Page 92 - Applied Process Design For Chemical And Petrochemical Plants Volume II

Distillation 81

the aavg as algebraic average, and the geometric means is In summary, the calculation procedure is as presented
used in these cases. by the authors:
For the systems rated above, the minimum reflux ratio
is [96]:

For extreme cases it may be necessary to calculate down Rmin = RF + ROF + RS (8- 153)
from the top and up from the bottom until each section
shows a fairly uniform temperature gradient from tray to
tray. Then the Fenske relation is used for the remaining
trays, using the conditions at the trays calculated as the This includes recognizing the contribution from the
terminal conditions instead of the actual overhead and feed (RF), “other feeds” (k~), and sidestreams (Rs). The
bottoms. RF portion is determined assuming no other feeds or side-
streams are present. The &F and Rs parts represent the
Chou and Yaws Method 1961 summation of the contributions of other feeds and side-
streams to the overall column minimum reflux ratio. The
This method for multicomponent distillation involving calculation sequence consists basically of three steps, here
more than one feed and more than one side stream reproduced by permission of Chemical Engineering,
requires a reliable minimum reflux. Chou and Yaws, April 25, 1988, all rights reserved [96] :

The column