Air Pollution Control - PowerPoint PPT Presentation

Loading...

PPT – Air Pollution Control PowerPoint presentation | free to view - id: 2ce84-MjU2M



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Air Pollution Control

Description:

Air Pollution Control. Indoor Air Quality Model. Read pages 509 535 Textbook ... Ca = pollutant concentration in outdoor air, g/m3 ... – PowerPoint PPT presentation

Number of Views:4565
Avg rating:3.0/5.0
Slides: 34
Provided by: kenp
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Air Pollution Control


1
Air Pollution Control
2
Indoor Air Quality Model
  • Read pages 509 535 Textbook

3
Indoor Air Quality Model
  • The following balance on a room in a house or
    office building can be used to evaluate the air
    quality.

Volume V Concentration C
Q, Ca
Q, C
Decay rate, -k
Emission rate, E
Source
Sink
4
Indoor Air Quality Model
C pollutant concentration in/out of the room,
g/m3 Q infiltration rate of air into and out of
the room, m3/s Ca pollutant concentration in
outdoor air, g/m3 E emission rate of pollutant
into room from indoor source, g/s k pollutant
reaction rate, s-1
5
Indoor Air Quality Model
The general solution
The steady state solution
If the pollutant is conservative and does not
decay with time or have significant reactivity
(e.g. k 0), or if the ambient concentration is
negligible and the initial indoor concentration
is zero then the following equation can be
derived.
6
Indoor Air Quality Model
Conservative pollutant
Example 6.6 A non-vented kerosene heater is
operated for one hour in an apartment having a
volume of 200 m3. The heater emits SO2 at a rate
of 50 ?g/s. The ambient air concentration (Ca)
and the initial indoor air concentration (Co) of
SO2 are 100 ? g/m3. If the rate of ventilation
is 50 L/s, and the apartment is assumed to be
well-mixed, what is the indoor air concentration
of SO2 at the end of one hour?
7
Indoor Air Quality Model
Example 6.6 - Solution The concentration may
be determined using the general solution form of
the indoor air quality model. The decay rate for
SO2 from Table 6-8 is 6.39x10-5 s-1 and 50 L/s is
equivalent to 0.05 m3/s.
8
Treatment of Emissions
  • Air Control Processes
  • Particulate Materials
  • Cyclone
  • Bag filters
  • Spray Towers or Scrubbers

9
Treatment of Emissions
  • Air Control Processes
  • Gaseous Removal Processes
  • Wet Scrubbers
  • Adsorption Processes
  • Incineration or flaring Processes

10
Treatment of Emissions
  • Cyclones

11
Treatment of Emissions
  • Cyclone
  • Dirty air containing the particulates is sucked
    in the side of the cyclone. The particle
    velocities are reduced due to friction at the air
    wall interface causing the particles to settle
    out.
  • Good for particles 10.0 ?m

12
Treatment of Emissions
  • Cyclone Standard proportions for a reverse flow
    cyclone

13
(No Transcript)
14
Treatment of Emissions
The efficiency of this cyclone can be described
mathematically using the following expression and
graph Lapple (1951)
  • d0.5 cut diameter, the particle size for which
    the collection efficiency is 50, ?m.
  • dynamic viscosity of gas, Pas
  • B entrance width, m
  • H height of entrance, m
  • ?p particle density, kg/m3
  • Qg gas flow rate, m3/s
  • ? effective number of turns made in traversing
    the cyclone as defined in the following equation

15
Treatment of Emissions
16
Treatment of Emissions
  • ?, the effective number of turns made in
    traversing the cyclone as defined in the
    following equation

Where L1 and L2 are the length of the cylinder
and cone, respectively.
17
Treatment of Emissions
Example 6-9. Determine the efficiency of a
standard cyclone having the following
characteristics for particles 10 ?m in diameter
with a density of 800 kg/m3. Cyclone barrel
diameter 0.50 m Gas flow rate 4.0 m3/s Gas
temperature 25oC
18
Treatment of Emissions
Example 6-9. Solution From the standard
cyclone dimensions we can calculate the
following B (0.25)(0.50 m) 0.13 m H
(0.50)(0.50 m) 0.25 m L1 L2 (2.00)(0.50 m)
1.0 m
19
Treatment of Emissions
Example 6-9. Solution From the gas temperature
and Table A-4 of Appendix A, the dynamic
viscosity is 18.5 ?Pas. The cut diameter is
then
The ratio of particle sizes is
From Figure 6-32 we can find the collection
efficiency is about 95 .
20
Treatment of Emissions
  • Bag Filters

21
Treatment of Emissions
  • Bag Filters
  • The filter bags are about 10 ft long and 8 inches
    in diameter and hung in a chamber. Dirty air
    containing the ash or dust moves up through the
    bag and traps the particles. Periodically the
    bags are shaken to remove the particles. Good
    particle removal in submicron range.

22
Treatment of Emissions
  • Spray Tower or Scrubber

23
Treatment of Emissions
  • Spray Tower
  • Counter current process where the air moves up
    and a fine spray is introduced into the column
    which absorbs the particles and the dirty water
    is removed at the bottom of the column. Can
    remove submicron particles.

24
Treatment of Emissions
  • Electrostatic precipitator

25
Treatment of Emissions
  • Electrostatic Precipitators
  • Used mostly in power plants because requires much
    power. Particles are negatively charged through
    a high voltage electrode and collect on the
    positive electrode. Effective in removing
    submicron particles.

26
Treatment of Emissions
  • Adsorption Process

27
Treatment of Emissions
  • Adsorption Process
  • Gases or volatile organic pollutants in air are
    fed through a column filled with granular
    adsorbent. The pollutants diffuse from the gas
    stream to the adsorbent surface where they are
    adsorbed within the adsorbent particles.

28
Treatment of Emissions
  • Incineration Process

29
Treatment of Emissions
  • Incineration Process
  • A fuel like natural gas is fed with air and the
    organic pollutants into a combustion chamber
    where the pollutants are oxidized to carbon
    dioxide and water. A catalyst can also be used to
    increase the combustion efficiency and reduce
    fuel costs.

30
Comparison of Treatment Efficiencies
31
Treatment of Emissions
  • Sulfur Dioxide Control
  • Primarily for coal fired power plants. Two
    methods for sulfur control
  • 1) Change to low sulfur coal
  • 2) Desulfurize the coal remove the iron pyrite
    (FeS2) by washing the coal. Removal of organic
    sulfur by gasifying the coal before combustion.

32
Treatment of Emissions
  • Sulfur Dioxide Control
  • Flue-Gas Desulfurization is where the flue gas
    containing the sulfur oxides is contacted with
    powdered lime in the gas stream forming

33
Comparison of Particle Removals
About PowerShow.com