What do you do when the tower fluctuates and the steam cannot be regulated?

Temperature changes must be caused by changes in the composition of the top and bottom of the tower. At this time, when adjusting the incoming and outgoing materials, we are afraid that unqualified key material indicators will affect the purity of the next tower or even the product.

If the steam cannot be adjusted, does it mean that the steam pressure or steam flow cannot be adjusted? If the pressure cannot be adjusted, the blowing flow rate of the distillation tower can be adjusted. Remember to empty and open the steam drum. Unstable steam pressure and changes in flow rate can easily bring water into the tower, causing tower flushing, with serious consequences. At this time, the following feeds can be appropriately reduced, and the side line extraction can be changed to manual control. There should be no problem with the quality.

I took a look and roughly understood what you said. Do you think this is the case? The heat source of the distillation tower is steam. As a result, the steam boiler failed and the steam pressure dropped, but production still needs to be maintained. Is this what you mean? This one doesn’t have to be complicated! To reduce the load of the tower, that is, on the premise of ensuring the temperature of each sensitive plate, reduce the feed to an appropriate amount, and the reflux should also be appropriately reduced. As for the next process, it will naturally need to be adjusted accordingly. There seems to be no issue worth hesitating about.

The friend on the 4th floor is right. At this time, you can only adjust the distillation tower by adjusting the feed volume, and at the same time make corresponding adjustments to the reflux volume.

Reduce the feed volume and adjust the production volume

Well, in fact, the steam pressure suddenly dropped at the beginning, and the operator asked to reduce the load in a short period of time. Because the operation was unskilled, the load was reduced, but the whole system was messed up. As a result, the temperature was wrong, and the liquid level was even wrong. Almost all the liquid levels at the bottom of the tower were high. A previous steam failure recovered in a short period of time. The operators had just adjusted various systems of the tower, and the steam pressure suddenly returned to normal. Then the entire line of the tower was dry. In order to prevent the dry tower from causing the bottom pump to run dry, several pumps were stopped in a short period of time. It seems that there is still a lack of experience. Only by actually performing the operation can you know how to adjust the entire system and how to choose important operations when a certain part of the parameters changes. Thank you for your discussion

Just reduce some load appropriately.

From what the original poster said, it can be seen that the operator's level is relatively limited. However, a more thorough solution is to introduce advanced control, which will automatically find the sensitive temperature for adjustment without over-adjustment or improper adjustment. Because the temperature of the tower has a lag, and the various control points are coupled to each other, if an average person makes adjustments when the conditions fluctuate, it will cause large fluctuations. If the interference fluctuation is not large and will be restored soon, be sure to pay attention to small adjustments. Even if there is a quality problem at that time, don't worry.

The feed should be reduced in time and the discharge volume at the bottom of the tower should be increased. At this time, if the product is unqualified, it can be recycled.

Not to mention advanced control, in fact, our DCS control system is already very good. Honeywell's system, DCS and FSC systems are said to be very famous, but the problem is that the first time driving is basically manual, the foreign instrument personnel came back for more than ten days and only completed a few comparisons. Complex control loops, but simple and cascade ones have not been dealt with, and most of our own instrumentation personnel have just come out of school with limited skills. Therefore, as long as many things can be done manually, there is no way to turn them into automatics. I gave the leader several suggestions, but the leader said, if you can do it manually, do it manually first. What's the rush? So what can we do, so when there is a relatively large fluctuation in the system, the operator will be exhausted. One operator has more than 20 screens and 7 or 8 towers, which is simply too busy. This time it is said that there is no need to adjust the PID parameters. There will be no problem if you directly use the manufacturer's own adjustment parameters and system. I didn’t dare to ask any more questions. I hope there won’t be any big problems when I drive again this time.~

Then I feel that the workload of the workers in your company is too heavy, and their appearance is too poor. “There is no need to adjust the PID parameters, just use the manufacturer's own adjustment parameters and system and there will be no problem." I don't think it is appropriate, at least it means that your company has too few experts. It takes an expert to handle it flexibly according to the actual situation. I have also entered the chemical industry not long ago. I think the poster should first reduce the reflux, reduce the extraction volume at the top of the tower, and reduce the feed (it is estimated that your company's distillation must be in the state of supercooled liquid, so this measure can be taken). If it can be stabilized, do not increase the extraction at the bottom of the tower. If it cannot be stabilized, slightly increase the extraction at the bottom of the tower. If there are experts who disagree with reducing reflow, please tell me. By the way, you can point out the reasons, theoretical explanations, etc. Thank you!

It is not undesirable to reduce the reflux, but the temperature at the top of the tower should be observed in time to ensure that the top components are qualified, because the top components will be unqualified after the reflux flow is lower than the minimum reflux. Secondly, as the separation power of the distillation tower, steam must be related to the load of the tower. When the power is large, the load is high, and the power is small and the load is low. When the steam pressure is low, priority should be given to stopping some equipment to ensure the normal operation of other equipment. Otherwise, no matter how good the operator is, he will not be able to make simultaneous linkage adjustments to the entire system.

Increasing the feed temperature and reducing reflux may achieve the goal. :lol :lol :lol

Adjust the feed volume and return volume, and at the same time cut out the product extraction line without entering the product tank. Wait for the return to normal and product analysis to pass before switching back to the product tank. If this process is short and the impact on product quality is not great, there is no need to cut out the product. ；

I would like to ask some questions about whether the distillation tower operation was trial-run before production? If there is a problem with the system output, are there operation records for maintaining full reflux operation (stop feeding)? If there are operation records, the amount of steam and reflux required should be compared with the amount of feed. If you can make good use of both operation records and quality control analysis records, you can analyze the appropriate operating parameters, and these parameters are the best records for production.

Directly use the parameters given by the manufacturer to adjust? Manually if possible? I fainted. I wonder how many people are allowed in a class in your company? The DCS hardware has improved, but the people's soft skills are not there, so it can't be used well. PID tuning is one of the most basic skills for instrument personnel, usually at the beginning of the installation. In many better factories, the operators will make rough adjustments.

Only increase reflux when the tower is dry. In this topic, it is generally wrong to increase extraction when the tower liquid level is high. The tower temperature will drop and the composition will change. Increasing extraction will cause light components to flow down the tower and the product will be unqualified. I was operating at that time, but things got messed up. Then a master stepped in and basically didn't adjust the tower. He put the steam in series with the temperature at the bottom of the tower, and adjusted the reflux a little and everything was fine.

May I ask which company you are from?

A master is a master. “Just cascade the temperature of the steam with the bottom of the tower and adjust the reflux a little and it will be OK." Fundamentally, we have grasped the three major balance relationships of distillation: material balance, gas-liquid balance and heat balance. When theory is transformed into practical operation, there are actually only a few keys to control.