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A mixture containing 65.0 mole% acetone (Ac) and the
Chapter 7, Problem 7.42(choose chapter or problem)
A mixture containing 65.0 mole% acetone (Ac) and the balance acetic acid (AA) is separated in a continuous distillation column at 1 atm. A flowchart for the operation is as follows:
The overhead stream from the column is a vapor that passes through a condenser. The condensed liquid is divided into two equal streams: one is taken off as the overhead product (distillate) and the other (the reflux) is returned to the column. The bottom stream from the column is a liquid that is partially vaporized in a reboiler. The liquid stream emerging from the reboiler is taken off as the bottoms product, and the vapor is returned to the column as boilup. Negligible heat is lost from the column, so that the only places in the system where external heat transfer takes place are the condenser and the reboiler.
| Stream Data | |||
| Feed | (1) | Liquid, \(67.5^{\circ}\rm{C}\), 65 mole% Ac, 35% AA | |
| Overhead | (2) | Vapor, \(63.0^{\circ}\rm{C}\), 98 mole% Ac, 2 % AA | |
| Distillate | (3) | ||
| Liquid, \(56.8^{\circ}\rm{C}\), 98 mole% Ac, 2% AA | |||
| Reflux | (4) | ||
| Bottoms | (5) | Liquid, \(98.7^{\circ}\rm{C}\), 15.5 mole% Ac, 84.5% AA | |
| Boilup | (6) | Vapor, \(98.7^{\circ}\rm{C}\), 54.4 mole% Ac, 45.6% AA |
\(\begin{array}{l} \text { Thermodynamic Data }\\ \begin{array}{lrrrr} \hline & & & {\hat{H}(\mathrm{cal} / \mathrm{mol})} \\ \hline & & {\text { Acetone }} & & {\text { Acetic Acid }} \\ T\left({ }^{\circ} \mathrm{C}\right) & {\hat{H}_{l}} & \hat{H}_{\mathrm{v}} & {\hat{H}_{l}} & \hat{H}_{\mathrm{v}} \\ \hline 56.8 & 0 & 7205 & 0 & 5723 \\ 63.0 & 205 & 7322 & 194 & 6807 \\ 67.5 & 354 & 7403 & 335 & 6884 \\ 98.7 & 1385 & 7946 & 1312 & 7420 \\ \hline \end{array} \end{array}\)
(a) Taking 100 mol of feed as a basis, calculate the net heat requirement (cal) for the process. (You may neglect heats of mixing, although doing so for dissimilar liquids like acetone and acetic acid may introduce some error.)
(b) For the same basis. calculate the required heat input to the reboiler and the required heat removal from the condenser.
Questions & Answers
QUESTION:
A mixture containing 65.0 mole% acetone (Ac) and the balance acetic acid (AA) is separated in a continuous distillation column at 1 atm. A flowchart for the operation is as follows:
The overhead stream from the column is a vapor that passes through a condenser. The condensed liquid is divided into two equal streams: one is taken off as the overhead product (distillate) and the other (the reflux) is returned to the column. The bottom stream from the column is a liquid that is partially vaporized in a reboiler. The liquid stream emerging from the reboiler is taken off as the bottoms product, and the vapor is returned to the column as boilup. Negligible heat is lost from the column, so that the only places in the system where external heat transfer takes place are the condenser and the reboiler.
| Stream Data | |||
| Feed | (1) | Liquid, \(67.5^{\circ}\rm{C}\), 65 mole% Ac, 35% AA | |
| Overhead | (2) | Vapor, \(63.0^{\circ}\rm{C}\), 98 mole% Ac, 2 % AA | |
| Distillate | (3) | ||
| Liquid, \(56.8^{\circ}\rm{C}\), 98 mole% Ac, 2% AA | |||
| Reflux | (4) | ||
| Bottoms | (5) | Liquid, \(98.7^{\circ}\rm{C}\), 15.5 mole% Ac, 84.5% AA | |
| Boilup | (6) | Vapor, \(98.7^{\circ}\rm{C}\), 54.4 mole% Ac, 45.6% AA |
\(\begin{array}{l} \text { Thermodynamic Data }\\ \begin{array}{lrrrr} \hline & & & {\hat{H}(\mathrm{cal} / \mathrm{mol})} \\ \hline & & {\text { Acetone }} & & {\text { Acetic Acid }} \\ T\left({ }^{\circ} \mathrm{C}\right) & {\hat{H}_{l}} & \hat{H}_{\mathrm{v}} & {\hat{H}_{l}} & \hat{H}_{\mathrm{v}} \\ \hline 56.8 & 0 & 7205 & 0 & 5723 \\ 63.0 & 205 & 7322 & 194 & 6807 \\ 67.5 & 354 & 7403 & 335 & 6884 \\ 98.7 & 1385 & 7946 & 1312 & 7420 \\ \hline \end{array} \end{array}\)
(a) Taking 100 mol of feed as a basis, calculate the net heat requirement (cal) for the process. (You may neglect heats of mixing, although doing so for dissimilar liquids like acetone and acetic acid may introduce some error.)
(b) For the same basis. calculate the required heat input to the reboiler and the required heat removal from the condenser.
ANSWER:Step 1 of 7
Take the basis as 100 mol feed.
\(n_{1}=100 \mathrm{~mol}\)
Write the mass balance as follows:
\(\begin{aligned} \mathrm{n}_{1} & =\mathrm{n}_{4}+\mathrm{n}_{5} \\ 100 \mathrm{~mol} & =\mathrm{n}_{4}+\mathrm{n}_{5} \end{aligned}\)
(1)
Here, \(n_{4}\) is the moles of distillate and \(n_{5}\) is the moles of the bottom product.