It’s not enough to design a safe and well-lined impoundment to hold all the coal ash residues produced by a power plant. There are also plenty of questions to answer about how the coal ash will be consolidated and transferred to the storage area, beginning with the fact that ash is usually extremely hot and full of live coals that can burn for weeks without proper treatment. Coal ash isn’t safe, or practical, to handle by hand due to the sheer volume produced. So, plants require extensive conveyor equipment to transfer the waste products from the cooling stack scrubbers and combustion chambers to the impoundments and basins. Here’s what to consider about cooling and handling challenges when dealing with coal ash residues.
Ash Collection
As with the rest of the handling and treatment process, coal ash is collected either in dry or wet form. Dry ash collection allows for the most control over how the waste is eventually handled, but it’s more expensive to install and maintain. Extra air volume is necessary to move all of the fly ash through filters, so it doesn’t escape through the vents or clog the system. It’s also incompatible with the designs of some coal fired power plants that generate large amounts of steam in the same areas where the ash is produced. Wet ash collection is common because rinsing out the ash also doubles as a cooling tower treatment method for achieving power generation goals. Yet, this means that extensive dewatering is necessary to achieve dry ash waste again if it’s preferred.
Dewatering Stages
If dry ash is preferred for landfill disposal, the ash has to be dried down to the stage where it’s around only 20% water by volume. This leaves the ash just wet enough to keep it from becoming a dust hazard while keeping it as light in weight as possible. With many coal ash slurries starting out at 60% to 90% water by volume to keep it flowing smoothly out of the boiler area, this kind of dewatering can use a lot of energy. The use of large-scale impoundments, with accelerated evaporation rates, can help cut dewatering costs without risking spills or containerization. Yet, this is only the case if the basin is lined.
Cooling Equipment
Creating a slurry is generally intended to function as the main cooling method as well. When ash is kept dry to control the weight, it’s usually cooled by the use of a large mechanical screw or conveyor belt system. Ash can be nearly 1500 degrees F when it comes out of the boiler and exposing conveyance systems or slurry piping to those kinds of temperatures can quickly wear out even the best equipment. These cooling units either double as or connect to transportation systems to move the ash from the boiler to the impoundment, tank, or other storage areas. The distance traveled by the coal ash must be long enough to give it ample time to cool, so many systems are longer than what’s strictly necessary for transportation. This kind of cooling equipment should also sort the various grades of ash so they can be reused as much as possible with minimal further treatment needed.
Coal ash residues are corrosive enough that they’re hard to handle even with the most durable equipment and materials. Aside from keeping workers protected with gloves and eye protection, installing the right cooling and handling equipment is essential to moving coal ash right from the boiler to the impoundment without spills or air quality issues. Complete the impoundment basin containment with the help of BTL Liners.
