The report gives Phase II results of a combined experimental/theoretical study to define the mechanisms and kinetics of the formation of NOx and other combustion pollutants. Two experimental devices were used in Phase II. A special flat-flame burner with a controlled-temperature post-flame zone was used to investigate combustion modification techniques used to control NOx emissions: staged combustion, water addition, exhaust gas recirculation, and degree of air preheat. Augmenting the Phase I (unmodified) combustion testing, a novel flow reactor--the adiabatic stirred combustor (ASC)--was built for use in Phase II. The ASC had two distinct zones: a stirred reactor zone, followed by a plug flow zone. Each zone incorporated special provisions to eliminate heat loss from the combustion process. This new device allowed kinetic studies unhindered by mixing or heat transfer limitations. ASC test results were compared with detailed kinetics calculations using a prescreened set of reactions from an evaluation of all possible uni- and bi-molecular reactions for species of importance to methane/air combustion. In contrast to previous comparisons, good matches were obtained for the methane/air system over the entire stoichiometry range. The comparisons showed strong interaction between hydro-carbon species and molecular nitrogen near stoichiometric and fuel-rich conditions.

Prepared by Exxon Research and Engineering Company, Linden, N.J., under contract no. 68-02-0224, ROAP no. 21BCC-013, program element no. 1AB014. Includes appendices.

Phase I. Unmodified combustion.--Phase II. Modified combustion.