Chemical Engineering - Mass Transfer - Discussion

Discussion Forum : Mass Transfer - Section 6 (Q.No. 46)
46.
A distillation column separates 10000 kg/hr of a benzene-toluene mixture as shown in the figure below :

In the figure xF, xD and xW represent the weight fraction of benzene in the feed, distillate and residue respectively. The reflux ratio is
0.5
0.6
1.0
2.0
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
5 comments Page 1 of 1.

Garima said:   1 decade ago
As applying mass balance
F= D+W
F*xf = D*xd+W*xw
D = 5000
And 8000 = D+L
L = 3000
R = 0.6
(3)

Shambhu padhiyar said:   7 years ago
Here, L/D = R.

Himanshu Lohiya said:   5 years ago
@Garima,

Here, You didn't count the mole fraction of the bottom product.
(1)

Yash said:   4 years ago
@Garima.

You are absolutely correct. Thanks.

Reece said:   2 years ago
@Aall.

Basis: 1-hr operation

Overall Material Balance (Entire System):
10,000 kg = D + B ---> Eqn [1]

Benzene Balance (Entire System):
0.50(10,000 kg) = 0.95D + 0.05B----> Eqn[2]

Equations [1] and [2] form a system of equations consisting of two equations and two unknowns. Thus, solving equations [1] and [2] simultaneously gives us:

D = 5,000 kg.
B = 5,000 kg.

Overall Material Balance (At Condenser):
8,000 kg = Lₒ + 5,000 kg---> [3]

Solving for the reflux stream using equation [3]:
Lₒ = 3,000 kg.

Reflux Ratio Equation:
R = Lₒ/D
= 3,000 kg/5,000 kg
= 0.60.
(1)

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