Combustion Emission and
Local Sources
Requirements for Combustion
Combustion
Oxygen
Fuel
Ignition source
Wood + Air + heat  ash + smoke + even more heat
Oxygen
• Atmosphere contains approx 20.8% O2
• Most of the mass in water is Oxygen (H2O)
• Most organic compounds (containing
carbon) also contain oxygen, such as
wood, which contains Carbon, Hydrogen,
Oxygen, minerals, metals, salts, etc.
Fuel (context – Wood)
• Wood is made up of carbon, hydrogen,
oxygen, salts, metals, calcium, potassium,
sulfur, etc.
– Depends on species
– Location (soils and atmospheric conditions)
– Age
– Size
Combustion
• A sequence of exothermic chemical
reactions between a fuel and an oxidant (a
compound that readily transfers oxygen
atoms) accompanied by the production of
heat.
Complete Combustion
Organics (CH2O) + O2 →CO2 +H2O + Heat
Wood Burning
• Occurs in three phases
– Moisture in the wood boils
– Gases are driven out (volatilization)
– Charcoal Burns >600 F
Emissions from Wood Combustion
‘Perfect’ Wood = Carbon, Hydrogen, and Oxygen
• Combustion = CH2O + O2 →CO2 +H2O + Heat
‘Real’ Wood = Carbon, Hydrogen, Oxygen,
Nitrogen, and minerals (Calcium, Potassium,
Sulfur, Chlorine, Lead, etc.). Ash comes from
the minerals present and other soil
contamination.
‘Real’ Air = Oxygen, Hydrogen, Nitrogen, etc.
Emissions from Wood Combustion
Incomplete Combustion
• PICs = CH2O + O2 + N2→CO2 +H2O + NO2 +
Heat
Products of Incomplete Combustion (PIC)
• Carbon Monoxide (CO)
• Nitrogen Dioxide (NO2)
• Formaldehyde, Acrolein, Benzene, Toluene, etc.
• Polyaromatic hydrocarbons
• Elemental carbon (soot)
Particulate Matter
• PM10 – very small droplets of condensed
organic vapors of wood tar and gases.
Mainly a result of unburned fuel.
• PM2.5 – a complex mixture that may
contain soot, smoke, metals, nitrates,
sulfates, dust water, etc.
Incomplete Combustion
• Caused by –
– Low temperatures
– Insufficient air
– Incomplete mixing
Sources of PM2.5
•
•
•
•
Light/Heavy duty vehicles (Transportation)
Open burning (Forestry/Residential)
Wood stoves (Residential)
Biomass boilers (Industrial)
• Questions