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Chemical Engineering - Mass Transfer - Discussion

Discussion Forum : Mass Transfer - Section 1 (Q.No. 31)
Mass Transfer
31.
As the reflux ratio in a distillation coloumn is increased from the minimum, the
slope of the operating line in stripping section decreases.
number of plates decreases very slowly first and then more and more rapidly.
total cost first decreases and then increases.
liquid flow increases while the vapor flow decreases for a system.
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
6 comments Page 1 of 1.
Kavya R said:   3 years ago
Reflux ratio is the boil-up rate to the take-off rate. If reflux increases, boil-up also increases (more vapour is sent back to the column, and less liq (W) is taken as the bottom product). The slope of Stripping O. L is L/ (L-W), if W decreases, the slope decreases. So, option A can be right.
Mithu said:   8 years ago
But, as the boil up ratio increases, then slope in stripping section decreases, as both boil up ratio and reflux ratio are different, so option A is incorrect. Moreover, option B, we can't say how slowly or rapidly it decreases, so the most appropriate answer is option C.

And, I agree @Dev.
Ramraja yadav said:   8 years ago
As reflux ratio increases the operating line of the stripping section move towards diagonal means slope decreases.

Also, no of required plate decreases as RR increases.

So, option A and B also correct.
Dev said:   1 decade ago
Here first fixed cost decreases due to no of theoretical plate decreases but operation cost increases due to high reflux rate for which condenser duty and reboiler duty increases.
(1)
Pegu said:   12 months ago
According to me both options A and C are correct.
Dev said:   6 years ago
Total cost = operating cost + fixed cost.
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