Emissions of primary concern for coal-fueled diesel cogeneration and electric power plants are nitrogen oxides, sulfur dioxide, particulate matter, and aromatic hydrocarbons. In addition, the exhaust particulate size distribution and ash content are relevant to durability of the exhaust valves, turbocharger, and other engine components. This paper summarizes preliminary measurements of “uncontrolled” emissions in the exhaust of a Cooper-Bessemer 33-cm (13-in.) bore, 400 rpm, single-cylinder research engine, operated on “engine-grade” coal-water fuel (0.5 percent ash, 1 percent sulfur, 8 μm mean size coal). Based on these results, we present a preliminary evaluation of emission control options for satisfying hypothetical future emission standards for 2–50 MW power plants. The paper describes coal-diesel component subsystems such as (a) “reburning” for reducing NOx and hydrocarbon emissions, (b) high- and low-temperature injection of calcium sorbents for SO2 capture, and (c) high-temperature bag filters for control of fine particles. The expected performance of a conceptual, integrated control system is presented.
In this study, a variety of piezoelectric pressure transducer designs and mounting configurations were compared for measuring in-cylinder pressure on a heavy-duty single-cylinder diesel engine. A unique cylinder head design was used which allowed cylinder pressure to be measured simultaneously in two locations. In one location, various piezoelectric pressure transducers and mounting configurations were studied. In the other location, a Kistler water-cooled switching adapter with a piezoresistive pressure sensor was used. The switching adapter measured in-cylinder pressure during the low-pressure portion of the cycle. During the high-pressure portion of the cycle the sensor is protected from the high-pressure and high-temperature gases in the cylinder. Therefore, the piezoresistive sensor measured in-cylinder pressure highly accurately, without the impacts of short-term thermal drift, otherwise known as thermal shock. Additionally, the piezoresistive sensor is an absolute pressure sensor which does not require a baseline or “pegging” on every engine cycle. With this measurement setup, the amount of thermal shock and induced measurement variability was accurately assessed for the piezoelectric sensors. Data analysis techniques for quantifying the accuracy of a piezoelectric cylinder pressure measurement are also presented and discussed. It was observed that all the piezoelectric transducers investigated yielded very similar results regarding compression pressure, start of combustion, peak cylinder pressure, and the overall heat release rate shape. Differences emerged when studying the impact of the transducer mounting (e.g., recessed versus flush-mount). Recessed-mount transducers tended to yield a more accurate measurement of the cycle-to-cycle variability when compared to the baseline piezoresistive sensor. This is thought to be due to reduced levels of thermal shock, which can vary from cycle-to-cycle.
The Babcock & Wilcox Company (B&W), under contract with the Electric Power Research Institute (EPRI), has designed and tested an advanced staged combustion system on a four million Btu/hr (4.2-million kJ/hr) scale. Results of these tests showed the potential to limit the emission of nitrogen oxides from coal-fired boilers to 100–150 ppm and identified a new kinetic mechanism for NO destruction. Subsequently, the correlations and initial design parameters derived from the small-scale tests were applied to a conceptual commercial system to ensure that this concept was indeed commercially feasible. These design considerations and the favored preliminary arrangement of a low-NOx combustion system will be discussed herein. Before commercializing this concept, however, further research is necessary. Testing on a nominal 50-million Btu/hr (53-million kJ/hr) prototype system is now in progress. Initial results indicate that NOx emission correlations and design parameters will need only slight revisions before the concept is ready for a field demonstration.
In this study, a variety of piezoelectric pressure transducer designs and mounting configurations were compared for measuring in-cylinder pressure on a heavy-duty single-cylinder diesel engine. A unique cylinder head design was used which allowed cylinder pressure to be measured simultaneously in two locations. In one location, various piezoelectric pressure transducers and mounting configurations were studied. In the other location, a Kistler water-cooled switching adapter with a piezoresistive pressure sensor was used. The switching adapter measured in-cylinder pressure during the low pressure portion of the cycle. During the high pressure portion of the cycle the sensor is protected from the high pressure and high temperature gases in the cylinder. Therefore, the piezoresistive sensor measured in-cylinder pressure highly accurately, without the impacts of short term thermal drift, otherwise known as thermal shock. Additionally, the piezoresistive sensor is an absolute pressure sensor which does not require a baseline or “pegging” on every engine cycle. With this measurement setup, the amount of thermal shock and induced measurement variability was accurately assessed for the piezoelectric sensors. Data analysis techniques for quantifying the accuracy of a piezoelectric cylinder pressure measurements are also presented and discussed. It was observed that all the piezoelectric transducers investigated yielded very similar results regarding compression pressure, start of combustion, peak cylinder pressure, and the overall heat release rate shape. Differences emerged when studying the impact of the transducer mounting (e.g., recessed vs. flush-mount). Recessed-mount transducers tended to yield a more accurate measurement of the cycle-to-cycle variability when compared to the baseline piezoresistive sensor. This is thought to be due to reduced levels of thermal shock, which can vary from cycle-to-cycle.
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