Air pollutants from burning fuels – catalytic converters and flue-gas desulfurisation
ChemistryApplied & Practical ChemistryAges 16–17
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Sign in to playAn engine, power-station and atmosphere model. Choose petrol, diesel or sulfur-containing coal, set the oxygen supply λ and the flame temperature, and read the carbon monoxide, soot, unburnt hydrocarbons, NOₓ and SO₂ produced per kilogram of fuel. Switch on a Pt/Pd/Rh catalytic converter, low-sulfur fuel or flue-gas desulfurisation to see the emissions fall, with balanced equations, effects (toxic gas, acid rain, global dimming, respiratory illness) and a results table.
Lesson: Air pollutants from fuels: incomplete combustion, NOₓ, SO₂, acid rain, catalytic converters and flue-gas desulfurisation
What it shows
Burning fuels releases more than carbon dioxide and water. Without enough oxygen, combustion is incomplete and gives toxic carbon monoxide, soot and unburnt hydrocarbons. At the high temperatures inside engines and furnaces, nitrogen and oxygen from the air combine to form nitrogen oxides, and any sulfur in the fuel burns to sulfur dioxide; both dissolve in rain to make acid rain. A three-way catalytic converter oxidises CO and hydrocarbons and reduces NO, but only works well when the mixture is close to stoichiometric (λ ≈ 1). Low-sulfur fuel and flue-gas desulfurisation with limestone remove most of the SO₂.
How to use
Choose a Fuel, then drag Oxygen supply λ and Flame temperature (λ = 1) and watch the bar chart of emissions per kilogram of fuel. Tick Catalytic converter for petrol or diesel, Low-sulfur fuel, or Flue-gas desulfurisation (FGD) for coal, and compare the faded bars before treatment with the solid bars. Press Record result to build a comparison table, and read the effects cards and balanced equations below.
Parameters you can change
- Fuel Petrol (modelled as octane, C₈H₁₈), Diesel (modelled as dodecane, C₁₂H₂₆), Coal containing sulfur (power station)
- Oxygen supply λ (relative to the amount needed for complete combustion) 0.6–2
- Flame temperature at λ = 1 1000–2400 °C
- Use low-sulfur fuel
- Fit a catalytic converter (petrol and diesel vehicles)
- Switch on flue-gas desulfurisation, FGD (coal power station)
Questions to explore
- Why does reducing the oxygen supply increase CO and soot but decrease NOₓ?
- Why does a three-way catalytic converter remove NOₓ only when λ is very close to 1?
- How many grams of SO₂ come from burning 1 kg of coal containing 2.5 % sulfur?
