Coal Combustion Residuals (CCRs) are defined by the EPA as “coal ash created when coal is burned by power plants to produce electricity. Coal ash is one of the largest types of industrial waste generated in the United States. In 2012, 470 coal-fired electric utilities generated about 110 million tons of coal ash.” Some power plants add pyrites and Gypsum to the CCR category as well. Basically, any waste generated in the burning of coal is included. In 2014 the EPA passed the Resource Conservation and Recovery Act that regulates the disposal of CCRs. Mainly the EPA is concerned with the “leaking of contaminants into ground water, blowing contaminants into the air as dust, and the catastrophic failure of coal ash surface impoundments.” Because of this many coal power plants are trying to devise ways to comply with the rule.
Two accidents helped to determine the scope of the new rule: the TVA Kingston Fossil Plant near Kingston, TN, and the Dan River power plant in Eden, NC. The TVA disaster was the result of an earthen dam failing allowing 1.1 billion gallons of coal ash sludge to flow into nearby rivers. The Dan River disaster was the result of a storm water pipe failing allowing 37,000 tons of ash and 27 million gallons of contaminated water to flow into the Dan River. The Kingston spill is estimated to have cost the TVA $1.2 billion to clean up, and the Dan River cleanup is estimated to have cost $102 million to date. Because of these disasters, many states have decreed that many ash ponds must be closed by January 1, 2019, and all of them must be closed by January 1, 2029.
The EPA has ruled that earthen dams with liquid coal ash sludge are no longer a viable means of dealing with (Coal Combustion Residuals) CCRs. Instead, systems are being built that utilize vacuum systems and pressure blowers to move the fly ash, bottom ash/pyrites, and gypsum to dry landfills instead. Consisting mainly of conveyors and silos, the ash is stored and then moved in batches to the landfill. Vacuum Exhausters are used to move the ash from hoppers in the power plant to ash silos with filter/separators. A pressure blower then moves the ash from the filter/separators to much larger ash silos that are then fed to trucks or conveyors for movement to dry landfills.
Said one director of a CCRT (Coal Combustion Residuals Treatment) system, “The CCRT is really going to simplify our movement of fly ash, bottom ash, and gypsum. It allows us to set up a separate control room for the handling of these materials, much as we do with coal and limestone, relieving the power plant operators from having to deal with it. Because of the design, we have a large amount of storage capacity so we can move the CCRs in batches instead of continuously like we did before. Now the power plant can produce ash all night long and just store it in the CCRT Ash Silos until morning when the CCRT system shift comes on and moves the ash from the silo. Additionally, we can decide what to do with the Gypsum (a by-product of scrubber operation) because we have a huge storage building. When we have a contract to sell the gypsum, it is moved onto a conveyor that takes the Gypsum to a truck loading station or a barge loading station. If we don’t have a contract, the Gypsum is moved by the same conveyors as the ash to the landfill.”
One of the challenges with any new technology introduced to a power plant is that many existing operators simply are not interested in learning how the system works. Because of the aging workforce issue in the industry, current operators either have decades of experience or are newly hired with next to none. Training on the new systems then becomes a challenge. However, personnel must be trained to run the system. Management must be diligent in ensuring that all documentation on the new system is handed over once the system is built. Building contractors are notorious for not doing so until much later than commissioning if at all.
With adequate training and competent operators, Coal Combustion Residual Treatment (CCRT) System can alleviate and simplify the movement of Coal Combustion Residuals (CCRs) at the power plant allowing the plant to comply with the EPA guidelines for the storage of CCRs and will prevent disasters like Kingston and Dan River.
