22 Questions
Which of the following is true about nitrogen oxides (NOx)?
NOx is a byproduct of combustion
What are the two primary components of nitrogen oxides (NOx)?
NO and NO2
Which type of nitrogen oxide (NOx) is rapidly formed at combustion temperatures exceeding 1500°C?
Thermal NOx
Which type of device measures the decrease in light intensity due to absorption and scattering?
a) Opacity meter
N0^; emissions consist primarily of which compounds?
d) NO and N02
Explain one method used to control sulfur dioxide and nitrogen oxides emissions.
b) Implementing flue gas desulfurization
Which of the following is a method used to control particulate matter in flue gas?
Cyclone separators
What is the percentage of ash in the original fuel that becomes fly ash and leaves with the flue gases in a fluidized bed furnace?
All of the ash
What is the efficiency of a cyclone separator in removing fine particulate matter?
90%
What is the method used to measure particulate matter in the flue gas using a transmissometer analyzer?
Measuring the transmission of light through the flue gas
Which of the following is a highly efficient method to remove NOx from exhaust gases?
Selective catalytic reduction (SCR)
At what temperature range can selective catalytic reduction (SCR) be used?
260°C to 650°C
What is the major component of acid rain?
Sulfuric acid (H2SO4)
What is the best control method for sulfur dioxide (SO2) emissions?
Burning fuels with no sulfur content
Which of the following is the formula mass for sulfur dioxide ($SO_2$)?
64
What is the mass of 5 kmol of carbon dioxide ($CO_2$)?
176
For complete combustion of 24 kg of carbon (C), what mass of oxygen ($O_2$) is required?
32 kg
A burner takes 20 kg/min excess air. If the theoretical air is 60 kg/min, what is the percent of excess air?
30%
Which of the following is a method for controlling N0^ in the combustion zone?
Restricting the amount of excess air used in combustion
What is the temperature range for selective non-catalytic reduction (SNCR) to be effective?
870°C-1000°C (1598°F-1832°F)
What is the purpose of flue gas recirculation in reducing thermal N0^?
To recirculate a percentage of the flue gas back to the burner
What is the reduction reaction for catalytic NOx removal?
Nitrogen oxide + Ammonia + Oxygen -> Nitrogen + Water 2N02 + 4NH3 + 02 -> 3N2 + 6H20
Study Notes
Nitrogen Oxides (NOx)
- Nitrogen oxides (NOx) have two primary components: nitrogen monoxide (NO) and nitrogen dioxide (NO2).
- Nitrogen dioxide (NO2) is rapidly formed at combustion temperatures exceeding 1500°C.
- NOx emissions consist primarily of NO and NO2.
Control of Emissions
- One method used to control sulfur dioxide and nitrogen oxides emissions is the use of scrubbers.
- Electrostatic precipitators are used to control particulate matter in flue gas.
- Cyclone separators have an efficiency of around 90% in removing fine particulate matter.
- Particulate matter in flue gas can be measured using a transmissometer analyzer, which measures the decrease in light intensity due to absorption and scattering.
- Selective catalytic reduction (SCR) is a highly efficient method to remove NOx from exhaust gases, effective in the temperature range of 300-400°C.
- Flue gas recirculation is used to reduce thermal NOx by reducing the flame temperature.
Acid Rain and Sulfur Dioxide
- The major component of acid rain is sulfuric acid, which is formed by the reaction of sulfur dioxide (SO2) with water and oxygen.
- The best control method for sulfur dioxide (SO2) emissions is the use of scrubbers.
Combustion and Stoichiometry
- The formula mass for sulfur dioxide (SO2) is 64.06 g/mol.
- The mass of 5 kmol of carbon dioxide (CO2) is approximately 220 kg.
- For complete combustion of 24 kg of carbon (C), approximately 64 kg of oxygen (O2) is required.
- If a burner takes 20 kg/min excess air, and the theoretical air is 60 kg/min, then the percent of excess air is 33.33%.
Test your knowledge on the formation of particulates in combustion processes! This quiz will cover topics such as the presence of ash in fossil fuels and biomass fuels, the different types of ash, and the characteristics of fly ash. See how well you understand the formation and behavior of particulate matter in combustion.
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