Schematic Overview of a Coal-Fired Power Station
A coal-fired power station converts the chemical energy stored in coal into electrical energy through a series of well-defined processes. The schematic layout typically includes key components such as the coal handling system, boiler, turbine, generator, condenser, and emissions control systems. Below is a detailed breakdown of how these systems work together to produce electricity efficiently.
1. Coal Handling and Preparation
Coal is delivered to the power plant via rail or ship and stored in large stockpiles. Before combustion, it undergoes crushing to reduce particle size, ensuring efficient burning. The crushed coal is then fed into pulverizers, which grind it into a fine powder. This powdered coal is mixed with preheated air and blown into the combustion chamber of the boiler.
2. Boiler and Combustion Process
The boiler is a critical component where combustion occurs. Inside the furnace, coal dust ignites at high temperatures, producing intense heat that converts water in the boiler tubes into high-pressure steam. Modern boilers use superheaters to further increase steam temperature, enhancing thermal efficiency. The combustion process also generates flue gases containing carbon dioxide (CO₂), sulfur dioxide (SO₂), nitrogen oxides (NOₓ), and particulate matter, which must be treated before release.
3. Steam Turbine and Electricity Generation
The high-pressure steam flows through pipes to drive the blades of a steam turbine. As the steam expands, its pressure drops, causing the turbine shaft to rotate at high speed. This mechanical energy is transferred to an attached generator, where electromagnetic induction produces electricity. After passing through the turbine, the exhausted steam enters a condenser for cooling and recycling.
4. Condenser and Cooling System
The condenser cools exhaust steam back into liquid water using cooling towers or water from nearby rivers/lakes. This condensed water is then pumped back into the boiler to repeat the cycle—a closed-loop system that conserves water while maintaining efficiency. Excess heat from condensation is often released via cooling towers as water vapor or warm discharge water (subject to environmental regulations).
5. Emissions Control Systems
Coal plants incorporate multiple pollution control technologies:
- Electrostatic Precipitators (ESP) or Baghouses: Remove fly ash particles from flue gases before they exit through chimneys.
- Flue Gas Desulfurization (FGD): Uses wet scrubbers or dry sorbent injection to reduce SO₂ emissions by over 90%.