Reference no: EM133337551

Requests:

Question 1. Preliminary considerations
• What is the mechanism of mass transfer dominating in membranes used to carry out gas permeation processes? Briefly describe it, highlighting what are the factors that affect permeance when such mechanism is responsible for mass transfer through a membrane.
• Amongst the material reported in Tab. 1 which one would you recommend? Why? Ex¬plain your answer quantitatively by reporting the calculations necessary to reach a con¬clusion.

Question 2. Consider a steady state continuous gas separation process, in which both the permeate and retentate sides can be considered well mixed, and the membrane is constituted of the most promising material available within those reported in Tab. 1.
• Draw a scheme of the unit clearly labelling all the streams and relevant variables.
• Completely characterise the steady state operation of this unit, by computing feed, perme¬ate and retentate flow rates, cut, and retentate composition.

Question 3. Consider now the same feed processed by a cascade of three membrane stages identical to the stage characterised in request number 2. The cascade is aimed to increase the concentration of oxygen in the permeate stream. The permeate of stages 1 and 2 is compressed to reach the same pressure (5+Y bar) on the feed/retentate side in all three stages. Also the permeate side is maintained at the same pressure of (5+Z) x 10-2 bar in all three stages.
• Draw a scheme of the cascade clearly labelling all the streams and relevant variables.
• Write the operating equation and rate transfer equation for a generic stage i, and com-pletely characterise the cascade by computing flowrates and compositions of permeate and retentate for all stages.
• Represent the operation of the three stages on the retentate/permeate composition plane, clearly indicating the curve corresponding to the rate transfer equation, and the curve corresponding to the operating equation for each stage.
• The retentate streams produced at each stage are collected in a single INI2 rich current. Draw a scheme of the process representing such stream, compute the flowrate and composition of this stream.

Question 4. Consider now a configuration in which the three identical stages characterised in request num¬ber 3 (single stage) are connected in parallel.
• Draw a scheme of the unit clearly labelling all the streams and relevant variables.
• Completely characterise the steady state operation of this process on the basis of the same feed flowrate computed for points 2 and 3, without constraining the permeate oxygen composition to the requested specifics of 48% in 02.

Question 5. Critically compare the configurations characterised at point 3 and 4.
• Which configuration is likely to require the highest capital/investment costs?
• Which one is likely to display the highest operating costs?
• Which one would you choose if your goal is to obtain the highest possible concentration of oxygen in the permeate?