Name or Student # ______________________________
CHEE 481 Air Quality Management
Test #1, Feb. 7, 2008
Notes:
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Open book test, the use of notes, books and calculators are permitted.
Time for test is 60 minutes.
Test consists of three (3) questions for a total of 20 marks – Question #1 is
worth 5 marks, Question #2 is worth 5 marks and Question #3 is worth 10
marks
Submit this test question sheet with your answer booklet
Question #1 (5 marks)
The graph shown in Figure 1 in this test paper displays the cumulative distribution for two types
of particulate materials that might occur in industrial processes. These distributions are depicted
by the straight lines, A and B, in this graph, presented as a log-normal cumulative distribution
(cumulative mass % as a function of particle diameter).
The data for the A distribution
represents a size distribution that might arise from very small particulates associated with a
combustion process. The B distribution is a size distribution for larger particles that might arise
in a materials processing operation (mining, food industry, pulp & paper, cement, etc.).
For each distribution, estimate the parameters ,  and the resulting form for the cumulative
distribution function F(z):
1 1
 erf(z / 2 )
2 2
ln(x) - ln(  )
Where z =
ln( )
F(z) =
Question #1
99
A
Cumulative distribution, %
98
B
95
90
84 %
80
70
50
50%
30
20
16 %
10
5
2
1
0.5
0.01
0.1
1
10
100
Particle diameter, microns
Figure 1. Cumulative distribution for two particulate samples depicted
by the lines A and B.
Question #2 (5 marks)
In assignment #1 the particulate collection efficiency in the human respiratory system was
depicted by the efficiency curves shown in Fig. 2. This behaviour is also typical of industrial
capture systems and can be divided up into three regimes:
Regime A – particles with dP < ~0.3 m where the capture efficiency increases with decreasing
particle size,
Regime B – particles in the range ~0.3 < dP < ~1 m where the capture efficiency is a minimum,
and
Regime C – particles with dP > ~ 1 m where the capture efficiency increases with particle size,
reaching a constant value of ~100% for larger particles with dP > ~10 m.
Describe briefly why the particulate capture efficiency typically follows this pattern for each
regime. In your description point out what capture mechanisms contributes to the observed
Particle capture efficiency, %
efficiency.
100
80
A
C
60
40
B
20
0
0.01
0.1
1
10
Particle size (dP), m
Figure 2. Typical particulate capture efficiency in the human respiratory system and industrial
capture processes as a function of particle diameter (diameter, dP).
Question #3 (10 marks)
A primary product in the cement industry is calcium oxide, CaO, obtained from the high
temperature calcining of CaCO3. Normally the CaO is almost fully recovered however some
product dust is also present in most calcining operations.
Cement plants have particulate
capture systems such as filters to remove this type of dust product from their air emission
sources. A cement plant proposes to shut down the pollution control system for an 8-hour shift
to perform necessary repairs on the unit. During this shutdown period, particulate emissions
from the main emission stack for the plant are expected to occur. You have been asked to
prepare an analysis of the potential impact of this emission source for the local Ministry of the
Environment office prior to receiving approval for this proposed shut-down. The primary impact
is expected to be a direct fall-out of the particulate in the local environment. The emitted
particulate material is released through a stack causing particles to be directed downwind at a
height of about 40 m above the ground. Particles can be assumed to acquire the local wind
velocity UW  5 m/s in the horizontal direction and a velocity component equivalent to the
particle terminal velocity in the vertical direction (no additional mixing occurs and g = 9.8 m/s2).
Particles in the size range of dP = 2.5 – 200 m are expected to be released. Estimate the range
of downwind distances, L, over which this particulate material might reach ground level.
Assume that air has a density, F = 1.18 kg/m3, and viscosity, F = 1.85  10-5 kg/m-s.
An MSDS summary sheet for CaO is given on the next page of this test paper showing some of
the health risks of this material. This information also indicates that the specific gravity of CaO
3.34 (i.e. density of CaO is 3.34 g/cm3). In your calculations, you should apply the Cunningham
correction factor assuming the mean free path for the air is   0.065 m. Also estimate the time
required for these particles to reach their terminal velocity.
W
C aO pa r tci el s
U px
H = 40m
U
U
C em en t
P al n t
L
py
Chemical Safety Data: Calcium oxide
Common
synonyms
Quicklime, burnt lime
Formula
CaO
Physical
properties
Form: White to light grey powdery solid
Stability: Stable, but reacts with moisture and absorbs carbon dioxide from the air.
Melting point: 2572 C
Water solubility: reacts
Specific gravity: 3.34
Principal
hazards
*** Contact with the eyes can cause serious irritation.
*** The solid is corrosive, so is likely to be harmful if swallowed or inhaled.
Safe
handling
Wear safety glasses. Minimize the amount of powder that gets into the air. Keep
off the skin.
Emergency
Eye contact: Immediately flush the eye with plenty of water. If irritation persists,
call for medical help.
Skin contact: Wash off immediately with soap and water.
If swallowed: Wash out the mouth with water if the person is conscious. Do not
induce vomiting. If the quantity swallowed is significant call for medical help.
Disposal
Small amounts of calcium oxide may be disposed of with normal laboratory waste,
unless local rules prohibit this.
Protective
equipment
Safety glasses.
Further
information
Calcium oxide
Chemicals in the HSci database
More extensive safety data