Technology augments fly ash recycling A new technology developed by EPRI, the science and technology organization for the energy industry, and Progress Materials, Inc. (PMI), reportedly improves the quality of fly ash so that it can be readily marketed. Sale of fly ash is a profitable business for many electric utilities. By some estimates,12 million tons of fly ash produced by coal-fired electricity plants in the United States are sold to the cement and concrete industries. This business may be in danger, however. Many utilities are finding that nitrogen oxide (NOx) reduction technology installed to meet the emissions standards of the 1990 Clean Air Act Amendments can increase the unburned carbon content of fly ash, making it unsuitable for cement and concrete.

A typical 800MW coal-fired plant creates more than 700 tons of ash each day. The ash is often used for landfill or piped into ash ponds, but a growing number of power producers are selling it as filler in concrete used in the construction of roadbeds, buildings, and other structures. This proper use of fly ash depends on the amount of carbon left in the ash after combustion-too much carbon makes it unusable.

The new technology, called Carbon Burn-Out (CBO), produces a high quality, low carbon fly ash, and the heat recovered in the process improves the efficiency of the host power plant. "Carbon Burn-Out improves fly ash quality by combusting the carbon contaminating the ash, and this carbon is the fuel for the CBO process," said Pete Hay, president of Progress Materials. "The heat recovered in the process improves the plant heat rate, which in turn reduces the emissions of carbon dioxide into the atmosphere."

The Carbon Burn-Out process is capable of handling variations in the carbon content of fly ash from the day-to-day operations within a single plant or from different generating stations and yielding a beneficiated product that is consistent in quality," says EPRI project manager, Tom Boyd. "By taking the higher carbon issue out of the equation, plant operators can focus on efficient boiler operation while maintaining environmental compliance," Boyd noted.

The positive environmental and business implications for U.S. fossil fuel plants are suggested by Tony Armor, EPRI's director of generation technology, who noted that in the United States 52 percent of the total electricity generated comes from burning coal, and more than 59 million tons of fly ash are produced each year. "Disposal of fly ash is difficult and expensive, and technologies that make the ash more marketable to the construction and agriculture industries are extremely important. Utilities that are concerned about excess carbon in ash should be aware of the solution that South Carolina Electric & Gas and EPRI have put in place."

South Carolina Electric & Gas began considering its alternatives for the processing of fly ash as soon as the Clean Air Act Amendments legislation was passed. "We anticipated that retrofitting low-NOx burners on our plants would increase the carbon in our fly ash, at least doubling the ash's loss on ignition from 2 to 5 percent to 10 or 15 percent," recalls Ted Frady, senior engineer in charge of SCE&G's ash utilization program. "SCE&G has been successfully marketing over 80 percent of its ash, and we have a vision of selling 100 percent," says Frady.

SCE&G decided to proceed with a full-scale facility based on the success of pilot plant tests on the SCE&G fly ash conducted by EPRI and Progress Materials. The beneficiated fly ash was evaluated by both SCE&G and its marketer, Southeastern Fly Ash Co. The plant, designed to produce approximately 160,000 tons of low carbon beneficiated fly ash per year, will be located at SCE&G's Wateree Station. Fly ash from Wateree, as well as two other SCE&G power stations, McMeekin and Urquhart, will be processed. The plant is expected to be in operation by the end of July 1998.

The successful development of the Carbon Burn-Out process offers utilities an alternative for landfilling fly ash in locations where fly ash markets exist. This process offers flexibility of changes in boiler operations and environmental controls on fly ash quality, and can also support fuel switching strategies. Benefits include reducing the quantity of landfilled ash, avoiding disposal costs, and improved plant heat rate.

For technical information, contact Thomas Boyd, EPRI Southeast Regional Manager-Generation by phone (704) 537-6033, fax (704) 547-6035, or e-mail tboyd@epri.com

Pacific Brick introduces inlay for precast, C-I-P "Other methods of bonding brick and concrete have been out there for some time, but Mbrick's patented design introduces true design flexibility and tremendous improvements to the practice of building with brick facades," states Joe Dinsdale, president of Pacific Brick Systems. Pacific Brick Systems is the exclusive dealer of Mbrick in nine western states. "It's applications in tilt-up, precast and cast-in-place construction are practically limitless."

The innovative edge of the Mbrick system involves the use of interlocking Brick Inlay Templates, or "BITs." Each BIT holds a thin brick, and when the BITs are snapped together, they can create a wide variety of bond patterns. Concrete is poured over the backside of the bricks, and after curing, the BITs are easily removed, revealing the finished brick veneer and perfectly formed, tooled (cove) mortar joints.

"The use of brick can greatly enhance a building's image and marketability, and the Mbrick system provides that enhancement at substantial savings of both time and money," states Dinsdale, a registered professional engineer with over 20 years experience in the construction industry. "Besides the beauty of brick for under $7 per sq. ft., there are several benefits on the job site, such as fewer weather delays, less site congestion and greater job safety. Plus, you'll avoid moisture problems and see reduced maintenance down the road."

