It´s again the time of the year when many power plants are struggling with freezing and poor performance of their filters. Let´s have a quick look at what is causing these problems and what solutions you may use to avoid them.
Typically, freezing is detected in power plants as the increase of filter dp causes direct power loss of a Gas Turbine (GT). In the worst case, the freezing of filters may be causing limitations of GT output due to restricted compressor air flow. Some GT´s have a bleed heating system redirecting part of the compressor hot air flow back to the inlet duct, while other GT´s only have high dp protection by shutting down a GT altogether.
As temperatures drop the humidity decreases, the icing problem is actually present within a narrow window of ambient conditions. This is not good news for a plant located north enough and close to the open sea. Luckily, understanding the root cause makes it easier to protect your GT against freezing.
Not all materials are as vulnerable to freezing. Plant managers know that to be running effectively in freezing conditions, plants should avoid using cellulose as filtration material and instead use synthetic materials. Cellulose as a material is absorbing moisture and when subjected to freezing conditions icing will block the pores of the material. Synthetic materials with woven like material structure are not as vulnerable to icing.
The phasing of filtration will also help to cope with icing issues. Thick and course pre-filters have wider material structure and hydrophobic material properties can eliminate most of the moisture without freezing problems. Moreover, fine and EPA filters need to have similar material properties to make the combination work under freezing conditions, and thus thin film filtration solutions should be avoided in such ice-cold environments.
In worst conditions still there is the last resort, which is to use heating before prefilters. Heating can be achieved with hot water running in riveted coils or with infrared heating. Hot water coils require more maintenance as they should be stand-alone systems, with non-freezing media (like glygol) with controls, pumps, valves. But if you have loss grade heat available, running costs can be relatively low.
Infrared heating only requires a light installation in the inlet duct but also requires an electrical feed and may be limited by the available capacity of the current transformer.
In some environments, we know that many plant managers accept freezing as a fact of life, and therefor also accept losses from freezing as a fact too. As this very short article states though, there are ways to combat freezing that are available in the market today.
If you are experiencing freezing problems with your current filtration system I hope this article might help guide you a little bit along the way to solving the problem. Solutions exist, but you can always just ask your friendly filter sales guy for advice too.
I’ll let you decide.
William Ruthin katu 1 / 48600 Kotka / Finland