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Show electricity. In addition to providing a valuable end-use for LFG, the composition of LFG offered the opportunity to reduce NOx emissions at the Grayson generating station. In a unique pannership between the City and a private developer, the Scholl Canyon LFG ~ted Partnership was formed to provide the compression and delivery of LFG to the Grayson generating station. The private developer's scope of responsibility was to fully finance, build, and operate the compression and delivery pipeline system. In return, the City would buy back the delivered LFG at a substantial discount against the spot market price of natural gas. Within the same time frame, the City contracted with AUS Combustion Company (AUSCC) to install a state-of-the-art low NOx system on Grayson Units 3 and 4. The low NOx system incorporated combustion-based NOx emissions controls, including low NOx burners (LNBs), FGR, and new distributed control system (DCS) controls. The system was also required to accommodate the combustion of LFG, natural gas, and No. 2 fuel oil. This paper presents the technical approach to the development and demonstration of the combustion system which was supplied to the City. The paper discusses design considerations and the development approach, and provides an overview of the system description and results obtained. Conclusions reached are also presented. 2.0 DESIGN CONSIDERATIONS The low NOx system was required to achieve certain NOx emissions limits on natural gas, LFG, and fuel oil as summarized in Table 1. The emissions limits included operation with and without FOR and reflected the furnace heat release intensity for Grayson Units 3 and 4. In general, higher NOx emissions limits were allowed for Grayson Unit 4 because of a more intense heat release in its furnace. -3- |