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Show -1- NOx REDUCTION TECHNIQUES FOR ROTARY KILNS by Dr. P.J. Mu11inger and Dr. B.G. Jenkins Fue1 and Combustion Techno1ogy Internationa1 Inc. ABSTRACT Rotary kilns operate at high temperatures, and therefore have high NOx emissions levels. Whilst, as a group of industrial furnaces they are not significant contributors to the total global NOx problem, these individual high levels obviously attract interest from regulatory authorities. The fundamentally different aerodynamics of rotary kiln flames, means that the techniques that have been developed for NOx control in power boilers and petrochemical operations cannot be applied to kilns. Recent CEMFLAM I trials at IFRF have provided the first comprehensive data sets on NOx generation in kiln type flames. This paper uses that data to compare its applicability to a number of commercially operating kilns and discusses the options for NOx reduction which those trials have highlighted. 1. INTRODUCTION Although rotary kilns are not a major contributor to the overall global NOx emissions compared with automobiles and electricity generation, the actual concentration of NOx emitted by an individual kiln is relatively high. As a result, kiln operators are coming under increasing pressure to reduce their NOx emissions. Rotary kilns operate at high temperatures and are amongst the highest temperature processes utilized by man. Most 6f the NOx formation in rotary kilns is therefore thermal NOx. For cement production, the NOx emissions can be dramatically reduced by using precalciner technology where a larger proportion of the fuel (up to 60%) is burnt at a much lower temperature and therefore forms little NOx. This option is only available for processes which can utilize ground powder as the feed. Precalciner technology is therefore not suitable for a dolomite kiln or kilns producing lime for the steel industry. Extensive research and development has been undertaken on NOx formation in power boilers and petrochemical heaters owing to their importance as NOx sources, and low NOx burners and other NOx reduction techniques are now commercially available. However, |