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Show JJa- H Low Emissions Boiler Shaped Flame Chemistry ROBERT L. VOGT Peabody Engineering Corporation Shelton, Connecticut, 06484-4676 U SA 203 259 1890, fax 203 259 1012 RVogtPE@aol.com INTRODUCTION Temperature peaks minimized about a desirably low mean, impose significantly advantageous limitations on the predominant reaction mechanisms in boiler burner hydrocarbon flames. Three conditions taken together enable environmentally beneficial low emissions of the major combustion derived pollutants; gentle diffusion of the oxidant into the reactant, immediately highly non-adiabatic reaction mechanisms, and high inert diluent content oxidant. Burner and flame technological advances n ow enable lower levels of all regulated pollutants, simultaneously, than ever before. Progress worldwide in legislating cleaner air has provided the impetus to utilize cutting edge technology to guarantee ever lower NOx, C O , VOCs, P M , PM10, P M 2 5 and other compounds leaving boiler stacks, including ozone and other species which are primarily formed downstream of the stack. Much of the performance uncertainty associated with emissions compliance is borne by the equipment manufacturers, particularly burner manufacturers. Improvements in boiler maintenance including minimization of tramp air and careful attention to steam plant operations will be ever more valuable in managing the cost of steam for the life of the plants. Increased overall system complexity will likely add to emissions performance risks as a result of Maximum Achievable Control Technology (MACT) and other Federal regulations promulgated during 1997 and 1998 in the U S A [1]. Meeting the emissions required by new environmental permits, which will likely be approved by the regulatory authorities only with lower emissions limits than ever before, will not only increase complexity in the burner system but also in the downstream systems. S C R and reburn technologies Copyright © 1998 by the author. All rights reserved. Presented to the American/Japanese Flame Research Committees International Symposium, October 11-15, 1998, Maui, Hawaii, USA. may be required, even with multi-fuel burners producing lower emissions than possible only a few years ago. Fuel switching, to higher cost, lower nitrogen and ash content fuels will, in some instances, become more economical than operating N H 3 consuming SCR, or other post treatment systems, near the tail end of the flue gas stream. Greater reliance on precision flame fit low emissions burners, and precision flame fit high efficiency C H 4 based rebum flames appears likely. Commercial and technological risks need to be carefully managed in order to realize the full potential of environmental benefits. Before the 1970s, steam boiler burner emissions compliance was technically low risk business. The burner's task was comparatively simple. It had to produce a stack opacity that was only faintly visible while maintaining a stable flame through a moderate turndown range. The burner manufacturer had to satisfy these minimum criteria, anyway, irrespective of emissions, in order to have a practical product that had good combustion efficiency and stayed clean for a reasonable operating time. There was no question as to who guaranteed the emissions. It was the burner manufacturer. By the 1980s, steam boiler emissions were the subject of thousands of pages of federal codes [2]. 40CFR60 added regulation of sulfur dioxide, nitrogen oxides, and total particulate matter to the list of emissions; opacity, carbon monoxide, and unbumed hydrocarbons which were being guaranteed. Stability was not to be compromised in the pursuit of reduced emissions. Moreover, the turndown range was broadening. With the exception of sulfur emissions, the burner manufacturer, more by default than desire, became the guarantor of the entire list. Today, the list of regulated airborne toxic substances has grown to 188 in the U S A [3]. All of the previously regulated substances are included. Some of them are regulated more stringently than ever while additional substances have been added that increase the technical difficulty, because reducing these additional |