Problems with catalytic fractionation

In actual production, it’s not like that, right! Let’s hear from others’ valuable opinions.

Is it because light oil has a lower density, which results in it occupying more volume?

The main advantage of the raw material is its resistance to cracking, which can prevent an increase in the liquid level at the bottom of the tower. In actual production, the liquid level at the bottom of the tower is closely related to factors such as the temperature of the baffle plates and the temperature at which diesel is extracted. It's just my personal opinion; I'd like to hear others' insights.

I have never seen such a situation; we are small devices, so I don’t know what kind of ones you use

It shouldn’t be this way. The feedstock is light, resulting in less coking. The bed temperature in the regenerator decreases; if the reaction temperature is kept constant, the catalyst-to-oil ratio will increase. Relatively speaking, the catalyst’s activity is higher, the feedstock cracks more easily, and the low liquid level in the distillation tower should decrease. Can the original poster provide your names and the source?

If the tower referred to by the original poster is a light diesel stripping tower, then it’s possible; however, the liquid level in such a tower is usually under automatic control, so the level changes don’t vary much.

As the raw material becomes lighter, the liquid level at the bottom of the tower should decrease.

Could the original poster tell us about the current temperature of the anti-reheat system?

It may be caused by vaporization during the distillation process

That’s not correct, right? With the same raw material, a higher degree of cracking occurs under the same conditions, which leads to a decrease in the liquid level at the bottom of the distillation tower

I disagree with the view that the raw material becomes lighter and the bottom liquid level rises; on the contrary, it is the heavier raw material that constitutes the main cause of an increase in the bottom liquid level, all other conditions remaining constant. . . Let’s start with the catalytic cracking mechanism. . . The earliest research on catalytic cracking started with diesel as the subject of study. In practical applications, as technology advanced and the performance of catalysts improved, processing of wax oil gradually began to be employed, along with the use of wax oil mixed with residue oil. Nowadays, crude residue is used in its entirety for such processes, and there are even reports of attempts to process reduced-residue oil directly. . . Generally speaking, the density and boiling range of catalytic feedstocks determine their weight. On the premise that other parameters remain essentially the same, as well as the processing plan and process parameters used being consistent, the lighter the raw material, the easier it is to crack; as a result, the amount of reprocessed oil and slurry will be very low. Under the same reaction temperature conditions, the proportion of gases in the gas-rich components obtained without catalysis is much higher than that in the gas-rich components from heavy catalytic feedstocks. Therefore, the liquid level at the bottom of the tower is initially quite low. . . Since, regardless of the density of the raw materials, the methods for controlling or adjusting the liquid level at the bottom of the distillation tower are essentially the same, any differences in actual control are mainly due to the operational practices of the workers on duty. . . The heavier the catalyst material, the greater the amount of slurry; it may also be necessary to operate the large and small external discharge lines in order to prevent the liquid level at the bottom of the distillation tower from rising too high. . . It is also necessary to increase the amount of slurry returning to the tower in order to raise the temperature at the oil and gas inlet and prevent coking. . . Haha. . . :lol

Hello: The catalytic raw materials are becoming lighter – does this not refer to the raw materials themselves being lighter? It is likely that the content at 350°C in the catalytic feed is too high; in other words, there is a high proportion of diesel components, which makes cracking difficult, resulting in an increase in the low liquid level in the distillation tower.

Stop talking so much upstairs. . . You surely know what is being catalytically processed, right? The catalytic feedstock becomes lighter. . . If you consider it to be higher than 350, then you’re thinking of more diesel; fortunately, you’ve studied petrochemical engineering. . . Gasoline can be cracked and re-cracked again; let alone diesel. Naphtha and diesel are the main raw materials for the ethylene industry, and of course cracking reactions also occur under the action of catalysts. . . If you think there are more ones from before 350, then it still appears to have a low density. . . The catalytic material is lightweight. . . When such raw materials are processed, overall, both the gas yield and the yields of gasoline and diesel are high, while the amount of oil slurry is lower. . . In the fractionation tower, there are fewer heavy components, so the liquid level is low. . . To maintain a certain liquid level in the distillation column, retention measures must be taken; as a result, there is almost no external oil slurry from such feedstock. . . I support the view from floor 12. . . . :lol

Also. . . If you have the chance, please go to the ethylene plant and see what its raw materials are You’ll suddenly see the light, young man. . . What is the technical basis for your claim that diesel does not crack easily? Both paraffin oil and residual sludge can be cracked. . . :lol

Is it because the raw materials have become lighter, and in order to maintain balance at the upper part, you are applying too much pressure downward, which causes the liquid level to rise?

Does that mean there is more heavy fuel in the raw materials, which increases the liquid yield? Is that what it means? Hehe, I don’t quite understand!

Under normal operating conditions, as the feedstock becomes lighter, the liquid level at the bottom of the distillation tower will definitely decrease. Since less of the raw material is converted into heavy components such as slurry, the liquid level at the bottom of the distillation tower must be lower. This is similar to the path to increasing reaction depth; take some time to understand it well.

I agree with the opinion of the moderator of Water Longevity on the sixth floor. In the actual catalytic production process, as the fresh feed becomes lighter (as judged by two key parameters: density and residual carbon, with the composition of the feedstock serving as a reference), the one-pass conversion rate increases under the same conditions; accordingly, the yields of liquid products (diesel, gasoline, and liquefied gas) also increase. As a result, the yields of reprocessed oil and slurry decrease, and the liquid level in the distillation tower drops. At this point, the amount of char formed as a result of the reaction will be insufficient, the bed temperature will be low, and there will not be much recycling of oil or slurry. In such cases, it is necessary to increase the processing volume or lower the reaction temperature, or to change the properties of the feed material. Otherwise, if the liquid level in the distillation tower becomes too low, it will be necessary to add more material back in. :Lol, for the same reason, as the crude oil becomes heavier, the liquid yield decreases; therefore, it is necessary to increase the amount of reprocessed oil and slurry to boost the yield. At this point, there is an excess of heat, so either the reaction temperature needs to be raised or the processing volume reduced. These past few days, our unit has processed a batch of wax oil; the yield was high and there was almost no loss of product. Last month, when processing heavy oil, the yield was low, and the liquid level kept dropping throughout the shift.

The raw material becomes lighter, the gasification rate is higher, so the liquid level at the bottom of the tower should decrease

May I ask the original poster: Do you mean that the raw materials become lighter, the reaction depth decreases, the temperature at the bottom of the distillation tower drops, and the liquid level at the bottom of the tower rises? If that’s the case, then it’s correct. Please take another close look at the operating procedures, and ask the experienced workers carefully. :) :)