The temperature at the top of the atmospheric pressure tower is high!
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Hello, everyone who is more experienced than me; I’m here to ask for help again. Our plant uses three-column distillation for methanol purification, and these past few days I have been troubled by the high temperature at the top of the atmospheric pressure column. The atmospheric tower in our plant is of the tray-and-packing composite type, with 26 trays in the retention section and four layers of packing in the distillation section. The specification requires that the tower top angle not exceed 70 degrees, but it often reaches 75 degrees nowadays. The reflux enters from the first layer of packing (counting from top to bottom); an abnormal phenomenon is that the temperature of the second layer of packing is higher than that of the fourth layer! (For example, the temperature is 75 degrees on the fourth layer, while it exceeds 85 degrees on the second layer.) What is the reason for this? Could it be that I set the reflux value too high? Another issue is that the feed temperature to the atmospheric pressure tower is high; the specified value is 75 degrees, but it currently reaches 100 degrees! ! ! The pressure tower is working fine, so what’s going on here? The manager keeps pressing me for higher production levels every day; I’m so confused! Everyone says that distillation is the most relaxed and hassle-free job, but why do I feel so tired? Ah, thank you all for your effort; please help me out! Thank you so much!
The feed temperature is high. What’s the temperature at the bottom of the tower? Also, is the reflux rate high? Is the pressure difference in the tower significant? Is the pressure in the tower too high? Find ways to reduce the feed temperature; moreover, the tower shouldn’t operate under light load – the load should be increased
The temperature at the top of the tower is the boiling point of methanol at that pressure. I wonder if it might be that the pressure at the top of the tower is too high, which is causing the high temperature there. Also, is the temperature at the bottom of the tower normal?
The bottom temperature is normal, and sometimes even a bit lower. If the pressure at the top of the tower is high, a high temperature can be understood, but when overheating occurs, the top of the tower is usually under no pressure! At this point, the pressure drop across the tower is greater. Some say it’s because the load on the pressurized tower is too low while the load on the atmospheric tower is too high – is that the reason? But if the extraction valve of the pressure tower is opened wider, it will cause severe pressure release in the tower, preventing pressure from being built up. What should be done?
There is a manual valve from the pressure column non-condensable gas to the atmospheric column cooler; please check whether it is in the open position. If it’s on, turn it off. If the reflux rate is too high, the temperature at the top of the tower will naturally increase. Calculate the reflux ratio for a tower operating at atmospheric pressure; if it exceeds 3, increase the amount of purified methanol extracted. You also said that the temperature of the filler in the second layer would be higher than that in the fourth layer. In my opinion, this is due to excessively high reflux rates. Increase the recovery rate of pure methanol, make some adjustments, see what happens, and then let me know the results.
An inversion has occurred; pay attention to adjusting the amount of water used for extraction.
The feed temperature for the atmospheric pressure tower is required to be 75 degrees. So what is the bottom temperature of the pressurized tower?
Adjust the load of the two towers; it’s possible that the load on the pressure tower is either too high or too low. The pressure in the atmospheric tower is too high. Atmospheric pressure distillation reflux is not appropriate.
The pressure in the tower bottom is between 125°C and 127°C. Currently, when the top of the atmospheric pressure tower is under pressure (around 20-30 kPa), the temperature at the top remains normal. However, sometimes the top of the tower comes to be at atmospheric pressure, and in that case the temperature rises above normal levels. It makes sense; without pressure, the temperature will definitely be high. The question is, where does the pressure go?
It is a common problem for the pressure at the top of an atmospheric pressure tower to be low or even negative. However, it’s strange that you say the pressure decreases while the temperature rises; when the pressure is low, the temperature should also be low. . . . . . Am I being biased? ?
It’s probably caused by the excessive return temperature. Is the pressure normal? Reduce the reflux temperature