Evaluation of gas-reburning and low NO{sub x} burners on a wall fired boiler. Technical progress report number 17, October 1--December 31, 1994

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. 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. With GR, about 80--85% 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%. This project is being conducted in three phases at the host site, a 172 MW wall fired boiler of Public Service Company of Colorado (PSCo), Cherokee Unit 3 in Denver, Colorado: Phase 1--Design and Permitting; Phase 2--Construction and Start-up; and Phase 3--Operation, Data Collection, Reporting and Disposition. Phase 3 activities during this reporting period involved initiation of the second generation gas reburning parametric testing. This technology utilizes enhanced natural gas and overfire air injectors with elimination of the flue gas recirculation system. The objective is to demonstrate NO{sub x} reductions similar to that of long term testing but with a reduced capital cost requirement through elimination of the FGR system