Use a Vent Condenser to Recover Flash Steam Energy

When the pressure of saturated condensate is reduced, a portion of the liquid "flashes" to low pressure steam. Depending on the pressures involved, the flash steam contains approximately 10% to 40% of the energy content of the original condensate. In most cases, including condensate receivers and deaerators, the flashing steam is vented and its energy content lost. To preserve the energy content lost in venting the flashed steam, a heat exchanger can be placed in the vent to recover this energy. The following table indicates the energy content of flash steam at atmospheric pressure. (Source: US Department of Energy)

Energy Recovery Potential of a Vent Condenser
Pipe Diameter (Inches)	Energy Content, MMBtu/year*
	Steam Velocity, feet/min
	200	300	400	500	600
2	90	140	185	230	280
4	370	555	740	925	1,110
6	835	1,250	1,665	2,085	2,500
10	2,315	3,470	4,630	5,875	6,945

* Assumes continuous operation, 70° F makeup water, and condensed steam at 100° F.

Example
Consider a vent pipe with the following conditions:

Velocity of flash steam:	_300 feet per minute
Diameter of vent pipe:	_4 inches
Hours of operation:	_8,000 hours per year (hr/yr)
Boiler efficiency:	_80%
Cost of fuel:	_US $8.00 per million Btu ($8.00/MMBtu)

Download the original US Department of Energy PDF document.

A vent condenser could condense the flash steam, transfer its thermal energy to incoming makeup water, and then return it to the boiler. Energy is recovered in two forms: hotter makeup water and clean, distilled condensate ready for productive use in your operation.

Referring to the table above, the potential energy recovered from the flashed steam is 555 MMBtu, based on 8,760 hours of annual operation. Correct this value for actual operating hours and boiler efficiency:

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Valutech supplies a wide range of steam specialty equipment including steam traps, boiler controls, clean steam generators and steam control valves. We conduct steam trap surveys to ensure that you minimise steam loss thus conserving valuable energy.

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The MK Series is a membrane thermostatic steam trap suitable for steam pressures up to 320 PSIG. The MK series features the unique membrane regulator capsule, which provides a very sensitive response characteristic and an excellent regulating accuracy throughout its operating range. More >>

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