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Inlet Bleed Heating Protects Your Compressor

If you are using a gas turbine as a source of electrical energy for your plant, it is important to learn how to optimize its operations. While you might not have all the technical background to understand the complex workings of a gas turbine, it is imperative to get some background into how different components in the system work together to power your plant. More importantly, you need to understand how best to improve the compressor in the gas turbine. Not only to extend its life but also save energy. Energy efficiency is a great concern in a world where most energy sources are getting depleted.

inlet bleed heating - compressor

Inlet Bleed Heating

This is where the issue of inlet bleed heating (IBH) comes in. The air drawn off the axial compressor is regularly referred to as bleed air. If it is re-circulated to the axial compressor, it will heat the inlet air and this is where the term inlet bleed air originates from. Away from the definitions, it is crucial to understand the importance of inlet bleed heating and how it protects your compressor.

When operating a gas turbine with reduced minimum Inlet Guide Vane (IGV) settings, you can extend the premix operating from 75% Base load to around 50% Base load. By reducing the minimum Inlet Guide Vane angle, the combustor can operate at a firing temperature that is high enough to allow premix operation.

When operating with reduced IGV angles, inlet bleed heating (IBH) is necessary. IBH protects the compressor from stalling as it relieves discharge pressure. It also increases inlet air temperatures again protecting the compressor.

This is why you should invest in an inlet bleed heat system not only to ensure a longer life of the turbine but also optimize operations. The system works by regulating compressor discharge bleed flow into a manifold situated in the compressor’s inlet air stream. This is done through the control valve, which regulates inlet heating air depending on the IGV angle. The inlet bleed flow is controlled to a maximum 5% of the entire compressor discharge flow at minimum IGV angles. With increase in the IGV angle opening, the inlet bleed flow decreases up to shutoff.

It is important to keep track of the command set point by the IBH control valve. If there is a variation between the command set point from the actual valve position, an alarm goes off to notify the operator. The role of the IBH system is to monitor temperature rise, which is an indicator of bleed flow. Feel free to contact us if you still have a question about Inlet Bleed Heating.