Draw rectification and stripping lines for a fractionation
column that is producing a distillate composition of 91.4 percent when feed is
36 percent in more volatile component.
The feed quality is 1.04 and the equilibrium data can be estimated by a
relative volatility of 4.12. The
residue composition is 0.565 percent.
Solution:
Equilibrium curve (y versus x) can be generated using the
relationship: y is equal to alpha x over (one plus (alpha minus one) times x).
Draw a diagonal line (45 degree slope).
Determine the value of the intercept, I, as xD
over (R plus one).
Locate point 1 having coordinates (0, I).
Locate point 2 having coordinates (xD, xD).
Join points 1 and 2 and draw a line, called rectification or top operating line (TOL).
Locate point 3 having coordinates (xF, xF).
Locate point 4 having coordinates (xF/q, 0).
Join points 3 and 4 and draw a line, called feed quality (q)
line and extend it beyond the equilibrium curve.
Locate the intersection of q-line and rectification line and
mark it as point 5.
Locate point 6 having coordinates (xW, xW).
Join point 6 and 5 and draw a line, called stripping or bottom operating line (BOL).
Determine the value of the intercept, I, as 0.477.
Locate point 1 having coordinates (0, 0.477).
Locate point 2 having coordinates (0.914, 0.914).
Join points 1 and 2 and obtain rectification line or TOL.
Locate point 3 having coordinates (0.36, 0.36).
Locate point 4 having coordinates (0.346, 0).
Join points 3 and 4 and draw q-line and extend it beyond the
equilibrium curve.
Locate the intersection of q-line and rectification line and
mark it as point 5.
Locate point 6 having coordinates (0.00565, 0.00565).
Join point 6 and 5 and draw a line, called stripping line or BOL.