A reboiler is a heat exchanger that provides heat to the bottom of a distillation column. There are several types of reboilers including kettle reboilers, thermosyphon reboilers, fired reboilers, and forced circulation reboilers. Kettle reboilers are simple devices where steam flows through tubes in a shell to heat liquid in the shell. Thermosyphon reboilers use density differences to circulate liquid without pumps. Fired reboilers use combustion to heat liquid circulating through tubes. Forced circulation reboilers use pumps to circulate liquid through shell and tube heat exchangers.

1. REBOILER
Figure 1: Schematic diagram of a continuous binary distillation column.
A reboiler is typically a heat exchanger used to provide heat to the bottom of an
industrial distillation column. It boils the liquid from the bottom of a distillation column to
generate vapors which are returned to the column to drive the distillation separation.
Proper reboiler operation is vital to effective distillation. In a typical continuous
distillation column, all the heat required for the distillation is provide by a reboiler.
Figure 1 is a schematic diagram of a typical industrial distillation column separating a
mixture of liquid components into two products using the heat provided by a kettle-type
reboiler.
Types of reboilers
The most critical element of reboiler design is the selection of the proper type of
reboiler for a specific service. Most reboilers are of the shell and tube heat exchanger
type and normally steam is used as the heat source in such reboilers. However, other
heat transfer fluids like hot oil or Dowtherm (TM) may be used. Fuel-fired furnaces may
also be used as reboilers in some cases. Commonly used heat exchanger type
reboilers are:

2. Kettlereboilers
Figure 2 depicts a typical steam-heated kettle reboiler used for heating industrial
distillation columns. Kettle reboilers are very simple and reliable. They may require
pumping of the column bottoms liquid into the kettle, or there may be sufficient liquid
head to deliver the liquid into the reboiler. In this reboiler type, steam flows through
the tube bundle and exits as condensate (i.e., condensed water). The liquid from the
bottom of the tower, commonly called the bottoms, flows through the shell side. There
is a retaining wall or overflow weir separating the tube bundle from the reboiler section
where the residual reboiled liquid (called the bottoms product) is withdrawn, so that the
tube bundle is kept covered with liquid.
Figure 2: A typical steam-heated kettle reboiler used for heating industrial distillation columns.
Thermosyphon reboilers
Figure 3 is a schematic diagram of a steam-heated, horizontal thermosyphon reboiler.
These do not require pumping of the column bottoms liquid into the reboiler. Natural
circulation is obtained by using the density difference between the reboiler inlet column
bottoms liquid and the reboiler outlet liquid-vapor mixture to provide sufficient liquid
head to deliver the tower bottoms into the reboiler. Thermosyphon reboilers are more
complex than kettle reboilers and require more attention from the plant operators.
There are many types of thermosyphon reboilers. They may be vertical or horizontal
and they may also be once-through or recirculating. Some fluids being reboiled may be
temperature-sensitive and, for example, subject to polymerization by contact with high

3. temperature heat transfer tube walls. In such cases, it is best to have a high liquid
recirculation rate to avoid having high tube wall temperatures which would cause
polymerization and, hence, fouling of the tubes.
Figure 3: A typical steam-heated,horizontal thermosyphon reboiler used for heating distillation columns.
Fired reboiler
Fired heaters (furnaces) are sometimes used (for example, in the distilling of crude oil
in petroleum refineries) as reboilers for the heating of large distillation columns. A pump
is required to circulate the column bottoms through the heat transfer tubes in the
furnace's convection and radiant sections.
Figure 4 is a schematic diagram of a fired heater being used in a configuration that
provides recirculation of the column bottoms liquid. However, with some relatively
minor changes inside the bottom section of the distillation column, a fired heater can
also be used in once-through configuration.
Typically, the heat source for a fired heater reboiler may be either fuel gas or fuel oil.
Coal would rarely, if ever, be used as the fuel for a fired heater reboiler because the

4. auxiliary equipment needed would make such a system very costly compared to using
gas or oil as the fuel.
Figure 4: A typical forced recirculation fired heater reboiler used for heating a distillation column.
Forced circulation reboilers
This type of reboiler uses a pump to circulate the column bottoms liquid through the
reboilers. Figure 4 is a schematic diagram of a typical steam-heated forced circulation
reboiler. Although Figure 4 depicts the steam flow as being one-pass through the
exchanger, a two-pass flow system could also be used
It should be noted steam is not the only heat source that can be used. Any available
process stream that is at a high enough temperature could be used for any of the many
shell and tube heat exchanger reboiler types.

5. Figure 5: A typical steam-heated forced circulation exchanger used for heating a distillation column.
References
1. Kister, Henry Z. (1992). Distillation Design, 1st Edition. McGraw-Hill. ISBN 0-07-034909-6.
2. King, C.J. (1980). Separation Processes. McGraw Hill. 0-07-034612-7.
3. Perry, Robert H. and Green, Don W. (2007). Perry's Chemical Engineers' Handbook,8th Edition.
McGraw-Hill. ISBN ISBN 0-07-142294-3.
PRACTICA DE AULA
DISEÑO DE HERVIDOR – VAPORIZADOR
Se quiere diseñar un Calderin de bombeo directo con ebullición isotérmica para
producir 18000 lb/h de vapor de propano a 265 psi usando alimento frío de un
almacenamiento a 80°F. El propano deberá hervir isotérmicamente a 210°F, para lo cual
se dispone de vapor de agua saturado disponible a 80 psig.
Se dispone para el servicio de un intercambiador 1-2 de 151/4 plg DI con 76 tubos de 1
plg DE, 16 BWG y 16’0” de largo, arreglados en cuadro con paso de 12, plg y dos pasos
en los tubos. Los deflectores están espaciados a 6 plg. ¿Qué área de transferencia
necesitará el proceso? ¿qué caída de presión alcanzará el intercambiador?