Engineering Questions with Answers - Multiple Choice Questions

# Separation Processes MCQ’s – Solid-liquid Cascades

1 - Question

A material balance for any soluble material B around any interior stage from n=2 to N-1 is:
a) Y n+1 S + X n-1 RF A =Y n S + X n RF A
b) Y n+1 S + X n-2 RF A =Y n S + X n RF A
c) Y n+1 S + X n+1 RF A =Y n S + X n RF A
d) Y n+1 + X n-2 RF A =Y n S + X n RF A
Explanation: Material balance for any soluble material B around any interior stage from n=2 to Y n+1 S + X n-1 RF A =Y n S + X n RF A Where Y j is the mass of solute per mass of solvent and F A is the mass flow rate of slurry and R is the constant ratio of mass of solvent to mass of insoluble solids.

2 - Question

Which equation holds true at equilibrium?
a) Y N+1 = Y N
b) X N = Y N
c) F B = F A
d) R 1 =R 2
Explanation: At equilibrium the concentration of B in each overflow equals the concentration of B in liquid part.

3 - Question

What is the formula for washing factor?
a) W= SRF A
b) W= RF A /S
c) W=SF A/R
d) W=S/RF A
Explanation: The formula for washing factor is W=S/RF A, where F A is the mass flow rate of slurry and R is the constant ratio of mass of solvent to mass of insoluble solids.

4 - Question

The concentration of solute is given by:
a) (F B /S)(1/W Nsub>n-1 )
b) (F B S)(1/W sub>n-1 )
c) (F B /S)(1/W sub>n-1 )
d) (F B S)(W sub>n-1 )
Explanation: The concentration of solute X N is given by (F B /S)(1/W sub>n-1 ) where S is the flow rate at stage N and F B is the mass flow rate of slurry and W is the washing factor.

5 - Question

What will be the concentration of solute in overflow doe N=2?
a) (F B /S)(1/W +1)
b) (F B /S)(1+W+W 2 /W 2 )
c) (F B /S)(1+W+W 2 /W)
d) (F B /S)(1+W/W 2 )
Explanation: (F B /S)(1/W +1) is the equation used. Now for N=2, (F B /S)(1/W +1)= (F B /S)(1/W +1)

6 - Question

Which of the following is true about cascades for a particular S?
a) Maximizes Y 1
b) Maximizes X N
c) Minimizes Y 1
d) Does not affect X N
Explanation: The cascade for any given S, maximizes Y 1 , the amount of B dissolved in a solvent nleaving stage 1.

7 - Question

The minimum amount of solvent required is underflow ratio is 0.5 and insoluble solids feed rate is 2000Kg/hr is:
a) 2000kg/hr
b) 1000kg/hr
c) 4000kg/hr
d) 500kg/hr
Explanation: S min =RF A , thus S min = 2ooo*0.5=1oookg/hr.

8 - Question

What is the washing factor if solvent feed rate is 3000kh/hr , underflow ratio is 0.5 and insoluble solids feed rate is 2000?
a) 2
b) 3
c) 4
d) 5
Explanation: Since W= S/RFA , W= 3000/2000*0.5=3.

9 - Question

The minimum amount of solvent required is underflow ratio is 0.3 and insoluble solids feed rate is 200Kg/hr is:
a) 50kg/hr
b) 600kg/hr
c) 666.66kg/hr
d) 60kg/hr
Explanation: S min =RF A , thus S min = 2oo*0.3=600kg/hr.

10 - Question

What is the washing factor if solvent feed rate is 2500kh/hr , underflow ratio is 0.3 and insoluble solids feed rate is 500?
a) 13.33
b) 166.66
c) 16.66
d) 133.33
Explanation: Since W= S/RFA , W= 2500/500*0.3=16.66.

11 - Question

What is the washing factor if solvent feed rate is 2500kh/hr , underflow ratio is 0.5 and insoluble solids feed rate is 2000?
a) 0.5
b) 1
c) 1.5
d) 2.5
Explanation: Since W= S/RFA , W= 2500/1000*0.5=2.5.

12 - Question

What is the washing factor if solvent feed rate is 2800kh/hr , underflow ratio is 0.7 and insoluble solids feed rate is 2000?
a) 1
b) 2
c) 3
d) 4
Explanation: Since W= S/RFA , W= 2800/2000*0.7=2.

13 - Question

What is the washing factor if solvent feed rate is 3000kh/hr , underflow ratio is 0.2 and insoluble solids feed rate is 10000?
a) 1
b) 2.5
c) 1.5
d) 4
Explanation: Since W= S/RFA , W= 3000/10000*0.2=1.5.

14 - Question

What is the washing factor if solvent feed rate is 1000kh/hr , underflow ratio is 0.1 and insoluble solids feed rate is 10000?
a) 1
b) 2
c) 3
d) 4
Explanation: Since W= S/RFA , W= 1000/10000*0.1=1.

15 - Question

What is the washing factor if solvent feed rate is 2300kh/hr , underflow ratio is 0.3 and insoluble solids feed rate is 2000?
a) 1.97
b) 2.33
c) 3.07
d) 3.83