How a coal-fired power station works
A coal plant is a steam-turbine plant. Burning coal heats water into high-pressure steam, which spins a turbine connected to a generator.
Drag to rotate · pinch to zoom · focus the model for arrow-key rotation, +/− zoom and Home reset.
Pulverised-coal steam plant. The boiler, turbine and emissions equipment are sectioned; the steam and flue-gas circuits remain distinct. Motion is slowed for inspection. Coloured overlays reveal flow through enclosed equipment; gold pulses show net electrical energy transfer, not individual electrons.
How it works
- Coal’s chemical energy
- Furnace heat
- Water / steam circuit
- Turbine shaft
- Generator
- Grid electricity
In a conventional coal station, the furnace supplies heat and the steam turbine converts part of it into mechanical work. Coal is prepared and burned with air; heat passes through boiler-tube walls into the water circuit. The two streams stay separate: flue gas goes toward emissions controls and the stack, while steam goes to the turbine. Reheating steam between turbine sections can improve the cycle and limit moisture in its later stages.
After expansion, a condenser transfers remaining heat to a separate cooling system and turns the turbine exhaust into liquid water. Pumps return it to the boiler. Mills, fans, pumps and treatment equipment consume electricity, so net export is lower than the generator’s gross output. Combustion also produces carbon dioxide, ash and pollutants requiring management. Particle filters and sulfur-removal equipment do different jobs from carbon capture; installing them does not make a coal plant carbon-free.
Inside the engineering
Follow the machinery, the working fluids and the electrical connection.
Mechanical
Conveyors and mills prepare the fuel. Fans move combustion air and flue gas, while their casings remain stationary. Steam expands through turbine stages; the condenser, condensate pump and feedwater pump return water to the boiler.
Thermal & chemical
Coal combustion transfers heat into water-wall and steam tubes. Particulate collection and wet sulphur-removal equipment treat the flue gas; they do not eliminate CO₂. Cooling-water circuits remove heat independently of the boiler’s working water.
Electrical
The turbine drives a generator through a shaft train. Three-phase connections carry output towards the transformer and grid. Mills, pumps and fans are important auxiliary loads, so net station output is lower than generator output.
Main types and variations
The model illustrates a pulverised-coal steam plant. Subcritical, supercritical and ultra-supercritical describe steam conditions; fluidised-bed describes the furnace, so those categories can overlap. Gasification combined cycle changes the conversion route more fundamentally. These labels do not identify the grade of coal being burned.
Subcritical steam cycle
The boiler operates below water’s critical pressure, where liquid water and steam can coexist during boiling. A typical drum boiler separates steam from circulating water, then superheats the steam before the turbine. The term describes pressure conditions, rather than whether the furnace burns pulverised fuel or uses another combustion arrangement.
What changes in practice
The steam drum and circulation system shape plant layout and operation. Raising steam conditions can improve cycle efficiency, but requires equipment designed for the higher stresses.
Mitsubishi Power: Steam power plants and boiler designs (PDF)
Supercritical steam cycle
At pressures above water’s critical pressure, heating does not cross a distinct liquid-to-vapour boiling boundary. A once-through boiler raises the fluid to the turbine’s required inlet conditions. This statement applies to that high-pressure heating path; the complete cycle still includes lower-pressure expansion, cooling and condensation.
What changes in practice
Higher operating conditions can extract more electricity from the same fuel input. Flow control and suitable boiler materials remain essential to managing heat transfer safely.
Maharashtra Directorate of Steam Boilers: Supercritical boilers
Ultra-supercritical steam cycle
Ultra-supercritical is an industry description for especially demanding steam conditions within the supercritical family, not a new phase of water. Higher steam temperatures and pressures increase the demands on boiler tubes, turbine parts, valves and welds. Advanced ultra-supercritical research pushes these material requirements further.
What changes in practice
Improved thermal efficiency can reduce fuel consumption per unit of electricity. Creep resistance, corrosion and fabrication capability constrain the materials and conditions engineers can select.
Fluidised-bed combustion
Upward-flowing air suspends and mixes a bed of hot solids with the fuel. Heat passes into boiler surfaces, and limestone can capture sulfur within the furnace. In a circulating design, separated solids return to the bed. The downstream steam turbine still converts boiler heat into electricity.
What changes in practice
Thorough mixing supports fuel flexibility and in-furnace sulfur control. Bed solids, ash and the remaining flue-gas pollutants still need appropriate handling and treatment.
Integrated gasification combined cycle
A gasifier converts coal into synthesis gas, mainly a combustible mixture of carbon monoxide and hydrogen. After particles and other contaminants are removed, this gas fuels a combustion turbine. Heat recovery supplies a steam turbine, combining gasification equipment with a gas-and-steam power cycle.
What changes in practice
Fuel cleanup happens before the gas turbine. Gasifiers, cleanup systems and often oxygen-production equipment add complexity; gasification alone does not mean carbon dioxide is captured.
Worth knowing
- Coal produces more carbon dioxide per unit of electricity than any other major source.
- Many countries are closing or converting coal plants.
- Biomass plants often use a very similar boiler and steam cycle.
See real examples
The atlas includes 2,333 coal records worldwide.
Show on the mapRelated answers
Textbook references
The science on this page follows these standard engineering textbooks. See the full bibliography.
- Steam: Its Generation and UseBoilers, combustion, steam generation and emissions control.
- Thermodynamics: An Engineering ApproachRankine cycle efficiency, reheat and regeneration.
Sources
Cutaways reveal enclosed equipment. Layouts, dimensions, materials and animation speeds are illustrative; this is an educational model, not a plant design or a thermodynamic simulation.