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Energy and Environment. E nvironmental consequences of combustion processes – Part I (Smog, Acid Rain, and ozone depletion). Dr. Hassan Arafat Department of Chem. Eng. An-Najah University. (these slides were adopted, with modification, from Ms. Paulina Bohdanowicz , KTH Institute, Sweden).

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Energy and environment
Energy and Environment

Environmental consequences of combustion processes – Part I(Smog, Acid Rain, and ozone depletion)

Dr. Hassan Arafat

Department of Chem. Eng.

An-Najah University

(these slides were adopted, with modification, from Ms. Paulina Bohdanowicz , KTH Institute, Sweden)


Source: WCI 2005


In order to meet forecasted global electricity demand it is estimated that 2000 MW of additional capacity will have to be installed every week over the next 20 years

Source: WCI 2005

Combustion chamber1
Combustion chamber

  • The type and quantity of compounds created depend on:

    • the type and composition of fuel,

    • combustion conditions (type of furnace, air:fuel ratio, and especially temperature)

    • CO2, depending on fuel composition and generator efficiency

    • Sulphur oxides (SOx) from sulphur oxidation - more than 95 % SO2, remaining is SO3

    • CO, depending on oxidation efficiency of fuel (up to 30% in incomplete combustion)

    • 20-90 % of N in fuel is converted into NOx. Additionally depending on the temperature of combustion and residence time, N from air combines with O from air

  • The extras ? - dioxines and furans (coming from combustion of chlorinated plastics)- highly carcinogenic and very dangerous, mainly in waste incineration plants

  • Coal: small quantities of uranium, radium and thorium present in the coal result in the radioactivity of the fly ash (of varying level)


  • Emissions of concern:

    • Particulates/fly and bottom ash

    • Carbon dioxide

    • Sulphur oxides

    • Nitrogen oxides

    • Carbon monoxide

    • Waste

Flue gas composition from a typical coal fired power plant
Flue gas composition from a typical coal-fired power plant

Source: Liss R., Saunders A., Power generation and the Environment, Oxford 1990; Turns S.R., An introduction to combustion, concepts and application, Singapore 2000

Energy and environment

Air Pollutants

  • Carbon monoxide

    • colorless, odorless, non-irritating poison

    • attaches to hemoglobin; reduces oxygen carrying capacity

    • results in headaches, drowsiness and asphyxiation

  • Hydrocarbons

    • denotes a large group of volatile organic compounds

    • some are carcinogens, poison etc.

  • Energy and environment

    Air Pollutants

    • Sulfur Dioxide

      • colorless corrosive gas

      • respiratory irritant and poison

      • can result in H2SO4

  • Particulates

    • small pieces of solid or liquid materials dispersed in the atmosphere

    • 0.005-100 um

    • reduction in visibility, respiratory problems

  • Energy and environment

    Air Pollutants

    • Nitrogen Oxides

      • critical component for smog formation

      • compounds acid precipitation problems

  • Photochemical Oxidants

    • products of secondary atmospheric reactions driven by solar energy

    • e.g., O3 PAN (peroxyacetyl nitrate), acrolein

    • strong oxidants, eye irritant etc.

  • Energy and environment

    Air Pollutants

    • Lead

      • released as metal fumes or suspended particles

        • 2 million metric tons per year

        • 5-10 times more in urban than rural areas when leaded gas is used

      • major source was leaded gasoline

  • Carbon Dioxide

    • generally considered non-toxic and innocuous

    • not listed as air pollutant

    • increasing concentrations have been related to global warming

  • Waste generated per year in a 1000 mwe coal power plant
    Waste generated per year in a 1000 MWe coal power plant

    Coal characteristics: CV of 20 MJ/kg and a sulphur content of 1%.

    Plant characteristic: efficiency 34%, electricity production 65% of the total electricity it is capable of producing (650 MW-years in one year)

    Comparative emission levels from a 300 mw power plant
    Comparative emission levels from a 300-MW power plant

    • Source: Interstate Natural Gas Association of America. Natural Gas and the Environment. (accessed March 18, 2002)

    Results of emissions
    Results of emissions

    • Local pollution with particulates and gases

    • Smog

    • Acid rains

    • Greenhouse effect/ Global warming

    • Thermal pollution from cooling waters

    • Waste generation

    Local air pollution1
    Local air pollution

    Atmospheric concentration of selected species
    Atmospheric concentration of selected species

