A catalyst-activity testing tool that helps manage selective-catalytic-reduction (SCR) systems used in power plants to control nitrogen oxides (NOX) emissions is now commercially available.

Most energy systems rely on combustion processes, which form NOX when fuel is burned at high temperatures, contributing to smog, acid rain and global warming. SCR systems control these emissions by injecting ammonia or urea into flue gas in the presence of a catalyst, converting NOX into nitrogen and water.

However, the ability of the SCR catalyst to convert NOX degrades over time, and the catalyst surface can become clogged with fly ash. Additionally, SCR systems contain multiple catalyst layers, which can decay at different rates, requiring layer-specific maintenance. To restore SCR performance, power plant maintenance staff can replace a layer of used catalyst with fresh catalyst, add an additional layer or do both. However, detecting catalyst deactivation is key for predicting remaining catalyst life, and the timing of maintenance is critical for catalyst management.

Developed by the Fossil Energy Research Corp. (FERCo), Laguna Hills, Calif., with funding from the U.S. Department of Energy, Knoxcheck online catalyst activity test system monitors catalyst activity in an SCR system without shutting down the unit to take catalyst samples.

Tested on a full-scale operating SCR reactor at Southern Co.’s Plant Gorgas Unit 10, the SCR-testing system produced results similar to those of traditional laboratory catalyst activity testing. Linked with catalyst-management software, the Knoxcheck technology helped Southern Co. make proactive decisions about the operation and maintenance of the SCR system and NOX compliance on the unit.

The Clean Air Interstate Rule requires deep reductions in NOX emissions in Eastern states by 2009. As a result, more power plant operators are moving toward year-round operation of SCR systems in an effort to comply. The ability of this test system to measure catalyst activity during any unit load condition without disruption permits power plants to continue operating with minimum downtime yet measure catalyst condition and plan for maintenance.

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