Complete Combustion

• CH4+2O2=CO2+2H2O
  

Incomplete Combustion

• CH4+1.5O2=CO+2H2O
• CO - extremely toxic gas (0.4% in air is fatal)
• Visual Signs :
  • Staining around the appliance (never acceptable)
  • Signs of sooting within the appliance (acceptable for live fuel burning)
  • Yellow flames within the appliance (acceptable for live fuel burning)
• Causes of Incomplete Combustion :
  • Insufficient air for combustion
  • Overgassing
  • Undergassing
  • Flame impingement - flames from different parts of a burner disturb each other
  • Flame chilling
  • Vitiation - reduced level of oxygen in the combustion air
    

Air Requirements for Combustion

• 1m³ of methane requires 2m³ of oxygen (10m³ of air)
• produces 1m³ of carbon dioxide and 2m³ of water vapour

Flames and Burners

• Post-Aerated Flames :
  • also known as a 'neat', 'luminous' or 'ragged' flame
  • air supplies the flame as it exits the burner
  • burn with incomplete combustion
  • used in a live fuel effect fires
• Pre-Aerated Flames :
  • can be partially aerated or Bunsen burner type
  • 50% of the air for combustion is supplied prior to combustion
• Pre-Mix Burners :
  • fan provides air under pressure
  • zero governor reduces the gas pressure to atmospheric pressure