One compliance option receiving growing interest by utilities is natural gas reburning, recently made commercially available. As many as five new reburning retrofit installations are pending or underway. GRI and its partners invested more than a decade in developing and field testing natural gas reburning on utility-scale boilers. This retrofit process was developed to offer utilities a flexible, cost-competitive way to achieve incremental NOx reductions. Reburning involves injection of natural gas above coal burners to create a fuel-rich zone, where chemical reactions reduce NOx to harmless nitrogen.
Air is injected above the reburning zone to burn out combustibles while minimizing NOx formation.
The degree of NOx reduction a utility must achieve depends, in part, on location, boiler design type, and the levels of NOx it currently emits. GRI is working on other versions of reburning that address these needs. Amine-enhanced in this case refers to urea. Initial testing in 1998 has been very encouraging. Testing continues this year.