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Show 4197299444 CORP. HQ 489 P03 MAR 17 '94 12:07 chemicals. It can also be employed for indirect heating applications. The technique is based on a novel burner which can produce very rich combustion products, especially with highly preheated combustion air. At hiQh temperatur~ any NOx that may have formed is reduced by the residual hydrogen contained in the combustion gases. This residual hydrogen and carbon monoxide is reacted to completion before leaving the furnace. This completion reaction is initiated at lower temperatures where formation of NOx is retarded. In this paper the theoretical background of the technique is discussed, the experimental facility used for demonstrating the concept is described, and major experimental results are given. Application of the new ultra low combustion technique to industrial processes is reviewed and its advantages are discussed. . Patent applications have been filed in an effort to protect the technology. INTRODUCTION Many techniques for reducing NOx during and after combustion of natural gas have been proposed. They can be divided into two major types: combustion modifications and flue gas treatment. For practical and economic reasons reduction of NOx during the combustion process itself has been the preferred method. It is recognized that high flame temperatures are the main cause for formation of high concentrations of NOx. As a result, high temperature processes in many primary industries are identified as major sources of NOx emissions. The use of energy saving techniques such as preheating combustion air contributes substantially to high flame temperatures and excessive formation of NOx. These adverse effects of preheated air on NOx emissions from high temperature processes severely limit the potential for saving energy for conservation efforts in many industries. During the past 10 years a number of combustion modification techniques have been proposed and used to reduce NOx by reducing flame temperatures. They include steam and water injection, external and internal flue gas recirculation, and staged combustion. These techniques seem to satisfy the need for relatively low temperature heating processes. As the process temperature increases it is not possible to maintain low enough flame temperatures to achieve acceptable levels of NOx. As a result, most combustion systems and equipment used for high , ' " \ ' |
