Experimental and numerical analysis of turbulent premixed combustion of low calorific value coal gases in a generated premixed burner

摘要

This study describes experimental and numerical studies of low-calorific value coal gas combustion under turbulent premixed combustion conditions. Any conventional natural gas burner is not convenient to burn a low calorific value coal gas efficiently and properly. Therefore, a newly generated premixed burner that can burn a low calorific value coal gas has been designed and manufactured in the present study. This burner has also got a hydrogen pipe (as non-premixed) by which hydrogen can be supplied into the flame zone in order to enhance the combustion performances of the low-calorific value coal gases. In the numerical part of this study, the generator gas has been modelled numerically by a computational fluid dynamics code. The predicted temperature distributions of the generator gas have been compared with the experimental data. According to the comparison, it can be said that the predicted temperature profiles are satisfactorily in good agreement with the experimental data in terms of trends and values. In the experimental part of the present study, the blast-furnace gas flame was not observed without hydrogen supply during the experiments as it includes few combustible gases excluding carbon monoxide. However, the maximum flame temperature of the generator gas was measured as of 1220.1 K without hydrogen supply. It has also been concluded that the flame temperatures of the low calorific value syngases were enhanced as the hydrogen was supplied from the center of the newly generated burner into the flame zone. In addition to the temperature measurements, emissions such as nitrogen oxide, carbon monoxide and carbon dioxide were also examined by a gas analyzer inside the combustor. The results show that the nitrogen oxide emission levels increase as the hydrogen is supplied into the flame region because of thermal nitrogen oxide mechanism. It may also be concluded that carbon dioxide levels ascend as hydrogen is supplied because of water gas shift reaction. It can be eventually concluded that the newly generated burner provides more stable flame and hydrogen addition improves the combustion performances of the low calorific value coal gases under premixed combustion conditions.