For more than two decades, ALSTOM Power Inc. (ALSTOM) has developed a range of low cost, in-furnace technologies for NOx emissions control for the domestic U.S. pulverized coal fired boiler market. This includes ALSTOM's internally developed TFS 2000 firing system, and various enhancements to it developed in concert with the U.S. Department of Energy (DOE). As of 2004, more than 200 units representing approximately 75,000 MWe of domestic coal fired capacity have been retrofit with ALSTOM low NOx technology. Best of class emissions range from 0.18 lb/MMBtu for bituminous coals to 0.10 lb/MMBtu for subbituminous coals, with typical levels at 0.24 lb/MMBtu and 0.13 lb/MMBtu, respectively. Despite these gains, NOx emissions limits in the U.S. continue to ratchet down for new and existing (retrofit) boiler equipment. If enacted, proposed Clear Skies legislation will, by 2008, require an average, effective, domestic NOx emissions rate of 0.16 lb/MMBtu, which number will be reduced to 0.13 lb/MMBtu by 2018. Such levels represent a 60% and 67% reduction, respectively, from the effective 2000 level of 0.40 lb/MMBtu. Low cost solutions to meet such regulations, and in particular those that can avoid the need for a costly selective catalytic reduction system (SCR), provide a strong incentive to continue to improve low NOx firing system technology to meet current and anticipated NOx control regulations. In light of these needs, ALSTOM, in cooperation with the DOE, is developing an enhanced combustion, low NOx pulverized coal burner which, when integrated with ALSTOM's state-of-the-art, globally air staged low NOx firing systems, will provide a means to achieve less than 0.15 lb/MMBtu NOx at less than 3/4 the cost of an SCR with low to no impact on balance of plant issues when firing a high volatile bituminous coal. Such coals can be more economic to fire than subbituminous or Powder River Basin (PRB) coals, but are more problematic from a NOx control standpoint as existing firing system technologies do not provide a means to meet current or anticipated regulations absent the use of an SCR. The DOE/ALSTOM program performed large pilot scale combustion testing in ALSTOM's Industrial Scale Burner Facility (ISBF) at its U.S. Power Plant Laboratories facility in Windsor, Connecticut. During this work, the near-field combustion environment was optimized to maximize NOx reduction while minimizing the impact on unburned carbon in ash, slagging and fouling, corrosion, and flame stability/turn-down under globally reducing conditions. Initially, ALSTOM utilized computational fluid dynamic modeling to evaluate a series of burner and/or near field stoichiometry controls in order to screen promising design concepts in advance of the large pilot scale testing. The third and final test, to be executed, will utilize several variants of the best nozzle tip configuration and compare performance with 3 different coals. The fuels to be tested will cover a wide range of coals commonly fired at US utilities. The completion of this work will provide sufficient data to allow ALSTOM to design, construct, and demonstrate a commercial version of an enhanced combustion low NOx pulverized coal burner. A preliminary cost/performance analysis of the developed enhanced combustion low NOx burner applied to ALSTOM's state-of-the-art TFS 2000 firing system was performed to show that the burner enhancements is a cost effective means to reduce NOx.
