Book Title
Chemical Process Safety: Fundamentals with Applications-- 4/e 4th Edition

978-0134857770 Chapter 5 Part 1

December 2, 2020
5-1. a. Acrolein C3H4O: M = 56.06 (Appendix E of text)
Convert 0.05 ppm to mg/m3. Use Equation (2-7) in text.
With in K, in atm and in g/g-mole.
Solve for (mg/m3):
The maximum concentration occurs at the center of the puff. Thus, Equation (5-11)
b. If the release is 10 m above the ground, Equation (5-25) now applies:
But note that the term before the exponential is equal to 0.115 mg/m3 from part a. Then:
Note that due to the large value of the z dispersion coefficient, the exponential term has
5-2. a. For this steady state plume, directly downwind on the ground, Equation (5-48) applies:
From Table 5-1, for a bright sunny day and 3.5 m/s wind speed, the stability class is B.
With in K, in atm and in g/g-mole.
Solve for (mg/m3):
Then, from Table 5-2 at x = 1,500 m for rural conditions and B Stability,
Substituting into Equation (5-48):
b. If the release is 10 m above the ground, Equation (5-20) now applies:
But note that the term before the exponential is equal to 0.115 mg/m3 from part a. Then:
We can ratio this with the conversion from ppm to mg/m3 from part a:
c. From Equation 5-22, the maximum concentration occurs at:
From the equations from Table 5-2, for B-stability, rural,
The max concentration occurs 58.9 m downwind.
Convert to ppm,
5-3. This a continuous release so it is a steady state plume.
The leak is at ground level.
Assume worst case conditions, F stability and 2 m/s wind speed and rural conditions.
The concentration along the centerline is given by Equation (5-48):
Solve for (mg/m3):
Convert the release rate into mg/s
5-4. The hardware configuration is shown below. The tank is connected to a regulator to
Some of the potential release scenarios are:
1. Leaks in the tank
Other scenarios are possible.
This is a burning dump releasing 3 g/s of NOx.
Assume a point source release on the ground.
For rural conditions, then from Table 5-2:
For urban conditions, then from Table 5-2:
Equation 5-17 applies:
For a rural release:
5-6. a. The HCl, no matter what the form (aqueous, pressurized vapor, or pressurized liquid, will
b. Assume worst case: a puff, stable conditions.
Equation 5-11 applies:
Equations for the dispersion coefficients are given in Table 5-3.
Solve by trial and error using a spreadsheet shown below:
c. The entire town may be affected by the release. A typical evacuation area is about 1 km
d. The railroad, US 1, M-52, Outer Road, South Road. Any intersection could be a high
g. Generally, evacuate toward the NE, away from the prevailing winds. However, this will
vary from day to day. Consider using the Smallville School, if the winds allow. Several
evacuation sites should be pre-planned and pre-coordinated.
h. The police should have experience doing this. Ensure that their plans adequately cover
From Chapter 3, Equation 3-12 applies:
The saturation vapor pressure is given in Appendix C:
Substituting into Equation 3-12:
Need to convert ppm to mg/m3. Use Equation 2-7:
The wind speed is:
From Table 5-1, the stability class is D.
Equation 5-17 applies:
Solve by trial and error using a spreadsheet:
5-8. From Table 5-4, the ERPG-1 for chlorine is 1 ppm.
Use Equation 2-7 to convert 1 ppm to mg/m3:
Use Equation 5-17 to compute the release rate:
Without any additional information, assume worst case conditions, i.e. F-stability and
2 m/s windspeed and rural conditions.
Then, from Table 5-2:
Solve for
Use Equation 4-50 to determine the hole size:
From Table 4-3 for chlorine,
. Then,
To solve this problem, we need to determine the instantaneous release which results in a
puff 4,000 m downwind with an isopleth of 0.1 mg/m3. The width of the puff must be
Use the isopleth equation, Equation (5-45) to determine the concentration at the center of
Determine the quantity released from Equation (5-41):
5-10. Evaporation from a liquid pool of benzene.
a. Use Equation 3-12 and 3-18 to determine evaporation rate.
From Equation 3-18:
b. From Appendix E for benzene:
This is solved by trial and error solution using the rural dispersion coefficients
equations in Table 5-2. The spreadsheet solution is shown below:
c. Use the isopleth equation, equation 5-28 to determine the max. width.
But the centerline concentration is found using Equation 5-17 shown above.
Substituting into the isopleth equation above:
5-11. Use the following considerations to develop your spreadsheet:
1. Break up the plume into fixed spatial increments, say 7 m. The result is not
dependent on this selection - it only affects the plot precision.
The plume length and width on the ground is significantly decreased as the release height
Part a:
5-12. The most direct approach is to use a coordinate system that is fixed on the ground at the
release point. Thus, Equation 5-25 is used with Equation 5-27. This gives,
Note that ut is the location of the center of the puff.
In order to reduce the number of spreadsheet cells, use a spreadsheet grid that moves with
the puff center. Use, let’s say, 50 cells on either side of the puff and specify a cell
increment size.
The procedure is the following: