Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.
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38 • August 2015 www.concreteproducts.com The facility entered the commercial phase earlier this year at the Santee Cooper Power Winyah Generating Station in Georgetown, S.C. It replaces a 10-year old thermal benefici- ation line that averaged 200,000–250,000 tons/year of con- crete-grade fly ash. To justify equipment replacement and boost output closer in line with market demand in the Car- olinas and neighboring states, SEFA Group engineers looked beyond fly ash for raw feed, determining their reactor could be tooled to process the station's impounded pond ash. Based on 6.5 acres leased from the state-owned Santee Cooper, STAR III opened with 450,000 tons' annual pro- cessing capacity, netting up to 300,000 tons of ASTM C618- grade product. "The Winyah STAR reduces what had been a much longer residence time to a little as 7 to 10 seconds, and lowers the carbon content of fly ash from 5–25 percent to an average of 0.2 percent," notes Knowles. "The reactor handles 18 to 50 tons per hour, depending on raw feed LOI, and recovers about 70 percent of the carbon's Btu value." The Winyah reactor is equipped with four lines, which can receive separate fine and coarse raw feeds. The reactor taps feed ashes' recoverable Btu to a point where, follow- ing start up fueling, the beneficiation process is self-sus- taining and exothermic: No fuel is required for continuous treatment, while excess heat can be drawn from the reactor for raw feed drying or sold to outside users. As ash rises through the refractory-lined steel vessel, air is injected at various locations to process the ash in stages to augment carbon removal or passivation. In extreme instances, a sin- gle piece of carbon char breaks into hundreds of spherical, pozzolanic particles. In a 2015 World of Coal Ash presentation, Knowles and colleagues John Castleman, P.E., and William Fedorka, P.E., offer further STAR III insight, describing the tech- nology as "Specifically designed and operated to reduce the heterogeneity of fly ash by eliminating or lowering the amount of unburned carbon and other contaminants, including unburned organics from alternative fuels. The plant operates at temperatures that are high enough to burn off residual organics comingled in the fly ash, includ- ing coal char particles. [It] can also be operated to reduce some types of agglomerates, improving particle size distri- bution, as well as to blend various coal fly ashes in order to reduce variations in ash chemistry or to optimize the per- formance of coal ash for particular ash utilization opportu- nities/markets." SUSTAINED STREAM Much like a cement or aggregate producer assessing lime- stone or granite reserves for mill or quarry development, The SEFA Group sited STAR III amid an abundant low-grade CCR impoundment, ultimately bound by the EPA final rule. "If the generating station shut down tomorrow, we would have enough raw feed for 20 years. That's what was needed to justify our investment at Winyah," says President Thom- as Hendrix. STAR III was financed through $40 million in S.C. Jobs Economic Development Authority bonds, he adds. It brings SEFA Group's payroll past 200, including an engineering and construction department, plus fleet of 70 tankers. Additional STAR installations and contracts are certain, as utility operators confront compliance with new ash storage, disposal and landfill operation guidelines, and sweeping changes across the power generation business disrupt the supply chain of a widely accepted pozzolanic powder. FEATURE BY DON MARSH Electric utilities are subject to increasingly stringent emissions controls and, potentially, forthcoming rules capping greenhouse gas emissions levels. For now, Santee Cooper maintains customary levels of coal and limestone (below, foreground), the latter used in scrubbers. Regardless of Winyah Station op- erating status, The SEFA Group has a 20-year lease for the STAR III facility, coupled with 11 million tons of pond ash "reserves." The U.S. Environmental Protection Agency published the final rule regulating Coal Combustion Residuals (CCR) on April 17, 2015. It regulates new and exist- ing CCR landfills and surface impoundments (i.e. ponds) at electric-generating stations as non-hazardous solid waste units under Resource and Recovery Act Subtitle D. These new rules provide similar protections to those for municipal solid waste landfills with their focus on protecting human health and the envi- ronment by addressing groundwater, structural integrity of impoundments, and specific requirements for using liners for all new CCR units. Groundwater mon- itoring is required for all continuing or closed CCR units; closure requirements include a 30-year monitoring period. These rules will increase costs related to disposal of coal ash moving forward, and extend the long-term liability asso- ciated with the risks of storing coal ash on the utility's property. — from "Reclaiming and Recycling Coal Fly Ash for Beneficial Reuse with the STAR Pro- cess," a 2015 World of Coal Ash presentation by The SEFA Group's Jimmy Knowles, John Castleman, P.E. and William Fedorka, P.E. FINAL COAL COMBUSTION RESIDUALS RULE