Ash Handling System In Thermal Power Plant

In thermal power plants, coal is used as a fuel for generating electricity. After burning of coal, 40 % of total coal consumption is converted into ash which need to be properly disposed-off from the thermal power plant.

Types of Ash Generated in Thermal Power Plant

• Bottom Ash – Ash generated below furnace of the thermal power plant is called the bottom ash. The value of bottom ash generated is around 20 % of total ash. Bottom ash is mostly coarse in nature hence it needs to be further crushed before being transported to ash handling system.
• Fly Ash – Around 80 % of ash generated in thermal power plant is fly ash. It is in form of very fine particles which is collected via economiser hopper, air-preheater hopper and electrostatic precipitator (ESP).

What is ash handling plant or ash handling system?

Ash handling plant or ash handling system in thermal power plant are used to cooled down the ash to manageable temperature, transferred to a disposal area or storage which is further utilized in other industries.

Equipment’s Used in Ash Handling System in Thermal Power Plant

• Electrostatic Precipitator (ESP)
• Feed/Discharge/Sluice Gate
• Clinker Grinder or Crusher
• Jet Pump
• Dewatering Bin
• Transfer Bin
• Storage Bin
• Dry Bottom Ash Conveyor
• Clinker Cooling Conveyor
• Dry Bottom Ash System
• Slurry Pump

Layout of Ash Handling Plant or Ash Handling System in Thermal Power Plant

Working of Ash Handling System in Thermal Power Plant

Ash handling system are generally divided into three types fly ash handling system, bottom ash handling system and ash slurry disposal system.

1. Fly ash handling system:

Fly ash is captured and removed from the flue gases by economiser, air-preheater and electrostatic precipitator (ESP) located at the outlet of the furnace and before the induced draft. The fly ash is pneumatically transported from collection hopper of economiser, air-preheater and electrostatic precipitator (ESP)  to storage silo for subsequent transport by trucks.

2. Bottom ash handling system :

It is collected in bottom hopper located under the furnace boiler. Due to coarse in nature it is treated through clinkers and grinders to normalize the bottom ash size. It is then transported to bottom ash silo for temporary storage or to ash pond in slurry form.

3. Ash slurry disposal system:

Ash received from bottom ash handling system is mixed with water in bottom ash silo. Slurry formed due to mixing of water and ash is transported to ash disposal area by using two system:

1. High concentration ash slurry disposal system – Slurry pump is used to transport ash slurry to ash disposal area via ash slurry transportation pipes.
2. Lean ash slurry disposal system – Slurry transported to a dewatering bin by a jet pump, and carried to an ash dump by truck after dewatering.

Wastewater from the dewatering bin goes into an ash sedimentation tank or an ash sedimentation pond for the sedimentation of ash particles and water without ash particles is supplied to jet pump by an ash handling pump. The ash particles which settle in the ash sedimentation tank and the water tank are returned to the dewatering bin by a sludge return pump.

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