Magnetrol® has recently released a new white paper on level instrumentation for the steam generation and condensate recovery cycle. This blog post, part of a series based on this white paper, will discuss how to reduce inefficiencies in deaerators and heat exchangers.
Deaerator Functions
The deaerator serves as an “open” type heat exchanger with its primary function being the removal of oxygen and other corrosive gases from the boiler feedwater. This is accomplished using steam, which can give up about 970 Btu per pound, to support the deaeration process as well as preheat boiler feedwater.
Any appreciable gain in boiler feedwater achieved through the process reduces the amount of energy (fuel) required at the boiler— in fact, every 10.8°F (6°C) rise in boiler feedwater amounts to a one percent savings in fuel cost. Inadequate level controls can inhibit the deaeration process (level too high) or reduce/shutdown feedwater flow to the boiler (level too low). The former affects hardware longevity and efficiency, while the latter risks production losses and possible damage to pumps.
In addition to the “open” or deaerating feedwater heater, the more common shell and tube heat exchangers/condensers can be found in larger scale steam generation cycles where their costs are offset by gains in thermal efficiency. The effectiveness of a shell and tube heat exchanger in transferring energy is contingent, barring hardware anomalies, on accurate level control.
Level Measurement Solutions
For more accurate measurement in deaerators, guided wave radar (GWR) is a preferred option. Since its performance and accuracy are not contingent on the specific gravity and/or inference, it can provide reliable measurements in all situations, including the difficult and turbulent process conditions of deaerators and feedwater heaters. In addition, GWR does not require external inputs or calibration to achieve specified performance. This effectively eliminates the introduction of errors during the calibration process or from external sources, i.e., pressure and temperature. With this high level of accuracy, operators can trust that their deaerators will be well controlled. MAGNETROL’s own GWR transmitter, the Eclipse® Model 706, also comes with probe options to further customize the instrumentation for the nuances of each specific application.
