Improved-performance knitted fibre mats as supports for pre-mixed natural gas catalytic combustion

As an improvement of previously developed catalytic burners based on LaMnO3 catalysts deposited on a FeCrAl alloy fibre mat (NIT100s by ACOTECH BV), new catalytic burners have been developed showing improved catalytic activity and sulphur resistance, a prevalent issue to be addressed owing to the presence of odorants (e.g. THT) in the natural gas distributed in the network. Such properties are entailed by adoption of new catalysts (LaMnO3 + 17MgO) developed on purpose, where the presence of MgO acts both as a structural promoter (reducing the average grain size of the perovskite catalyst by nearly one order of magnitude) and a sulphur-poisoning preventing agent (by selectively reacting with SO2 originated from the combustion of the odorant). The performance of the new catalytic burner is compared in this paper to those of the non-catalytic burner and the previously developed LaMnO3-catalysed burner in both fresh and aged status as a function of the prevalent parameters affecting the combustion regime (specific power input e, excess of air E-a). Particularly promising results are enlightened at low Q and E-a values (<250 kW m(-2) and 10%, respectively), where the non-catalytic burner and the aged LaMnO3-catalytic burner entail unacceptable high CO emissions (well exceeding 100 ppmv). A preliminary mono-dimensional modelling of the combustion in the porous burners including heat, mass and momentum balances in the combustion chamber and a pseudo-homogeneous approach to the description of the behaviour of the porous burner is presented. Model calculations obtained through ad hoc developed code (FASTEST) show just encouraging results that pave the way towards further improvements of the modelling tool. <(c)> 2001 Elsevier Science B.V. All rights reserved.