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Show INTRODUCTION One major factor delaying the important energy conservation step of major increases in coal usage for steam generation is that of considerably increased air pollution when compared with gaseous and liquid fossil fuels. This problem is continuously accentuated by increasingly stringent legislation. The oxides of nitrogen (NOx) are one such pollutant group which already is subject to control legislation in the United States, Japan and West Germany and shortly it is likely that NOx emission legislation will be enforced even wider in Western Europe. Consequently the IFRF has been undertaking investigations on behalf of the Dutch Government with the objective of characterising the NOx control method of "Staged Air Combustion" in terms of technique and success with a view to providing information with which: - practical low NOx pulverised coal burners may be designed and operated in the Netherlands - realistic pollution legislation may be formulated. This paper discusses work executed by the IFRF during the last eighteen months on the subject of staged air combustion control of NOx formation and emission as applied to pulverised coal firing. The work entailed two combustion trials, namely AP 11 and AP 12, executed at a pilot scale of 2.5 MW and 0.18 MW total thermal input respectively, with a range of coal types being fired. Specifically the effect on NOx emissions, from staged and non-staged flames, of coal type, input and hardware features of the staged mixing burner were examined and results are presented herein. LOW NOx COMBUSTION PRINCIPLES NOx produced in pulverised coal flames originates from both nitrogen present in the combustion air and in the coal. The resultant emissions are classified as thermal and fuel NOx respectively. By using artificial oxidants such as Ar/02/C02, fuel NOx has been observed to account for 70 - 90% of the total NOx [ 1]. Fuel NOx - 3 - |