The top temperature is high while the middle temperature is low; why?
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Hello everyone, I have a question. I’m working with a pressure distillation column operating at 0.5 Mpa, using external reflux. The substances to be separated are highly volatile substances at negative temperatures. In this column, which is over 10 meters tall, there is a problem of temperature inversion – that is, the temperature in the middle of the column is lower than the temperature at the top. Moreover, the temperature at the top is not the boiling point of the substances to be separated; it is 7 to 8 degrees higher than that boiling point. What could be causing it?
As the title suggests, are there any particular things to keep in mind regarding the connection of this heat exchanger with the distillation tower and the reflux tank?
I was wondering, is it common in industry to install the reflux pump near the reflux tank?
Could the original poster post a simple diagram? That would make it easier for everyone to figure out the cause
There is a problem with the distributor of your return feed. The return fluid is not evenly distributed, resulting in channeling. Either there’s a problem with your tray, causing the cold liquid returning to flow downward from one side.
Check this: 1. Water is present in the raw materials; this water turns into steam, which carries heat to the top of the tower； ⒉The thermometer is not working; contact the instrumentation team to have it calibrated.
May I ask the original poster, what is the temperature of the liquid in the bottom reactor vessel?
Another situation is when the temperature measurement point in the middle is very close to your feed or return pipe.:lol
It’s definitely the temperature measuring instrument that’s inaccurate; this phenomenon occurs for a short period of time. Other factors might be responsible, but it’s impossible for this situation to persist over an extended period
Hehe, it’s a short-term issue; perhaps the feed temperature dropped suddenly (if the feeding is at the middle of the tower), which disrupted the temperature gradient； But soon your tower collapses. If this occurs while all feed materials and products are functioning normally, it indicates a problem with the instruments; have someone take a look at them. There is another scenario: there is a tower on the outside, with a separate interior section; the material is drawn out from the middle, cooled, and then sent to the tower below. For example, the tower used in ADIP might work this way. Hehe, no cheating allowed, OP
Could it be that the heat transfer is uneven? The temperature measured at the top of the tower is the gas phase temperature, while the temperature measured in the middle is the liquid phase temperature. If issues such as liquid phase skew on the top tray lead to a reduced heat transfer efficiency, the temperature at the top of the tower will be higher than that in the middle of the tower.