Evaluation of Gas Reburning and Low-NOx Burners on a Wall-Fired Boiler; a DOE Assessment

The results from the GR-LNB technology demonstrated by EER at Cherokee Station approached, but did not meet, the CCT project's performance objectives. Acceptable unit operability was achieved with both the GR and the LNB components. The gas reburning component of the process appears to be broadly applicable for retrofit NO{sub x} control to most utility boilers and, in particular, to wet-bottom cyclone boilers, which are high NO{sub x} emitters and are difficult to control (LNB technology is not applicable to cyclone boilers). GR-LNB can reduce NO{sub x} to mandated emissions levels under Title IV of the CAAA without significant, adverse boiler impacts. The GR-LNB process may be applicable to boilers significantly larger than the demonstration unit, provided there is adequate dispersion and mixing of injected natural gas. Major results of the demonstration project are summarized as follows: NO{sub x}-emissions reductions averaging 64% were achieved with 12.5% gas heat input in long-term tests on a 158-MWe (net) wall-fired unit. The target reduction level of 70% was achieved only on a short-term basis with higher gas consumption. The thermal performance of coal-fired boilers is not significantly affected by GR-LNB. Convective section steam temperatures can be controlled within acceptable limits. Thermal efficiency is decreased by a small amount (about 0.8%), because of increased dry gas loss and higher moisture in the flue gas as a result of the GR process. Furnace slagging and convective section fouling can be adequately controlled. Because of the higher hydrogen/carbon (H/C) ratio of natural gas compared with coal, use of the GR process results in a modest reduction in CO{sub 2} emissions. SO{sub 2} and particulate emissions are reduced in direct proportion to the fraction of heat supplied by natural gas