Discussion: The issue of mid-pressure reflux in atmospheric and vacuum distillation?

I don’t understand what it means. Is it to use slag removal for mid-stage reflux?

It refers to the mid-stage reflux in the atmospheric pressure column; is it cyclic reflux in the reduced pressure column?

Why is the removal of slag not progressing smoothly? What is the cause? Does the poster want to drill new holes in the tower wall to create a return flow? :o

If the removal of slag for external disposal is not smooth, the system should be in a circulating mode; what does reflux mean?

Please note: The question is—can mid-stage reflux be introduced into the atmospheric pressure tower at this time!

At this time, it is necessary to promptly draw the liquid level in the tower to an appropriate position; as the temperature rises, reflux at the top of the tower should be established first, followed by reflux in the middle section. Diesel can be used as a substitute for the oil used for reflux in the middle section during the initial stage.

Using slag reduction for mid-stage reflux seems a bit problematic, right? The slag reduction ratio results in oil with a much higher density; it is impossible to vaporize such oil once it is introduced. The light oils present in it also find it difficult to be extracted at the intermediate temperature levels, while the heavier components cannot return to the bottom of the tower. This leads to disruptions in the operation of the distillation tower, and it is difficult to restore normal operation

What the original poster is referring to is overfilling of the tower due to the inability to send out the residue oil; this kind of problem occurs very rarely in production. When export is hindered, the production rate should be reduced and the temperature lowered promptly. Overfilling of the tower only happens as a result of improper operations. If overfilling has already occurred, using mid-stage reflux will not be very effective, and it may even have the opposite effect. In such cases, the contaminated oil should be sent to the reject stream as soon as possible to restore normal operation

This situation isn’t likely to be caused by an overflow in the tower; rather, the tower is already full. Reflux cannot be used at this point – it’s only possible to proceed after lowering the liquid level and then gradually replacing the liquid. Otherwise, your heat exchange equipment will get contaminated!

At the beginning of operation, it is generally not possible to flush the tower; only flooding the tower is feasible. The fluid sent out cannot be returned; this is different from the situation in normal production when the residue pump fails to deliver sufficient flow.

Midstream reflux can be established, but first the feed rate needs to be reduced. Check whether the side-line products are qualified; if not, discard the unqualified products. The only long-term solution is to identify the reason for the poor discharge of residue oil: Is the pump not properly selected? Issues with pipeline valves? Excessive pressure drop? Otherwise, coking is likely to occur at the bottom of the tower.

If delivery is not smooth, a closed-loop circulation can be used.

Where was this atmospheric and vacuum distillation unit designed? If the transfer of residue oil is hindered, which tower could experience overpressure? Here, I can only provide an answer based on my own understanding: 1. I believe that the slag cannot be removed; first and foremost, the vacuum distillation tower will be affected, as the slag at the bottom of the tower will end up in the various side streams of the vacuum distillation process, resulting in excessive residue content in the products obtained. It is possible to apply pressure at the middle stage, but unless the issue of removing the slag is resolved, the problem will still remain unsolved. . . If the removal of slag for external disposal is not smooth, the amount of slag to be processed should first be reduced and the temperature lowered; if that doesn’t work, vacuum should be removed or a closed-loop circulation system should be adopted. Once the cause is identified, operations can resume normally. . . 2. If your unit is operated at atmospheric pressure only without pressure reduction, then the solid residues cannot be discharged outside, and the consequences of this are far more severe than the tower flooding accidents caused by discharging slag under reduced pressure. . . The quality of gasoline and diesel just can’t be maintained at all. . . It might also cause contamination of the finished cans. The corrective measure is to operate in a closed-loop cycle or at a reduced capacity until the cause is identified, after which normal operation can resume. . . :lol