Experimental and theoretical studies of environmental aspects of natural gas combustion

摘要

The thesis deals with natural gas combustion covering three subjects. The subjects cover structure and emissions of oxides of nitrogen, development and characterization of gas burners, and emission characteristics of gas turbines. Work included a comprehensive programme on emissions of oxides of nitrogen (NO(sub x)), from pure diffusion flames, partially premixed flames and gas/oil diffusion flames. These experimental results are new in the literature. The results are used to verify and develop scaling laws for the emission index from jet flames. These are based on the fundamental structure of these flames. They are unique as the make it possible to estimate pollutant emissions of NO(sub x) from large offshore flames from simple main flow parameters. The results can be, and are used for this purpose in the offshore industry. Expressions for flame height and liftoff are also developed that can be used for calculting flame sizes and impacts on safety for design of burner systems. Four different burner concepts are addressed. The reduction of emissions of NO(sub x) was the prime target for developing these new burners. Two diffusion flame and two premixed flame burners are evaluated and a reduction in NO(sub x) of 70-80% is achieved for these burners with levels of NO(sub x) below 20 ppmvd at 3%O(sub 2) being reported. Internal flue gas recirculation and staging of air gave the best results in this study. There is a coupling between the pure diffusion flame characteristics and the diffusion flame burners. A useful correlation of NO(sub x) emissions from gas fired turbines is developed from field measurements of emissions offshore. This correlation and the results prove to be useful for the evaluation of the pollutant impacts of gas turbines in Norway. 158 refs., 94 figs., 28 tabs.