On the accident handling plan for standardized delayed coking units

1 Emergency shutdown of the plant 1.1 The plant requires an emergency shutdown in the following situations: 1) There is a prolonged interruption of water, electricity, steam, air, etc., to the plant. 2) In the event of severe leakage, fire, or explosion that may cause serious damage to the equipment or lead to personal injuries, and when the situation becomes uncontrollable. 3) Equipment failures such as sticking of the four-way valve, malfunctions in key pumps and units occur, making it impossible to restore operation in the short term. 4) All DCS engineer stations and control stations are faulty. 5) In the event of irresistible natural forces such as earthquakes and floods. 1.2 Handling principles 1) During an emergency shutdown, it is necessary to prevent the accident from worsening and to avoid the occurrence of further incidents, as well as to prevent personal injuries, environmental pollution, and equipment damage. 2) When the equipment is severely leaking and on fire, it is necessary to quickly isolate the individual unit of the equipment, remove all materials from it, and reduce the pressure within the equipment. 3) During emergency shutdown, it is necessary to ensure that the equipment does not experience overheating or overpressure, there are no leaks, the media do not mix with each other, and the heating furnace does not suffer from coking. 1.3 Accident handling methods 1) Report immediately to the workshop and production scheduler. 2) Emergency shutdown of the heating furnace. On-site verification confirmed that the emergency shutoff valve for the fuel gas to the main burner was closed and the main burner was extinguished; the combustion of the pilot light was also checked ； Open steam injection valves FV1112/1–4 of the heating furnace tubes to full capacity ； Manually change forced ventilation to natural ventilation. 3) Stop the feed pump P1102 of the heating furnace; verify that the pressure behind the control valve is below 1.0 MPa of steam pressure, and after dehydrating the steam, purge the four feed furnace tubes into the production tower. 4) Shut down the compressor urgently, close the compressor’s inlet and outlet valves as well as the anti-surge valve, and use the inlet flare valve to control the pressure at the top of the distillation tower. Close the 3.5MPa steam inlet isolation hand valve and the backpressure isolation hand valve; open the 3.5MPa steam and 1.0MPa steam pipe warming exhaust valves to warm the pipes, and open the machine’s drain valve ； Ensure the barring gear is functioning properly. 5) A manual valve is installed together with the rich oil absorption control valve FV1206, the lean liquid control valve FV1302, and the rich liquid control valve LV1304 to prevent cross-flow between high and low pressures. 6) Shut off the rich gas water washing. 7) Redirect the shipped products to the substandard production line. 8) Control the liquid level in steam generator V1105 properly; direct the steam to vent, and use 1.0 MPa steam for the convective superheating tubes in the heater. Stop T1103 stripping steam. 11) Maintain pressure with the pressure control valve PV1304 of the absorption stabilization and dry gas desulfurization system. 10) Other cases shall be handled in accordance with the operating procedures as appropriate.

A few days ago, we experienced an accident in which both the DCS system and the SIS system stopped working. The most important things to keep in mind during an emergency shutdown are: 1) During such a shutdown, it is necessary to prevent the accident from worsening or leading to further incidents, in order to avoid injuries to people, environmental pollution, and damage to equipment. 2) During emergency shutdown, it is necessary to ensure that the equipment does not experience overheating or overpressure, there are no leaks, the media do not mix with each other, and the heating furnace does not suffer from coking. By achieving the above two points, handling coking accidents is almost half done.

As long as the key equipment does not experience overheating, overpressure, or damage, the rest will need to be handled based on the actual conditions on site

You can tell me your email address, and I’ll send it to you; I hope it will be useful to you :) :)

Thank you for your advice. My email address is: zhaizhq@lypcc.com.cn

2.2 Emergency Shutdown 1. Situations requiring an emergency shutdown: 1) Leakage and fire at the furnace inlet and outlet, furnace tubes, oil transfer lines, or from the furnace outlet to the coke tower or associated instruments. 2) Radiation extraction to the heating furnace leaked and caught fire, and it could not be isolated. 3) Leakage at the flanges of the distillation tower and its associated valves. 4) Leakage in the oil and gas line of the coke tower or in other areas that cannot be isolated. 5) Complete power outage, DCS system failure. 2. Steps for emergency shutdown: 1) The inspection staff detects the accident and notifies the control room via walkie-talkie; the shift leader confirms the need for an emergency shutdown, and at the same time informs the fire department and dispatch to assign guides. 2) Close the two dry gas control valves of the internal heating furnace, and open the control valves for the six steam injection lines (open lines 1 and 2 fully, open line 3 halfway, opening them in sequence); in case of a fault with the control valves, use the bypass line. Stop the radiation pump for outdoor operations, close the pump outlet, and close the preheating valve. Regarding the gas control valve manual valve. When the furnace tube leaks, stop the blower, turn off the permanent light, and activate the emergency steam. 3) Fractionation tank stop area pumps, feed pump. Increase the intensity of each reflux to maintain proper temperature and control the top pressure. Stop the compressor as appropriate, discharge the residue oil externally, and collect diesel for replacement. 4) After 30 minutes of tube purging at the coke tower, switch the 15-meter line to the vent tower; stop the emergency cooling oil and the defoamer depending on the temperature. If there is a leak in the feed stub, top or bottom cover of the coke tower, switch to the backup tower ； In the absence of a backup tower, increase the water supply to the external cooling tank, open the four-way bypass manual valve, and switch the four-way valve to the bypass mode (if the vent tower is being used to replace the oil at the bottom of the tower, first ensure that there is an unobstructed exit route). Increase the water supply to the external cooling tank as well, paying attention to the temperature of the cooled fluid. 5) Absorb and stabilize pressure as well as maintain liquid level. 6) If the absorption stabilization system leaks, stop the compressor first ； The crude gasoline pump failed to meet the standards ； Increase the flow rate of liquefied gas delivery to full capacity, and open the pressure relief valve of the stabilizer to full extent ； Open the dry gas valve leading to the desulfurization control valve; when the pressure reaches that of the desulfurization tower, close the manual valve ； Open the safety valve bypass to relieve pressure.