What are the factors that cause the anti-surge valve of a methanol synthesis compressor to open automatically?
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In a 600,000-ton methanol plant, the anti-surge valve of the methanol synthesis compressor opened automatically 4 times within one month. Analysis of reasons: What are the factors that cause the anti-surge valve of the methanol synthesis compressor to open automatically? 1) Process issues ； 2) Valve issues ； 3) Equipment issues ； 4) Instrument issues ； 5) Control system issues. The compressor of this 600,000-ton methanol plant experienced operational issues, with the anti-surge valve of the methanol synthesis compressor opening automatically 4 times. After 4 inspections, it was found to be a process issue each time. In 3 cases, the decrease in gas volume and the drop in flow rate and pressure were caused by issues in the previous processing steps ； In one instance, the automatic adjustment of the carbon dioxide supplementation system caused the valve to close too quickly.
Process issues: 1. The operating conditions of the system fluctuate excessively, especially regarding pressure. Since the surge point is directly affected by the pressure difference in the throat of the inlet flow meter, a sudden drop in inlet pressure can cause surging even before the compressor system reaches its surge point; the large pressure difference then causes the surge point to cross the surge protection line and the actual surge line, leading to surging. The reasons include the shutdown of the previous system’s compressor, failure of the automatic control valve leading to its closure, liquid resistance in the separator, collapse of the packing filter, activation of the safety valve, or rupture of equipment pipes. 2. Excessive pressure buildup or differential pressure in the system downstream of the compressor leads to high outlet pressure; faults in the vent valves of the synthesis system, liquid resistance in the methanol separator, and problems with proper cooling in the methanol cooling tower can also contribute to this issue. 3. The speed at which the manual control valves in the entire system are adjusted is too fast, especially those shut-off valves that have a significant impact on gas flow and pressure. 4. Too rapid changes in load. Control system issues: 1. The distance between the surge protection setting and the actual surge line is too small; for centrifugal compressors that are subject to system fluctuations, this distance should be increased. 2. The straight pipe sections required for the flow meter do not meet the specifications; in particular, issues with the inlet filters and tees mean that even minor pressure fluctuations in the system can cause the displayed flow rate to be inaccurate. 3. The thermal resistors and pressure transmitters have large accuracy errors or are malfunctioning. 4. The control valves at the inlet are faulty. 5. The PID parameters set for various automatic control valves are unreasonable, resulting in too rapid, too slow, or overly drastic changes in the regulated parameters, such as those in the carbon supplementation flow control valve. Valve-related issues: 1. Problems with the pneumatic anti-surge valve, such as poor air supply, blockages, or leaks, which can cause the air-actuated surge valve to open automatically. 2. Malfunctions in the two-position five-way solenoid valves associated with the surge valve, or problems with the electrical control system. 3. Faults in the surge valve itself. Equipment-related issues: The flow channels of the equipment’s impellers are too narrow, and the diffuser sections are poorly designed