9.3 Flue Gas Analysis

Flue gas composition analysis is crucial for understanding combustion efficiency and environmental impact. It involves examining major components like CO2 and H2O, as well as pollutants like CO and NOx, to assess fuel utilization and emissions.

Interpreting flue gas data helps optimize combustion processes and reduce harmful emissions. Key calculations include air-fuel ratios and excess air percentages, while environmental considerations focus on reducing greenhouse gases and other pollutants through various control technologies.

Flue Gas Composition and Analysis

Composition of flue gases

Top images from around the web for Composition of flue gases

• 

  Collision Theory | Chemistry: Atoms First View original

  Is this image relevant?

• 

  Frontiers | Carbon Capture From Flue Gas and the Atmosphere: A Perspective View original

  Is this image relevant?

• 

  Atmospheric Gasses | Physical Geography View original

  Is this image relevant?

• 

  Collision Theory | Chemistry: Atoms First View original

  Is this image relevant?

• 

  Frontiers | Carbon Capture From Flue Gas and the Atmosphere: A Perspective View original

  Is this image relevant?

1 of 3

Top images from around the web for Composition of flue gases

• 

  Collision Theory | Chemistry: Atoms First View original

  Is this image relevant?

• 

  Frontiers | Carbon Capture From Flue Gas and the Atmosphere: A Perspective View original

  Is this image relevant?

• 

  Atmospheric Gasses | Physical Geography View original

  Is this image relevant?

• 

  Collision Theory | Chemistry: Atoms First View original

  Is this image relevant?

• 

  Frontiers | Carbon Capture From Flue Gas and the Atmosphere: A Perspective View original

  Is this image relevant?

1 of 3

• Major components of flue gas comprise bulk of emissions
  • Carbon dioxide (CO2) primary product of complete combustion
  • Water vapor (H2O) forms from hydrogen in fuel
  • Nitrogen (N2) mostly from combustion air passes through unchanged
  • Oxygen (O2) excess air not consumed in combustion
• Minor components and pollutants present in smaller quantities
  • Carbon monoxide (CO) indicates incomplete combustion
  • Sulfur oxides (SOx) form from sulfur in fuel (coal, oil)
  • Nitrogen oxides (NOx) high-temperature reaction between N2 and O2
  • Particulate matter includes ash, soot, and unburned fuel particles
• Properties of flue gas affect dispersion and heat recovery
  • Temperature ranges from 120-400℃ depending on process
  • Pressure slightly above atmospheric aids exhaust
  • Density varies with temperature and composition
  • Specific heat capacity important for heat recovery calculations

Interpretation of flue gas data

• Indicators of complete combustion show efficient fuel use
  • High CO2 concentration suggests thorough fuel oxidation
  • Low CO concentration indicates minimal incomplete combustion
  • Low unburned hydrocarbons show effective fuel utilization
• Factors affecting combustion efficiency impact overall performance
  • Air-fuel ratio determines available oxygen for reaction
  • Mixing of fuel and air ensures uniform combustion
  • Residence time in combustion chamber allows reaction completion
• Methods of flue gas analysis provide composition data
  • Gas chromatography separates and quantifies gas components
  • Infrared spectroscopy measures absorption of specific gases
  • Electrochemical sensors detect O2, CO, and NOx concentrations
• Key parameters to evaluate assess combustion process
  • Combustion efficiency measures heat released vs. fuel energy content
  • Excess air percentage indicates air supply above stoichiometric requirement
  • Fuel consumption rate determines overall process economics

Calculations from flue gas composition

• Air-fuel ratio calculation determines combustion stoichiometry
  • Stoichiometric air-fuel ratio theoretical minimum air required
  • Actual air-fuel ratio accounts for excess air
  • $\text{Air-fuel ratio} = \frac{\text{Mass of air}}{\text{Mass of fuel}}$ used in process calculations
• Excess air percentage calculation quantifies additional air supplied
  • \text{Excess air (%)} = \frac{\text{Actual air} - \text{Stoichiometric air}}{\text{Stoichiometric air}} \times 100 assesses combustion control
• Orsat analysis for flue gas composition measures CO2, O2, and CO
• Dry basis vs. wet basis calculations account for water vapor presence
• Use of combustion charts and tables simplifies complex calculations

Environmental impact of emissions

• Environmental impacts of flue gas emissions affect air quality
  • Greenhouse effect (CO2) contributes to global warming
  • Acid rain (SOx, NOx) damages ecosystems and infrastructure
  • Smog formation (NOx, VOCs) reduces visibility and harms health
  • Particulate matter pollution causes respiratory issues
• Emission control technologies reduce pollutant release
  • Scrubbers for SOx removal use alkaline solutions (limestone slurry)
  • Selective catalytic reduction for NOx control uses ammonia and catalyst
  • Electrostatic precipitators for particulate matter create charged particles
• Strategies for reducing emissions improve environmental performance
  • Fuel switching to cleaner alternatives (natural gas, biomass)
  • Improved combustion efficiency reduces overall emissions
  • Flue gas recirculation lowers flame temperature, reducing NOx
• Regulatory standards and compliance ensure environmental protection
  • Emission limits set maximum allowable pollutant concentrations
  • Monitoring requirements include continuous emission monitoring systems
  • Reporting and documentation provide transparency and accountability