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Show INTRODUCTION Within this paper and presentation, information will be presented on the technology & applications experience of the Exxon THERMAL DENOx Process. Specifically, details are given for two circulating fluidized bed boilers which have been operating for more than 2 years while achieving between 65% and 75% NOx reduction for wood and coal fuels. Since no catalyst is necessary to assist in the reduction of Nitrogen Oxide in the flue gas with Ammonia, the THERMAL DENOX Process is classified as a Selective Non-Catalytic Reduction (SNCR) post-combustion NOx control technology. Over 125 commercial installations of the Exxon THERMAL DENOx Process have been designed, installed and operated since 1975. Recent developments of interest include operation with aqueous ammonia as well as anhydrous ammonia. THE THERMAL DENOX PROCESS The THERMAL DENOx process is a selective non-catalytic process for the reduction of NOx emissions from stationary combustion sources. The process was patented by Exxon Research and Engineering Company in the mid 1970s, and has been finding applications ever since 1975. The THERMAL DENOx Process is based on a gas phase, homogeneous reaction between NOx and ammonia which produces nitrogen and water. While operating the process, aqueous or anhydrous ammonia is vaporized and injected with a carrier gas, either low pressure steam or compressed air, into the fluegas through nozzles mounted in the walls at a location selected for optimum reaction temperature and residence time. The optimum temperature for NH3 injection is between 1600°F and 2000°F, but, with the injection of Hydrogen along with the NH3 and carrier, the optimum temperature can be shifted to as low as 1300°F. The injection of NH3 into the flue gas results in numerous intermediate chain branching reactions which can be summarized by the two simplified reaction path equations Summarized as: NO + NH3 + 02 ==> N2 + H20 (Desired DENOx Reaction) NH3 + 02 ==> NO + H20 (Undesired Reaction) Please note that the THERMAL DENOx process has no measurable effect on CO, C02, and SOx emissions. |