Methane combustion over low-emission catalytic foam burners

Fully pre-mixed porous burners, in which methane combustion takes place clo se to the burner surface are stimulating an increasing interest since they allow lower fame temperatures and NO, emissions, due to rapid heat removal, thanks to either radiative or convective transfer mechanisms. The present investigation enlightens the further advantages obtainable via the depositi on of suitable catalysts onto a porous burner. An industrial ceramic foam s upport was considered for this purpose: two foam supports were deposited wi th the LaMnO3-perovskite catalyst, according to two different techniques bo th based on in situ pyrolysis. For one support (the surface-catalysed burne r) the catalyst was deposited, as a thin layer (about 1 mm deep); onto the outlet burner surface (burner-deck), the region where most of the combustio n is expected to take place. For the other one (the fully-catalysed burner) , the catalyst was deposited within the entire foam matrix. The two catalyt ic burners and a reference non-catalytic one were comparatively tested in a pilot plant (maximum power of about 30 kW corresponding to about 1600 kW/m (2)). All three burners showed excellent NO, (<70 ppmv for excesses of air >20%) and HC emissions (<10 ppmv). Conversely, the CO produced at low super ficial power (<300 kW/m(2)?) and excess air (<10%) values was much higher f or the non-catalysed burner than for the catalytic ones. Furthermore, the c atalyst entailed another positive effect: at the lowest superficial power ( 190 kW/m(2)) it stabilised the combustion towards lower excesses of air; to the benefit of higher thermal efficiency, (C) 2000 Elsevier Science B.V. A ll rights reserved.