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Mass Transfer - Engineering

Q1:

Back-trapping in a distillation column

A increases tray efficiency.

B decreases tray efficiency.

C reduces pressure drop.

D is desirable, as it provides improved vapour-liquid contact.

ANS:B - decreases tray efficiency.

Back-trapping in a distillation column typically decreases tray efficiency. Here's why:

  • Back-trapping occurs when liquid flows down a tray in a distillation column but is hindered from flowing down further by a buildup of liquid on the tray above.
  • This buildup of liquid prevents efficient downflow of liquid, which can lead to reduced surface area for vapor-liquid contact and decreased mass transfer efficiency.
  • As a result, back-trapping tends to decrease the efficiency of the tray in promoting vapor-liquid contact and separation of components.
  • Back-trapping does not necessarily affect pressure drop or improve vapor-liquid contact; instead, it hinders the proper functioning of the tray by impeding the flow of liquid.
Therefore, back-trapping in a distillation column typically decreases tray efficiency.