Emergency shutdown steps for hydrorefining

Principle of emergency shutdown: (1) In the event of a major accident in the plant, and when various efforts to address the issue fail to eliminate the accident or maintain normal operation, an emergency shutdown should be carried out. (2) In the event of an accident at a peripheral device that poses a serious threat to the safe operation of this device, emergency shutdown must be carried out. (3) If a fire breaks out in the equipment, posing a serious threat to its safe operation, emergency shutdown must be carried out. (4) In the event of a equipment failure, the backup equipment fails to start, posing a threat to the safe operation of the facility, an emergency shutdown should be carried out. (5) If a utility system fails and cannot be restored in a short time, operations should be halted immediately. (6) In the event of a sudden explosion of high-pressure pipelines or equipment in the reaction section for unknown reasons, an emergency shutdown must be carried out. (7) An emergency shutdown shall be initiated if the temperature at any point in the reactor exceeds 28°C above the normal level, or if it exceeds 425°C. (8) In the event of a disruption in the feed oil and the accident may further escalate, an emergency shutdown can be carried out. (9) In the event of a hydrogen supply interruption that cannot be resolved in a short time, an emergency shutdown can be carried out. (10) Receive an emergency shutdown order from the command system. Emergency Shutdown Method (1): Emergency Shutdown by Unloading Pressure from the Unit (M) – Based on the situation of the accident, determine that it is necessary to carry out an emergency shutdown by unloading pressure from the unit. – Contact the dispatch team and the workshop to report the situation. – Contact the flare team to prepare for pressure release. – Contact the reforming and hydrogen production units; stop receiving hydrogen gas and get ready for an emergency shutdown. – Contact the tank farm to stop feeding raw materials. – Activate the 0.7 MPa/min emergency pressure release button. – Switch the ESD display to “Interlock Logic Diagram (Unit)” (M). – Confirm that XCV1106 is in the open state on the ESD display (P). – Verify on-site that XCV1106 is indeed open (I). – Confirm that the system pressure has dropped significantly. – If pressure release causes leaks at the reactor’s inlet and outlet flanges, activate the protection steam for those flanges (P). – Confirm that the operating raw material pumps have stopped. – Close the electric valve at the outlet of the raw material pumps. – Close the flow control valve at the outlet of the raw material pumps (P). – Confirm that the operating new hydrogen generator has stopped. – Close the third-stage outlet valve of the stopped new hydrogen generator. – Set the load switch to the “0” position (P). – Confirm that the self-protection valve of the main burner in F1101 is closed (P). – Confirm that the main burner in F1101 is extinguished. – Close the dual valves in front of each main burner in F1101. – Redirect the high-pressure gas to the flare. – Close the valves for feeding catalyzed diesel into the unit. – Close the valves for feeding straight diesel into the unit. – During the pressure reduction process, control the liquid levels in D1102, D1103, D1104, and LI250 (I). – Confirm that the temperatures at various points in the reactor bed are within normal operating ranges (I). – Confirm that the system pressure has dropped to 2.0 MPa. – Shut down the recycle hydrogen compressor according to the shutdown procedures. – Open the 3.5 MPa steam drain valve and the steam vent valve (I). – Confirm that the system pressure has dropped below 0.05 MPa. – Close the emergency pressure release valve XCV1106 (M). – Confirm that the reaction system has been depressurized urgently. – Open the cross-connection valves for lines E1110A and B (M). – Confirm that high-pressure gas cannot be continuously fed into low-pressure sections. – Inform the operators to switch to an internal short-cycle operation in the distillation system. – Adjust the unit’s short-cycle process (without using the D1104 cycle). – Inform the tank farm to use an alternative route for handling unwanted oil. – Reduce the bottom temperature of C1101 by 25°C per hour until it reaches 220°C. – Reduce the bottom temperature of C1102 by 25°C per hour until it reaches 220°C. – Control the liquid levels in all containers and towers in the distillation system. – Control the pressures in all containers and towers in the distillation system.

Emergency Shutdown Method (2): Emergency Shutdown Without Unloading Pressure from the Unit (M) – Based on the situation of the accident, determine that it is necessary to carry out an emergency shutdown without unloading pressure from the unit. – Contact the dispatch team and the workshop to report the situation. – Contact the flare team to prepare for pressure release. – Contact the reforming and hydrogen production units; stop receiving hydrogen gas and get ready for an emergency shutdown. – Contact the tank farm to stop feeding raw materials (I). – Confirm that K1101 is operating normally. – Shut down P1101A and P1101B according to the procedures. – Set the new hydrogen generator to zero load (P). – Confirm that the main burner in F1101 has been automatically extinguished (P). – Confirm that the pilot light in F1101 is burning properly. – Redirect the high-pressure gas to the flare. – Reduce the system pressure at a rate of 1.5 MPa per hour until it reaches 8.0 MPa. – Close the valves for feeding catalyzed diesel into the unit. – Close the valves for feeding straight diesel into the unit (I). – Confirm that the temperatures at various points in the reactor bed are below normal levels (I). – Confirm that the outlet temperature of F1101 is below 270°C. – Ignite and heat F1101 according to the procedures. – Control the reactor’s inlet temperature at 270°C. – Control the system pressure at 8.0 MPa. – Control the liquid levels in D1102, D1103, D1104, and LI250 within normal ranges (M). – Confirm that the reaction system has been shut down urgently. – Open the cross-connection valves for lines E1110A and B (M). – Confirm that high-pressure gas cannot be continuously fed into low-pressure sections. – Inform the operators to switch to an internal short-cycle operation in the distillation system. – Adjust the unit’s short-cycle process (without using the D1104 cycle). – Inform the tank farm to use an alternative route for handling unwanted oil. – Reduce the bottom temperature of C1101 by 25°C per hour until it reaches 220°C. – Reduce the bottom temperature of C1102 by 25°C per hour until it reaches 220°C. – Control the liquid levels in all containers and towers in the distillation system. – Control the pressures in all containers and towers in the distillation system