Short Answer:

The purpose of combustion in power plants is to convert the chemical energy of fuel into heat energy by burning it in the presence of oxygen. This heat energy is then used to produce steam, which drives turbines to generate electric power. Combustion is the main process through which energy is released from fuels such as coal, oil, or natural gas.

In simple words, combustion in power plants helps to produce heat required for steam generation. This steam drives turbines that rotate generators to produce electricity. Without combustion, thermal power plants cannot function, as it provides the essential heat energy needed for power production.

Detailed Explanation :

Purpose of Combustion in Power Plants

Combustion is the most fundamental process in thermal power plants. It is the chemical reaction between a fuel and oxygen, which produces heat energy that is used to convert water into steam. This steam then drives a turbine connected to an electric generator, producing electricity. The main purpose of combustion in power plants is to release heat from the fuel efficiently and safely, ensuring maximum power generation with minimum energy loss.

The combustion process in power plants forms the heart of energy conversion — it transforms the stored chemical energy of fuels like coal, oil, or natural gas into usable thermal energy. This heat is then converted into mechanical and electrical energy through the Rankine or Brayton cycle, depending on the type of power plant.

1. Role of Combustion in Energy Conversion

The major purpose of combustion in a power plant is to convert chemical energy into thermal energy. When a fuel burns in the presence of oxygen, its molecules react with oxygen molecules, forming new compounds and releasing large amounts of heat.

For example:

 

This heat energy is absorbed by water in a boiler to produce high-pressure steam. The steam then expands in a turbine, producing mechanical power, which is converted into electrical energy through a generator.

Thus, combustion acts as the starting point of power generation by providing the necessary heat for steam production.

2. Purpose and Importance of Combustion in Power Plants

The purposes of combustion in a thermal power plant can be understood through the following points:

1. Heat Generation for Steam Production:
   • The main purpose of combustion is to release heat energy from the fuel.
   • This heat is transferred to water in the boiler to convert it into high-pressure steam.
   • The steam is then used to drive turbines and generate electricity.
2. Conversion of Chemical Energy into Thermal Energy:
   • Combustion converts the chemical energy stored in fuels such as coal, oil, or gas into thermal energy.
   • This energy is used to maintain the desired boiler temperature and pressure.
3. Maintaining Boiler Efficiency:
   • Proper combustion ensures maximum energy release with minimal fuel wastage.
   • Incomplete combustion reduces efficiency and produces harmful gases like CO.
4. Supporting Continuous Power Generation:
   • In a power plant, combustion is a continuous process to maintain steady power output.
   • It ensures a constant supply of steam to the turbine for continuous electricity generation.
5. Economic Operation:
   • Efficient combustion reduces fuel consumption, thereby lowering operational costs.
   • It also minimizes pollution and increases equipment life.
6. Environmental Control:
   • Controlled combustion helps reduce emissions by ensuring complete fuel burning.
   • This limits pollutants like carbon monoxide (CO), soot, and unburnt hydrocarbons.

3. Combustion Process in Power Plants

The process of combustion in a thermal power plant involves several steps:

1. Fuel Supply:
   • The fuel (coal, oil, or gas) is supplied to the furnace of the boiler.
   • In coal-fired plants, pulverized coal is used for better burning efficiency.
2. Air Supply:
   • Air (containing oxygen) is supplied using fans to support combustion.
   • The amount of air is controlled to maintain the correct air-fuel ratio.
3. Ignition:
   • The fuel-air mixture is ignited, and the combustion process begins.
4. Heat Transfer:
   • The hot flue gases produced during combustion transfer heat to the water in the boiler tubes.
   • This process converts water into steam at high pressure and temperature.
5. Flue Gas Removal:
   • After releasing heat, the cooled flue gases are passed through an economizer, air preheater, and finally released through the chimney.

This combustion system is designed to achieve complete burning of fuel, maximum heat recovery, and minimum emissions.

4. Conditions for Efficient Combustion

Efficient combustion in power plants requires:

1. Proper Air-Fuel Ratio:
   • Adequate oxygen ensures complete combustion, avoiding wastage of fuel.
2. Sufficient Mixing of Air and Fuel:
   • Proper mixing allows uniform burning, leading to higher heat release.
3. Right Temperature:
   • The combustion temperature must be high enough to maintain continuous burning.
4. Continuous Fuel and Air Supply:
   • Ensures steady combustion and consistent heat production.
5. Proper Maintenance:
   • Regular cleaning of burners and inspection of furnace conditions maintain efficient operation.

5. Effects of Combustion on Power Plant Performance

Combustion directly affects the performance, efficiency, and reliability of power plants.

• High Efficiency:
  Efficient combustion leads to higher steam temperature and pressure, improving turbine output and overall plant efficiency.
• Low Emissions:
  Complete combustion minimizes pollutants like CO and particulate matter.
• Fuel Economy:
  Proper combustion ensures complete fuel utilization, reducing fuel consumption.
• Equipment Life:
  Uniform combustion reduces soot deposits and corrosion in boiler tubes, extending life.

6. Environmental Importance

Combustion also plays a crucial role in reducing pollution when properly controlled.
Modern power plants use low NOx burners, flue gas recirculation, and air staging techniques to minimize harmful gases. Efficient combustion reduces:

• Carbon monoxide (CO) emissions,
• Unburned hydrocarbons,
• Soot particles, and
• Greenhouse gases (CO₂) through better fuel efficiency.

Conclusion

The purpose of combustion in power plants is to produce the heat energy required to convert water into steam for power generation. It is the primary process that drives the entire operation of thermal power plants. Proper and efficient combustion ensures maximum energy release from fuel, improved boiler performance, and reduced environmental pollution. By maintaining the correct fuel-air ratio and operating conditions, combustion efficiency can be optimized, leading to higher overall plant efficiency and lower fuel costs. In short, combustion is the foundation of thermal power generation and a key factor in energy efficiency and sustainability.