Historical Solutions
HISTORICAL SOLUTIONS
Inlet air mass density is crucial to increasing maximum gas turbine performance. Conventional cooling techniques, such as evaporative cooling and fogging, increase the moisture content of the inlet air, preventing maximum air mass density and thereby diminishing the effectiveness of inlet air cooling on the gas turbine.
Direct Evaporative Cooling - Direct Evaporative Cooling works by allowing inlet air to pass through wetted media.
- In this process, moisture evaporates and cools in the inlet air.
- Consequently, the direct evaporative process introduces moisture into the inlet air.
- The moisture limits the density reduction of the inlet air, reducing mass flow into the gas turbine, reducing overall output.
Fogging - Fogging cools air by injecting a fine mist of de-ionized water into the inlet air stream.
- Evaporation of the water cools the inlet air temperature.
- Similar in concept to direct evaporative cooling, fogging introduces moisture limiting the density reduction of the inlet air, reducing mass flow into the gas turbine, reducing its overall output.
- Fogging can introduce non-evaporated water droplets into the turbine inlet, with the potential to damage the compressor.
- Special de-ionized water treatment is required in fogging systems to prevent mineral carryover.
- It is well known that de-ionized water is aggressive on equipment.
- Compressor degradation and failure associated with over-fogging can limit its application with many combustion turbine manufacturers.
Refrigeration - Refrigeration achieves greater inlet air cooling than direct evaporative and fogging techniques.
- Refrigeration cools without introducing moisture into the air stream, allowing for denser inlet air.
- However, it requires high power off-takes, or parasitic loads, that lead to higher overall heat rates.
- Direct refrigeration is a complex system that needs cooling towers, multiple pumps and piping, constant water conditioning, and often results in higher maintenance costs.
- A cooling coil required for direct refrigeration systems results in higher pressure drops.
