A Primer on Coal Ash Handling Systems

In , the United States produced over 131 million tons of coal combustion products from the nation&#;s 1,308 coal-fired power plants. This 131 million tons of residuals must go somewhere, and has to be handled in a precise, controlled manner &#; especially ever since the EPA, under the Obama administration, began to tighten regulations and create new restrictions on coal ash.

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Coal ash handling systems are created to safely and efficiently transfer ash from boilers to storage units, where they are then finally disposed of in a responsible manner. There are several types of solids that constitute &#;coal ash&#;, and several ways of handling residuals from the burning of coal.

Here is a brief primer on coal ash, two types of handling systems, and the industry&#;s shift from wet coal ash handling systems to dry coal ash handling.

An Overview of Coal Ash

Coal ash is a part of what are called coal combustion residuals (CCR), primarily because the residuals from burning coal are more than ash; they also include solid materials. In this context,

CCR consists of four different solids: fly ash, bottom ash, boiler slag, and flue gas desulfurization material. Fly ash is fine ash that is generated by burning coal and is pushed out of the boiler by flue gases. This is typically removed from chimneys before it reaches the open air by particle filtration equipment.

Bottom ash is the ash that accumulates in the bottom of a boiler. It is non-combustible and accumulates in ash hoppers below the boilers. Bottom ash, unlike fly ash, is typically in solid form that must be ground down.

Both bottom ash and fly ash have to be safely and efficiently removed from the boiler system to a disposal system that adheres to regulations. Due to the unique nature of each, separate systems have been created to handle each.

Fly Ash Handling Systems

The challenge of a fly ash handling system is to remove fly ash before it enters the outside air. Fly ash systems are constructed from heavy-duty, abrasion-resistant steel for reduced wear and maintenance. The ash is directed horizontally or vertically using vacuums to a filter receiver that then processes the ash into lockhoppers and bins.  The ash is then fed via feeders and pumps to beneficiation equipment that helps translate the ash into recyclable material that is often used in cement, cinder blocks, and other building materials.

Eventually, the ash is sent to storage domes before being diverted to loadout silos that load ash onto vehicles for transport to external storage (or to material processing plants for inclusion in concrete and other materials).

Bottom Ash Handling Systems

Bottom ash can be more complex than fly ash due to the physical nature of it versus fine particulate ash. The combustion residuals at the bottom and sides of a boiler are scraped or moved into an ash hopper located below the boiler. They are then fed into a conveyor system that uses air (or in some cases, water) and a conveyor/drag chain assembly to carry the solids along in an airtight space to a primary crusher. The crusher reduces the solids into a more manageable size. This is then carried via conveyor to a secondary crusher to further reduce the particulates before being located into a bottom ash storage bin or silo. From there, the ash is often carried away for external transport using loadout silos.

Shifting from Wet to Dry Coal Ash Handling

Prior to the mid-&#;s, coal ash handling systems were primarily wet. Bottom ash conveyors were usually submerged in water, and water was also used in fly ash handling. This creates environmental concerns, though; the process generated slurry that was stored in ash ponds across the nation that have the potential to leak into groundwater, which is what has happened in North Carolina with several Duke Energy installations.

Dry ash handling was invented in the &#;s as a way to avoid these problems. It has been steadily phased in, although the process had to be accelerated by the EPA beginning with the Obama administration. Currently, two-thirds of plants that use ash ponds that dry fly ash handling systems. Most bottom ash handling systems remain wet. Many plants intend to eliminate ash ponds, but not necessarily eliminate water from bottom ash handling.

With new regulations from the EPA, however, more and more plants are moving toward completely eliminating water from the process altogether.

For those who still use wet bottom ash handling, recirculation systems can convert wet sluice assemblies into dry ash systems in a relatively short amount of time. The recirculation system is intended to reduce the moisture content of the ash while re-using the water for additional cycles. There are also other systems that make use of water-less ash handling.

Wet-to-dry conversion can help reduce costs by reducing water use by millions of gallons a year per plant, and can be a more efficient and compliant way of handling ash in the future.

ProcessBarron Coal Ash Handling Systems

ProcessBarron has decades of experience in constructing modern, technologically-advanced coal ash handling systems for use throughout North and South America.  Our systems are designed to reduce wear and tear, lower the need for maintenance, and improve efficiency all while complying with all existing regulations.

Contact ProcessBarron for more information on modern coal ash handling system construction and conversion for a facility.

One of the best methods to generate electrical energy is the conversion of thermal energy by burning organic fuel, such as coal or oil, in thermal power plants. But such energy generation leaves large amounts of waste, which can be dangerous if not treated properly. However, thermal power systems are significant for fulfilling the world&#;s energy requirements.

Coal is used as a fuel for power generation in thermal power plants. The ash content of coal is up to 40 per cent when burned. Handling ash poses specific challenges as it exits the furnace at high temperatures and releases toxic gases. To help with this situation, we have ash handling systems, so lets take a look at what an ash handling system is.

A] What is Ash Handling?

Ash handling systems are mechanical devices that correctly dispose of the ash. So, after the coal has been burned, the ash from the coal is collected and disposed of. Before disposing of it, it must be cooled down to a manageable temperature. It is then transferred to a disposal or storage area and used in various industries, such as cement plants, construction, and other similar places. It also has a vital role because industry standards and environmental procedures need to be followed for correct disposal.

