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Show lier work £5J at the IFRF has demonstrated the difficulty in achieving this and yet maintaining the short intense flames required for horizontally opposed fired power station boilers which rely on intense mixing between the fuel and combustion air and tend to give high oxygen concentrations in the pyro-lysis zone. Thus, to overcome this situation, a solution is to split the combustion air flow, develop a fuel rich primary zone with good mixing using part of the combustion air and add the remainder of the combustion air separately to complete com-* bustion and maintain approximately the flame length. In the next stage of the development, a prototype burner was designed and constructed at reduced scale such that mixing control parameters (e.g. velocity and swirl of the secondary air; ratio of secondary and tertiary air mass flow rates etc), could be conveniently varied. This burner was employed in trials on the IFRF furnace nr. 1 £l3j fitted with water-cooling loops in order to obtain boundary conditions similar -to those of a full scale boiler. The furnace was fired at 2.3 MW using coal of a similar quality, dryness and fineness to that which would be used in the final demonstration trials. The object of the pilot scale trials was to optimize the burner operating variables in terms of NOx~emissions and flame length at nominal load and in turndown conditions. Examples of the results Ql3J of these trials are given in fig.8, in which NOx_emission in the exhaust is plotted against primary zone stoichioraetry. It may be seen that decreasing the primary zone air ratio', np, (i.e. increasing the degree of staging), decreased the NOx~emissions down to a minimum at which the flame became unacceptable. At turndown the emission levels were lower but otherwise followed a similar trend. The levels obtained were sufficiently low to warrent the development of a full scale burner (70 MWe) and twentyfour of these were fitted during the latter half of 1978 to a 700 MWe power station of Saarberg-werke (SBW) and certainly in the short term have been successful [ll] in reducing the NOx-emissions to an acceptable level with no deleterious side effects. Long term assessment is still in progress at the time of writing. POLICY FOR THE 19 80*3 The long term research objectives of the IFRF are reviewed regularly but particularly towards the end of the seventies, due to the rapidly changing world energy scene, the importance of a well-organized policy for the eighties became clear. To achieve this, in addition to the normal policy making routes described before, all members were directly involved through questionnaires. Thus, because of the international and multi-disciplinary £l3] R. PAYNE : nAa turreep orotf otnh e thIeF RFt,es tiitnsg deoffi ntihtei oSnt eiofn mutlhlee ri ndsutsa-ged mixing burner. IFRF Doc.nr. F 09/a/16 (1979) - 15 - |