Catalytic combustion of low heating value (LHV) fuels from gasification of biomasses has attracted attention in recent years in order to reduce net CO2 emissions in the atmosphere. A European project, ULECAT, has been undertaken to investigate this matter along with combustion of diesel fuel since 1996. This paper describes part of the work performed in the mathematical modelling task of this project in connection with the analysis of atmospheric pilot scale experiments. Simulation results obtained with a single channel 2D model of the monolith catalyst are presented and compared with experimental results obtained in an atmospheric pilot scale facility. From this analysis a quantitative description of the role of the different governing phenomena in determining the combustor performance is derived and discussed to provide insight into the catalyst behaviour under severe conditions. The most critical parameters in the simulations are also identified and discussed. (C) 2000 Elsevier Science B.V. All rights reserved.