Air and Water Pollution Prevention and Control Engineering
Homework # 4
1.- Write a ~250 word essay describing the key characteristics of particulate air pollutants encountered in the
location where you live or work.
Airborne particulates are rarely homogeneous; they vary greatly in size and shape and their chemical composition
is determined by factors specific to the source and location of the emissions.
The relatively low levels of PM10 (20 micrograms/ scm) and PM 2.5(10 micrograms/ scm) in CT can partly be
attributed to clean fuels such as natural gas and propane, as well as the majority of our power generation coming
from out of state. However there are power plants, and they do contribute somewhat.
We will assume that 80% of PM in Hartford is derived from vehicles- specifically the incomplete combustion of
gasoline. The majority of the chemical composition will be consistent with that of a gasoline light duty vehicle,
composed mostly of carbonaceous material, heavy hydrocarbons and hydrated sulphuric acid, and some other
pollutants such as iron as rust, base metals, soot and tars. Measurement and characterization of these particles
require elaborate sampling procedures and sophisticated analytical methods. To measure the chemical
composition of PM chromatography and mass spectrometry.
http://ec.europa.eu/transport/roadsafety_library/publications/particulates_d2.pdf
2.- The attached excel spreadsheet contains some air pollutant particle size data (in micrometers). Carry out a
statistical analysis of the data. Is the log-normal distribution a good fit to the data? I don’t know how to use
lognorm function
Data
Natural log
3.- Consider air pollutant particles of the same material (density = 1000 kg/m3) but in the size range from 10 to
1000 micrometers. Make a table containing the computed values of the terminal velocities of the particles and
comment on your results.
4.- Particle laden polluted air is made to flow at an average speed of 0.1 m/s into a simple settling chamber of
height 0.1 m and length 10 m. Assume the size of particles in the air is between 1 and 10 micrometers and that
their densities are in the range of 500 to 2000 kg/m3. Calculate and plot the particle collection efficiency of the
chamber as a function of particle size and density. Comment on your results.
n(Dp)=(VtL)/(UaH)
how do I plot with 2 variables?
Efficiency will increase as size increases and density decreases?
5.- Particle laden air is passed through a cyclone of diameter 1 m. Assume the size of particles in the air is between
1 and 30 micrometers, that the air flow rate into the cyclone is in the range between 1 and 100 m3/s and that the
density of the particles is 2000 kg/m3. Calculate and plot the particle collection efficiency of the cyclone as a
function of particle size and air flow rate. Comment on your results.
6.- Particle laden air is passed through an electrostatic precipitator (radius 0.1 m, height 3 m). . Assume the size of
particles in the air is between 0.1 and 1 micrometers, that the air flow rate into the precipitator is 0.1 m3/s and
that the effective electric field on the particles es 106 V/m. Calculate and plot the particle collection efficiency of
the electrostatic precipitator. Comment on your results.
Don’t know how to use e in excel
7.- A cigarrete filter is consists of 50 micrometer diameter fibers with a fiber fraction of 0.5. When smoking air is
inhaled at a velocity of ~ 0.03 m/s. If the individual fiber collection efficiency of typical particles in cigarret smoke
is assumed ~ 0.01 determine the length of filter capable of providing overall collection efficiency of 0.99.
.99=1-exp[-4*.5*.01*L/>.5*50E-6)
Ln(.99)=ln(1)-[]
L=1.25E-5 meters or 12.5 micrometers