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Show Other benefits of cofire at Ford included extension of the low load turndown from a previous minimum capacity of 40,000 lb/hr to 25,000 lb/hr with cofire. S 0 2 emissions were also reduced proportional to the displacement of the coal. Capitol Power Plant To heat the nations Capitol and associated buildings, the Capitol Power Plant operates two 160,000 lb/hr Wickes coal-fired spreader stoker boilers. Typical maximum steaming rate for the coal-fired stoker units is 120,000 lb/hr. One of the boilers was retrofit with dual Coen CoFyr burners in December 1997, and tested in February - April 1998. The combined firing capacity of the gas burners was 60 MMBtu/hr. The primary incentive for the gas cofire system was to trim NOx emissions. A secondary objective was to give faster cleaner lightoffs and rampup to full load. The boiler was tested across the nominal load range of 75.000 lb/hr to 120,000 lb/hr. Measurements included continuous monitoring of 02, C O , C 0 2 , N O x, and S02, E P A Method 17 for particulate loading, and grab samples of fuel and ash streams. Figure 6 shows the response of NOx emissions to cofire for low, intermediate and high boiler loads. Gas cofire in the range of 17 to 21 percent reduced N O x emissions by 17 to 19 percent. These reductions were sufficient to meet the plant goals for N O x trim The excess oxygen levels for these tests were high, in the range of 9 to 12 percent. Spot tests, particularly at the low load condition, suggested that additional N O x reductions were achievable by reducing the high levels of excess air, although continuous operation at lower excess air would require a change in control system which was beyond the scope of the current modifications. Also, operation at low excess air levels would require more extensive testing to access effects on grate thermal response and long term ash properties. -•-•-•- LowLcod - -_- - Intermedate Lead Hic^i Load 0% 5% 10% 15% 20% 25% Gas Cofire, % Figure 6. Capitol N O x Emission Results. 8 |