# 4.29: Untitled Page 84

- Page ID
- 18217

## 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