This set of Mass Transfer Interview Questions & Answers focuses on “Operating Line Concept for Absorption”.
1. Spray tower is a _______ process.
b) Counter current
Explanation: Here, the gas is passed through the bottom and the liquid is sprayed at the top.
2. Find the rate of non-diffusing solute, if the mole fraction of the gas phase is 0.65 and the diffusing rate is 70 moles/hr.
a) 2 4.5 moles/hr
b) 200 moles/hr
c) 18.18 moles/hr
d) 37.7 moles/hr
Explanation: Gs= G(1-y)
3. In an absorber, lower denser materials are sent through the bottom and the higher denser materials are sent through top
Explanation: For reducing the pumping cost and to create sufficient pressure drop.
4. Stripper= (1/X)
Explanation: Stripper is liquid to gas transfer but absorber is gas to liquid transfer.
Explanation: For stripper, the solute gets transfer from liquid to gas so the operating line is below the equilibrium line.
6. Find the slope of the operating line
Here, the concentrations are represented in mole ratio. The value of (Y1-Y2)/(X1-X2) =2. Find the slope of the operating line.
Explanation: For a counter current process, Y1- Y2 = Ls/Gs(X1-X2)
Ls/Gs= slope of the operating line = 2.
7. Have a look on the below diagram
Here, DE and DP are the operating line. Also Y and X are the concentrations in mole ratio for gas and liquid phase.
It’s clearly a representation of an absorber. For the operating line DE minimum liquid is required
Explanation: DP line requires minimum liquid because the composition is increased to X2.
8. If the operating line touches the equilibrium line, the separation is possible in an absorber.
Explanation: At that point, the slope of operating line will be equals to the slope of the equilibrium line. So the Absorption factor becomes equal to one, the separation is not possible.
9. For the Absorber design, the plotting with mole ratio helps to find the
a) Slope of operating line
b) Slope of equilibrium curve
c) Minimum number of trays
d) Maximum number of trays
Explanation: The plot with mole fraction will give an operating line as a curve; it will be very difficult to find the slope of the operating line. Therefore the use of mole ratio plot will give us a liner operating line.
10. Given for an absorber, the minimum non diffusing liquid flow rate is 20 moles/hr and the non diffusing gas flow rate is 30 moles/hr. As the actual liquid flow rate is 2.5 times the minimum. Find the slope of the operating line.
Explanation: Ls= 2.5 (Ls min)
Slope= (2.5 x 20)/30 =1.67.
Sanfoundry Global Education & Learning Series – Mass Transfer.
To practice all areas of Mass Transfer for interviews, here is complete set of 1000+ Multiple Choice Questions and Answers