December 2, 2020

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

Repeat this problem for 37 cu m and PL=30

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

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

Repeat for C0 coxygen concentrations of 0.02 and 0.05%

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) 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.

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

Equation 7-22

52

Method 1

Method 2

Repeat these calculations for a charge rate of 0.568 cu m/min

Method 1

Method 2

Problem 7-6

Determine the capacitance of vessel volumns of 250, 500, 750, and 920

gallons.

Solution 7-6

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

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

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