Page 81 - Applied Process Design For Chemical And Petrochemical Plants Volume II

70 Applied Process Design for Chemical and Petrochemical Plants

The recoveries of the non-key components are estimat-
ed by first calculating the correlation constants:
(8- 126)
bHK/f& = 0.9539, given
Solving for recovery of component i in the distillate A=-log( 0.9539 )
gives
1 - 0.9539
+
di/fi = (loA qB)/(l 1oA qB) (8-127)
= -log 20.69 = -1.3158
From a material balance, recovery of component i in the
bottoms is dLK/fm = 0.9484, given
0.9484 ) ( 0.9539 )I
bi/fi = 1/(1 + aiB) (8-128) aLK = 1.45, from Table 83

The correlation constants required for Equations 8-127
and &128 are obtained by specifying a desired recovery of 1 - 0.9484 1 - 0.9539
the light key component LKin the distillate and the recov- B= log 1.45
ery of the heavy key component HK in the bottoms. Then
the constants are calculated as follows: = (log 380.3)/(10g 1.45) = 15.988

The recovery of component M in the distillate is then
(8- 129) dM/fM = (10-1.3158 2.3015.988)/(1 + 10-1.3158 2.3015.988)
= 0.99997, from Equation 8-127

The recovery of component M in the bottoms is
bM/fM = 1/(1 + io-1’3158 2.3015.988)
= 0.00003, from Equation 8-128
Example 8-22: Multicomponent Distillation by Yaw‘s Repeating Equations 8-126 and 8-127 for each of the
Method [ 1241 (used by permission) other non-key components in the feed mixture gives the
results shown in Table 84. Good agreement was demon-
Assume a multicomponent distillation operation has a strated.
feed whose component concentration and component rel-
ative volatilities (at the average column conditions) are as Algebraic Plateto-Plate Method
shown in Table &3. The desired recovery of the light key
component 0 in the distillate is to be 94.84%. The recov- Like any plate-to-plate calculation this is tedious, and in
ery of the heavy key component P in the bottoms is to be most instances does not justify the time because shorter
95.39%.
Table 8-4
Results for Example 8-22 for Multicomponent
Table 8-3 Distillation
Yaws’ Method for Selected Distillation Recovery from a
Specific Feed for Example &22 Percent recovery
In dist. In btms.
Component fi ai Component (100 Wfi) (100 bi/fi)
0.10 2.30 M 99.997 0.003
0.13 1.75 N 97.731 2.269
0.25 1.43 0 (LK) 94.840 5.160
0.23 1 .oo p (HK) 4.610 95.390
0.13 0.90 Q 0.889 99.111
0.08 0.83 R 0.245 99.755
0.06 0.65 S 0.005 99.995
-
Used by permission, Hydrocarbon Processing, Yaws, C. L., et a1 V. 58 No. 2 Used by permission, Hydrocarbon Processing Yaws, C. L., et al V. 58 No. 2
(1979), p. 99, Gulf Pub. Co., all rights reserved. (1919), Gulf Pub. Co., all rights reserved.