Evaluation of gas-reburning and low NO{sub x} burners on a wall fired boiler. Technical progress report No. 19, April 1, 1995--June 30, 1995

Abstract

Clean Coal Technology (CCT) implies the use of coal in an environmentally acceptable manner. Coal combustion results in the emission of oxides of nitrogen (NO{sub x}), which are precursors of both acid rain and ozone formation. The primary objective of this CCT project is to evaluate the use of Gas Reburning and Low NO{sub x} Burners (GR-LNB) for NO{sub x} emission control from a wall fired boiler. It is anticipated that, if the demonstration is successful, the GR-LNB technology could become commercialized during the 1990`s and will be capable of (1) achieving significant reduction in the emissions of nitrogen oxides and sulfur dioxide (another acid rain precursor) from existing facilities to minimize environmental impacts such as transboundary and interstate pollution and/or (2) providing for future energy needs in an environmentally acceptable manner. Low NO{sub x} burners are designed to delay the mixing of the coal fuel with combustion air to minimize the NO{sub x} formation. Typically, one may obtain up to 50% reduction in NO{sub x} emissions through the use of LNB. For LNB applications, the technology is developed and a number of LN-B designs are commercially available. With GR, about 80-85 percent of the coal fuel is fired in the main combustion zone. The balance of the fuel is added downstream as natural gas to create a slightly fuel rich environment in which NO{sub x} is converted to N{sub 2}. The combustion process is completed by over-fire air addition. SO{sub x} emissions are reduced to the extent that natural gas replaces sulfur-containing coal. The level of NO{sub x} reduction achievable with 15-20% natural gas is on the order of 50-60%. Thus the emission reduction target of the combination of these two developed technologies is about 70%.