| OCR Text |
Show SECTION 1.0 INTRODUCTION There is continuing regulatory pressure to reduce emissions of oxides of nitrogen (NOx) from combustion processes. Requirements for NOx reduction from existing sources have been exerted primarily on utilitiy boilers since they axe a major emission source, are relatively large individual sources, and are semi-public or public utilities already heavily regulated but in a noncompetitive market. New mobile sources have been regulated for several years with allowable emissions decreasing with time. Industrial stationary sources have received less attention but new rules are requiring minimum emissions for new sources, emission tradeoffs for construction or expansion, and, to an increasing extent, emission reductions on existing sources. NOx is a product of reactions of nitrogen and oxygen in the high temperature flame zone of a combustion device. There are two basic approaches to reducing NOx emissions. First, NOx formation rates can be reduced by modifying the combustion process in various ways. This approach is generally termed combustion modification and it has been widely utilized for NOx control. Second, after NOx is formed in the combustion process, the flue gas can be treated to remove NOx from the mixture. This approach is generally termed flue gas treatment or post-flame treatment, and it has been utilized in Japan but it is just now being introduced to United States usage. The purpose of this paper is to review the methods available for NOx reduction and'provide some general information and guidelines on applicability, development status, and relative cost. This information is not intended to apply directly to any specific installation but rather to provide industry facing NOx reduction requirements with some guidelines and judgement about alternative approaches and their values. 4-1 P-233 |
