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 doesn’t 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 Company

5200 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