23-Chem-A2 Unit Operations and Separation Processes, December 2017: worked solutions

Paper format. National Exams — 16-CHEM-A2 Unit Operations and Separation Processes, December 2017. 3 hours, open book (one text). Six problems — Part A Unit Operations (A1–A3) and Part B Separation Processes (B1–B3), each worth 25 marks; the rubric asks for at least two problems from each part (only the first two per part are marked). All six are worked below for completeness as a study resource.

Reference texts. McCabe, Smith & Harriott, Unit Operations of Chemical Engineering (7th ed.); Geankoplis, Transport Processes and Separation Process Principles (4th ed.); Coulson & Richardson, Chemical Engineering Vol. 2 (particle technology, absorption, drying, crystallization); Treybal, Mass-Transfer Operations (3rd ed.); Perry's Chemical Engineers' Handbook (9th ed.).

Notes on chart / model reads. A1's minor-loss balance uses the Blasius smooth-pipe friction factor $f=0.079\,Re^{-0.25}$ (Fanning) — valid to $Re\approx10^5$, and all three test points fall in $3.8$–$8.9\times10^4$; the 1.5 m is taken as the head lost across the pipe-and-valve test section, because also charging an exit velocity head would make the measured open-valve flow physically impossible (see A1). B1(b) reads the Sherwood/Eckert flooding line supplied with the paper at abscissa $0.061$, giving flooding ordinate $\approx0.17$ (graphical, $0.16$–$0.18$), with the tabulated packing factor $F=160\ \text{ft}^{-1}$ converted to $525\ \text{m}^{-1}$ for the SI form of the ordinate. B3(a) sizes the vessel from its starting liquor volume, allowing for the water evaporated during the batch. Engineering choices are flagged in Check callouts.

23-Chem-A2 Unit Operations and Separation Processes: December 2017

Part A — Unit Operations