Basic ash handling System
Ash handling?
Ash handling refers to the method of collection, conveying, interim storage and load out of various types of ash residue left over from solid fuel combustion processes.
The most common types of ash resulting from the combustion of coal, wood and other solid fuels.
- Bottom ash
- Fly ash
Bottom Ash:
Ash generated below furnace of the steam generator is called the bottom ash. The Value of bottom ash generated is around 15-20 % of total ash. Bottom ash is mostly coarse in nature hence it need to be futher crushed before being transported to ash handling system. It is collected in furnace bottom hopper 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 from.
Fly Ash:
Ash generated in the economiser hopper, air-prehetater hopper (APH) and electrostatic precipitator (ESP) which got carried out with the flue gas is generally called fly ash. It is around 75-80 % of ash generated in thermal power plant.
In Coal power plant:
In thermal power plant, coal is used as a fuel for generating Steam. After burning of coal 30 - 40 % of coal Consumption is converted into ash which need to be properly disposed-off from the thermal power plant.
The operation of ash handling plants
- removal of ash from the furnace ash hoppers.
- transfer of the ash to a fill or storage and disposal ash.
- Waste land site may be reserved for the disposal of ash.
Handling Equipment should perform the following functions:
- Capital investment, operating and maintenance charges of the equipment should be low.
- It should be able to handle large quantities of ash.
- clinkers, soot, dust etc. Create troubles, the equipment should be able to handle them smoothly.
- The equipment should be corrosion and wear resistant.
Ash handling System:
The Modern ash handling system usually used in power plants are.
- Belt Conveyor / Mechanical conveyor system
- Pneumatic system
- Hydraulic System
Belt Conveyor / Mechanical conveyor system:
In this system ash cooled by water seal falls on the belt conveyor and is carried out continuously to the ash bunker. The ash is then removed to the dumping site from the ash bunker with help of trucks.
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| Belt Conveyor |
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| Belt conveyor |
Pneumatic System:
In this system ash from the boiler furnace outlet falls into a crusher, where larger ash particles are crushed to small sizes. The ash is then carried by a high velocity air to the point of delivery. Air leaving the ash separator is passed through filter to remove dust etc. So that the exhaust handles clean air which will protect the blades of the exhaust-er.
A typical ash handling system may employ vacuum pneumatic ash collection
with ash conveying from several ash pick up stations and resulting in
delivery to an ash storage silo for interim holding prior to load out
for disposal or reuse. Pressurized pneumatic ash conveying may also be
employed.
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| Pneumatic System |
Hydraulic System
Ash from the furnace grate, falls into a system of water possessing high velocity and is carried to the sumps. It is generally used in large power plant.
Types of hydraulic system
- Low pressure Hydraulic system.
- High pressure Hydraulic System.
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Basic ash handling System
Reviewed by Thermal Power Tech
on
September 25, 2019
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Reviewed by Thermal Power Tech
on
September 25, 2019
Rating:
Good knowledge
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