Page 206 - Chemical engineering design

A] ... .. .. .A/... .. .. .B/... .. .. .C/.. .. ... .D/. .. ... ..E/... ... ..F/.. .. ... .G/.. .. .. ..H
98 FLOW-SHEETING 183
99
100
101 Recycle flow composition
102
103 alpha 1, 5, 4 D 0.05
104
105 Component 1 2 3 4 Total
106
107 Flow 10.85 0.01 0.00 10.31 21.17
108
109 Percent 51.26 0.05 0.00 48.70
110
111
112

Figure 4.19a.

A] .. .. .. . .A/... .. .. .B/.. ... .. .C/.. ... .. .D/.. .. ... .E/.. .. .. ..F/. ... .. ..G/.... .. ..H
98
99
100
101 Recycle flow composition
102
103 alpha 1, 5, 4 D 0.0053
104
105 Component 1 2 3 4 Total
106
107 Flow 10.85 0.01 0.00 1.08 11.94
108
109 Per cent 90.88 0.08 0.00 9.04
110
111
112

Figure 4.19b.

Step 9: Change the values of the appropriate split fractions, or fresh feeds, in the
primary table, Figure 4.15, and observe the changes to the calculated values: which will
carry through the spread sheet automatically. Iterate on the values until the desired result
is obtained.

Comments on the first trial solutions
Table 4.3 shows the feed of each component and the total flow to each unit. The compo-
sition of any other stream of interest can be calculated from these values and the split-
fraction coefficients. The compositions and flows should be checked for compliance with
the process constraints, the split-fraction values adjusted, and the calculation repeated,
as necessary, until a satisfactory fit is obtained. Some of the constraints to check in this
example are discussed below.