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 the quarter included continuation of the equipment fabrication effort for pilot system components. Successful proof-of-performance testing of the IGT-designed pilotscale natural gas-fired coal preheat combustor was completed by IGT during the quarter. The combustor was then disassembled and shipped for installation in the pilot-scale test system in BBP's Coal Burner Test Facility (CBTF) in Worcester, MA. Delivery of the balance of the pilot system components from the fabricator began near the end of the quarter, with components being installed in the pilot test facility as they were received.

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.

Gas Technology Institute (GTI) has been advancing the POGT concept since 1995. The progress to date of a GTI-led team on the development and testing of a POGT prototype, and POGT-based systems are presented. There are two main features that distinguish a POGT from a conventional gas turbine: the design arrangement and the thermodynamic processes used in operation. One unique feature is utilization of a non-catalytic partial oxidation reactor (POR) in place of a typical combustor. An important secondary distinction is that a much smaller compressor is required, one that typically supplies less than half of the air flow required in a conventional gas turbine. From a thermodynamic point of view, the working fluid provided by the POR (a secondary fuel gas) has much higher specific heat than complete combustion products. This allows higher energy per unit mass of fluid to be extracted by the POGT expander than is the conventional case. A POR operates at fuel rich conditions, typically at equivalence ratios on the order of 2.5, and virtually any hydrocarbon fuel can be combusted. Because of these fuel rich conditions, incomplete combustion products are used as the hot section working fluid. A POGT thus produces two products: power and a secondary fuel that usually is a H2 rich gas. This characteristic can lead to high efficiencies and ultra-low emissions (single digit NOx and CO levels) when the secondary fuel is burned cleanly in a bottoming cycle. When compared to the equivalent standard gas turbine bottoming cycle combination, the POGT provides an increase of about 10 percentage points in overall system efficiency. Two areas of recent development are addressed in the paper: POGT development and experimental evaluation of a 7 MWth pressurized non-catalytic POR installed at GTI; and examples of POGT-based systems for combined generation of power, heat, syngas, hydrogen, etc. The POGT design approach to convert an existing engine into a POGT by replacing its combustor with a POR together with concomitant modifications of other engine components is discussed. Experimental results of the POR operation include descriptions of major operating conditions: start up, light off conditions, lean combustion mode, lean-to-rich transition, and operation in rich partial oxidation mode at different loads and air to fuel ratios. The overall efficiency of a POGT two-stage power system is typically high and can approach 70% depending on the POGT operating conditions and the chosen bottoming cycle. The bottoming-cycle can be either a low pressure (or vacuum) combustion turbine, or an internal combustion engine, or a solid oxide fuel cell, or any combination of them. In addition, the POGT can be used as the driver for cogeneration systems. In such cogeneration systems the bottoming cycle can be a fuel-fired boiler, an absorption chiller, or an industrial furnace. The POGT is ideally suited for the co-production of power and either hydrogen, or synthesis gas (syngas), or chemicals. Some of these important applications are discussed.

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...

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