Combustion of Fuels Lecture Notes

Introduction

• Combustion is the chemical process involving the burning of fuels such as coal, petrol, charcoal, LPG.

Objectives

• Explain combustion and its types.
• Define ignition temperature.
• Describe the necessary conditions for combustion.
• Describe fire extinguishers.
• List types of combustion.

Combustion

• Example: Burning magnesium wire produces heat, light, and magnesium oxide.
• Coal Combustion: Produces carbon dioxide, heat, and light.
• Both examples involve substances reacting with air's oxygen to produce heat and light.

Combustible vs Incombustible Substances

• Combustible: Substances that catch fire, e.g., paper.
• Incombustible: Substances that do not catch fire, e.g., glass.

Conditions Necessary for Combustion

• Air: Necessary for burning.
• Ignition Temperature: The lowest temperature at which a substance catches fire.
  • Example: Paper burns with a matchstick; wood does not without reaching its ignition temperature.
• Inflammable Substances: LPG and petrol catch fire easily due to low ignition temperature.

Fire Extinguishers

• Fire Needs: Oxygen, heat, fuel.
• Water: Lowers temperature and cuts off air supply.
  • Not suitable for electrical or oil fires.
• Carbon Dioxide Extinguishers: For electrical and oil fires; cuts off oxygen by covering the fire.

Types of Combustion

• Rapid Combustion: Quick burning, e.g., LPG in kitchens.
• Spontaneous Combustion: Occurs without external ignition, e.g., white phosphorus, forest fires, coal mine fires.
• Explosion: Produces heat, light, and sound, e.g., fireworks.

Summary

• Combustible substances burn in the presence of air.
• Oxygen is necessary for combustion.
• Ignition temperature is critical for a substance to catch fire.
• Various types of combustion include rapid, spontaneous, and explosion.