(113f) Non-Catalytic Multi-Fuel Reformer for Syngas Production for Fuel Cell Applications

Recently, a two-layer porous burner has demonstrated the capability of producing hydrogen-rich gas from heavy liquid fuels in a steady rich flame [1] based on a patented device developed in Cambridge University for gaseous and light liquid fuels [2]. In this paper, heavy liquid fuel reforming to syngas is presented over a wider range of conditions, configurations and fuels. Previous works on the thermal (non-catalytic) partial oxidation of fossil fuels include filtration wave, parallel channel, spouted bed combustor and two-layer porous burner concepts [3?7]. The novelty of this work consists of the stabilization of steady rich pre-vapourised heavy liquid fuels inside a two layer porous inert matrix at different equivalence ratios and thermal powers (defined as the fuel mass flow rate times its lower heating value). This work is based on the principle of superadiabatic combustion. The superadiabatic effect consists in the local occurrence of higher flame temperatures compared to the adiabatic temperature through the sensible enthalpy recirculation from the flame to the preheat zone by means of radiation and conduction heat transfer mechanisms occurring in the inert porous matrix. In the experiments described here, the liquid fuel/air flame is stabilised between a flame trap porous layer and a large pore ceramic foam layer, where the actual reforming process takes place. The atomization and mixing of the fuel is carried out through a commercial air-assisted nozzle, whereas the vaporization is achieved by preheating the oxidizing air. The mixture is then ignited at the interface by four spark-plugs and the reaction zone quickly extends inside the porous matrix. The products of the partial oxidation are sampled by a water-cooled probe and analyzed using a Gas Chromatograph calibrated for permanent gases and light hydrocarbons. The syngas composition has been investigated for various equivalence ratios. The experimental results have also been compared to the equilibrium mole fractions calculated at the adiabatic flame temperature by means of the CEA NASA code. Different configurations of the reactor have been tested and different fuels (n-heptane, diesel, biodiesel and Jet A-1) have been reformed in syngas. Fig. 1 reports the syngas molar fraction trend of Diesel and Biodiesel reforming against the equivalence ratio. Particulate formation has been investigated to assess the soot beahaviour for each fuel. Finally, few tests have been performed with a steam reforming commercial catalyst (Sud-chëmie G90-EW) driven by the heat and water provided by the upstream partial oxidation in order to reduce the light hydrocarbon presence in the off gas and increase the hydrogen molar fraction. The present work demonstrates the ability of the designed burner in reforming different heavy liquid fuels in a hydrogen-rich gas ready for a CO clean up stage for fuel cell applications in a robust and practical device. The best performance in terms of conversion efficiency (over 60%) and soot formation occur around an equivalence ratio of 2. [1] A. Pastore, E. Mastorakos, Rich n-heptane and diesel combustion in porous media, Exp. Thermal Fluid Sci. 2009, in press. [2] H. Pedersen-Mjaanes, L. Chan, E. Mastorakos, Hydrogen production from rich combustion in porous media, Int. J. Hyd. Engy. 30 (2005) 579-92. [3] M. K. Drayton, A. V. Saveliev , L. A. Kennedy, A. A. Fridman, Y. Li. Syngas production using superadiabatic combustion of ultra-rich methane-air mixtures, Proc. Comb. Inst. (1998) 1361?7. [4] I. Schoegl, S.R. Newcomb, J.L. Ellzey, Ultra-rich combustion in parallel channels to produce hydrogen-rich syngas from propane, Int. J. Hyd. Engy. 34 (2009) 5152-63. [5] Z. Al-Hamamrea, S. Voß, D. Trimis, Hydrogen production by thermal partial oxidation of hydrocarbon fuels in porous media based reformer, Int. J. Hyd. Engy. 34 (2009) 827-32. [6] F.J. Weinberg , T.G. Bartleet, F.B. Carleton, P. Rimbotti, Partial oxidation of fuel-rich mixtures in a spouted bed combustor. Combust. Flame (1988) 235?9. [7] D. Trimis, F. Durst, Combustion in a Porous Medium-Advances and Applications, Combust. Sci. Technol. 121 (1996) 153-68.