As the exclusive dealer for the Mbrick system, Pacific Brick provides product support during the design and specification phase of a project, CAD shop drawings, samples and submittals at the contract phase, as well as field support during installation. "Our field people are experienced in the installation of Mbrick," states Dinsdale. "We will provide detailed drawings and onsite support from delivery to completion."

Information on Mbrick can be obtained from Joe Dinsdale at 503/827-7353; 800/387-6945; Web Page: www.pacbricksys.com

Testing measures concrete wall performance Dramatic images of 2 Yen 4s strewn across the landscape in the wake of this spring's tornadoes bring up the question: What role does construction play in tornado safety? Tests at Texas Tech show that wall construction can make a world of difference.

The greatest inherent danger to people and property during the high winds of tornadoes and hurricanes is the debris carried in the high winds. Flying at such intense velocity, wreckage can cut right through a building wall and endanger the people inside. Tests conducted by Texas Tech University's Wind Engineering Research Center offer dramatic proof that concrete walls withstand flying debris from tornadoes and hurricanes-and outperform their wood and steel counterparts.

To duplicate tornado-like conditions in the laboratory, researchers shot wall sections with 15-lb. 2 Yen 4 lumber "missiles" at up to 100 mph, simulating debris carried in a 250-mph wind. These conditions cover all but the most severe tornadoes. Hurricane wind speeds are less than the speeds modeled here. Missile testing designed to demonstrate damage from hurricanes uses a 9-lb. missile traveling about 34 mph.

Researchers tested 4 Yen 4-ft. sections of concrete block, several types of insulating concrete forms, steel studs, and wood studs to rate performance in high winds. The sections were finished as they would be in a completed home: drywall, fiberglass batt insulation, plywood sheathing, and exterior finishes of vinyl siding, clay brick or stucco.

All the concrete wall systems survived the tests with no structural damage. Lightweight steel and wood stud walls, however, offered little or no resistance to the "missile." The 2 Yen 4 ripped through them.

Reinforced concrete homes have proven their wind-resistance in the field during tornadoes and hurricanes. In Urbana, Ill., a recently constructed insulating concrete form home withstood a 1996 tornado with minimal damage. In the Liberty City area of Miami, several homes built using the shotcrete technique survived Hurricane Andrew in 1992. In both cases, neighboring homes were destroyed."The results of the tests were not surprising, but they were dramatic," says Donn Thompson, Portland Cement Association's (PCA) residential technology program manager. "Concrete walls meet both the criteria needed to protect occupants in a severe storm-structural integrity and missile shielding ability."

Seeing is believing. A new 8-minute video shows the wall tests, providing visual evidence of concrete's resistance to wind-driven debris-the biggest threat to lives and property in hurricanes and tornadoes. Copies of the video, Built-in Safety (VC511) are available from PCA for $4.95 plus shipping and handling by calling 800/868-6733. For information on building concrete homes, visit the website or call the concrete home hotline toll-free at 888/333-4840.

Manual underscores concrete's strength The U.S. Army Corps of Engineers recently gave concrete twice the service life of alternative pipe materials in its newly updated engineering manual titled, "Conduits, Culverts and Pipes" (EM 1110-2-2909).

The manual, which provides guidance on the construction of conduits, culverts and pipes used in civil works projects, gives concrete pipe an estimated service life of 70 to 100 years, which the manual states is approximately two times that of steel and aluminum. The manual also states that long-term material properties be used in the design, and designers should not expect a service life of greater than 50 years for plastic materials.

The manual outlines specific uses for reinforced concrete pipe such as for dams, urban levees and other levees where public safety is at risk or substantial property damage could occur. The guidelines include warnings about the use of corrugated metal pipe in such structures as rural levee systems stating that, among other problems, corrugated metal is subject to chemical and galvanic corrosion. The Army Corps recommends a life-cycle cost analysis be performed when using CMP in civil works projects.

In a separate manual titled "Life Cycle Design and Performance" (EM 1110-2-8159), the Army Corps sets forth a policy requiring design engineers to implement 100-year life cycle concepts into planning and design considerations for major civil works projects, despite higher first costs. "Design engineers are to use materials and project components with a proven history of long-term reliable performance," the manual states.

"We are very pleased with this recognition," said Jeffrey I. Enyart, president of the American Concrete Pipe Association. "For decades, concrete pipe has been unsurpassed as the strongest and most dependable drainage conveyance material available."

The Association's Government Relations Committee has lobbied for nearly two years to ensure the recognition of concrete's strength and durability under Army Corps guidelines. Copies of the manuals can be obtained from the Army Corps, or by contacting the American Concrete Pipe Association's Resource Center at 800/290-2272 (ACPA), or by fax at 972/291-0622.