Introduction to air pollution controls

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1/05/2018
ENGR405
Industrial Pollution Control:
Introduction to Air Pollution
Airborne Pollution
Handout #1
Associate Professor, Matthew Watson
Office: LINK 402
Email: [email protected]
Who’s fault is it?
Who’s responsible for Air Pollution?
• Big oil companies?
• Power companies?
• The government?
• America…. China… India?
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What can I do about it?
• As an individual consumer:
• Vote with your wallet
• Make informed decisions about how you live your life
• What are your most polluting activities?
• Is a H2 powered vehicle pollution free? Electric vehicle? What about solar/wind power?
• Influence others
• As an engineer:
• Act with integrity
• Realise that pollution often = waste
• Work with marketing or commercial functions to differentiate your product or
service through environmental stewardship
What is Air Pollution
• A working definition:
• “Substances changing the natural composition of air” – Baumbach, “Air
Quality Control” page 1
• Natural sources
• Man-made (anthropogenic) sources
• Industrial sources – the focus of this class
• Household/Consumer
• What is the make-up of air?
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Industrial Sources of Air Pollution
• Some examples
•
•
•
•
•
Coal fired boiler – particulates, NOx, SOx, heavy metals, CO, CO2
Agriculture and Food Industry – odors
Surface coating (paints etc) – organic solvents
Chemical Process Industry – you name it…
Metallurgical and Mineral Products Industry – particulates, NOx, SOx, heavy
metals, CO, CO2
• Pharmaceutical Industry – amines, ethers, aromatic and aliphatic HCs,
alcohols, ketones and esters
• Petroleum – VOC vapour emissions (spills, leaks, and other releases)
• Pulp and Paper – particulates, sulphur, various organics
Focus on Combustion related pollution
• Why?
• The topic is too broad for 12 lectures!
• Combustion is used in many industries (as well as automobiles, and
household heating)
• It involves particulate and gaseous pollutants
• Principles can be applied broadly to other air-borne pollutants
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Air Pollutants in the Atmosphere
Baumbach – Air Quality Control
The importance of thermal gradients
• Action of gravity on air column:
For any movement of a parcel of
air over a height ∆z, it will
undergo a temperature ∆T
based on the following
conservation of energy:
•  ∆ + ∆ = 0
• Any adiabatic change in
potential energy is converted to
enthalpy of the ideal gas
Baumbach – Air Quality Control
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Influences of wind, turbulence and
topography on smoke stack plumes
• Fig 3.4
Baumbach – Air Quality Control
Flow past a cylinder
• http://en.wikipedia.org/wiki/Rey
nolds_number
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Inversion
Baumbach – Air Quality Control
Elevated Inversion
Baumbach – Air Quality Control
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Elevated Inversion
Some photos of Inversion
• http://en.wikipedia.org/wiki/Inv
ersion_(meteorology)
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Pollutants in
the Atmosphere
Baumbach – Air Quality Control
Pollutants in
the Atmosphere
• Figure 3.21
Baumbach – Air Quality Control
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SOx, NOx, and oxides of
Carbon
SOx
• SOx = sulphur oxides
• SOx refer to:
• SO3
• SO2
• Product of fossil fuel (oil and coal) combustion
• SO2 is the dominant SOx; SO3 is only produced in small quantities
• SOx are important as they are a precursor to acidic rain
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Sources of SOx
Natural
Anthropogenic
Sources of SO2
Auckland
Christchurch
Ministry of the Environment (2003). Emission Inventories for CO, NOx, SO2, ozone, benzene
and benzo(a)pyrene in New Zealand: Air Quality Technical Report No. 44.
