When absorbing a sparingly soluble gas into a liquid solvent, what condition applies ___________________?
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Answer: B. Liquid side mass transfer co-efficient should be increased
Explanation
Sparingly soluble gases present significant mass transfer resistance exclusively within the liquid film. Increasing the liquid-side mass transfer coefficient directly reduces the dominant liquid-phase resistance. Enhancing the liquid mass transfer coefficient improves the overall absorption rate for the system. Mass transfer resistance in absorption columns is divided between gas and liquid boundary films. Solubility determines the Henry's law constant which dictates which fluid phase controls resistance. Coefficients like liquid film mass transfer coefficients depend on fluid turbulence and diffusivity.
Carbon dioxide absorption into water is mass transfer limited primarily by the liquid phase. Designers increase liquid turbulence using packing materials to boost the liquid-side mass transfer coefficient. Improving gas-side properties yields negligible benefits when liquid-side resistance controls the process. Increasing the gas-side mass transfer coefficient fails because gas resistance is negligibly small. Decreasing the liquid-side mass transfer coefficient would severely impair the absorption process rate. Keeping the mass transfer coefficient constant prevents optimization of the packed absorption column.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
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Answer: B. 8.5 × 10-4
The mass transfer flux calculation uses the overall liquid-side coefficient and concentration differences. Multiplying the mass transfer coefficient by the driving force yields the correct molar flux value. Applying the...
Q2. When absorbing a sparingly soluble gas into a liquid, what is observed regarding the_____________________?
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Answer: B. Liquid side coefficient should be increased
Sparingly soluble gases have very high Henry's law constants making liquid-phase resistance dominant. Controlling resistance means that changing the liquid-side mass transfer coefficient alters the total rate. Enhancing...
Q3. Under what circumstances will both the operating and equilibrium lines in an absorber be linear_______________________?
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Answer: C. Dilute solution and isothermal operation
Dilute solutions maintain nearly constant total molar flow rates throughout the absorption column height. Isothermal operation ensures that the equilibrium partition coefficient remains constant across all stages. Consta...
Q4. For a single-component absorption column, when is the operating line strictly linear if plotted in terms of ______________ units?
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Answer: B. Mole ratio
Mole ratio units normalize concentrations against inert carrier components maintaining constant molar flows. Constant molar gas and liquid flow rates result in a straight operating line on graphical plots. Using mole fra...
Q5. Solvents possessing low viscosity are favored for gas absorption due to their____________________?
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Answer: D. All A., B. and C.
Low viscosity solvents flow easily through pipes and packing materials reducing frictional pressure losses. Reduced pumping pressure drops lower the overall capital and electrical energy operating costs. Lower viscosity...
Q6. Why are the wet bulb and adiabatic saturation temperatures nearly identical for an air-water system at ambient conditions__________________?
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Answer: A. Water has a high latent heat of evaporation
The Lewis number relates thermal diffusivity to mass diffusivity in simultaneous heat and mass transfer. For air-water systems at ambient conditions the Lewis number is very close to unity. Unity Lewis number means heat...