Steps for pressure swing adsorption shutdown, and precautions

Normal shutdown procedure: 1) First, inform the upstream and downstream units to make the necessary adjustments. 2) On the DCS, reset the operation button to the STOP position and close all programmable valves. 3) Close the raw gas inlet valve, product gas outlet valve, desorbed gas outlet valve, and flare line interface valve, thereby isolating the hydrogen purification system from areas outside it. 4) Run the system through a few steps using the operation button on the DCS, causing the PSA programmable valves to act several times so that the pressures in each tower are roughly equal and all remain at a high positive pressure. 5) Shut down the hydraulic pump station. Thus, the entire normal parking process is completed. After parking, the hydrogen purification system is under positive pressure and isolated from the boundary zone. Therefore, the system can remain in a safe parked state for an extended period of time. However, since flammable and explosive gases remain in the system after parking, the entire area remains a explosion-proof zone, and welding is strictly prohibited. After normal shutdown, the pressures in all adsorption towers of the unit are equal, and the DCS program is reset; therefore, when starting up again, the normal startup procedures must be followed.

Emergency shutdown: In the event of an accident with this unit or with the units upstream or downstream of it, an emergency shutdown is required. The steps for carrying out this shutdown are as follows: 1) Use the shutdown password on the DCS to set the operation button to the STOP position, and close the programmable valves. At the same time, the program will automatically remember the state when parking. At this point, the system is already in emergency stop mode.

Temporary parking: If a short-term stop is necessary for work purposes (no more than 1 hour), temporary parking is allowed, and the procedures are the same as those for emergency parking. Upon emergency shutdown or restart after a temporary stop, since the program still retains the conditions from the time of shutdown and the pressures in each adsorption tower remain the same as at that time, it is possible to resume operation directly from those conditions, allowing the system to return to its normal operating state without any disruptions. It has little impact on product purity. The steps are as follows: 1) Verify that the pressure in each adsorption tower matches the paused status displayed on the DCS. 2) Check the pressure history record of the adsorption tower to confirm that there have been no significant changes in pressure. 3) On the DCS, change the status of the run button from STOP to RUNNING, and the system will then enter normal operation. Be sure to note: 1. Before restoring operation using this method, it is necessary to confirm that the pressures in each adsorption tower are consistent with the status set during shutdown. Otherwise, once it is started, the gas from the high-pressure tower could flow into the low-pressure desorption system, causing an accident! 2. If the pressure in the adsorption tower does not match the displayed value, the valve must be operated manually to gradually release the pressure in the adsorption tower before restarting the system. The method for releasing pressure is to fully open the desorption gas air conditioning control valve PIC2007 and its bypass, and then open the flushing outlet program-controlled valve XV2007.

Will the equalization method mentioned on the second floor cause the safety valve of the analytical gas cylinder to activate?

Reply to 5# apooly1002: Due to internal leakage in the programmable valve, during the system pressure retention phase, gas leaks from the high-pressure tower to the low-pressure tower, causing its pressure to rise. To address this issue, it is necessary to quickly open and close the programmable valve, and then use a control valve to vent the gas with a pressure higher than the set value to the flare (it would be best if this gas can be sent to the furnace, depending on the layout of your installation).

Let’s talk about the steps for stopping the machine before maintenance: 1. Reduce the raw material load； 2. Reduce the speed of the desorption gas compressor ； 3. Stop the vacuum pump ； Shutting down procedure ； 4. All feed gas is transferred out ； 5. Close the raw gas valve ； 6. Close the hydrogen valve. 7. Gradually reduce the speed of the degassing compressor until it stops ； 8. Through the appropriate process, the system is depressurized to atmospheric pressure ； 9. Nitrogen purging to acceptable level ； 10. Stop the hydraulic oil pump. Precautions: 1. Inform the upstream and downstream units in advance to prepare for reducing flow rate ； 2. The desorption gas compressor is controlled via backflow motion to prevent surging ； 3. Stop the vacuum pump: first close the inlet valve, then cut off the power supply ； 4. If the outlet pressure of the desorption gas compressor is lower than the pressure in the pipeline network, close its outlet valve; all of the feed gas must be diverted out ； 5. Stop the hydraulic oil pump, be careful not to let the oil tank leak