Page 254 - Separation process engineering

the feed bubble-point temperature. Use a matrix to solve the mass balances. Use bubble-point
calculations for one iteration toward a solution for stage compositions and to predict new
temperatures that could be used for a second iteration. Report the compositions on each stage and in
the reboiler, and the temperature of each stage and the reboiler.

Solution

This is a long and involved problem. The solution will be shown without all the intermediate
calculations.

Start with a bubble-point calculation on the feed, . This converges to T = 60°C at p =
202.6 kPa. The K values are K = 3.00, K = 1.05, K = 0.072.
C5
C8
C4

Next, calculate flow rates
L = (L/D)(D) = (1.5)(550) = 825 kmol/h = L , L 2
1
V = L + D = 1375 kmol/h = V , V , V 4
3
2
= L + F = 1825 kmol/h = L 3

B = 450 kmol/h = L 4

Calculate matrix variables A, B, C, D for each component (see Table 6-2 for n-C solution).
4

Table 6-2. Matrix calculations for Example 6-1 for n-C 4