ASH HANDLING IN THERMAL POWER PLANT

ASH HANDLING SYSTEM IN THERMAL STATION

In thermal power plants, coal is used as a fuel for generating electricity. After burning of coal, 40% of the 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

 

1.    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.

2.    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 by economiser hopper, air preheater Hopper and electrostatic precipitator.

 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 utilised in other industries.

LAYOUT OF ASH HANDLING SYSTEM IN THERMAL STATION

 

Working of Ash handling system in thermal power plant:

 Ash handling system generally divided into three types in the fly ash handling system, bottom 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 located at the outlet of the furnace and before the induced draft.The fly ash is penumatically transported from collection Hopper of economizer, air preheater and electrostatic precipitator to storage silo for subsequent transport by trucks.

 2. Bottom Ash handling system: it is collected bottom Hopper located under the furnace boiler. Due to course in nature it is treated through clinker and grinders to normalise the bottom Ash size. It is then transported to bottom ash silo for temporary storage or 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 vai 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 as particles is supplied to a jet pump by an ash handling pump. The ash particles which settle in the sedimentation tank and the water tank are returned to the dewatering bin by a sludge return pump.