HEATEC BULLETINProduct news from Heatec Inc., an Astec
Industries Company 5200 Wilson Road, Chattanooga, TN 37410
423-821-5200 800-235-5200 Heatec.com
March 2010
Choosing a heating system for fuel gasThis power generation
facility heats natural gas with a combination Heatec thermal fluid
heater and heat exchanger
through the coil and carries the heat to the heating tubes
inside a nearby heat exchanger.
The fuel gas flows through the shell of the heat exchanger where
it is heated by its heating tubes. The thermal fluid circulates
continuously through the heater and heat ex-changer tubes.
Water bath heaters are usually limited in size, ranging from
about 0.5 to 9 million Btu/hour. But thermal fluid heaters range
from 0.5 million to 70 million Btu/hour. So heating capacity could
be the deciding factor. However, when both systems offer suitable
sizes, it is appropriate to look closely at the advantages of both
systems.
Initially, a water bath heater will usually cost less than a
combination thermal fluid heater and heat exchanger of comparable
heating capacity. The water bath heater is usually a much simpler
heater. It doesnt need a pump or a three-way control valve. And it
may use either a natural
The choice of a heating system for heating fuel gas often
narrows down to one of two systems:
1. A water bath heater or2. A combination of a thermal fluid
heater and heat
exchanger
A water bath heater typically consists of a shell that con-tains
a fire tube and serpentine heating coil. A burner is mounted on one
end of the fire tube, which doubles back to an exhaust stack. The
shell is filled with a solution of water-glycol, which is heated by
the fire tube. The heated solution heats the serpentine coil and
the product that flows through it.
A typical thermal fluid heater consists of a shell that
con-tains a helical coil. A burner is mounted on one end of the
shell and fires through the helical coil. The burner heats the coil
directly with its hot gases, which double back to an exhaust stack.
Thermal fluid, (water-glycol) is pumped
BAFFLES
FLOW OFGAS
SHELL SIDEGAS INLET
THERMAL FLUID OUT
OUTLETPLENUM
INLETPLENUM
THERMAL FLUID IN
TUBE SHEET
FLOW OF THERMAL FLUID
SHELL TUBE BUNDLE
SHELL SIDEGAS OUTLET
HEAT EXCHANGER
draft burner or a forced-draft burner. But despite these
advantages a combination thermal fluid heater and heat exchanger
may be a better choice.
A combination thermal fluid heater and heat exchanger has many
important advantages:
Higher thermal efficiency Lower emissions Lower liquid volume
Faster reaction time Better temperature control Easier to maintain
Longer heater life Closed system eliminates frequent refilling
The thermal efficiency of a thermal fluid heater is usu-ally
about 15 percent higher than a water bath heater. The higher
efficiency results in significantly less fuel usage.
The thermal fluid heater has lower emissions because of its
higher thermal efficiency.
The thermal fluid heater system uses less liquid and has faster
fluid velocity than a water bath heater. Consequently reaction time
is faster and provides better temperature con-trol. And there is
less liquid to maintain.
The heating bundle in the heat exchanger used with the thermal
fluid heater is much easier to replace than the coil inside a water
bath heater. It also costs less than the coil in the water bath
heater. The helical coil in the thermal fluid heater rarely
requires maintenance.
Components of the thermal fluid heater and the heat ex-changer
are subjected to somewhat lower temperatures than the fire tube of
a water bath heater. Consequently they will last longer.
The water bath heater is an open system that is subject to
evaporation. Accordingly it requires routine additions of
water-glycol solution. The thermal fluid system is a closed system
that rarely requires additions of fluid.
We offer both types of systems in order to satisfy customer
preferences.
Actually, the heating systems discussed above are only two of
many types of heating systems that we offer. We provide heating
systems for numerous applications and industries.
Publication 3-10-231 Heatec, Inc, 2010
HEATEC,INC. an Astec Industries Company5200 WILSON RD
CHATTANOOGA, TN 37410 USA 800.235.5200 FAX 423.821.7673
heatec.com
EXPANSION CHAMBER
BURNER WITH BLOWER*
FIRE TUBE
HEATER SHELL
EXHAUST STACK
SERPENTINE COIL
AQUATEC WATER-BATH HEATER
GAS INLET
GAS OUTLET
*NOTE: NATURAL DRAFT BURNERS ARE NON-MODULATING AND HAVE NO
BLOWER
