Control of NOx by combustion process modifications
A theoretical and experimental study was carried out to determine lower bounds of NOx emission from staged combustion of a 0.7%N #6 fuel oil. Thermodynamic and chemical kinetic calculations have shown minimum NOx emissions at fuel rich stage equivalence ratios between 1.6 and 1.8 and fuel rich stage...
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Cambridge, Mass. : Massachusetts Institute of Technology, Energy Laboratory, 1981
2011
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| Online Access: | http://hdl.handle.net/1721.1/60488 |
| _version_ | 1826217965844955136 |
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| author | Beř, J. M. Jacques, Malcolm T. Farmayan, W. F. |
| author2 | Massachusetts Institute of Technology. Northeast Utilities Service Company. Energy Laboratory. Electric Utility Program. |
| author_facet | Massachusetts Institute of Technology. Northeast Utilities Service Company. Energy Laboratory. Electric Utility Program. Beř, J. M. Jacques, Malcolm T. Farmayan, W. F. |
| author_sort | Beř, J. M. |
| collection | MIT |
| description | A theoretical and experimental study was carried out to determine lower bounds of NOx emission from staged combustion of a 0.7%N #6 fuel oil. Thermodynamic and chemical kinetic calculations have shown minimum NOx emissions at fuel rich stage equivalence ratios between 1.6 and 1.8 and fuel rich stage temperatures in the range of 1900 to 2100 K (2960 to 3812 0F). |
| first_indexed | 2024-09-23T17:11:32Z |
| id | mit-1721.1/60488 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T17:11:32Z |
| publishDate | 2011 |
| publisher | Cambridge, Mass. : Massachusetts Institute of Technology, Energy Laboratory, 1981 |
| record_format | dspace |
| spelling | mit-1721.1/604882019-04-10T12:59:12Z Control of NOx by combustion process modifications Beř, J. M. Jacques, Malcolm T. Farmayan, W. F. Massachusetts Institute of Technology. Northeast Utilities Service Company. Energy Laboratory. Electric Utility Program. Nitrogen oxides. Combustion engineering. Petroleum as fuel A theoretical and experimental study was carried out to determine lower bounds of NOx emission from staged combustion of a 0.7%N #6 fuel oil. Thermodynamic and chemical kinetic calculations have shown minimum NOx emissions at fuel rich stage equivalence ratios between 1.6 and 1.8 and fuel rich stage temperatures in the range of 1900 to 2100 K (2960 to 3812 0F). In the experimental investigations the use of the MIT Combustion Research Facility permitted the detailed study of aerodynamically complex industrial-type turbulent flames in thermal and chemical environments similar to those in utility boiler furnaces. The primary stage fuel equivalence ratio, the flow and mixing pattern in the flame, the level of air preheat and the mode and quality of fuel atomization, were varied to determine their effect upon the NOx and combustibles emission. Unstaged flame studies were carried out to establish baseline data for comparison with those obtained in fuel rich-lean staged flames in which a fuel rich stage was formed near the burner and the lean stage was established by the admixing of the rest of the combustion air at a distance farther downstream. Results of the computational modeling studies have shown that in the fuel rich zone of the flame the fuel bound nitrogen compounds (FBN) can be converted to molecular nitrogen, N2, which renders the FBN innocuous for forming NOx in the lean stage of the flame. Care has to be taken however to ensure that the mixing of the secondary air with the products from the fuel rich stage does not produce high flame temperatures, in excess of 1800K (27800K) and hence "thermal NOx." The modeling studies have shown also that the FBN conversion to N2 goes through a minimum as the fuel equivalence ratio is varied and that this minimum is lower, and shifts more towards the fuel rich as the fuel rich stage temperature is raised. The experiments guided by the modeling have led to significant reduction in NOx emission; NOx was reduced from a level of 0.51 lb/106 Btu (400 ppm @ 3% 02) in a single stage flame to 0.10 lb/106 Btu (80 ppm @ 3% 02) in staged combustion when the fuel equivalence ratio in the fuel rich stage was maintained in the range of =1.5 to 1.7 (50 to 70% fuel rich), very close to that predicted from the model. The overall excess air was maintained in all experiments at EA=10%, and the combustibles (soot) emission was generally low, always well below the emission standard of 0.1 lb/106 Btu. It is considered that an important factor in the very low NOx emission levels obtained in this study is the favorable mode of secondary air admixing with the fuel rich flame gases which ensure complete combustion without any additional "thermal" NOx formation. It is emphasized that the conditions for these experiments were carefully selected to approach optimum values for the concentration and temperature history of the fuel. The tight controls of combustion aerodynamics and of the heat extraction along the flame available in the MIT Combustion Research Facility were highly favorable for the physical realization and experimental study of these flames. Due to the practical difficulties in controlling mixing and heat extraction in existing utility boiler furnaces, it is not considered realistic to expect the same low NOx and soot emission levels by combustion WINY modifications. It is thought that the results of this study should be used as guidance in design strategy for low NOx emission from the combustion of high nitrogen-bearing fuels rather than as an indication of the absolute levels of NOx which can be achieved by staged combustion techniques in utility boilers. Because of the significance of the flow and mixing pattern in the flame for both the formation of NOx and carbonaceous particulates it is recommended that in the second phase of this study the effect of mixing and heat extraction along both single and multiple staged flames be studied in more detail with a view of application of these controls to the combustion in large utility boilers. 2011-01-11T05:42:29Z 2011-01-11T05:42:29Z 1981 http://hdl.handle.net/1721.1/60488 07760815 Energy Laboratory report (Massachusetts Institute of Technology. Energy Laboratory) no. MIT-EL 81-001. 155 p application/pdf Cambridge, Mass. : Massachusetts Institute of Technology, Energy Laboratory, 1981 |
| spellingShingle | Nitrogen oxides. Combustion engineering. Petroleum as fuel Beř, J. M. Jacques, Malcolm T. Farmayan, W. F. Control of NOx by combustion process modifications |
| title | Control of NOx by combustion process modifications |
| title_full | Control of NOx by combustion process modifications |
| title_fullStr | Control of NOx by combustion process modifications |
| title_full_unstemmed | Control of NOx by combustion process modifications |
| title_short | Control of NOx by combustion process modifications |
| title_sort | control of nox by combustion process modifications |
| topic | Nitrogen oxides. Combustion engineering. Petroleum as fuel |
| url | http://hdl.handle.net/1721.1/60488 |
| work_keys_str_mv | AT berjm controlofnoxbycombustionprocessmodifications AT jacquesmalcolmt controlofnoxbycombustionprocessmodifications AT farmayanwf controlofnoxbycombustionprocessmodifications |