Level Measurement Solutions for Blowdown

An important part of steam generation is the quality of the steam generated. Maintaining water quality in the boiler within design parameters ensures the highest quality steam possible while minimizing blowdown of the boiler, both of which improve energy and resource management.

Continuous or manual blowdown of the boiler minimizes scale accumulation and corrosion resulting from impurities in the water. The blowdown provides a means of accommodating liquid and impurities from the boiler, with the latter facilitating energy recovery through the use of flash steam.

Level Measurement Considerations

Taking advantage of a specific technology’s ability to reliably address the level measurement in either of these vessels, especially the blowdown flash tank, in a plug-and-play type installation and commissioning format is an easy way to ensure optimal performance. This forgoes calibration, external hardware or inputs.

Estimates of up to 49 percent of the energy can be recovered through the use of flash steam routed to heat exchangers or the deaerator to preheat boiler makeup water or support the deaeration process, respectively. In addition, better level control technology at the boiler side eliminates energy losses resulting from unnecessary blowdown to prevent carryover conditions.

The performance of any level technology relative to instrument induced errors, calibration nuances, and vulnerabilities to process dynamics can have an immediate and adverse impact on fuel consumption. Seamless response to changes in demand and reducing maintenance associated with the instrumentation or damage to hardware are residual benefits that have their own financial ramifications; these aspects should also be considered when implementing any technology.

Level Measurement Solutions for Deaerators

With proper level control and instrumentation, every part of the steam generation cycle can be managed for optimal efficiency. 

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.

deaerators

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, magnetrol 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.