A Non-Catalytic Fuel-Flexible Reformer

摘要

A compact, non-catalytic, thermal partial oxidation fuel reformer was developed based on the Swiss-roll heat-recirculating combustor concept with the reforming reactions take place at elevated temperature in the centrally-located combustion chamber of a spiral heat exchanger. In this reformer, the reactants (hydrocarbon fuel and air) are preheated by the partial oxidation products of combustion resulting in a reaction temperature that is higher than the adiabatic flame temperature which accelerates chemical reaction rates and leads to partial oxidation product compositions approaching the chemical equilibrium state, yielding high H_2 and CO (syngas) concentrations without requiring an external heat source. No catalyst is needed, thus eliminating undesirable issues associated with catalytic based reformers including sulfur poisoning and carbon deposition. In addition, the Swiss-roll combustor is compact and thermally efficient due to the high effectiveness of the spiral heat exchanger. Using a 6-turn Swiss-roll reformer (5 cm tall, 8 cm overall diameter) and a rich propane-air premixed feedstock with equivalence ratio = 3, experiments showed that more than 75% of input chemical enthalpy remains in the reformate (18% H_2 and 18% CO). Consequently, of the total input chemical enthalpy of 2400 W, only about 600 W is released as thermal enthalpy during partial oxidation to self-sustain the reaction. The effect of fuel-to-air ratio was studied to evaluate its effect on the H_2 and CO yields. Fuel flexibility was tested using different fuels (propane, n-heptane and JP-8); at the same equivalence ratio and flow rate, similar results were obtained for all three fuels. No visible soot formation was observed in the flame/flare at the exit from the reformer when reforming propane or n-heptane. Current work aims to optimize the reformate product for portable solid oxide fuel cell generators.