For a cooling top pumparound for a vacuum tower, which is more useful: to use a larger flow rate (140 m3/h) at higher temperature (78C) or use smaller flow rate (100 m3/h) at lower temperature (70C)
Answers
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21/04/2017
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Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
I assume the size of the heat exchanger is a variable in your question. If so, the answer is that it doesn't matter. The system, pump and exchanger is designed to achieve a target overhead vapor temperature, however it is attained. There is a design guide for that temperature.
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20/04/2017
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Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
Normally more hotter flow is better but to some extent it depends on what you are trying to accomplish. If you are trying to minimize load on the first stage ejector, you would probably get a lower tower outlet temperature (and lower load on the ejectors) with the cold PA temperature. If you are trying to maximize heat recovery into crude oil and/or prevent forming ammonium chloride salts in the vacuum tower, then the higher temperature is going to be better.
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