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), n ew catalytic burners have been developed showing improved catalytic activit y and sulphur resistance, a prevalent issue to be addressed owing to the pr esence 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 ne arly one order of magnitude) and a sulphur-poisoning preventing agent (by s electively 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-catal ysed burner in both fresh and aged status as a function of the prevalent pa rameters 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 burne r and the aged LaMnO3-catalytic burner entail unacceptable high CO emission s (well exceeding 100 ppmv). A preliminary mono-dimensional modelling of the combustion in the porous bu rners including heat, mass and momentum balances in the combustion chamber and a pseudo-homogeneous approach to the description of the behaviour of th e porous burner is presented. Model calculations obtained through ad hoc de veloped code (FASTEST) show just encouraging results that pave the way towa rds further improvements of the modelling tool. <(c)> 2001 Elsevier Science B.V. All rights reserved.