Q2. It is desired to obtain drinking water from seawater at 20°C using a tubular membrane unit with a total membrane area of 2x10<sup>6</sup> ft<sup>2</sup>. Seawater containing 3.3 wt% NaCl (as dissolved solid) is fed to the membrane unit with a pressure of 1800 psia. 37900 m<sup>3</sup>/day of drinking water is obtained with a NaCl concentration of 0.06 wt% the permeate side pressure is 60 psia. a) Which membrane process is appropriate to perform this separation? Draw the unit schematically. [5 pts] b) What is water flux in gal/(day-ft<sup>2</sup>)? [5 pts] c) What is the driving force for solvent transport through the membrane? [3 pts] d) What is the permeance for water in gal/(day-ft<sup>2</sup>-psi) if mass transfer resistances are negligible? [12 pts] e) Calculate the concentration polarization factor and check whether it is significant. [10 pts] Note: Be careful in unit conversions! Additional Data: Feed-side Reynolds number and Schmidt number can be taken as 10500 and 600, respectively. The diffusivity of NaCl in water in the feed-side is 1x10<sup>-5</sup> cm<sup>2</sup>/s. The tube diameter of the tubular membrane is 0.5 cm.
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Given the high pressure on the feed side (1800 psia) and the low pressure on the permeate side (60 psia), the process used is likely Reverse Osmosis (RO). This process is suitable for desalination of seawater to reduce the high salt concentration to potable Show more…
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