Oil and gas production handbook An introduction to oil ... - ABB Group
Oil and gas production handbook An introduction to oil ... - ABB Group
Oil and gas production handbook An introduction to oil ... - ABB Group
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Figure 8. Compressor state diagram<br />
The operating characteristics are defined by the manufacturer. In the<br />
diagram above, the blue lines mark constant speed lines. The maximum<br />
operating limits are set by the orange line as described above. The surge<br />
domain is the area <strong>to</strong> the left of the red surge curve.<br />
The objective of compressor performance control is <strong>to</strong> keep the operating<br />
point close <strong>to</strong> the optimal set point without violating the constraints by means<br />
of control outputs, such as the speed setting. However, <strong>gas</strong> turbine speed<br />
control response is relatively slow <strong>and</strong> even electric mo<strong>to</strong>rs are not fast<br />
enough, since surge response must be in the 100 ms range. <strong>An</strong>ti-surge<br />
control will protect the compressor from going in<strong>to</strong> surge by operating the<br />
surge control valve. The basic strategy is <strong>to</strong> use distance between operating<br />
point <strong>and</strong> surge line <strong>to</strong> control the valve with a slower response time, starting<br />
at the surge control line. Crossing the surge trip line will cause a fast<br />
response opening of the surge valve <strong>to</strong> protect the compressor.<br />
Operation with recirculation wastes energy (which could result in<br />
unnecessary emissions) <strong>and</strong> produces wear <strong>and</strong> tear, particularly on the<br />
surge valve. Each vendor supplies several variants of compressor control<br />
<strong>and</strong> anti-surge control <strong>to</strong> optimize performance, based on various corrective<br />
<strong>and</strong> predictive algorithms. Some strategies include:<br />
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