Evaluation of Gas Reburning & Low NOx Burners on a Wall Fired BoilerPerformance and Economics Report Gas Reburning-Low NOx Burner System Cherokee Station Unit 3 Public Service Company of Colorado PDF Download

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Book Description
Under the U.S. Department of Energy's Clean Coal Technology Program (Round 3), aproject was completed to demonstrate control of boiler NOX emissions and to a lesserdegree, due to coal replacement, SO2 emissions. The project involved combining GasReburning with Low NOX Burners (GR-LNB) on a coal-fired electric utility boiler todetermine if high levels of NOX reduction (70%) could be achieved. Sponsors of the projectincluded the U.S. Department of Energy, the Gas Research Institute, Public ServiceCompany of Colorado, Colorado Interstate Gas, Electric Power Research Institute, and theEnergy and Environmental Research Corporation. The GR-LNB demonstration wasperformed on Public Service Company of Colorado's (PSCO) Cherokee Unit#3, locatedin Denver, Colorado. This unit is a 172 MW wall-fired boiler that uses ColoradoBituminous, low-sulfur coal. It had a baseline NOX emission level of 0.73 lb/106 Btu usingconventional burners. Low NOX burners are designed to yield lower NOX emissions than conventional burners. However, the NOX control achieved with this technique is limited to 30-50%. Also, withLNBs, CO emissions can increase to above acceptable standards. Gas Reburning (GR)is designed to reduce NOX in the flue gas by staged fuel combustion. This technologyinvolves the introduction of natural gas into the hot furnace flue gas stream. When combined, GR and LNBs minimize NOX emissions and maintain acceptable levels of COemissions. A comprehensive test program was completed, operating over a wide rangeof boiler conditions. Over 4,000 hours of operation were achieved, providing substantialdata. Measurements were taken to quantify reductions in NOX emissions, the impact onboiler equipment and operability and factors influencing costs. The GR-LNB technologyachieved good NOX emission reductions and the goals of the project were achieved. Although the performance of the low NOX burners (supplied by others) was less thanexpected, a NOX reduction of 65% was achieved at an average gas heat input of 18Y0. Theperformance goal of 70% reduction was met on many test runs, but at a higher reburn gasheat input. S02 emissions, based on coal replacement, were reduced by 18Y0. Theperformance goal of 70% reduction was met on many test runs, but at a higher reburn gasheat input. S02 emissions, based on coal replacement, were reduced by 18Y0. Toward the end of the program, a Second Generation gas injection system was installed. Higher injector gas pressures were used that eliminated the need for flue gas recirculationas used in the first generation design. The Second Generation GR resulted in similar NOXreduction performance as that for the First Generation. With an improvement in the LNBperformance in combination with the new gas injection system, the reburn gas could bereduced to 12.5% of the total boiler heat input to achieve al 64?40 reduction in NO, emissions. In addition, the OFA injectors were modified to provide for better mixing tolower CO emissions.