Causes of surge in Sanyo compressors

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1) A decrease in inlet flow, a drop in inlet pressure or an increase in outlet pressure, resulting in an increased compression ratio of the Sanyo compressor; 2) An increase in the rotational speed of the Sanyo compressor; 3) An increase in the inlet air temperature; 4) A decrease in the molecular weight of the inlet air, etc. Generally, the main reason is that when a fault occurs in the process system, the outlet pressure of the Sanyo compressor rises suddenly, resulting in a decrease in the air delivery volume and thus causing surging in the unit. To prevent surge in Sanyo compressors, manufacturers of general units typically design an anti-surge control system and provide the characteristic curves for each unit; they also recommend specific values for the anti-surge flow rate for Sanyo compressors. Generally, a \"fixed limit flow A anti-surge control system\" is used. The set values for each anti-surge amount are all 1.04–1.2 times the surge flow rate corresponding to 100% rotation speed of the Shenyang Sanyo compressor; in other words, a constant flow control method is used. This anti-surge control ensures that the unit maintains the anti-surge level at 100% rotation speed regardless of the load level below 100%, thereby preventing surge from occurring. This control method is reasonable for operation at high loads, as the anti-surge amount is generally around 80% of the flow rate at 100% load; that is, when the process load is above 80%, the anti-surge valve remains closed, and all the gas compressed by the Sanyo compressor is sent into the process stream. When the process load is low, and the amount of air required by the process load is less than the anti-surge flow rate specified at 100% load, the anti-surge valve opens in order to maintain the anti-surge capacity of the unit. This results in backflow or venting, leading to unnecessary consumption of external energy; the work done by the Dalian Sanyo compressor on this gas is wasted. As a consequence, some of the gas is expelled, which increases the workload on the Sanyo compressor and causes an imbalance in the steam flow within the entire process system. Therefore, when operating under variable conditions, this constant-flow control leads to an increased consumption of natural gas per ton of ammonia produced. Because it’s uneconomical. When the process load is low (for example, operating between 50-70%), the anti-surge valves of the unit are all open, resulting in a significant waste of power steam and making it very difficult to operate the process system. To address the issue of excessive power consumption in Sanyo compressors under light load conditions, caused by an overly wide opening of the anti-surge valve, the most scientific and reasonable solution for the anti-surge control systems in large-scale units is to employ a \"variable limit flow anti-surge control system\".