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# Distillation Design MCQ’s – Reflux Stage Relationships

Fenske’s Equation can be written as

a) N_{min} = S/ ln α

b) N_{min} = ln S/ ln α

c) N_{min} – 1 = ln S/ ln α

d) N_{min} + 1 = ln S/ ln α

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Answer: b

Explanation: The Fenske’s equation is given by this equation Nmin = ln S/ ln α, where N is the number of trays and alpha is the relative volatility.

The term S in the Fenske’s equation, is given as

a) (x_{LK}x_{HK})D(x_{LK}x_{HK})B

b) (x_{LK}x_{HK})D(x_{LK}x_{HK})L(x_{LK}x_{HK})R

c) (x_{LK}x_{HK})L(x_{LK}x_{HK})V

d) (x_{LK}x_{HK})HK(x_{LK}x_{HK})LK

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Answer: a

Explanation: The term S in the Fenske’s equation is given as (x_{LK}x_{HK})D(x_{LK}x_{HK})B, representing High and Low keys of the gas and liquid phases.

^{N}√α_{N} this equation is called as

a) Sorel’s Method

b) Polson Equation

c) Fenske’s Equation

d) Gilliland Equation

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Answer: c

Explanation: Fenske’s Equation that is rigorous, Gilliland Equation are used and based on the trial and error basis

Calculate ln S? If X_{LK}=0.41 and X_{HK} = 0.005 and X_{L}= 0.417 and X_{H}= 0.01, then

a) 9.45

b) 8.90

c) 8.137

d) 7.98

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Answer: c

Explanation: As ln (0.41/0.005) (0.417/0.01) = 8.137.

A non-key component may be distributed if

a) Close to that of one key

b) The Specified separation is sloppy

c) Intermediate between keys

d) Intermediate one key

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Answer: b

Explanation: For distributed systems the Specified separation is sloppy, while for the distributed system it is close to that of one key

In a distillation operation, the reflux ratio may vary between

a) Zero and one

b) Zero and infinity

c) Minimum and infinity

d) One and two

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Answer: a

Explanation: L_{0}/D Varies from zero to one, as the ratio cannot be more than one because that will cause the failure of the column.

Most distillation columns are designed for reflux ratio between

a) 3 to 5 R_{min}

b) 1.2 and 1 .7 R_{min}

c) 2 to 10 R_{min}

d) 0.2 to 0.7 R_{min}

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Answer: b

Explanation: This is the most suitable for 1.2 and 1.7 R_{min} times reflux ratio, this also reduces the operating and the final cost of the system.

If Component is non-distributed, then

a) D_{R} >1

b) D_{R}<1

c) DR=0

d) DR=∞

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Answer: a

Explanation: If component is non-distributed then D_{R} >1 contained entirely distillate, while if components are distributed they are entirely withdrawn.

If Component is distributed, then

a) 0< D_{R}> 1

b) 0< DR< 1

c) DR= 0

d) DR < 0

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Answer: b

Explanation: If Component is distributed then 0< D_{R}< 1, D_{R} is recovery component, if D_{R} = 0 then there exists no distributed components in the systems.

Underwood’s equation can be used to find

a) Distributed components

b) Non distributed components

c) Reflux for components

d) Non reflux components

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Answer: a

Explanation: Underwood’s equation can be used to find Distributed components (n) including key.