How does Vapor/ Liquid ratio at the bottom tray and Reflux to Feed ratio affect stripping quality? What happens when number of trays is increased?
Answers
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11/09/2012
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A:
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Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
The separation achieved at each theoretical stage depends on equilibrium which is affected by the relative quantities of the vapor and liquid on the tray as well as the compositions of each. We say that the equilibrium is “driven” in one direction or the other when one of these quantities or compositions is changed. Changing the reflux ratio and reboiler duty change the quantity and composition of liquid relative to the feed quantity and composition in the section above the feed tray, and the quantity and composition of vapor relative to feed material on trays below the feed tray. Due to the changes in equilibrium, changes in product compositions are seen. Both the rectifying and stripping “qualities” are affected.
Adding trays simply increases the number of opportunities for the heat and mass transfer to occur, thus changing the overhead or bottoms compositions.
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