Experimental Study on Catalytic Combustion of Methane in a Microcombustor with Metal Foam Monolithic Catalyst

Utilizing catalysts in microcombustors is probably an excellent practical solution to stabilize fuel combustion because of the relatively fast reaction speed. In the present work, the monolithic catalyst Pd/A2O3/Fe-Ni with metal foam as matrix was used inside a 5 mm in diameter microcombustor. Then the effects of inlet velocity and equivalent ratio on catalytic combustion characteristics of methane were studied experimentally. The results showed that the methane and air mixture with the stoichiometric ratio Φ = 1.0 could be ignited at v = 0.2–0.6 m/s. The velocity of premixed mixture had a great influence on the catalytic combustion of methane. The larger the inlet velocity, the higher the temperature and the brighter the flame were. The experiment results also showed that the equivalence ratio had a large essential impact on the catalytic combustion, especially for the lean mixture of methane and air. It seemed the addition of the porous matrix with catalysts could significantly extend the limits of stable combustion. In the detection of exhaust gas, CO selectivity increased and CO2 selectivity decreased with the equivalence ratio. When Φ was between 0.94 and 1.0 m/s, a little amount of hydrogen was produced due to the lack of oxygen. The measured conversion of methane to CO and CO2 was very high, usually greater than 99%, which indicated the excellent performance of the catalyst.