ENVE 4003

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ENVE 4003

• PARTICULATE MATTER
• Sources, characteristics, size distribution

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PARTICULATE MATTER

• Wide range of particle sizes from diverse sources
  (Fig. 8.1 de Nevers)
• Distribution by surface area in an industrial
  atmosphere (Fig. 8.9 de Nevers)
• Primary Coarse, from mechanical attrition
• Secondary Fine, from combustion, evaporation,
  condensation
• Human health concern for PM2.5

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PARTICLE DIAMETER

• Non-spherical diameter of sphere with equal
  volume
• Fine particles Aerodynamic diameter
• Diameter of a water droplet with similar
  aerodynamic behaviour
• Cascade impactor

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Cascade Impactor
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Electrical Low Pressure Impactor (ELPI) DEKATI
http//www.dekati.com/elpi2.shtml

• Operation principle The gas sample containing
  the particles is first sampled through a unipolar
  corona charger. The charged particles then pass
  into a low pressure impactor with electrically
  isolated collection stages. The electric current
  carried by charged particles into each impactor
  stage is measured in real time by a sensitive
  multichannel electrometer. The components are
  housed in a single compact unit. Standard RS232
  port is provided for communication with a laptop
  or PC computer. The particle collection into
  each impactor stage is dependent on the
  aerodynamic size of the particles. Measured
  current signals are converted to (aerodynamic)
  size distribution using particle size dependent
  relations describing the properties of the
  charger and the impactor stages.

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Dekati ELPI
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Figure 8.1 de Nevers

• Sizes and characteristics of airborne particles

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Figure 8.9 (8.11) de Nevers

• Distribution of particles by surface area in an
  industrial atmosphere

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Figure 8.10 (8.12) de Nevers

• A truck with three different sizes of particles

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Figure 6-5 Davis Cornwell

• The human respiratory system

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Table 7-8 Peavy, Rowe, Tchobanoglous

• Particulate size and respiratory defense mechanism

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Figure 4-33 Davis Cornwell

• Predicted regional deposition of particles in the
  respiratory system

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Figure 7-5 Peavy, Rowe, Tchobanoglous

• Retention of particulates in the lungs

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SURFACE AREA AND VOLUME

• For small particles surface forces become
  important
• Electrostatic
• Van der Waals

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FLUID-PARTICLE INTERACTION
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LOWER LIMIT OF STOKES REGION
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CORRECTION TO STOKEs CD
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TERMINAL SETTLING VELOCITY

• Balance between gravity and drag forces
• (Figure 8.5 de Nevers)
• Can be used to determine the size of settling
  chambers for removing dust particles from gas or
  liquid streams

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Figure 8.4 (8.6) de Nevers

• Terminal settling velocities for spherical
  particles with s.g. 2.0 in standard air

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Figure 8.5 (8.7) de Nevers

• Terminal settling velocities for spherical
  particles of different densities in air and water

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PARTICLE SIZE DISTRIBUTION

• Gaussian, or normal

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ALTERNATE FORM FOR GAUSSIAN DISTRIBUTION
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GAUSSIAN DISTRIBUTION, INTEGRATED FORM

• (Table 8.3 de Nevers)
• Probability scale a scale linear in z
• Gaussian distribution gives linear plot on
• normal (y axis) vs probability (x axis)
  coordinates
• Slope standard deviation
• mean value is at z 0

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Table 8.3 de Nevers
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Figure 8.8 de Nevers

• Graph with (log) probability scale

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THE LOG-NORMAL PARTICLE SIZE DISTRIBUTION

• Log-normal distribution gives linear plot on
• logarithmic (y axis) vs probability (x axis)
  coordinates
• Slope standard deviation
• mean value is at z 0

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MEAN PARTICLE DIAMETERVolume (mass), surface,
number, and Sauter

• It is possible to define different mean diameters
  based on the type of cumulative fraction we use.
  
• Which one is appropriate depends on the
  application.
• For any particle size distribution,

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MEAN PARTICLE DIAMETERVolume (mass), surface,
number, and Sauter
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DISTRIBUTION FUNCTIONS, MEANS, and TAILS

• Distribution function parameters (mean and
  standard deviation) are obtained by fitting the
  data
• They generally do a good job in the middle of the
  range
• Beware of extrapolating beyond the data range
• Example 8.8 de Nevers, predicts 6 men taller than
  10 feet (3 m) in the United States based on
  height distribution statistics