Catalytic chimney flaming

The spontaneous combustion of oil and gas is closely related to the temperature in the regenerator, as well as to the combustion air. Fortunately, it was dealt with promptly; otherwise, it could have led to a serious accident.

It’s normal; it’s correct to do that. If not, it will cause the blast door of the chimney to fly open.

Let’s analyze why oil and gas penetrate into the regenerator after the feed is cut off What can we do if we encounter such a situation again to prevent it from happening?

It’s very dangerous; wasn’t the feed cut off in time?

The feeding time is set too late, and moreover the differential pressure between the two reactors isn’t adjusted properly; the pressure in the reactor is too high while the pressure in the regenerator is too low, which is very dangerous

When the power to the unit is lost, the main air supply is interrupted, and the pressure difference between the two vessels is disrupted; this inevitably causes the reaction gases to enter the regenerator, resulting in yellow smoke being emitted from the chimney. In severe cases, flames may appear. Even if the safety systems are activated promptly, it is still difficult to prevent smoke emission. Once, during the commissioning of a new unit, the safety valves remained open after they were activated, and flames emerged from the chimney for about 5 minutes; the flames were extinguished only after the valves controlling the nozzle walls were closed. Fortunately, the steam supply was not interrupted – it was a truly terrifying experience, and I still feel scared when I think back to it

Due to a sudden power outage, the catalytic unit lost external steam supply for unknown reasons. After stopping the feed, quickly close the regeneration and standby valves. The reaction and regeneration processes immediately relieve the pressure; if the live valve does not close properly during normal operation, the operator should close it manually, but be careful not to close it too tightly.

Analysis: After the device lost power, the main air supply was interrupted, causing the pressure in the regenerator to drop rapidly. If the reaction settler could not vent gas quickly, a positive pressure difference occurred. The external steam supply was also interrupted for unknown reasons. The feed nozzles were closed relatively late, resulting in poor atomization; as a result, the stripping effect in the settler was inadequate. Catalyst containing oil droplets was fed into the regenerator, and since there was no main air supply, these oil droplets could not burn. Oil and gas mixed with this mixture entered the chimney, where their high concentration led to ignition by the high-temperature exhaust gases from the CO boiler. If the concentration reaches the explosive limit, the consequences would be disastrous. The worst off are the operators. One should strive to improve their professional skills on a regular basis, so as to be able to handle emergencies decisively and ensure the safety of life-saving equipment.

Analysis: After the device lost power, the main air supply was interrupted, causing the pressure in the regenerator to drop rapidly. If the reaction settler could not vent gas quickly, a positive pressure difference occurred. The external steam supply was also interrupted for unknown reasons. The feed nozzles were closed relatively late, resulting in poor atomization; as a result, the stripping effect in the settler was inadequate. Catalyst containing oil droplets was fed into the regenerator, and since there was no main air supply, these oil droplets could not burn. Oil and gas mixed with this mixture entered the chimney, where their high concentration led to ignition by the high-temperature exhaust gases from the CO boiler. If the concentration reaches the explosive limit, the consequences would be disastrous. The worst off are the operators. One should strive to improve their professional skills on a regular basis, so as to be able to handle emergencies decisively and ensure the safety of life-saving equipment.

In this case, there is only a result, no process. It’s quick.

Hehe, that happened in our factory in 1996 as well; at that time, we resolved the issue by immediately using emergency steam from the main air system.

Fortunately, it was oil that entered the regenerator; if it had been the pressure in the regenerator that caused air to enter the settler, then when that air met the oil and gas, an explosion would have occurred!

After a power outage, the two units enter self-protection mode and all slide valves close automatically. The first thing the operator needs to do is check whether the slide valves have closed properly; if not, they must be closed manually. Local hydraulic control can be used for this purpose, as it is much faster than using hand wheels. As long as the slide valves are closed properly, even in the absence of accident steam, at most the regenerator’s dead zone will be affected – nothing that serious will happen

The device experienced a sudden power outage; our workshop requested that the operator check whether the automatic protection system had activated, and if not, to activate it manually. On the outside, check whether the feed inlet valve and the feed return valve are operating, and close the two manual valves of the feed nozzle; also check whether the plug valve and the regeneration slide valve are closed. The operators on site promptly opened the flare valve at the compressor inlet to relieve pressure in the settler, preventing the disruption of pressure balance – these are the first actions that must be taken as they represent the first step toward ensuring safety! When an emergency occurs in the facility, safety must come first; without safety, there can be no talk of production! Only when safety is ensured will we consider minimizing losses in efficiency and equipment!

Catalysts cause chimneys to catch fire; we encountered that once last week. During the night shift, there was an unexpected short-term power outage, so the beds had to be left in a dormant state. As a result, after the cutting, flames erupted from the catalytic chimney for several minutes. It happened right when we were taking over the night shift; we had never seen anything like that before, and our legs turned to water at that moment. Thankfully, nothing happened. Post-analysis: After cutting the material, the main air supply was interrupted, the steam pressure was insufficient, which disrupted the pressure balance between the two vessels and resulted in a positive pressure difference. The flare system was not activated in time, allowing the reaction gases to enter the regenerator; this led to yellow smoke being emitted from the chimney, and eventually a fire broke out.

What those upstairs mentioned is merely the issue of untimely handling of power outages. Some time ago, here we experienced a false level reading due to a malfunction in the liquid level sensor in the stripping section; the operators opened the valve too quickly, causing large amounts of oil and gas to enter the regenerator along with the catalyst. The pressure imbalance forced us to stop the process, and we had to restart it by injecting material again to resume production. The technical skills and sense of responsibility of employees in the reaction position are extremely important.

In catalysis, it is especially important to prevent reaction oil vapor from entering the regenerator; in other words, under all circumstances, efforts must be made to avoid the entry of reactor oil vapor into the regenerator. During operation, it is absolutely necessary to ensure that the regenerator’s inclined tubes or material legs are not under vacuum. In the event of such a situation, the main air supply must be shut off first; once the temperature of the regenerator bed drops, accident steam from the main air supply should be used to strip the regenerator, thereby reducing the oil vapor present in it.

Speed it up, close the slide valve completely, and close the feed control valve. When there is a material level, oil will not be carried into the regenerator. I have been working in this facility for 15 years, and I have seen the chimneys emit yellow smoke and catch fire on many occasions. The worst case was when a crack appeared in the chimney as a result of an explosion. The reason for this is mostly that the feed pneumatic gate valve closes slowly, and during the supply of main air and the self-protection mode of the two devices, the slide valve fails to close completely due to loss of tracking. Later, our engineers added displays for the input signals and valve position feedback signals on the DCS, making it easy to determine whether the valves were fully closed. Once it is detected, it’s quick to manually pull it to fully closed as well. It’s also important to close the feed manual valve tightly! During the incident when our chimney exploded, it was because a manual valve on one of the nozzle feed collectors wasn’t closed, which allowed a large amount of oil to enter the settler. When fluidization was restored, boom! This post was last edited by mjl25mp6 on 2008-1-3 00:21]

1. If the feed supply is interrupted, emergency feeding systems must be activated immediately; operators need to go to the site to check whether these emergency systems are functioning properly. 2. If the main air supply is interrupted, emergency systems for the main air and differential pressure must be activated right away, and relevant valves should be closed. Otherwise, it’s easy for the two vessels to connect with each other. In the situation described by the poster, no such measures were taken, and as a result, when the main air supply was interrupted, the pressure in the vessel dropped sharply, causing the material level in the reactor to become under vacuum. Fortunately, no explosion occurred. It’s necessary to draw proper lessons from this...