The residual product, which may contain ashes or gases, will be collected by an Electrostatic Precipitator (ESP) and stored in the hoppers at the bottom of the ESP. After that, they are transported out of the ESP into an ash handling system by compression or vacuum. The ashes are then collected, stored, and loaded in batches into a storage silo.

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The different types of ash that are left behind include:

• Bottom Ash
• Bed Ash
• Fly Ash
• Ash Clinkers

Discover the Right Ash Handling System for Your Industry

B] Importance of Fly Ash Handling Solutions

In this day and age, the requirement for energy generation is enormous, which results in the burning of organic fuel. The ash produced by burning this fuel is in the thousands of tonnes. This could have debilitating and adverse effects on the environment and people. This is why fly ash handling solutions need to be properly and correctly followed.

Since a large amount of waste is generated, that can have harmful effects. Hence, it cannot be mishandled at any phase in the system. These are the phases:

1. Removal of Ash

When coal or any fuel is burned, it leaves a large amount of ash. This residual ash needs to be removed from the furnace, and keeping hot ash in it is harmful. It can cause wear to the furnace inside, affecting the furnace&#;s efficiency in burning fuel.

2. The Quenching Process

The ash is removed and quenched, meaning it is passed through or dipped in water to prevent harmful consequences. This is done in a separate container. This process is done to cool the ash to a manageable temperature and lessen its corrosiveness. When it is quenched, it prevents the particles from scattering and avoids clinker (stony, hard particle) formation.

3. Transportation

The ash is then transported to storage. Depending on the plant&#;s needs, there are various transportation systems. Following systems can be used to transport ash in an ash handling system:

• Mechanical System
• Pneumatic System
• Hydraulic System
• Water-jetting System

4. Collection

After transportation, the ash is collected and then stored in ash bunkers. Later, it is used in industries or disposed of in ponds.

C] Types of Ash Handling Systems

The different types of ash handling systems are:

1. Hydraulic System

This System is used for larger power plants. The ash from the furnace falls into a water system that has a high velocity and carries the ash to sumps. Here, the water and ash are separated. It is then taken to a dumpsite in wagons, rail cars, and trucks. A conveyer belt or grab buckets can be used to load it. The System is healthy, clean, dustless, and completely enclosed. It does not harm the people working in it. The hydraulic System can also handle molten ash and break it into smaller pieces.

Hydraulic systems are mainly of two types: high-pressure hydraulic systems and low-pressure hydraulic systems.

(i) High-pressure System

This System operates intermittently. Here, the hoppers are fitted with water nozzles at the top and sides. The top nozzle quenches the ash, whereas the side nozzles give the ash its driving force&#;on the top and the sides. The ash then flows with the water to a receiving hopper or sump. Here, the ash is separated from the water. The ash is then transported out via carriages using water once more. The high-pressure System is expensive to operate and install.

(ii) Low-pressure system
In this system, a trough or drain is placed beneath the boilers. Then, water flows through the trough. The ash falls into the trough and is carried by water to the sumps. It is here that the ash and water are passed through a screen to separate them. Water is pumped back to the trough, then used to remove ash again through the carrier and sent out to the dumping site.

2. Pneumatic System

The pneumatic System uses air to drive ash through a pipe. The ash is then passed to the crushers through a conveying pipe from the boilers. Ash is collected in ash hoppers by sucking air through the delivery end; this makes the ash flow into separators. Exhaust fans are employed to filter and exhaust dusty air. This system is generally used to dispose of ash.

It can handle 5 to 30 tonnes of ash per hour. The ash can be transported over long distances, reducing the difficulty. The only disadvantage is that these large systems require high maintenance and labor costs. As a result, it must be constantly managed.

3. Mechanical System

This system includes wheelbarrows, bucket elevators, belt conveyors; railroad cars; motor trucks; etc. This System is used in smaller power plants. The ash is collected through ash outlet doors and transferred to containers. A bucket elevator is attached to collect ashes. Before it is transferred to a type of ash handling conveyer belt, it must be quenched. The ash is then allowed to fall through the water seal. The cooled down ash is carried to a dump site over the conveyer belt. This is continuous, and the power is low, but it can deliver 3 tonnes of ash per hour. The overall life of the belt is around five years if it is maintained properly.

4. Water-Jetting System

In the System, water comes out of the quenching nozzle and is used to cool ash. The ash is made to fall into the trough and then removed.

#Note: What type of ash handling system will be used depends on the waste disposal. Factors to take into consideration are its maintenance capabilities, whether it can be used for either a small or large plant. Thus, you must contact an ash handling system manufacturer in India to help you out with finding the right ash handling system for you.

There should also be ample availability of water for cooling down ash. For example, the plant should be near a river or a reservoir. To avoid transmission costs, the plant should be near a loading center. The plant should be at a faraway distance from areas where there is a huge population to prevent radioactive hazards. Since the waste is radioactive, the plant should have space to dispose of it properly.

Conclusion

To avoid any consequences, it is essential to handle fuel very carefully. It should also be disposed of correctly. This is why an ash handling system is crucial in thermal power plants. Ash handling system ensures the process is environmentally friendly and normally runs without issues. However, maintenance of the system is vital. Any thermal power plant must choose an ash handling system depending on its requirements. At the same time, ensure that the System runs efficiently, the equipment is thoroughly maintained, and costs are taken care of. This will result in good returns for the power plant.

Contact us to discuss your requirements of Ash Handling Pump wholesaler. Our experienced sales team can help you identify the options that best suit your needs.