Ash Handling Systems

Mister KhanSLIET, Sangrur

INTRODUCTION• Ash handling systems are required for

removal of bottom ash and fly ash from coal fired boilers.

• Burning of Coal leads to generation of Ash can be the non- combustible part of fuel, or generated after the burning of the coal.

Difficulties in the handling & Disposal:

1. It is hot when it is comes out of the boiler furnaces.

2. It produces dust nuisance.3. Poisonous gases are produced.4. It has corrosive action.5. It forms clinkers by fusing together in lumps.

Principle requirements of an ash handling plant

The plant should be able to handle large clinkers, boiler refuse, soot dust etc.

The plant should be able to deal with hot and wet ashes and operate with little noise.

The operating and maintenance charges should be minimum..

The plant should be able to handle requiisite quantity of ash daily.

Types of Ash

Bottom Ash Fly Ash

Fly Ash• Residual of Coal Combustion• Comprises of fine particles that rises with Flue

Gases• All types of fly ash includes substantial

amounts of silicon dioxide and Calcium Oxide• Size range – from 0.5 µm to 100 µm

COMPONENT OF GAS IN DIFFERENT COAL

Bottom Ash• Non- Combustible Part of Combustion• Comprises traces of combustibles embedded in

forming clinkers and sticking to hot side walls of a coal-burning furnace

• The clinkers fall by themselves into the water or sometimes by poking manually, and get cooled

• May be used as an aggregate in road construction and concrete

Various types of handling system

Wheel Barrows (Manual Handling)Mechanical Handling

bucket elevator bucket conveyor centrifugal discharge bucket elevator

Steam jet systemPneumatic-conveyor systemhydraulic or gravity system

Wheel barrows

• The ash is collected directly through the ash outlet doors from the boiler into the containers, operated manually. The barrows move on the rails towards the dumping site, this is done manually or mechanically. This system is suitable for small stations.

Mechanical handling

• Bucket elevator : the bucket elevator is a useful equipment if a vertical lift is involved in movement of ash, such as to load a conveyor. Where a continuous pivoted type of bucket is used, the bucket being attached to an endless chain & passing over the coal bunker for handling coal.

Belt Chain Conveying System

• Belt conveyors are used to dispose the bottom ash from scraper chain conveyor to bottom ash silo.

• Employ continuously operating or submerged belt conveyor running below boiler furnace.

• SCC system receives hot clinker, slag and ash falling from the boiler, through a transition chute to water filled trough.

• The trough containing the conveyor is filled with water for quenching of bottom ash.

• Bottom ash discharged onto scraper chain conveyor , where it is fed to grinder that crushes it to 25mm size.

• The crushed bottom ash conveyed to bottom ash silo by belt conveyors.

• The crushed bottom ash conveyed to bottom ash silo by belt conveyors.

Belt Chain Conveying System

centrifugal discharge bucket elevator

• The centrifugal discharge-bucket elevator is commonly used, when ashes must be elevated from a lower level to ground level especially if the quantity if the quantity of ashes formed can be handled in 1 to 2 hr. operation. This type of elevator consists a continuous chain to which buckets are attached at regular intervals.

centrifugal discharge bucket elevator

Steam jet system

When the path of travel of ash is not straight & there is little space for other type of handling equipment, this system is useful. This system utilizes jets of high pressure steam, blowing in the direction of travel through a conveying pipe in which the ash from the boiler ash hoppers is fed.

• The Steam Jet System uses low volume, medium pressure air stream.

• Operating pressure upto 5 kg./cm2 high capacity conveying line.

• Conveying distance upto 1500 meters. • The material air ratio is in the range of 20 -

100 to 1.

OPERATIONAL PRINCIPLE

• As soon as the ash level reaches a fixed level in the collecting hopper, the level probe senses its presence, it allows the system to initiate a conveying cycle.

• The inlet valve opens to allow the ash to gravitate into the conveying vessel, till it closes automatically.

• On closure of the valve, the conveying vessel gets pressurized and the material resistance helps pressure build up which conveys the material through pipe in the destination silo.

• When conveying is complete which is sensed by the control system, air supply to the system is stopped and system is ready for the next cycle

Pneumatic conveyer system

This system has been specifically developed for the handling of both abrasive & very fine, dusty materials such as ashes, fly ash & soot. It is particularly well adopted to boiler plants from which the ashes & fly ash must be transported some considerable distance for final disposal, i.e. plants which are located in more or less congested districts.

Fly Ash Reuse

• Concrete production, as a substitute material for Portland cement • sand Embankments and other structural fills • Grout and Flowable Fill production • Waste stabilization and solidification• Cement clinkers production - (as a substitute material for clay)• Mine reclamation • Stabilization of soft soils • As Aggregate substitute material (e.g. for brick production) • Mineral filler in asphaltic concrete • Agricultural uses: soil amendment, fertilizer, cattle feeders, soil

stabilization in stock feed yards, and agricultural stakes Loose application on rivers to melt ice

• Loose application on roads and parking lots for ice control

Thank You !!!