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SO2
S + O2 ↔ SO2
• Colourless gas
• Detected by taste & smell at 1,000 – 3,000 µg/m3
• Pungent, unpleasant odour
• SO2 readily dissolves in water to form sulphurous acid (H2SO3)
• About 30% of SO2 is converted to sulphate aerosol particles
SO2 health effects
• SO2 can cause respiratory problems, such as bronchitis
• It can irritate your nose, throat and lungs
• It may cause coughing, wheezing, phlegm and asthma attacks
• SO2 has also been linked to cardiovascular disease
• Children, adults with lung disease and asthmatics are more
sensitive to SO2
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SO2 exposure guidelines - WHO
• WHO guidelines for
ambient SO2
concentrations are:
• 20 μg/m3 24 hour
average
• 500 μg/m3 10 min
average
• There is no annual
guideline (not
needed)
http://www.who.int/phe/health_topics/outdoorair/outdoorair_aqg/en/
SO2 exposure guidelines - NZ
• The New Zealand ambient air quality guidelines (2002) (not
legislative requirements) for SO2 are:
Concentration (µg/m3) Time average
Allowable exceedances
per year
350
1 hour
9
570
1 hour
0
120*
24 hour
-
• Only the 1-hour average guidelines were adopted into the
National Environmental Standards (2005) (legislative
requirements)
• Ministry for the Environment is investigating if the 24-h
guideline value should align with the WHO
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SO2 levels in NZ
• 9 sites monitor SO2 in New Zealand
• In 2012, none of the 9 sites breached the short-term
(one-hour) national standards
• 3 peak sites exceeded the WHO short-term (daily)
guideline for SO2
• Woolston, Chch (exceeded the guideline 54 times over the
year)
• Mount Maunganui (exceeded the guideline 69 times over
the year)
• Auckland waterfront (exceeded the guideline 13 times over
the year)
Ministry for the Environment and Statistics New Zealand (2014). New Zealand’s
Environmental Reporting Series: 2014 Air domain report.
SOx, NOx, and HCs
Oxidation of SO2
Baumbach – Air Quality Control
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NOx
• NOx = Nitrogen oxides
• NOx group includes:
•
•
•
•
•
•
•
NO
NO2
N2O – greenhouse gas
NO3
N2O5
HNO3
HNO2
• NO & NO2 are the most important nitrogen
oxides in urban areas
Sources of NOx
Natural – 30%
Anthropogenic – 70%
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Sources of NOx
Auckland
Christchurch
Ministry of the Environment (2003). Emission Inventories for CO, NOx, SO2,
ozone, benzene and benzo(a)pyrene in New Zealand: Air Quality Technical Report
No. 44.
NO
• NO = nitric oxide
• NO it created during high temperature
combustion processes
Heat
1. N2 + O2 ↔ 2NO
2. N2 + O ↔ NO + N
3. N + O2 ↔ NO + O
• Not known to be toxic to humans
• NO rapidly oxidises in air to form NO2
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NO2
• 10 % of NO2 is formed during high temperature processes
• Rest is formed by the reaction of NO with O2 or O3
2NO + O2 ↔ 2NO2
or
NO + O3 ↔ NO2 + O2
• Prevalent air pollutant:
• It is one of the species responsible for acidic rain
• Key species in the formation of photochemical smog
• It causes adverse health effects
Atmospheric NO2
• Characteristic
reddish-brown colour
• Sharp, biting odour
• Corrosive
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NO2 health effects
• Airway inflammation in healthy people
• Increased respiratory symptoms
• Decreased ability to fight infections in the lungs
• Reduced lung function growth in children
• Association between NO2 in the air and increased daily mortality
rates and hospital admissions for respiratory disease
London the most polluted city in the world?
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Indirect NO2 health effects
• NO2 can also indirectly effect peoples health
• The release of NO2 is associated with the release of other pollutants
(particulate matter & benzene) which effects health
• NO2 reacts with hydrocarbons under the presence of sunlight and heat to
form ozone, which adversely effects health
• NO2 reacts with ammonia, moisture and other compounds to form
particles, which causes additional health problems
NO2 exposure guidelines WHO
• WHO guidelines for
ambient NO2
concentrations are:
• 40 μg/m3 annual
mean
• 200 μg/m3 1 hour
average
http://www.who.int/phe/health_topics/outdoorair/outdoorair_aqg/en/
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NO2 exposure guidelines - NZ
• The New Zealand ambient air quality guidelines (2002)
(not legislative requirements) for NO2 are:
Concentration (µg/m3) Time average
Allowable exceedances
per year
200
1 hour
9
100
24 hour
-
• Only the 1-hour average guideline was adopted into
the National Environmental Standards (2005)
(legislative requirements)
• The WHO annual average guideline was not adopted
by New Zealand
SOx, NOx, and Hydrocarbons
Reactions of Nitrogen Oxides
• NO + O3 (k2) NO2 + O2
• Photostationary Balance:
• NO2 + hv (290-430nm) (k3) NO + O
• O+O2+M  O3 + M (fast)
• Overall Equilibrium Reaction:
• NO2 + O2 (k2) (k3)  NO + O3
Baumbach – Air Quality Control
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SOx, NOx, and Hydrocarbons
Reactions of Carbon Compounds
• Long lasting: CH4 – 8yrs; n-butane 4.5 days; ethane 45 days
• CO is formed by decomp. of methane, terpenes from conifers,
incomplete combustion
• CO reacts with OH radicals in atmosphere  CO2 and H radicals
• CO consumed by microbial action in the soil
COx
• COx = carbon oxides
• COx includes:
• CO2 – greenhouse gas
• CO
• CO2 is formed from the complete combustion of carbonaceous
material
• CO is formed from the incomplete combustion of carbonaceous
material
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CO
• CO is an odourless, colourless, & tasteless gas
• It is poorly soluble in water
• Sources:
•
•
•
•
•
•
•
•
Vehicles
Coal power plants
Steam boilers
Waste incinerators
Volcanoes
Fires
Gas cookers
Wood-burning stoves
Sources of CO
Auckland
Wellington
Ministry of the Environment (2003). Emission Inventories for CO, NOx, SO2, ozone, benzene
and benzo(a)pyrene in New Zealand: Air Quality Technical Report No. 44.
