For power plants located in moisture-rich environments, such as coastal locations, high levels of humidity, rain, fog, mist and sand can damage and impair the performance of the gas turbine. Coalescers are installed to remove moisture and liquid phase corrosives from the airstream — protecting the downstream filters and the turbine. In this blog, we will look at the coalescing process, issues with today's coalescers, and explore the effectiveness of a new coalescer technology.
This white paper, "Improving Filter Life in Harsh Environments", details comprehensive field tests conducted to test the effectiveness of a new coalescer technology designed to improve filter performance and protect gas turbines. Download now.
Coalescers remove moisture by agglomerating water droplets, making them larger and heavier. This allows a large proportion of the droplets to drain away rather than continue in the airstream, which helps avoid these two problems:
1. Small liquid droplets allowed to travel downstream can become embedded between the pleats of the filter (pleated filters are the current standard design for high-efficiency filter products). This impediment to the air can lead to differential pressure spikes. This can lead to an accelerated differential pressure increase in certain conditions such as fog, causing gas turbine alarm and trip levels to be reached quickly.
2. Small liquid droplets can also form mud caused by:
In either case—and especially with mud—it is common to see a differential pressure spike.
Unfortunately, the use of a compressed air pulsing system has a limited effect. The system would have to exceed normal operating limits to obtain the inertial forces required to overcome the surface and frictional effects present and adequately remove the embedded liquid and/or sticky dust.
Historically, coalescer media has been similar to what is used in dust filtration. Thus, they naturally capture dust in addition to liquid, which can result in block up, differential pressure increase and, in high-dust environments, three other problems:
For example, in a typical, self-cleaning filter house, the high-efficiency cartridge filters are protected from the elements by weather hoods. (see figure to the left). This arrangement provides basic protection only against big, heavy rain droplets. It does not protect filters against exposure to fine and light fog droplets. Exposure of the filter elements to fine water particles in the form of fog leads to wet filters and reduced filter life, manifested as high differential pressure across the filters and/or the gas turbine alarm being reached. If the high-efficiency filter is not hydrophobic (not moisture repellent), moisture droplets (potentially containing salts) will leach through the filters resulting in:
Coalescers on the market today exhibit problems such as:
Whether the trouble stems from dust, fog or sand, power plants operating in harsh environments need an effective solution with coalescers to protect both the life of the high-efficiency filters and the performance of the gas turbine. The clearcurrent TS1000 coalescer panel filter from Parker, for example, uses a new technology to provide fine mist/fog removal effectiveness combined with significantly low dust removal efficiency.
Unlike traditional coalescers, the TS1000 coalescer panel uses 100 percent synthetic high-performance woven mesh that catches small liquid droplets, combines them with larger ones, then drops them out of the airstream while allowing bypass of sand and dust particles.
“The clearcurrent TS1000 has excellent fine mist/fog removal effectiveness with significantly low dust removal efficiency ... It provides superb performance during the fog season with low risk of clogging during a sand storm. In the end, it requires much less attention from the operator and helps reduce the maintenance to a minimum.”
— Tim Nicholas, powergen market manager, Parker Hannifin
Other features and benefits include:
Three comprehensive field tests were conducted to demonstrate the effectiveness of the TS1000 over competitive coalescers. The results showed the clearcurrent TS1000 coalescer panel filter went about three times longer than other products tested before needing to be cleaned, and when it did need cleaning, the work was quicker and extended the life of the coalescer for up to 12 months.
The clearcurrent TS1000 coalescer panel filter helps maintain gas turbine inlet air quality, whether the harsh environment produces dust, fog or sand. Not only does it improve the overall coalescing performance, but it also delivers low pressure drop, requires low maintenance and extends service life to achieve better gas turbine operation.
To see the detailed field test data, download the full white paper "Improving Filter Life in Harsh Environments: Reducing Maintenance Costs, Extending Filter Life and Delivering Better Performance for Gas Turbines".
This post was contributed by Tim Nicholas, powergen market manager, Parker Gas Turbine Filtration Division.