Separation Process Principles- 2n - Seader & Henley - Solutions Manual

9 025 08125 x at 09 x at 010 09 01 from

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: integral ln(W0/W) 0.2561 0.2506 0.2449 0.2392 0.2333 0.2273 0.2212 0.2149 0.2085 0.2020 0.1953 0.1885 0.1816 0.1745 0.1672 0.1599 0.1523 0.1446 0.1368 0.1288 0.1207 0.1124 0.1039 0.0953 0.0866 0.0776 0.0685 0.0592 0.0498 4.483 4.575 4.674 4.780 4.894 5.017 5.150 5.293 5.449 5.618 5.803 6.006 6.228 6.474 6.746 7.050 7.390 7.773 8.209 8.709 9.286 9.960 10.759 11.719 12.894 14.364 16.257 18.783 22.322 0.00453 0.00462 0.00473 0.00484 0.00496 0.00508 0.00522 0.00537 0.00553 0.00571 0.00590 0.00612 0.00635 0.00661 0.00690 0.00722 0.00758 0.00799 0.00846 0.00900 0.00962 0.01036 0.01124 0.01231 0.01363 0.01531 0.01752 0.02055 0.00453 0.00915 0.01388 0.01872 0.02367 0.02876 0.03398 0.03935 0.04488 0.05059 0.05650 0.06262 0.06897 0.07558 0.08247 0.08969 0.09728 0.10527 0.11373 0.12272 0.13235 0.14271 0.15395 0.16625 0.17988 0.19519 0.21271 0.23326 W/W0 1.000 0.995 0.991 0.986 0.981 0.977 0.972 0.967 0.961 0.956 0.951 0.945 0.939 0.933 0.927 0.921 0.914 0.907 0.900 0.893 0.885 0.876 0.867 0.857 0.847 0.835 0.823 0.808 0.792 A plot of the ethanol mole fraction in the instantaneous distillate as a function of mol% distilled is given on the following page. Exercise 13.12 (continued) Analysis: Rayleigh distillation (continued) Exercise 13.12 (continued) Analysis: (continued) Distillation with 2 stages plus a reboiler: To obtain the maximum cumulative distillate purity for 20 mol% distilled, operate close to total reflux, L/V = 1. The relationship between yD and xW in Eq. (1), with x = xW and y = yD, is obtained from a McCabe-Thiele diagram by drawing a series of operating lines of slope = L/V = 1 (45o line). For each operating line, starting from the intersection with the 45o line, which is yD, 3 stages are stepped off to determine the corresponding xW. A typical construction that starts from yD = 0.65 is shown on the next page, where the xW = 0.02. Other sets of values are given in the following table, which also includes values of the integrand, f = 1/(yD - xW), from which the integral is evaluated by the trapezoidal rule with variable increments of ∆xW. For example, the increment of the integral from x1 to x2 is (x1 - x2)(f1/2 + f2/2). The increments are summed over the region from xW = 0.033 to the value corresponding to 20 mol% distilled. xW yD from McCabe-Thiele f = 1/(yD - xW) 0.033 0.030 0.020 0.010 0.005 0.001 0.663 0.66 0.65 0.61 0.55 0.40 1.587 1.587 1.587 1.667 1.834 2.506 Increment of Integral Cumulative ln(W0/W) 0.0048 0.0159 0.0163 0.0088 0.0087 0.0048 0.0207 0.0370 0.0458 0.0545 From the above table, at xW = 0.001, a very low value, ln(W0/W) = 0.0545. Thus, W/W0 = 0.947 or only 5.3% distilled. Thus, essentially all of the ethanol will be distilled when 20 mol% of the charge has been distilled. The composition of the cumulative distillate is given by Eq. (13-6), which becomes: yD avg = W0 x0 − Wx x0 − W / W0 x 0.033 − 0.8(0.0) = = = 0165 . W0 − W 1 − W / W0 1 − 0.8 It should be noted from the above table that if only 5.3 mol% of the charge were distilled,...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online