    Source: Siemiński M., Środowiskowe zagrożenia zdrowia, Warszawa 2001

    Urban air quality

    19.7% of EU inhabitants are exposed to excessive levels of ozone (2000)

    9.6% - Denmark

    18.3% - Finland

    41.2% - Greece

    69.9% - Italy

    95.4% - Austria

    36.2% of EU inhabitants are exposed to excessive levels of particulate matter (PM10) (2000)

    36.2% - Denmark

    56.0% - Sweden

    95.6% - Netherlands

    97.6% - Greece

    100.0% - Italy

    100.0% - Portugal

    Urban air quality

    Energy and environment
    Smog ozone (2000)

    Energy and environment

    Form of air pollution in which atmospheric visibility is partially obscured by a haze consisting of solid particulates and/or liquid aerosols

    Occurs mainly in urban areas but not exclusively

    Smoke + fog = smog


    Sulphur smog london smog

    History partially obscured by a haze consisting of solid particulates and/or liquid aerosols

    dates back to the 14th century

    the "Killer Smog" reported in 1952, claimed 4000 fatalities in London - by far the most devastating event of this type in recorded history.


    Inefficient combustion of high-sulphur coal => high concentration of unburned carbon soot and other particulates, acidic sulfate aerosols (such as sulfuric acid, H2SO4) as well as elevated levels of sulphur dioxide.

    SO2 and soot, => sulphuric acid, sulfate aerosols

    Characteristic brownish haze - formed usually under conditions of high humidity and relatively low temperatures, characterised by reducing and acidic properties.

    In case of humid atmospheres carbon particulates serve as condensation nuclei for water droplets resulting in formation of fog, highly irritant.

    Classical smog can persist for days when atmospheric conditions allow.

    Sulphur smog / London smog

    Sulphur smog london smog1
    Sulphur smog / London smog partially obscured by a haze consisting of solid particulates and/or liquid aerosols

    Batter Sea power station, London, UK

    Sulphur smog london smog2

    Impacts partially obscured by a haze consisting of solid particulates and/or liquid aerosols

    Deterioration of human made structures and materials

    Deterioration of flora

    Respiratory problems, allergies, asthma, lung damage


    Burning of lower S-content coal

    Desulphurisation of flue gases

    Clean Air Acts, Sulphur Protocol

    Sulphur smog / London smog

    Photochemical smog la smog

    process by which ozone is being created at low altitudes – ground level

    encountered in automobile rich cities – with specific climatic conditions


    mid-1940s - repeated occurrence of heavy injury to vegetable crops in the Los Angeles area - traced to high concentrations of ozone that appeared to be created at low altitudes

    Photochemical smog / LA smog

    Photochemical smog la smog2
    Photochemical smog / LA smog ground level

    Los Angeles

    Photochemical smog la smog3
    Photochemical smog / LA smog ground level



    Las Vegas

    Asian brown cloud
    Asian Brown Cloud ground level

    Asian brown cloud1

    Aerosols, ash, soot ground level

    3km thick

    80% man-made



    local wood /dung /kerosene burning,

    forest fires – clearing

    can travel half way round the globe in a week

    solar radiation reduced by up to 15%

    Hundreds of thousands of deaths annually (2mln in India alone)

    Acid rain

    Warming of the atmosphere

    Climate changes (floods & draughts)

    Other Brown Clouds: South America, Mediterranean

    The regional and global impact of the haze will intensify over the next 30 years

    Asian Brown Cloud

    Photochemical smog la smog4

    Impacts ground level

    Impaired visibility

    Eye and respiratory system irritants

    Damage to lung tissue

    Vegetation damage

    Contribution to acidic deposition

    Materials destruction (rubber and some plastics)

    Photochemical smog / LA smog

    Energy and environment

    Photochemical smog / LA smog ground level

    • How to reduce smog (main goal is to reduce VOC and NOx):

      • PCV valves

      • Leak-proof caps

      • Tune-up

      • Emission tests

      • Catalytic converters

      • Public transportation

    Energy and environment

    Acid Rain ground level

    Acid rain

    History ground level

    First studies on rain chemistry were conducted in late 1800s, but modern investigations date back to 1960s.

    Nowadays the chemistry of atmospheric precipitation is fairly well known.

    The phenomenon of acid rain has been known and studied from 1950s.

    1960 – lowered fish production in Scandinavian lakes

    In 1972 it became an international public policy issue at the first United Nations Conference on the Environment held in Stockholm.

    The transboundary effect of atmospheric pollution has been officially accepted, based on the fact that sulphur and nitrogen oxides are commonly emitted in one location while the acid deposition occurs in distant area.

