HANGZHOU NUZHUO TECHNOLOGY GROUP CO.,LTD.

Why does it take time to start and stop a PSA nitrogen generator? There are two reasons: one is related to physics and the other is related to the craft.

1.Adsorption equilibrium needs to be established.

PSA enriches N₂ by adsorbing O₂/ moisture on the molecular sieve. When newly started, the molecular sieve should gradually reach a stable adsorption/desorption cycle from an unsaturated or contaminated by air/moisture state in order to output the target purity during the stable cycle. This process of reaching a steady state requires several complete adsorption/desorption cycles (typically ranging from tens of seconds to several minutes/tens of minutes, depending on the bed volume and process parameters).

 2.The pressure and flow rate of the bed layer are stable.

The adsorption efficiency of PSA is highly dependent on the operating pressure and gas velocity. When starting up, the air compressor, drying system, valves and gas circuits need time to pressurize the system to the designed pressure and stabilize the flow rate (including the action delay of the pressure stabilizer, flow stabilizer controller and soft start valve).

3.Recovery of the pretreatment equipment

Air filtration and refrigerated dryers/desiccants must first meet the standards (temperature, dew point, oil content); otherwise, the molecular sieves may be contaminated or cause fluctuations in purity. The refrigerated dryer and the oil-water separator also have a recovery time.

 4.Delays in the emptying and purification process

During the PSA cycle, there are replacement, empting and regeneration. The initial replacement and regeneration must be completed at startup to ensure that the bed layer is “clean”. In addition, purity analyzers (oxygen analyzers, nitrogen analyzers) have response delays, and the control system usually requires continuous multi-point qualification before outputting the “qualified gas” signal.

 5.The sequence of valves and control logic

To prevent damage to the molecular sieve or the generation of instantaneous high-concentration gas, the control system adopts step-by-step switching (on/off section by section), which itself introduces a delay to ensure that each step reaches stability before moving on to the next one.

 6.Security and Protection policy

Many manufacturers incorporate strategies such as minimum operating time and protection delay (reverse blowing/pressure relief) into their software and hardware to prevent frequent starts and stops from damaging equipment and adsorbents.

In conclusion, the start-up time is not a single factor but is caused by the accumulation of several parts, including pretreatment + pressure establishment + adsorption bed stabilization + control/analysis confirmation.

Contact Riley to get more details about the PSA oxygen/nitrogen generator, liquid nitrogen generator, ASU plant, gas booster compressor.

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Email: Riley.Zhang@hznuzhuo.com