When a distillation column receives a saturated vapor feed, what is the corresponding value of ‘q’? (where q represents the fraction of the feed stream that is liquid ?
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Answer: A. 0
Explanation
A saturated vapor feed has a liquid fraction q of zero because none of the entering stream is liquid. The feed quality parameter q represents the fraction of liquid present in the incoming distillation feed stream. Saturated vapor enters the column entirely in the vapor phase, making the liquid fraction equal to zero. Distillation column feed condition is quantified by the q-value parameter on McCabe-Thiele diagrams. Feed thermal condition determines the intersection locus of the q-line with enriching and stripping operating lines. A saturated vapor feed yields a vertical q-line with an infinite slope on the graphical separation diagram.
A q-value of 1 corresponds to a saturated liquid feed entering the distillation column. Stating q equals 1 for a vapor feed confuses the liquid fraction with solid or gaseous phase definitions. Zero represents the correct liquid fraction for saturated vapor, making alternative positive values incorrect.
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