Many regions of the world are experiencing ever-growing demand for electricity, and at the same time, permitted emissions from power plants have been reduced to meet air quality standards. Fossil fuel power plants are a source of CO2, which is one of the greenhouse gases that is regulated and of global concern due to its impact on climate change. The burning of coal, an abundant fuel resource in many of the worlds’ developing regions, produces CO2 – but coal is likely to remain a dominant fuel source for electricity generation in many countries for years to come.

Because of this, power generators have invested heavily in technologies that produce power more efficiently with fewer emissions. Plants that operate supercritical and ultra-supercritical boilers operate at higher temperatures and pressures than traditional utilities, using supercritical steam to increase plant efficiency and reduce greenhouse gases produced per unit of power generated. Supercritical coal-fired power plants with efficiencies of at least 45 percent have much lower emissions than subcritical plants. Globally, more than 400 supercritical plants are in operation.

Challenge

Supercritical plants operate at pressures over 3,200 psi (220 kPa) and temperatures over 1,000 F (538 C). Because of these high pressures and temperatures, a supercritical power plant must use more expensive turbines, once-through boilers, higher temperature/strength alloys for equipment, and comingle boiler water and steam into the same fluid stream.

Supercritical and ultra-supercritical plants use a one-through design with only one water-steam loop in the system. This means that any contaminant that enters gets recirculated throughout, so feedwater purity is extremely important as it can be a potential source of contaminants. Sliding loads can mean more corrosion in system elements, so corrosion monitoring also is important.

...Relying on standard sample conditioning solutions rated only for normal conditions can result in safety factors less than normally accepted under sound engineering practice.

Because pressures and temperatures in supercritical and ultra-supercritical plants exceed the ratings of many commercially available sample coolers used in steam and water sample conditioning and analysis systems, relying on standard sample conditioning solutions rated only for normal conditions can result in safety factors less than normally accepted under sound engineering practice.

Solution

For one supercritical power plant customer in Poland, a unique Sentry® sample cooler was designed with a rating that exceeded most common specifications for supercritical steam and water sampling. The right solution for maintaining safety and efficiency was created through detailed customer application design reviews and using careful material selection.

The sample coolers were made from Alloy 625 seamless tube, which can withstand the stress of elevated temperatures and pressures needed to be rated for supercritical and ultra-supercritical applications. The effort put into the sample cooler design then was applied to the other critical, high consequence sample conditioning components.

Other recommendations for this customer included:

• Mandated secondary sample cooling
• Sentry DCCP degassed cation conductivity panel for cycle chemistry validation to lower masking effects of CO2

• A Sentry CPS corrosion sampler for monitoring corrosion particulate and ionic matter circulating in condensate/feedwater systems

We also can design and manufacture sample cooler models to meet ultra-supercritical power plant applications with even higher pressure and temperature ratings to 1150°F at 5175 psig (621°C at 356 barg).

Learn more about our sample cooler solutions for supercritical and ultra-supercritical power plants.