A water solution containing 0.005 mole fraction of benzoic acid is to be extracted using pure benzene as the solvent. If the feed rate is \(100 \mathrm{~mol} / \mathrm{h}\) and the solvent rate is \(10 \mathrm{~mol} / \mathrm{h}\), find the number of equilibrium stages required to reduce the concentration of benzoic acid in the aqueous solution to \(0.0001 \mathrm{~mol}\) fraction. Operation is isothermal at \(280 \mathrm{~K}\) (water and benzene are insoluble at this temperature), where the equilibrium data can be represented as (Wankat, 1988)

\(\mathrm{mol}\) fraction of benzoic acid in water \(=0.0446 \times(\mathrm{mol}\) fraction of benzoic acid in benzene)

Problems 7.9 to 7.12 refer to the system water (A)-chlorobenzene (B)-pyridine (C) at 298 K. Equilibrium tie-line data taken from Treybal (1980) in weight percent are given in Table 7.7.

Data From Problem 7.9 to 7.12:-

Problem 7.9:- 

Plot the equilibrium data for the system water-chlorobenzene-pyridine in right-triangular coordinates.
Problem 7.10:- 

It is desired to reduce the pyridine concentration of \(5000 \mathrm{~kg} / \mathrm{h}\) of an aqueous solution from \(50 \mathrm{wt} \%\) to \(5 \mathrm{wt} \%\) in a single batch extraction with pure chlorobenzene. What amount of solvent is required? Solve on right-triangular coordinates. Corroborate your results using the Mathcad or Python programs of Appendix G-1 and G-2.

Data From Appendix G-1:-

Data From Appendix G-2:-

Problem 7.11:-

A \(5000-\mathrm{kg}\) batch of pyridine-water solution, \(50 \mathrm{wt} \%\) pyridine, is to be extracted with an equal weight of pure chlorobenzene. The raffinate from the first extraction is to be reextracted with a weight of pure solvent equal to the raffinate weight, and so on ( \(S_{2}=R_{1}, S_{3}=R_{2}\), etc.). How many ideal stages and what total solvent are required to reduce the concentration of pyridine to no more than \(2 \mathrm{wt} \%\) in the final raffinate?
Problem 7.12:-

A pyridine-water solution, \(50 \mathrm{wt} \%\) pyridine, is to be continuously and countercurrently extracted at the rate of \(2.25 \mathrm{~kg} / \mathrm{s}\) with pure chlorobenzene to reduce the pyridine concentration to \(2 \mathrm{wt} \%\).

(a) Determine the minimum solvent rate required.

(b) If \(2.3 \mathrm{~kg} / \mathrm{s}\) of solvent is used, calculate the number of theoretical stages required, and the flow rates of final extract and raffinate.

Transcribed Image Text:

Table 7.7 Water-Chlorobenzene-Pyridine Equilibrium Data Chlorobenzene-phase, wt% Chlorobenzene Pyridine Water Water-phase, wt% Water Chlorobenzene Pyridine 0.05 99.95 0.00 99.92 0.08 0.00 0.67 88.28 11.05 94.82 0.16 5.02 1.15 79.90 18.95 88.71 0.24 11.05 1.62 74.28 24.10 80.72 0.38 18.90 2.25 69.15 28.60 73.92 0.58 25.50 2.87 65.58 31.55 62.05 1.85 36.10 3.95 61.0 35.05 50.87 4.18 44.95 6.40 53.00 40.60 37.90 8.90 53.20 13.20 37.80 49.00 13.20 37.80 49.00 Source: Data from Treybal (1980) at 298 K and 1 atm. "Water and chlorobenzene phases on the same line are in equilibrium.