| A steam-methanol membrane reformer was designed, constructed and evaluated. The intended application of the reformer is to supply hydrogen to a polymer electrolyte membrane fuel cell, as such, the hydrogen product stream must maintain a CO concentration less than 10 ppm. Additional design parameters include, a nominal hydrogen output of 300 We (3.7 SLPM), and a volume restriction of approximately 500 ml. With the exception of the integrated Pd-Ag hydrogen membrane purification unit, the construction of the unit was preformed in-house. The operating region was restricted to a maximum pressure of 13.8 bar and a maximum catalyst bed temperature of 300°C. The latter restriction is due to catalyst deactivation, while the former is due to the physical limitations of the membrane unit. The intent of the study is to experimentally confirm the advantages inherent to membrane reforming over a non integrated system including, a thermodynamic equilibrium advantage, a kinetic advantage and a reduction in size and volume. The study revealed that the reformer was membrane limited. The capacity of the membrane unit was such that only 130 We (1.6 SLPM) of permeate hydrogen could be produced. Furthermore, the development of pinholes in the membrane unit resulted in the contamination of the permeate. As a result of the membrane limitations the advantages of the membrane reformer were only partially realised. The advantages are most apparent when operating conditions promote hydrogen permeation and hydrogen recovery is high. The thermodynamic equilibrium advantage was observable in the gains of methanol conversion and total hydrogen production, particularly at low inlet feed rates. The kinetic advantage was only partially realised and was seen as a decrease in the rate of CO production due to the shift in the water-gas-shift equilibrium as hydrogen was removed. |
