Low volatile coals will play a large role in meeting growing needs for electricity in the 21st century and are utilized in an increasing number of countries.Besides this low volatile coals have more abundant reserves than other coals.The combustion behavior of low volatile coals differs distinctly from standard bituminous coals.To use this fuel successfully in boilers built for fuels with a higher volatile content certain measures are needed to improve ignition,flame stability and char burnout.Furthermore improved measures have to be developed to keep the Nox emission limits.At the University of Stuttgart,the combustion behavior and the Nox-reduction efficiency of in-furnace DeNOx technologies are investigated at an electrically heated bench-scale entrained flow reactor which provides the possibility of evaluating the effect of different parameters independently.At this electrically heated bench-scale test facility a large variety of coals,bituminous and low volatile,from Europe,South Africa,North America,South America,Australia and Asia,have been examined during the last few years.For these coals the investigated parameters have been combustion temperature,stoichiometry in the fuel rich primary zone for air and fuel staging,residence time and combustion air temperature.A comprehensive data set is obtained for a number of coals of different types (volatile matter,nitrogen content,fuel-ratio,etc.) with the main focus on Nox emissions,combustion behavior and burnout.For all coals in-flame measurements for char (N and C content) and flue gas (NO,Nox,HCN,NH3,CO,O2,CO2) have been carried out to examine the release and conversion of nitrogen and carbon of the char during the combustion.
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