Thermal Power Plant Draught and Coal Handling Systems

Posted on Oct 4, 2026 in Mechanical Engineering

1. Explanation of Draught System

Draught System in Thermal Power Plant:

Draught is the pressure difference that causes the flow of air into the furnace and flue gases out of the boiler.
Its main purpose is to supply sufficient oxygen for proper combustion of fuel and remove the resulting flue gases.
Natural Draught: It is produced by a tall chimney due to the difference in density between hot flue gases and outside air.
Forced Draught: A forced-draught (FD) fan forces fresh air into the furnace under pressure.
Induced Draught: An induced-draught (ID) fan draws flue gases from the furnace and sends them towards the chimney.
Balanced Draught: It uses both FD and ID fans to maintain nearly atmospheric pressure inside the furnace.
A proper draught system ensures continuous air supply and effective removal of flue gases.
It improves combustion efficiency, boiler performance, and overall plant operation.

Coal and Ash Handling Plant:

Coal Handling Plant: It is the system used for receiving, transporting, storing, crushing, and supplying coal to the boiler of a thermal power plant.
Coal Receipt: Coal is brought to the plant by rail, road, or waterways and unloaded using suitable unloading equipment.
Coal Storage: The received coal is stored in a coal yard or bunker to maintain a continuous supply during interruptions in transportation.
Coal Crushing: Large pieces of coal are passed through crushers to reduce their size before feeding it to the boiler.
Coal Feeding: Conveyors and feeders transport the crushed coal to the pulverizer or boiler furnace for combustion.
Ash Handling Plant: It collects, transports, and disposes of the ash produced after burning coal in the boiler.
Bottom Ash: Heavy ash particles settle at the bottom of the furnace and are removed using scrapers, conveyors, or water-based systems.
Fly Ash: Fine ash carried with flue gases is collected using electrostatic precipitators (ESPs) or bag filters.
Ash Transportation: Collected ash is transported through pneumatic, hydraulic, or mechanical systems to storage or disposal areas.
Ash Utilization: Fly ash and bottom ash can be used in cement, concrete, bricks, blocks, and road construction, reducing disposal problems.

Co-Generation System Overview:

Co-generation is the simultaneous production of electrical energy and useful thermal energy from a single fuel source.
It is also known as a Combined Heat and Power (CHP) system.
In this system, the heat normally wasted during electricity generation is recovered and utilized for useful purposes.
The main components include a prime mover, generator, heat recovery unit, and heat distribution system.
The recovered heat can be used for steam generation, heating, drying, and industrial processes.
Fuels such as coal, natural gas, biomass, and industrial waste can be used in co-generation systems.
It provides higher overall efficiency because both electrical and thermal energy are obtained from the same fuel.
It reduces fuel consumption, energy cost, and environmental pollution.
Co-generation systems are commonly used in sugar industries, chemical plants, paper mills, hospitals, and hotels.
It can reduce transmission losses when electricity and heat are generated close to the point of consumption.

Draught System Details:

Draught is the pressure difference that causes the flow of air into the furnace and flue gases out of the boiler.
Purpose: It supplies sufficient air for proper combustion of fuel and removes the flue gases produced during combustion.
Natural Draught: It is produced by a chimney due to the difference in density between hot flue gases and atmospheric air.
Forced Draught (FD): A fan forces fresh air into the furnace under pressure, ensuring adequate air supply for combustion.
Induced Draught (ID): A fan draws flue gases from the furnace and passes them towards the chimney, maintaining a slight negative pressure in the furnace.
Balanced Draught: It uses both FD and ID fans to maintain approximately atmospheric pressure inside the furnace.
Air and Gas Flow: The draught system maintains continuous movement of air through the furnace and flue gases through the boiler and chimney.
Importance: A proper draught system improves combustion efficiency, boiler performance, and safe removal of flue gases.