CHE 441
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LAST NAME, FIRST
Problem set #5
Figure 1b PFD for the Production of Acrylic Acid from Propylene
1. For the accrylic process shown in Figure 1b (Turton et al, Analysis, Synthesis, and Design of
Chemical Processes), check the design specifications for the reflux pump P-305 (shaft power =
1.2 kW, Pout = 3.31 bar) against the heuristics in Table 3.5. You can neglect the frictional loss in
the lines so that the pressure increase across the pump may be estimated to be the static head
between V-302 and top of T-305 (you can use the tower height, 25 m, for the calculation) plus
the pressure drop across the control valve (Table 3.4). Flow of acetic acid (stream 18 + stream
19) is 5650 kg/h. Density of acetic acid at 46oC is 1020 kg/m3.
2. For the accrylic process shown in Figure 1b, check the design specifications for the acid reflux
drum V-302 (D = 1.0 m, L = 2.5 m) against the heuristics in Table 3.2. Flow of acetic acid
(stream 18 + stream 19) is 5650 kg/h. Density of acetic acid at 46oC is 1020 kg/m3.
3. Normal butane (A), C4H10, is to be isomerized to isobutane (B) in a plug-flow reactor1. The
reaction is to be carried out adiabatically in the liquid phase under high pressure using essentially
trace amount of a liquid catalyst which gives a specific rate constant of 31.1 h-1 at 360oK.
Calculate the fractional conversion of a PFR with a volume of 3.0 m3 necessary to process 150
kmol/h of a mixture 80 mol % n-butane and 20 mol % i-pentane, which is considered an inert.
The feed enter at 330oK.
1
Fogler, H. S., Elements of Chemical Reaction Engineering, Prentice Hall, 1999, pg. 454
k
A 
B
kb

Data: HRx =  6,900 J/mol, Cp,n-B = CpA = 141 J/moloK, Cp,i-B = CpB = 141 J/moloK, Cp,i-P =
k
161 J/moloK, activation energy = 65.7 kJ/mol, CA0 = 9.3 kmol/m3, Keq =
= 3.03 at 333oK.
kb
4. A two-stage steam jet is to be used on a large vacuum system. It is estimated that 10 kg of air
must be removed from the system each hour. The vapors being removed will contain water vapor
at a pressure equivalent to the equilibrium vapor pressure of water at 15oC. If a suction pressure
of 50 mmHg absolute is to be maintained by the steam jet, estimate the kilograms of steam per
hour that will be required to operate the jet. Use the following table.
Average consumption in kg/h of 775-kPa steam in a steam-jet ejector to provide
Various levels of vacuum
Capacity
Wt% net
Suction pressure, mmHg absolute
(kg/h)
dry air in
12.5
25
37.5
50
75
100
gas-vapor gas-vapor
323222221mixture
stage stage stage stage stage stage stage stage stage
handled
4.5
100
33
45
27
32
26
23
19
17
26
4.5
70
27
38
21
27
22
19
16
14
29
4.5
40
20
31
15
21
21
15
12
10
31
4.5
10
11
20
7
13
13
8
6
5
34
Note: the dry air is noncondensibles.
150
1stage
16
17
18
19
5. Hydrogen gas at a temperature of 20oC and an absolute pressure of 1380 kPa undergoes
compression to 4140 kPa. If the mechanical efficiency of the compressor is 55 percent on the
basis of an isothermal and reversible operation, determine the kilograms of hydrogen that can be
compressed per second when the power supplied to the compressor is 224 kW. Assume that the
kinetic energy effects can be neglected. Also evaluate the mechanical efficiency of the
compressor on the basis of an adiabatic and reversible operation. Assume that a single-stage
compressor is used and the ratio of Cp/Cv remains constant at 1.4.
6. A centrifugal fan is used to remove stagnant air in a large hangar at a pressure of 100 kPa and
a temperature of 32oC and discharge it externally at a pressure of 103 kpa and a velocity of 40
m/s. Determine the power requirement needed for the removal of 4.7 std m3/s of air. The
efficiency of the fan can be assumed to be 65 percent.
7. What power input in kW will be required to mix a rubber latex compound with a viscosity of
1.2×105 cP and a density of 1121 kg/m3 in the same mixer that was used in Example 12-6 (Peters
and Timmerhaus). Would there be any difference in the power requirement if baffles were added
to the mixing tank?
8. What power will be required to mix an aqueous solution of 50% NaOH in a baffled tank, 2 m
in diameter? The mixing will be performed in the vertical tank filled to a height of 2 m by a disk
turbine with six flat blades. The turbine is 0.67 m in diameter and positioned 0.67 m above the
bottom of the tank. The turbine blades are 0.134 m wide and turn at 90 r/min. The solution has a
viscosity of 0.012 Pa∙s and a density of 1500 kg/m3.