Coking production

Leakage and fire at the tower top flanges, tower wall flanges, etc.! You can change the tower in advance; if that’s not possible, switch to the startup line and go straight to the oil dumping tank! But we once had a fire before as well, caused by purging the quench oil line! It seems that there’s relatively little coking that’s on fire! Our old workshop’s tower caught fire twice! This post was last edited by chengkang on 2009-3-24 07:29]

The causes of the fire include leaks in the oil and gas flanges at the top of the tower, leaks in the quench oil flanges, as well as leaks in the flanges connecting other additives to the top of the coke tower or problems with the gaskets. In addition, human factors related to other operational procedures, such as inadequate consideration, unclear handovers, and incorrect procedures, also led to the leaks. In short, oil refining is a complex process; one must think carefully and consider various aspects before doing anything.

I think there are fewer cases of coking without fire. The temperature of the coking materials is high, and any leakage that comes into contact with air will cause a fire. The direct cause of fires at the top and bottom of the tower is always leakage; there are many indirect causes as well, such as equipment aging, damaged gaskets, valve leaks… As for the situation described by the poster, I believe it’s necessary to replace the tower in advance and then take emergency action according to the accident response plan

Flange leakage on the overhead oil and gas line, quench oil flange, and overhead cover leakage. If the switching condition is not met, the feed line is switched to feed from the top of the new tower, while the oil stripping process continues at the bottom of the tower.

We once encountered a fire at the top of the preheating tower, which was extremely difficult to handle. The only option at that time was to reduce production urgently and carry out work on the tower while it was still in operation. It was windy from the north, with temperatures around minus 9 degrees Celsius; we spent nearly 6 hours at the top of the 60-meter-tall tower, and we were almost frozen to death. It gives one a deep understanding of just how tough working in coking is.

If a fire breaks out suddenly at the top of a coking tower, it is usually due to a leak in the flanges. If no significant leaks are detected during pressure testing and oil/gas preheating, then providing protective steam and tightening the flanges under pressure should resolve the issue.

When available, switch to the new tower and use steam to purge the old tower

Reduce furnace temperature, cut off the tower, and blow steam. Fires at the top of the tower are relatively rare; usually, it is due to leaks in the oil and gas flanges. It’s also possible that the defoamer line or the cover hydraulic press have been leaking oil for a long time, and thus have been damaged by the heat from the tower.

1. Extinguish the fire. 2. If the leakage amount is small, production can be continued with 1.0 MPa steam as a shield. The pressure at the top of the coke tower is not high, so steam can completely seal it off! 3. If the leakage is severe, and if the preheating tower is at 300 degrees, switch over immediately after cleaning the oil! If the temperature is too low, it can be quickly preheated and then switched! 4. If the top of the preheating tower catches fire, pressure can be released to handle the situation; after that, preheating can be resumed. However, depending on the production situation and the time required to address issues, it’s okay to reduce the quantity appropriately!

The temperature at the top of the coke tower changes at least once a day, going from 420 degrees to room temperature, and then back from room temperature to 420 degrees. Leaks in the flange gaskets are something normal; as long as regular inspections are carried out and any oil leaks are addressed promptly, there should be no problems. We have had this issue before; now we conduct inspections every hour, and if any leakage is detected, it is addressed immediately. If the gaskets are faulty, they are replaced after the decoking process is completed. If there is a leak in the weld, as long as it’s not severe, steam can be used for shielding. A preheating temperature of 250 degrees should be sufficient to allow the tower to be replaced. It’s important to remove all the oil from the oil dumping tank, as this can have an impact on the distillation tower; however, in an emergency situation, the priority is to ensure the safety of the affected area.

Leakage and ignition at the flanges on the top or bottom cover are issues that older installations are likely to encounter firsthand. I remember one particularly severe incident in which all the instrument cables located at the top of the tower were burned up; it was quite difficult to deal with the situation, and to this day it’s hard to tell which cable was connected to what. Since then, efforts have been made consciously to improve the sealing of the top and bottom covers as well as to conduct pressure testing checks, and the situation has indeed improved significantly; those tragic scenes have not occurred again. In the face of such an emergency, when it’s not possible to switch towers, the only option is to operate the furnaces separately – of course, with a process setup of two towers per furnace, this also means shutting down the operation. It doesn’t really make much sense in terms of lowering blood pressure; although this is what is done every time, it isn’t the fundamental solution to the problem.

There are many reasons: loose screws on the top cover, leaks in the quench oil flanges, leaks in the defoamer pipelines, and leaks in the oil-gas line flanges. Steam can be used as well; if the problem cannot be resolved, switch to another tower’s operation line for a closed-loop circulation