Anti-icing options for turbine inlet

Anti-icing mechanisms are generally used on gas turbine inlets when the air temperature is between -5 to 5°C and the relative humidity is above 70%. Icing on the filter is also influenced by the velocity of air.

Icing on the filters raises the pressure drop of the system, diminishing the power output and can lead to the turbine shutting down. As pressure drop increases, turbine efficiency and power output drops. A differential of 100 Pa (0.40’’ water) lowers power output by 0.2% and raise fuel consumption by 0.1%. Raising the inlet air temperature also diminished the risk of ice formation in the turbine bell mouth. Icing in the compressor could damages the turbine internals.      

Pulse filter media velocities are usually lower than static filter media velocities and the pulsing mechanism helps dislodging the snow and ice. This can diminish the requirement for anti-icing protection on the filter, but won't help for the risk on the turbine bellmouth.

In order to offer a viable defence against static filter icing inlet, air must be heated by at least 7-8°C. There are usually various ways of achieving this depending on the situation:

Anti-icing by mixing the ambient air with hot air 

The hot air can be taken from: 

  • hot air from the gas generator compressor bleed. In this case, hot air is sent through pipes from the compressor bleed into a reservoir tank, and is distributed through anti-icing nozzle in the opposite direction of the air flow. Taking hot air from the compressor affects the turbine output, usually to a maximum of 2%. This type of system can be offered silent to meet noise reduction requirement. 
  • hot air from the GT enclosure cooling air exhaust.  Here, ducting brings the hot air in front of the filter and it’s distributed through the ducting.  A bypass damper is installed to redirect the air when the anti-icing is not required, per example in the summer. 

Anti-icing with a steam or hot water coil 

Using an inlet heat exchanger upstream of filters can also been done with a coil if there is steam or hot water available or with glycol if another source of heat available close by. As this system obstructs the air flow, it has the inconvenience of adding permanent pressure drop to the system.

Anti-icing with electric resistance

Using electric resistance heating upstream of filters – usually consisting of tightly pack of aluminum fins or other conductive material. As with above, this also adds permanent pressure drop to the system.

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