# 4.29: Untitled Page 84

## Chapter 4

and the volumetric flow rate is

2

Q  v  

z

o

r

(3)

For this process, determine the molar flow rate of species A in terms o c ,  , and

A

v  . When   0 5

. , determine the bulk concentration, 

z

cA b ,and the area‐

averaged concentration,  c

A . Use these results to determine the difference between

and  c

A Q .

4‐13. A flash unit is used to separate vapor and liquid streams from a liquid stream by lowering its pressure before it enters the flash unit. The feed stream is pure liquid water and its mass flow rate is 1000 kg/h. Twenty percent (by mass) of the feed stream leaves the flash unit with a density 3

  10 kg / m . The

remainder of the feed stream leaves the flash unit as liquid water with a density 3

  1000 kg / m . Determine the following:

1. The mass flow rates of the exit streams in kg/s.

2. volumetric flow rates of exit streams in m3/s.

Section 4.6

4‐14. Show that Eq. 4‐79 results from Eq. 4‐78 when either

or x is constant

A

over the area of the exit.

4‐15. Use Eq. 4‐79 to prove Eq. 4‐80.

4‐16. Derive Eq. 4‐82 given that either v n or  A is constant over the area of the exit.

4‐17. Prove Eq. 4‐86.

Section 4.7

4‐18. Determine

and the unknown mole fractions for the distillation process

described in Sec. 4.7 subject to the following conditions:  Multicomponent systems

150

Stream #1

Stream #2

Stream #3

M 1 = 1200 mol/h

M 2 = 250 mol/h

M 3 = ?

x A = 0.3

x A = 0.8

x A = ?

x B = 0.2

x B = ?

x B = 0.25

x C = ?

x C = ?

x C = ?

4‐19. A continuous filter is used to separate a clear filtrate from alumina particles in a slurry. The slurry is 30% by weight of alumina that has a specific gravity of 4.5. The cake retains 5% by weight of water. For a feed stream of 1000 kg/h, determine the following:

1. The mass flow rate of particles and water in the input stream 2. The volumetric flow rate of the inlet stream in m3/s.

3. The mass flow rate of filtrate and cake in kg/s.

4‐20. A BTX unit, shown in Figure 4.20, is associated with a refinery that produces benzene, toluene, and xylenes. Stream #1 leaving the reactor‐reforming Figure 4.20. Reactor and distillation unit

unit has a volumetric flow rate of 10 m3/h and is a mixture of benzene ( A), toluene ( B), and xylenes ( C) with the following composition: 3

3

c   6,000 mol/m ,

c   2 , 000 mol/m ,

c   2 , 000 mol/m3

A 1

B 1

C 1

151