Investigations on a new internally-heated tubular packed-bed methanol–steam reformer

Abstract

Small-scale reformers for hydrogen production through steam reforming of methanol can provide an alternative solution to the demand of continuous supply of hydrogen gas for the operation of Proton Exchange Membrane Fuel Cells (PEMFCs). A packed-bed type reformer is one of the potential designs for such purpose. An externally heated reformer has issues of adverse lower temperature in the core of the reformer and significant heat loss to the environment thus impacting its performance. Experimental and numerical studies on a new concept of internally heated tubular packed-bed methanol–steam reformer have been reported in this paper with improved performance in terms of higher methanol conversion and reduced heat losses to surroundings. CuO/ZnO/Al2O3 is used as the catalyst for the methanol–steam reforming reaction and a rod-type electric heater at the center of the reactor is used for supplying necessary heat for endothermic steam reforming reaction. The vaporizer and the reformer unit with a constant volume catalyst bed are integrated in the annular section of a tubular reformer unit. The performance of the reformer was investigated at various operating conditions like feed rate of water-methanol mixture, mass of the catalyst and reforming temperature. The experimental and numerical results show that the methanol conversion and CO concentration increase with internal heating for a wide range of operating conditions. The developed reformer unit generates 50–80 W (based on lower heating value) of hydrogen gas for applications in PEMFCs. For optimized design and operating conditions, the reformer unit produced 298 sccm reformed gas containing 70% H2, 27% CO2 and 3% CO at 200–240 °C which can produce a power output of 25–32 W assuming 60% fuel cell efficiency and 80% of hydrogen utilization in a PEMFC.