The project seeks to develop and validate a new pulverized coal combustion system to reduce utility PC boiler NO x emissions to 0.15 lb/million Btu or less without post-combustion flue gas cleaning. Work during previous reporting periods completed the design, installation, shakedown and initial PRB coal testing of a 3-million Btu/h pilot system at BBP's Pilot-Scale Combustion Facility (PSCF) in Worcester, MA. Based on these results, modifications to the gas-fired preheat combustor and PC burner were defined, along with a modified testing plan and schedule.During the current reporting period, a revised subcontract was executed with BBP to reflect changes in the pilot testing program. Modeling activities were continued to develop and verify revised design approaches for both the Preheat gas combustor and PC burner. Reactivation of the pilot test system was begun with BBP personnel. A presentation on the project results to date was given at the NETL-sponsored 2002 Conference on SCR and SNCR for NOx Control on May 15-16, 2002 in Pittsburgh PA. EXECUTIVE SUMMARY Project Objectives:The overall project objective is the development and validation of an innovative combustion system, based on a novel coal preheating concept prior to combustion, that can reduce NO x emissions to 0.15 lb/million Btu or less on utility pulverized coal (PC) boilers. This NO x reduction should be achieved without loss of boiler efficiency or operating stability, and at more than 25% lower levelized cost than state-of-the-art SCR technology. A further objective is to make this technology ready for full-scale commercial deployment in order to meet an anticipated market demand for NO x reduction technologies resulting from the EPA's NO x SIP call.

The overall project objective is the development and validation of an innovative combustion system, based on a novel coal preheating concept prior to combustion, that can reduce NO x emissions to 0.15 lb/million Btu or less on utility pulverized coal (PC) boilers. This NO x reduction should be achieved without loss of boiler efficiency or operating stability, and at more than 25% lower levelized cost than state-of-the-art SCR technology. A further objective is to ready technology for full-scale commercial deployment to meet the market demand for NO x reduction technologies. Over half of the electric power generated in the U.S. is produced by coal combustion, and more than 80% of these units utilize PC combustion technology. Conventional measures for NO x reduction in PC combustion processes rely on combustion and post-combustion modifications. A variety of combustion-based NO x reduction technologies are in use today, including low-NO x burners (LNBs), flue gas recirculation (FGR), air staging, and natural gas or other fuel reburning. Selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR) are post-combustion techniques. NO x reduction effectiveness from these technologies ranges from 30 to 60% and up to 90-93% for SCR. Typically, older wall-fired PC burner units produce NO x emissions in the range of 0.8-1.6 lb/million Btu. Low-NO x burner systems, using combinations of fuel staging within the burner and air staging by introduction of overfire air in the boiler, can reduce NO x emissions by 50-60%. This approach alone is not sufficient to meet the desired 0.15 lb/million Btu NO x standard with a range of coals and boiler loads. Furthermore, the heavy reliance on overfire air can lead to increased slagging and corrosion in furnaces, particularly with higher-sulfur coals, when LNBs are operated at sub-stoichiometric conditions to reduce fuel-derived NO x in the flame. Therefore, it is desirable to minimize the need for overfire air by maximizing NO x reduction in the burner. The proposed combustion concept aims to greatly reduce NO x emissions by incorporating a novel modification to conventional or low-NO x PC burners using gas-fired coal preheating to destroy NO x precursors and prevent NO x formation. A concentrated PC stream enters the burner, where flue gas from natural gas combustion is used to heat the PC up to about 1500°F prior to coal combustion. Secondary fuel consumption for preheating is estimated to be 3 to 5% of the boiler heat input. This thermal pretreatment releases coal volatiles, including fuel-bound nitrogen compounds into oxygen-deficient atmosphere, which converts the coal-derived nitrogen compounds to molecular N 2 rather than NO. Design, installation, shakedown, and testing on Powder River Basin (PRB) coal at a 3million Btu/h pilot system at RPI's (Riley Power, Inc.) pilot-scale combustion facility (PSCF) in Worcester, MA demonstrated that the PC PREHEAT process has a significant effect on final NO x formation in the coal burner. Modifications to both the pilot sys...

During the current quarter, twenty-two pilot tests were conducted with Central Appalachian (CA) caking coal. The objective for these tests was to achieve continuous operation of the pilot system at its design coal feed rate of 156 lb/h, without plugging or agglomeration in the combustor. One combustor air distribution method tested achieved continuous operation at 110 lb/hr, and inspection of the combustor afterward indicated that this method has potential to solve the caking problem. The NOx results from the pilot caking coal runs indicate that even greater NOx reduction is possible with CA coal than with the PRB coal tested, to levels near 100 ppmv or lower at 4-6% exit oxygen. It was therefore decided to conduct additional pilot tests of the air distribution method to determine how to incorporate this into a workable CA combustor design. Based on current weather and manpower restrictions at the site, this pilot testing is expected to be started in February.

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