Method of optimizing two distillation columns using different pressures?
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For example, in atmospheric and vacuum distillation, an atmospheric pressure condenser can be used in combination with a vacuum reboiler. There are likely many methods; I have tried two of them. In one approach, the atmospheric pressure column is not equipped with a condenser, and the reduced pressure column is not equipped with a reboiler, with a heat exchanger being used to connect the two columns. It looks clearer this way, but it doesn’t seem to converge very well. 2 Both atmospheric and vacuum distillation units are equipped with condensers and reboilers; a virtual stream is taken from the top of the atmospheric column, and another virtual stream is taken from the bottom of the vacuum column. This method converges relatively well. I would like to ask everyone if there are any other methods? ? Also, what is the general purpose of setting up virtual logistics?
It feels like a tongue twister~~~:o
Another approach is to use define for the load, directly referencing the condenser or reboiler load, without the need to use virtual streams.
The CN control module can be used to match the condenser and reboiler, but I haven’t used it yet. Has anyone used the CN control module?
1 I think the reason it’s difficult to converge is that, after being separated, convergence also follows a sequence. And if they are not separated, they converge together while running. 2 Waiting for experts to answer; I’m not sure either
The first case mentioned should be a feedback loop, and convergence in such a situation is rather difficult. Someone mentioned using DEFINE to define compliance; I think that’s roughly the first case. I also want to ask whether the condenser and reboiler can match perfectly?