Estimation of methane partial oxidation reciprocal flow filtration combustion reactor performance in the case of its scale up (flow rates G = 4, 40, 400 and 4000 Nm(3)/h) as well as parametric study of the bigger scale reactor is performed numerically. It is shown that residence time growth with reactor scale up is compensated with maximum temperature decrease. Reduced aspect ratio reactors are considered for higher productivity systems. Parametric study performed for G = 400 Nm(3)/h reduced aspect ratio reactor show: Phi = 2.7 equivalence ratio is optimal to maximize conversion ratio and H-2 output concentration; smaller porous media particle d(0) = 2-3 mm should be used for lower specific mass flow rates G(m) = 0.5-1 kg/m(2)/s and bigger particles - for higher G(m); porosity variation m = 0.4-0.55 does not influence conversion ratio; kaowool insulation layer increase from 3 to 10 cm results in similar to 1% growth of conversion ratio while further increase up to 50 cm provides less than 0.5% gain. The results may be utilized for bigger scale reactors design, optimization and exploitation. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.