In industries where coal is burned to produce energy, managing ash becomes crucial for both operational efficiency and environmental sustainability. It is done by an ash handling system.
These systems are designed to collect, store and dispose of ash produced during combustion at facilities such as coal-fired power plants – helping ensure minimal environmental impact and compliance with regulatory standards.
Central to the efficiency of these systems is the integrated pipework that aids in the transportation of ash from the combustion area to storage or disposal sites.
The role of an ash handling system
An ash handling system is designed to remove ash generated from the combustion of solid fuels like coal, wood and biomass. In a typical thermal power plant, ash is produced in two forms:
- Fly ash: Fine particles carried away with exhaust gases.
- Bottom ash: Coarse particles that settle at the bottom of the furnace.
These ash particles must be efficiently and safely removed from the combustion area to prevent equipment damage, maintain optimal plant operation and ensure environmental compliance.
Types of ash handling systems
There are various types of ash handling systems. Each one is suited to a specific kind of ash or plant layout. The two most common types are:
- Pneumatic Ash Handling System: Uses air pressure to transport ash through pipes.
- Hydraulic Ash Handling System: Uses water or slurry to move ash through pipelines.
Both systems rely heavily on pipework to efficiently transfer the collected ash to storage or disposal areas.
How pneumatic ash handling works
A pneumatic ash handling system uses compressed air to transport fly ash through a network of pipes to a storage or disposal area. The key steps include:
Collection
Fly ash is collected from the flue gases by electrostatic precipitators or bag filters, where it is separated from the exhaust stream.
Conveyance
Once collected, the ash is transported by a pneumatic conveying system. Compressed air is injected into the system through a set of pipes.
The air moves through the pipes, picking up the fine ash particles and pushing them toward the designated ash storage bins or silos.
Storage
The ash is directed to storage containers or silos. From here, it can be further processed or transported for disposal.
Pipework in pneumatic systems is typically made of stainless steel or other corrosion-resistant materials.
They must withstand high velocities and potential abrasiveness from the transported ash. To help with this, they can be coated with an alumina filled impact resistant epoxy wear compound.
A wear compound applied over equipment coming into contact with highly abrasive materials takes the brunt of the impact damage, protecting the metalwork.
Proper pipe design is also crucial. Excessive bends or rough surfaces inside the pipe can lead to blockages or wear, reducing efficiency.
How hydraulic ash handling works
In hydraulic ash handling systems, water or a water-based slurry is used to transport bottom ash. These systems are commonly used for handling the larger, heavier particles that make up bottom ash.
Collection
Bottom ash is collected at the base of the furnace or boiler, typically using a water-cooled drag chain conveyor or a rake conveyor.
Conveyance
The collected bottom ash is mixed with water to form a slurry. This slurry is then pumped through a series of pipes to an ash pond or silo for further handling or disposal.
Storage and Disposal
Slurry is typically transported to a disposal site, where the ash can be separated from the water for proper disposal.
In hydraulic systems, the pipework used is generally larger in diameter than pneumatic systems and made from materials like carbon steel. Greater resistance to corrosion from water and ash particles is required.
Additionally, slurry pipes need to be designed with enough slope and velocity to prevent sedimentation and ensure smooth flow.
Importance of pipework in ash handling systems
Pipework is central to both pneumatic and hydraulic ash handling systems. Here is why it plays such a crucial role:
Transport efficiency
The design, diameter and length of the pipes directly affect the efficiency of ash transportation. A well-designed piping system ensures minimal friction, optimal flow and reduced energy consumption.
Durability
Ash can be abrasive, especially when transported at high velocities in pneumatic systems. Therefore, the materials used in pipe construction must be durable enough to withstand wear and tear without corroding or breaking down.
Minimising blockages
Ash tends to clump or settle in pipelines, leading to blockages. Proper pipe sizing, alignment and regular maintenance are necessary to prevent this issue.
Safety and environmental considerations
Both types of systems need to minimise the risk of ash leakage or spillage. Properly sealed pipe joints, the right choice of materials and regular monitoring ensure that ash is securely contained within the pipework, preventing environmental contamination.
Advanced considerations for ash handling pipework
Over the years, advanced technologies have been incorporated into ash handling systems to further enhance performance. Key considerations include:
Automated monitoring and control
Modern systems use sensors to monitor the flow and pressure within pipes, alerting operators to potential blockages or pressure drops. This helps in real-time management of the ash-handling process.
Specialised pipe coatings
Some systems use specialised epoxy coatings on the interior of pipes to reduce wear and corrosion caused by the abrasive ash.
Energy efficiency
Advanced pneumatic systems use low-energy blowers to reduce the overall power consumption of the system, ensuring that the pipework remains efficient without consuming excessive energy.
Ash handling systems and their integral role
Ash handling systems are integral to industries that rely on the combustion of solid fuels, particularly in power plants.
The proper design, maintenance and operation of the pipework in these systems are essential for ensuring the smooth transport of ash whilst maintaining efficiency and safety.
By understanding the key elements of both pneumatic and hydraulic systems – and the vital role of pipework – industries can better manage their waste products, reduce their environmental footprint and enhance overall plant performance.
Through careful design and innovative technologies, the ash handling process continues to evolve, ensuring that future operations remain sustainable and efficient.
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