What relative volatility ensures a highly efficient separation in a binary system_______________?
Show answer Hide answer
Answer: B. > 1
Explanation
A relative volatility significantly greater than one indicates widely differing component vapor pressures. Large vapor pressure differences make fractional distillation highly efficient and economically viable. Values near one represent difficult separations requiring excessive stages and reflux energy. Relative volatility measures the separation difficulty between two components in a mixture. Fractional distillation exploits boiling point discrepancies represented mathematically by relative volatility. High relative volatility reduces both required column height and reboiler energy consumption.
Chemical engineers screen binary mixtures to ensure relative volatility exceeds threshold limits for distillation. Petrochemical separation processes are designed around high relative volatility component pairs. Azeotropic distillation is used when relative volatility approaches unity and standard distillation fails. A relative volatility of one means components boil identically and cannot be separated via distillation. Values less than one invert component volatilities and complicate standard rectifying column operations. A value of 0.5 represents an impossible direct separation scenario without adding third component solvents.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. To achieve maximum absorption efficiency inside a gas-liquid absorption column___________________?
Show answer Hide answer
Answer: C. Both gas as well as liquid streams should be distributed uniformly
Uniform distribution of both gas and liquid streams prevents fluid channeling in absorption towers. Channeling bypasses active packing surfaces, reducing the effective interfacial area for mass transfer. Achieving maximu...
Q2. Channelling within a packed bed absorption column is identified through____________________?
Show answer Hide answer
Answer: B. Sharp drop in pressure drop
Channelling creates localized low resistance pathways where fluids bypass the main packed bed. Bypassing reduces the frictional pressure drop across the packed column quite noticeably. Monitoring pressure drop helps oper...
Q3. What parameter does HETP remain invariant with in an absorber____________________?
Show answer Hide answer
Answer: D. None of these
HETP varies with liquid and gas flow rates as well as physical properties and packing types. Because HETP depends on hydrodynamic mass transfer coefficients, it is not invariant with flow rates. Column designers must cal...
Q4. In vapor-liquid contacting devices, how is the overall gas-phase mass transfer coefficient KG related to individual phase coefficients KG and KL ___________________ ?
Show answer Hide answer
Answer: B. 1/KG = 1/KG + m/KL
Overall gas phase mass transfer resistance equals individual gas resistance plus liquid resistance times slope. Multiplying liquid phase resistance by the equilibrium line slope m accounts for concentration scales. Inver...
Q5. When do the HETP and HTUOG values coincide in a packed tower (where, HETP = height equivalent to a theoretical plate, HTUOG = overall gas phase height of a transfer unit)?
Show answer Hide answer
Answer: C. Both A. & B.
Straight operating and equilibrium lines provide a constant concentration driving force throughout the tower. Parallel lines ensure that local mass transfer conditions match global column separation performance. Mathemat...
Q6. Within a moderately sized packed absorption column, how can fluid channeling—which is most pronounced with stacked packings—be minimized through the ratio of tower diameter to packing diameter ?
Show answer Hide answer
Answer: C. > 8:1
Wall channeling occurs when liquid flows preferentially down the smooth inner walls of packed columns. Maintaining a column to packing diameter ratio greater than eight to one minimizes this wall effect. Larger ratios en...