The combustion of rich mixtures of methane representing natural gas in air or oxygenated air, involving the uncatalyzed partial oxidation of methane is examined analytically. A detailed chemical kinetic scheme for the oxidation of methane, made up of 108 simultaneous reaction steps with 28 reactive species, was employed. The role of various operating parameters in establishing the yield of hydrogen is presented and discussed. The results are considered over the temperature range 800-2000 K, pressures up to 50 atm and equivalence ratios of up to 3.4. This analysis is carried out in turn for isothermal, constant pressure and constant volume combustion processes. An assessment of the effectiveness of the controlled recirculation of combustion and exhaust gases to the feed or the early stages of the reaction in enhancing the reaction and conversion rates of the methane into hydrogen was also made. There are optimum conditions which can be employed for such recirculation to yield a significant increase in the conversion rates.
