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Solution of equations, feeds to units
Table 4.3.
3
Unit Component CHEMICAL ENGINEERING 4 Total
1
2
1 1k 110.85 0.01 0.0 10.31 121.17
2 2k 11.09 98.01 98.0 10.31 217.41
3 3k 1.11 19.6 98.0 200.51 319.22
4 4k 11.07 97.81 0.0 208.3 317.19
5 5k 10.96 0.98 0.0 206.22 218.16
Recycle flow from the second column
This should approximate to the azeotropic composition (9 per cent alcohol, 91 per cent
water). The flow of any component in this stream is given by multiplying the feed to the
column ( 5k ) by the split-fraction coefficient for the recycle stream (˛ 15k ). The calculated
flows for each component are shown in Table 4.4.

Table 4.4. Calculation of recycle stream flow
Component 1 2 3 4 Total
5k 10.96 0.98 0.0 206.22
˛ 15k 0.99 0.01 1 0.05
Flow
˛ 15k 5k 10.85 0.01 0 10.31 21.17
Per cent 51.3 0.05 0 48.7

Calculated percentage alcohol D 51.3 per cent, required value 91 per cent. Clearly
the initial value selected for ˛ 154 was too high; too much recycle. Iteration, using the
spreadsheet, shows the correct value of ˛ 154 to be 0.0053, see Figure 4.19b.

Reactor conversion and yield
alcohol in alcohol out 11 21 110.85 11.09
Conversion D D D
alcohol in 11 110.85
D 90 per cent, which is the value given
acetone out 22 98.01
Yield D D D
alcohol in alcohol out 11 21 110.85 11.09
D 98.3 per cent, near enough.

Condenser vapour and liquid composition

The liquid and vapour streams from the partial condenser should be approximately in
equilibrium.
The component flows in the vapour stream D ˛ 32k 2k and in the liquid stream D
˛ 42k 2k . The calculation is shown in Table 4.5.
These compositions should be checked against the vapour-liquid equilibrium data for
acetone-water and the values of the split-fraction coefficients adjusted, as necessary.