    In Sweden and Norway around 90% of the acid deposition comes from other countries, primarily UK, Germany, Poland and other Central Europe countries. Canada receives major acid contribution form the US.

    Acid Rain

    Source: Van Loon G.W., Duffy S.J., 2000.

    Acid rain1
    Acid Rain ground level

    • Rain that is more acidic than normal because it contains sulfuric acid or nitric acid

    • result of SOx, NOx, acidic particulates in air

    • involves all forms of acid deposition, even if rain is not involved

    • Utility plants contribute to 70% SO2 production and 30% NOx production in USA

    • Coal contains as high as 5% sulfur

    Sox emissions of energy options
    SOx emissions of energy options ground level

    Source: Boyle et al. 2003

    Nox emissions of energy options
    NOx emissions of energy options ground level

    Source: Boyle et al. 2003

    Impacts of acid rain

    Acidification of water ecosystems ground level

    Natural surface waters - pH of 6-8, acidified waters pH 3 (conditions unbearable for many aquatic species, which eventually die, and lakes become lifeless)

    Today some 14000 lakes in Sweden are affected by acidification. Similar situation is in Canada

    Nitrogen can induce eutrophication, which results in depletion of oxygen in water, further affecting the aquatic flora and fauna

    Impacts of acid rain

    Impacts of acid rain1

    Acidification of soil ecosystems ground level

    Areas with highly siliceous bedrock (granite, gneisses, quartzite, and quartzstone - acidic) – most vulnerable (Scandinavia, Canada, United Kingdom and Alps).

    Acid deposition - enhances leaching of important cations such as calcium, potassium, magnesium and sodium - unavailable to plants as nutrients (soil depletion)

    Reduced fertility of soil

    Some metals (i.e. aluminium, and mercury) leach from acidified soils into waters

    Impacts of acid rain

    Impacts of acid rain2

    Damage of flora ground level

    A 1999 survey of European forests - one out of every four trees suffered the loss of 25% or more leaves or needles

    Decay of structural materials

    Marble, sandstone, rubber, metals

    Herten, Germany, 1908 & 1969

    Impacts of acid rain

    Impacts of acid rain3

    Human health problems ground level

    respiratory problems including lung disorders, asthma, and bronchitis due to suspended atmospheric sulphates

    indirect effect of acidification on humans is related to the presence of toxic metals in the food chain

    Impacts of acid rain


    Conventions/Targets ground level

    the Convention on Long Range Transboundary Air Pollution (1994 Sulphur Protocol) – with amendments

    5th Environmental Action Programme and by the Council of Ministers of the Environment)

    1999 Gothenburg Protocol to Abate Acidification, Eutrophication and Ground-Level Ozone



    The annual cost of the multi-effect protocol is estimated at the level of 2.8 billion euro for the year 2010.

    The returns, in the form of improved health and reduced corrosion to buildings would by that same year amount to euro 12.8 billion.

    Plus there are benefits that do not carry a price tag…


    Energy and environment

    Ozone Depletion the level of 2.8 billion euro for the year 2010.

    Energy and environment

    Ozone Depletion the level of 2.8 billion euro for the year 2010.

    • Stratospheric Ozone absorbs harmful ultraviolet (<340nm) radiation from the Sun

    • 1% loss of ozone = 2% increase in UV radiation = 106 extra cancers

    • ozone hole = 7.7 million sq. miles

    • CFCs & HCFCs are the primary causes

    Antartic arctic ozone hole

    Ozone hole above the the Antarctic on October 3, 1999 (NASA satellites)

    A record size of ozone hole was 10.5 million square miles on Sept 19, 1998

    Red color would denote high ozone levels; blue denotes low

    Antartic/Arctic ozone hole

    Ozone layer depletion

    Impacts satellites)

    Humans (a 10% drop in stratospheric ozone levels is likely to lead globally to

    300000 more skin cancers,

    1.6 million more eye damage – cataracts) per year

    Reptiles (damage to eggs)

    Plants (reduced photosynthesis, increased sensitivity to stress)

    Damage to marine ecosystems (direct and indirect)

    Ozone layer depletion

    Ozone what s being done
    Ozone: What’s Being Done? satellites)

    • Montreal Protocol (1985)

    • complete phase-out of CFCs by 2000

    • critical need to come up with inexpensive non-halogenated coolants

    • if everyone abides, ozone loss should peak between 2001 and 2005

    • ozone levels should return to normal