Some questions regarding the shutdown of atmospheric and vacuum distillation units

1. At what time will the steam generator be shut down? How was the process? (1) Normal shutdown procedure? ① As the plant stops operating and the flow rate decreases, the heat source flow also reduces, and the feedwater amount is automatically decreased as well. The level of liquid in the drum is kept under control. When the plant stops generating steam or almost no steam is produced in the drum, the steam supply is disconnected from the system piping network and diverting it to vent instead. ? ② After the heat source of the generator is interrupted, stop the deoxygenated water supply; after cooling for a while, open the drain valve of the generator. ? (2) Steps to shut down in emergency situations? ① Slightly increase the flow rate of the intermediate return stream for heat exchange to maintain normal production. ? ② Open the hot oil feed valve of the generator. ? ③ Gradually close the inlet and outlet valves of the heat source of the generator. ? ④ Stop the water supply. ? ⑤ Valve to cut off the connection between the generated steam and the system pipeline network. ? ⑥ Slowly open the generator’s manual vent valve and steam discharge valve.

2. How to shut down the oil sealing system? How should the time periods be allocated? Here, the oil sealing process makes use of reduced-pressure reflux oil; once the volume and temperature are lowered and there is no liquid level left in the oil sealing tank, the oil sealing pump is stopped, and the various end-point oil sealing valves are closed. 3. How can oil be removed more scientifically? How are the steps? Here, once the temperature of the closed-loop oil drops below 45°C, the oil is sent back to the crude oil tank through an oil return line. Then diesel is used to clean the large circulation system; once the oil at the sampler in the residue oil system is no longer viscous, it is again sent back to the crude oil tank. After that, a thorough cleaning agent is used for cleaning, and finally all the oil is returned to the crude oil tank area, where it is removed using steam. If a full cleaning is not possible, then clean it thoroughly with diesel; it’s best to use catalyzed diesel rather than straight-run diesel.

4. Where are the start and stop points for the induced draft fan? Here, when the outlet temperature of the atmospheric pressure furnace drops to 250°C and the outlet temperature of the reduced pressure furnace drops to 300°C, all valves supplying gas to the heating furnace are closed. Then the flue dampers are opened, and the induced draft fan as well as the blower are stopped. After the temperature inside the furnace drops below 100°C, the natural ventilation doors are opened to allow ventilation and cooling. In fact, the blower can also be started to facilitate forced ventilation and cooling when the furnace temperature is below 100°C, allowing for a faster rate of cooling.

We simply replace it with light crude oil; there is no chemical cleaning nor diesel circulation. The scanning time should be longer.