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Health effects of CO
• CO reacts with haemoglobin to form carboxyhaemoglobin
• Toxics effects are caused by hypoxia
•
•
•
•
•
•
•
Dizziness
Nausea
Confusion
Disorientation
Neurological and neurobehavioural effects
Cardiovascular effects
Developmental effects
• The most vulnerable are middle-aged & elderly with heart
conditions and foetuses
Leading cause of unintentional and
suicidal poisonings
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CO exposure guidelines - WHO
• WHO guidelines for
ambient CO
concentrations are:
•
•
•
•
100 mg/m3 in 15 min
60 mg/m3 in 30 min
30 mg/m3 in 1 h
10 mg/m3 in 8 h
CO exposure guidelines - NZ
• The New Zealand ambient air quality guidelines
(2002) (not legislative requirements) for CO are:
Concentration
(mg/m3)
Time average
Allowable exceedances
per year
10
8 hour
1
30
1 hour
-
• Only the 8-hour average guideline was adopted
into the National Environmental Standards (2005)
(legislative requirements)
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Dispersion Model: Pasquill-Gifford based on
Gaussian distribution
Dispersion Model: Pasquill-Gifford based on
Gaussian distribution
•  , ,  =

2  ℎ
 −
2
22
.  −
− 2
22
+  −
+ 2
22
•  , ,  = Concentration at position x,y,z (g/m3)
•  = Emission mass flow (g/s)
•  = effective height of emission source (m)
•  ,  = horizontal and vertical dispersion factors – which are
functions of x
• ℎ = Wind velocity as a function of altitude
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Dispersion Model: Pasquill-Gifford based on
Gaussian distribution
sy
sz
Dispersion Model: Pasquill-Gifford based on
Gaussian distribution
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Dispersion Coefficients Table
Effects of Air Pollution
• Well known green house gas effects and global climate change
• Particulate matter can shield earth from sun’s radiation – volcanic
activity
• Acid rain affects building materials (such as sandstone and marble)
• Acidification of soil can affect crop yield
• Pollutants affect plant health and crop yield
• Impact on Human health
• PM10 increases risk of deep vein thrombosis, heart disease and stroke
Baumbach – Air Quality Control
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Acid rain
• Pure water has a pH of 7.0 (neutral)
• Natural, unpolluted rainwater actually has a pH of about 5.6
(acidic)
• The natural acidity of rainwater comes from the natural presence
of CO2 found in the troposphere
CO2 +H2O → H2CO3
• Anthropogenic activity produces additional acid-forming
compounds in far greater quantities than the natural sources of
acidity
• In some instances, the pH of rainwater can be <3
Effects of acidic rain
• Acidification of
lakes/streams
• Damages trees at high
elevations
• Damages sensitive
trees
• Accelerates the decay
of building materials
and paints
• Decays statues
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Effects of acidic rain
Acid rain formation
• NO2
3NO2 + H2O → 2HNO3 + NO
or
NO2 + OH + M → HNO3 + M
or
NO2 + O3 + H2O → 2HNO3 + O2
• SO2
SO2 + O → SO3
SO3 + H2O → H2SO4
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Transboundary pollution
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http://ecan.govt.nz/services/online-services/monitoring/air-pollution/Pages/data-from-past-years.aspx
Christchurch Air
More recent recorded highs
WHO guidelines:
50mg/m3 24hr avg,
10mg/m3 annual avg.
Christchurch annual avg. 20
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