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Coal Combustion By-Products (CCBs)

How can research solve the problems?

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Mercury Removal

Currently, coal-fired electric utilities are implementing technologies to remove mercury from their emissions. The two most likely mercury removal technologies are the addition of scrubbers and carbon injection. These technologies will produce changes in the CCB's the utilities produce, and thus radically change the existing market for CCB's. Research can help address these changes in the following ways:

Carbon Injection: In this approach, activated carbon is injected into the flue gas to adsorb mercury before it exits the stack. While this approach will likely reduce mercury emissions, it will also produce a significant amount of solid waste. Since the fly ash will now contain activated carbon, it will no longer be useable in cement and concrete, one of the major utilization markets. Research is currently in progress to process the ash to selectively remove the activated carbon so that the ash can be used in concrete. Additional research is being done to treat the activated carbon in the ash so that it will not be detrimental to concrete. Still more research is under way to produce sorbents that do not contain activated carbon, but are still effective for removing mercury.

Scrubbers: Another way to reduce mercury emissions is to treat the flue gas in a limestone scrubber, the same technology many utilities already use to reduce SO2 emissions. This approach is much more costly than carbon injection, but since so many utilities plan on using it, the amount of scrubber by-product that will be produced will be significantly increased. Research will play a significant role by developing new uses for the scrubber by-products, such as new types of cements and grouts.

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