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Title: Effects of partial pressure of oxygen on the stability of axial, oxy-coal, turbulent diffusion flames: Topical report task 8
Authors: Zhang, Jingwei
Wendt, Jost O. L.
Issue Date: 31-Jul-2009
Publisher: University of Utah, Institute for Clean and Secure Energy
Citation: Topical Report: Task 8
Type: report
Pages: 58
Abstract: Oxy-fuel combustion of pulverized coal with flue gas recirculation is potentially one of the few technologies that may allow CO2 sequestration technologies to be applied to existing coal-fired boilers. One issue of interest is to understand and predict the effects of the near-burner zone environment consisting of O2 and CO2 (instead of N2). The purpose of this research is to better understand the effect of partial pressure of O2 (PO2) on flame stability, which becomes another degree of freedom not present during air combustion. The data obtained were designed to form an experimental basis for validation of coal-jet ignition models. These models can play a useful role in predicting flame attachment and flame stability for retrofit of oxy-coal combustion into existing boilers. Type zero axial flames, which can be accurately characterized, are chosen to represent the near-burner zones of tangentially fired furnaces or cement kilns, where burner swirl is absent. This topical report describes: (1) the design attributes of a 100 kW test oxy-fuel combustor, together with an ancillary O2 and CO2 supply system. One challenge that was satisfactorily resolved was the steady feeding of 2 5 kg/hr coal into an axial burner to produce Type zero axial turbulent diffusion flames in a steady enough fashion to allow quantification of the data. (2) the methodology developed to quantify flame stand-off distance, flame length, and flame luminosity using image processing techniques. (3) the results showing the effect of PO2 in secondary O2/CO2 stream on flame stability, flame length and flame luminosity at the same adiabatic flame temperature comparing with O2/N2 environment. (4) the results showing the effect of PO2 in the primary (transporting) stream on the axial flame stand-off distance. Statistical studies, including probability distribution function (PDF) data, on the flame stand-off distance, are provided to quantify this effect. The results indicated that flame stand-off distance is not a continuous variable, and attachment/detachment passes through a sudden transition. In addition, the secondary stream preheat plays an important role on the coal ignition. Primary PO2 has a first-order effect on flame stability and axial coal jet ignition.
URI: http://hdl.handle.net/123456789/10926
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