What are the conditions under which the emergency pressure relief valve in a hydrocracking unit closes?
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The hydrocracking unit is equipped with pressure relief valves at 0.7 MPa/min and 2.1 MPa/min. Once these pressure relief valves open, what are the conditions under which they close? The bed temperature level and whether the fresh hydrogen compressor and circulation pump are in operation should be taken into consideration
1. Handling after low-speed pressure relief is activated: The low-speed pressure relief can be activated only when the recycle hydrogen compressor is stopped. Additionally, all temperatures in the reactor will drop to 28°C below normal levels. If the reactor temperature rises significantly, the high-speed pressure relief valve is activated. 2. High-speed pressure relief system: When the temperature of the cracking reactor reaches the design value, the high-speed pressure relief system will automatically activate and open. The operator can manually initiate rapid pressure relief. The same automatic response as low-speed pressure relief. Shutdown of the cyclic hydrogen compressor: Once high-speed pressure relief is activated, it can be turned off only after the system pressure of the unit has been relieved.
Shut-down conditions: 1. The furnace goes out； ⒉The temperature rise in the reactor bed is less than 10 degrees ； ⒊The circulation machine starts to circulate.
For start-up at 0.7, the cycle hydrogen compressor is still operating; it can be turned off when the reactor temperature drops below 30°C of the normal level. If the cycle hydrogen compressor stops due to interlocks and 0.7 is activated, then waiting until the pressure drops to 0.5 MPA is required. For start-up at 2.1, full pressure release is necessary; if the temperature still cannot be controlled, nitrogen purging is the only option. With pressure release at 0.7, full release is also possible, but this is done in order to shorten the time required for startup, as long as the temperature is below 30°C of the normal level
2.1 Once started, it must go all the way. The reaction pressure is 0.07 MPa; it can be turned off only when the bed temperature stops rising. The conditions for turning off 0.7 are as follows: 1. If the circulation pump stops operating, 0.7 can only be released to its lowest level, with the reaction pressure remaining at 0.07 MPa, and it can be turned off only when the bed temperature stops rising. 2. If the circulation pump continues to operate and the bed temperature is 30 degrees below normal, then 0.7 can be turned off. 3. If the circulation pump can be started again promptly after it stops operating and operates normally for more than 10 minutes, with the bed temperature being 30 degrees below normal, then 0.7 can also be turned off