Methane Catalyst Regeneration with Hydrogen Addition

Increasing use of renewable energy places greater emphasis on peaking power production for times when renewable sources cannot meet total demand. Gas engines are a viable choice for peaking power plants. During combustion of natural or biogas, however, unburned fuel, especially methane, tends to remain in the exhaust gas. Pd-Pt/Al2O3 catalytic converters are proven to be the most efficient for methane conversion but they are easily poisoned by sulphur and water from the exhaust. A poisoned catalyst is inactive and its methane conversion is low. It might be possible to revive the catalyst by regeneration. According to the literature, hydrogen injection is one of the most effective regeneration methods. The aim of the present study was to find out whether hydrogen injection at three different temperatures enhances regeneration of a Pd-Pt/Al2O3 catalytic converter. The research was conducted in an engine laboratory and the exhaust gas was from a high-speed engine, modified to run with natural gas. The effect of the catalyst regeneration was measured by analyzing the methane conversion as well as SO2 concentrations downstream from the catalyst. Multiple H2 injection concentrations (1% to 2.5%) and periods (10 minutes to 1 hour) were used in the experiments. Results show the lowest exhaust temperature of 380 °C was insufficient for the catalyst to activate. In terms of methane conversion, the experiments at 500 °C were more successful, but no long-lasting effect was achieved by regeneration. In all experiments, sharp peaks of SO2 were registered in the exhaust gas immediately after the start of the regeneration. This indicates that H2 reacts in the catalyst and releases SO2. Further studies are required to improve the regeneration process and to evaluate the long-term effects of regeneration at high temperatures.