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Problems and Solutions for Chapter 7
Problem 7-1
Use a vacuum purge to reduce the oxygen concentration to 1 ppm. The
vessel has a volume of 3.78 cu m, the vacuum goes to 20 mm Hg
absolute, the temperature is 24 deg. C and the highest pressure is 1 atm
Determine the number of purges, and the total nitrogen used. Repeat this
process for a vessel with a volume of 37 cu m and a minimum vacuum of
30 mm Hg.
Solution 7-1
0.454
Repeat this problem for 37 cu m and PL=30
0.454
Problem 7-2
Use a pressure purge to reduce the oxygen concentration to 1 ppm. The
vessel has a volume of 3.78 cu m, the pressure goes to 4136 mm Hg
absolute, the temperature is 24 deg. C and the lowest pressure is 1 atm
Determine the number of purges, and the total nitrogen used. Repeat this
process for a vessel with a volume of 37 cu m and a maxium pressure of
3000 mm Hg.
Solution 7-2
0.454
Repeat this problem for 37 cu m and PL=30
Problem 7-3
Use a sweep through purge to reduce the oxygen concentration from 100
% air (21 % oxygen) to 1.25 % oxygen. The vessel has a volume of 7500
gallon. Determine the cu m of nitrogen required if the nitrogen contains
0.01 % oxygen. Repeat this problem with nitrogens containing 0.02 %
oxygen and 0.05 % oxygen.
Solution 7-3
1
Repeat for C0 coxygen concentrations of 0.02 and 0.05%
required for C0 = 0.05 % oxygen
Problem 7-4
A 2000 cu m vessel contains liquid methanol and it needs to be purged to
prepare for vessel entry. It should be purged initially with nitrogen (98 %
nitrogen and 2 % oxygen from a membrane process) and then purge with
air to get the fuel composition down to 0.1 % of the TLV. Use sweep
through purging, assuming a pressure of 1 atm. 25 deg C, and the purging
rates (for nitrogen and air) are 10 cu m/min.
Determine a) the composition of fuel in the tank after draining, b) the
target fuel composition after purging with nitrogen (with 2 % oxygen), c)
the quantity of nitrogen sweep through gas required, and d) the quantity
of sweep through air required.
Solution 7-4
a) the composition of fuel in the tank after draining,
b) the target fuel composition after purging with nitrogen (with 2 % oxygen),
c) the quantity of nitrogen sweep through gas required to purge from the initial
to the target composition is:
d) the quantity of sweep through air required.
C2 C0
c2) the quantity of nitrogen sweep through gas required to purge from the initial
to the target composition is:
d2) the quantity of sweep through air required.
959085 100
05
10
15
00
Inert
20
80
Target
Sketch for Problem 7-4
Problem 7-5
Use Figure 7-14 to determine the a) the voltage and accumulated charge
between the nozzle and the tank, and b) the energy accumulated in the
liquid. Do this for two different charge rates; i.e 0.003785 and 0.568 cu
m/min.. Given: Hose length of 6.1 m, hose diameter of 5.1 cm, liquid
conductivity of 1E-08 mho/cm, dielectric constant of 25.7, vessel volume
is 1.1 cu m, and a density of 0.88.
Solution 7-5
100
Equation 7-22
52
10 1 exp / ( )
amp
52
22
10 (/) 1exp /((/))
amp
I
smsmmmss
Method 1
Method 2
Therefore this is a hazardous situation.
Repeat these calculations for a charge rate of 0.568 cu m/min
Method 1
Method 2
Therefore this is a very hazardous situation.
Problem 7-6
Determine the capacitance of vessel volumns of 250, 500, 750, and 920
gallons.
Solution 7-6
2.879
3.082
9.768 10 11
1.046 10 10
Problem 7-7
Charge one vessel with carbon black using two charging methods, one 1)
pouring from an open vessel, and 2) pneumatic transport. Assume the
charged vessel has a volume of 1.89 cu m and feed rate is 5 kg/s.
Determine the accumulated charge and the energy to see if the energy
exceeds the MIE of dusts.
Solution 7-7
2) Work this out for transporting the carbon using pneumatic transport
Joules, Equation 7-21
2Cap
Problem 7-8
Charge one vessel with carbon black using one charging methods; i.e.
pouring from an open vessel. Assume the charged vessel has a volume of
1.89 cu m and feed rate is 0.1 kg/s. Determine the accumulated charge
and the energy to see if the energy exceeds the MIE of dusts. Does the
lower charge rate, compared to Problem 7-7 lower the potential hazard?
Solution 7-8
Problem 7-9
Determine the concentration of toluene over a diked area. Where the diked
area is 100 sq ft, and the dike is in a process area 2500 sq ft. The
temperature is 65 deg F.
P1
TF 65 Deg F
Solution 7-9
5
MW
100
Problem 7-10
Repeat Problem 7-9 with a diked area of 2.32 sq m, and a process area of
46.5 sq. m. The temperature is 18.33 deg. C.
Solution 7-10
Problem 7-11
Repeat Problem 7-10 with a diked area of 2.32 sq m, and a process area
of 46.5 sq m, but with a drainage pit that has a drain area of 0.018 sq m..
The temperature is 18.33 deg C.
Solution 7-11
