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