphons and forced circulation reboilers offer more operational flexibility. Effective reboiler operation is essential for distillation to separate components by vaporizing the liquid stream from the column bottom.

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468 views12 pages

Types of Reboilers

Reboilers are heat exchangers that provide heat to the bottom of distillation towers. There are three main types of reboilers: kettle reboilers, which have a pool of boiling liquid on a tube bundle; thermosyphon reboilers, which use density differences to circulate liquid either vertically or horizontally; and forced circulation reboilers, where the fluid is pumped through the exchanger. Kettle reboilers are the simplest design but thermosyphons and forced circulation reboilers offer more operational flexibility. Effective reboiler operation is essential for distillation to separate components by vaporizing the liquid stream from the column bottom.

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Ruchit Patel
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TYPES OF REBOILERS

PROCESS DESIGN OF REBOILERS


Reboilers are usually heat exchangers used to provide
heat to the bottom of industrial distillation towers.
Design correlations for reboilers and vaporizers are
same. In a reboiler, part of liquid is vaporized while in
a vaporizer the entire feed of liquid is vaporized.
Effective reboiler operation is essential for effective
distillation. In a typical distillation column, all the
steam leading to the separation comes from the
reboiler. The reboiler can receive a liquid stream from
the column bottom and vaporize the stream partially
or completely. Steam generally provides the heat
needed for evaporation.
TYPES OF REBOILERS

Kettle Reboiler
Thermosyphon Reboiler (horizontal and
vertical)
Forced circulation Reboiler
Kettle Reboiler
KETTLE REBOILER
* Kettle reboilers are the easiest type of reboiler design
you could use for your distillation process. A kettle
reboiler is designed to allow a heating fluid to pass
through tubes that are covered in the liquid you want
to be distilled.
* They hold a boiling liquid pool on a tube bundle, either
by level or use of an internal overflow weir.
* In this type of reboiler, heating surface is immersed in
the pool of liquid and pool boiling of liquid takes place.
* Boiling fluid side pressure drop is negligible, hence it is
preferred with high vacuum distillation column.
THERMOSYPHON REBOILER
✔ A more complex type of reboiler is the thermosyphon, which comes in
two primary types: vertical and horizontal. The type of thermosyphon
that is used will depend on the orientation of the heating fluid tubes
and the flow of the liquid.

✔ Density difference between the inlet liquid and the outlet vapor/liquid
mixture drives the liquid. Vertical types may have the vaporization on
either the tube-side, which is most common, or shell-side. Horizontal
types nearly always have boiling on the shell-side. Systems can be
once-through or include recirculation (recycle of liquid in the outlet).
Recirculation allows for higher total vapor output at a low vaporization
fraction on each pass. Vertical thermosyphons in vacuum services
often suffer from boiling point suppression due to static head.
Horizontal Thermosyphon reboiler :
Horizontal Thermosyphon reboiler

• The process fluid is on the shell side and heating medium is on the
tube side
• A mixture of vapor and liquid leaves the reboiler and enters the
base of the column, where it separates
• It has high circulation ratios and lower vaporization fractions
• Less susceptible to fouling
VERTICAL THERMOSYPHON REBOILER
VERTICAL THERMOSYPHON REBOILER

* Boiling liquid usually flows through the tubes


* Heating medium on the outside of the tubes
* It has high heat transfer coefficients
FORCED CIRCULATION REBOILERS

The fluid is pumped through the exchanger and the vapor


formed is separated in the base of the column.
Forced circulation reboilers offers greater operational
flexibility than thermosyphon reboilers but at a higher
operating cost.
REFERENCE

* Sinnott, R. K. Coulson & Richardson’s Chemical


engineering, Vol 6, 3/e. Oxford: Butterworth
Heinemann, 2003.

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