Discussion on energy saving through variable frequency speed control of refrigerant compressors
Thread Content
Dear experts, various process packages for LNG are currently available. The refrigerant compressor is generally the load with the highest power consumption. If variable frequency speed control is used for this compressor in the process, can it help save energy? And how should it be implemented? I’ve done it before; we can discuss it!
Why isn’t anyone answering? Have you never been in contact with it, or?
Changing the frequency of the compressor can certainly save energy. The problem is that the allowable range of variations in the design operating conditions for LNG plants is quite limited; so is it still necessary to use variable-frequency drives for the refrigeration compressors?
We don’t use variable frequency technology; our power consumption doesn’t increase when we’re operating at full load
In my opinion, does the operating point of a refrigeration compressor change frequently? If the operating point remains stable, then it makes no sense for an inverter to be used to save energy. If the operating point changes frequently, the frequency converter may provide energy-saving benefits. The use of an inverter is not primarily a energy-saving feature, but rather a change in the operating point of the compressor.
Is your refrigerant compressor centrifugal or reciprocating? Centrifugal compressors use inlet guide vanes to regulate the load, while those driven by steam turbines can be adjusted using either the turbine speed or the inlet guide vanes. Reciprocating compressors can be regulated through variable-frequency motors or by changing the lift of the air valves in an infinite range of steps; operating in reverse flow is certainly not energy-efficient.
We are reciprocating compressors. Variable-frequency motors are used. It’s not very useful. Always pay attention to the compressor’s exhaust pressure; high loads can easily damage the inverter:@:@
In this project, screw compressors are used for the refrigerant compression; a frequency converter is employed only during startup, while during operation, a slide valve is used to achieve stepless adjustment. Since the amount of BOG inlet gas varies, the slide valve offers a wider range of adjustment than a frequency converter, and using a frequency converter in low-load conditions can easily lead to resonance.
The IGV can be used to adjust the start-up of the refrigerant centrifugal compressor