North / South America
New technology to treat PAC tainted Fly Ash for concrete applications
Jun, 20 2012
FlyAshDirect and BASF have jointly developed a new chemical solution to treat powder activated carbon (PAC) tainted fly ashes in order to make them usable for concrete applications.
Every year, more than 10 million tons of fly ash is constructively utilized as a partial substitute for cement in concrete applications in the United States. However, fly ashes get tainted when they are exposed to PAC, a widely used material for mercury emission control at coal burning power plants. When PAC injection systems are installed before the power plant’s particulate control device, activated carbon will be deposited by them onto the fly ash when it passes through the flue gas, consequently increasing loss on ignition or carbon level in the fly ash byproduct.
PAC can be 1000 folds more absorptive when compared to natural carbon, which means air entraining admixtures will be absorbed by it when utilized in concrete. This results in freeze thaw durability, which makes the fly ash unusable. Mercury controls become mandatory at several coal burning power plants in the United States and Canada because of current air pollution regulations. This has already negatively affected the quality of several million tons of fly ash.
At present, FlyAshDirect owns and runs CarbonBlocker at five power producing facilities across the Ohio Valley region and has treated more than 2 million tons of fly ash for ready mix concrete applications. The company, which owns separate patents on the chemistry and injection system, actually devised the technology to handle the impact of natural or unburned carbon, a result of ineffective burning conditions such as low NOx burners in the boiler.
After recognizing the advantages of the technology, BASF Construction Chemicals Division teamed up with FlyAshDirect to further advance the chemistry to deal with the problem associated with PAC tainted fly ashes and they are now ready to commercialize the latest technology.
CarbonBlocker is an effective method for using trace amounts of liquid chemistry to change fine powders’ properties in a bulk flow environment. BASF and FlyAshDirect consider expanding this key benefit to other innovative and special chemistries to treat several construction materials.
By Nick Gilbert
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