Fuel processor with vanadium alloy membranes for converting CH_4 into ultrapure hydrogen to generate electricity via fuel cell

摘要

Membrane technologies allow for significant simplification of the scheme of hydrocarbon conversion for obtaining ultrapure hydrogen to feed low-temperature fuel cells. However, commercially available membranes for hydrogen extraction utilize Pd alloys and therefore are expensive even while being not very efficient. Recently developed membranes of vanadium alloys demonstrate high efficiency combined with high practical utility. These features, for the first time, allowed for design and manufacture of a fuel processor prototype based on non-palladium membranes. 18 tubular-shaped membranes of vanadium alloy, 6 mm in diameter and 23.5 cm in length, were welded in a completely leakproof membrane system. This membrane system was integrated into a classic CH4 steam conversion scheme, which comprised a reformer followed by a single-step water gas shift reactor. The reformer was designed to convert 75% of CH4 to hydrogen, with the rest providing heat required for the reaction. At CH4 consumption of 6 slpm, steam-to-carbon ratio of 3, and total pressure of water-gas shift mixture of 1.2 MPa, the membrane system was extracting 80% of produced hydrogen, and as a result the fuel processor was providing 12 slpm of ultrapure hydrogen at 0.15 MPa to feed a 1 kW polymer electrolyte membrane fuel cell. As part of the fuel processor, the membrane system kept its initial throughput and perfect tightness through all the experimental process.