Emissions

Abstract

Emissions from combustion of fossil fuels are of great concern due to their impact on the environment and public health. The primary combustion products, carbon dioxide (CO₂) and water (H₂O), affect the environment through greenhouse effects and potential localized fog. Both products are inherent to the combustion of fossil fuels and their emission can only be reduced through modifications in the fuel or by exhaust treatment. The other major pollutants from combustion are secondary products and include carbon monoxide (CO), unburned hydrocarbons (HC), soot, nitric oxides (NO_x), sulfur oxides (SO_x), and oxides of metals. Pollutants cause health problems in humans and animals and can contribute to acid rain. Topics included in this chapter are: (1) the negative effects of combustion products, (2) parameters affecting the formation of pollutants, (3) pathways of pollutant formation and methods of control, and (4) methods of emission quantification.

Exercises

• 9.1. A mixture of gases containing 3% O₂and 60% N₂by volume at room temperature is suddenly heated to 2,000 K at 1 atm pressure. Assume that the fractions of O₂and N₂are unchanged by the sudden gas heating process. Find the initial rate of formation of NO (ppm/s) after the mixture is heated. Indicate whether the NO formation rate will then increase or decrease as time progresses. Use the Zeldovich mechanism and assume there is no hydrogen in the mixture. Repeat the same analysis at a temperature of 1,200 K.

  EPA Pollution Standards

  Pollutant	Criteria pollutants
  	Description	Sources	Health effects
  Carbon monoxide (CO)	An odorless, tasteless, colorless gas which is emitted primarily from any form of combustion	Mobile sources (autos, trucks, buses), wood stoves, open burning, industrial combustion sources	Deprives the body of oxygen by reducing the blood’s capacity to carry oxygen; causes headaches, dizziness, nausea, listlessness and in high doses, may cause death*
  Hydrocarbons (HC)	Unburned, partially burnt fuel	Mobile sources (autos, trucks, buses), formed by the incomplete combustion of fuel	When combined with sun light produces photo chemical (smog)
  Lead (Pb)	A widely used metal, which may accumulate in the body	Leaded gasoline, smelting, battery manufacturing and recycling	Affects motor function and reflexes and learning; causes damage to the central nervous system, kidneys and brain. Children are affected more than adults
  Ozone (O3)	Formed when nitrogen oxides and volatile organic compounds react with one another in the presence of sunlight and warm temperatures. A component of smog	Mobile sources, industry, power plants, gasoline storage and transfer, paint	Irritates eyes, nose, throat and respiratory system; especially bad for those with chronic heart and lung disease, as well as the very young and old, and pregnant women
  Nitrogen dioxide (NO2)	A poisonous gas produced when nitrogen oxide is a by-product of sufficiently high burning temperatures	Fossil fuel power, mobile sources, industry, explosives manufacturing, fertilizer manufacturing	Harmful to lungs, irritates bronchial and respiratory systems; increases symptoms in asthmatic patients
  Particulate Matter PM10PM2.5	Particles of soot, dust, and unburned fuel suspended in the air	Wood stoves, industry, dust, construction, street sand application, open burning	Aggravates ailments such as bronchitis and emphysema; especially bad for those with chronic heart and lung disease, as well as the very young and old, and pregnant women
  Sulfur dioxide (SO2)	A gas or liquid resulting from the burning of sulfur-containing fuel	Fossil fuel power plants, non-ferrous smelters, kraft pulp production	Increases symptoms in asthmatic patients; irritates respiratory system

  Air Quality Standards

  New standards for particulate matter smaller than 2.5 μm in size (PM_2.5) and ozone were adopted by EPA in 1997.

  Pollutant	National		Washington state
  	Primary	Secondary
  Carbon monoxide (CO)
  8 h average	9 ppm	9 ppm	9 ppm
  1 h average	35 ppm	35 ppm	35 ppm
  Lead (Pb)
  Quarterly average	1.5 μg/m3	1.5 μg/m3	No standard
  Nitrogen dioxide (NO 2 )
  Annual average	0.053 ppm	0.053 ppm	0.05 ppm
  Ozone (O 3 )
  1 h average	0.12 ppm	0.12 ppm	0.12 ppm
  8 h averageb	0.08 ppm	0.08 ppm	No standard
  Particulate Matter (PM 10 )
  Annual arithmetic mean	50 μg/m3	50 μg/m3	50 μg/m3
  24 h average	150 μg/m3	150 μg/m3	150 μg/m3
  Particulate Matter (PM2.5)
  Annual arithmetic mean	15 μg/m3	15 μg/m3	No standard
  24 h	65 μg/m3	65 μg/m3	No standard
  Sulfur dioxide (SO 2 )
  Annual average	0.030 ppm	No Standard	0.02 ppm
  24 h average	0.14 ppm	No Standard	0.10 ppm
  3 h average	No standard	0.5 ppm	No standard
  1 h average	No standard	No standard	0.40 ppmb
  Total suspended particulates
  Annual geometric mean	No standard	No standard	60 μg/m3
  24 h average	No standard	No standard	150 μg/m3

  1. Primary standards are listed in this table as they appear in the federal regulations. Ambient concentrations are rounded using the next higher decimal place to determine whether a standard has been exceeded. The data charts in this report are shown with these un-rounded numbers.
  2. Details of the national standards are available in 40 CFR Part 50
  3. ppm parts per million, μg/m³micrograms per cubic meter
  4. ^a0.25 not to be exceeded more than two times in any 7 consecutive days
  5. ^bEight hour ozone standard went into effect on September 16, 1997, but implementation is limited.