The top and bottom temperatures of the distillation tower decrease with each operation
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There is a strange phenomenon: there are many loops in the process, and each time it runs, the temperatures at the top and bottom of the distillation tower decrease. When the tower starts operating, the temperature at the top is around 58 degrees, but it drops to 40 degrees later on. The composition of the mixture doesn’t change much. I set the convergence accuracy for the composition to 0.001, while using the system’s default value for temperatures. If I set the temperature threshold to something like 0.1, it becomes very difficult to achieve convergence – the process won’t converge even after running all night. I would appreciate advice from experts on how to resolve this issue
By looking at my previous posts, I can see that this problem has been resolved; it was because there was a small amount of non-condensable gas in the cycle that wasn’t removed, and over time this led to an increase in its quantity. As a result, the temperature at the top of the tower decreased. In terms of engineering design, it’s necessary to address the issue of removing such non-condensable gas. I hope this will be helpful to those who encounter the same situation
Top poster: A few days ago, while the process was stable in a separation tower, it was observed that the temperature at the top of the tower was slightly low. Experienced operators assumed that non-condensable gas had accumulated at the top of the tower, so they activated the flare line of the reflux tank to vent gas, and as a result the temperature at the top increased