No abstract

In this work, a reliable kinetic reaction mechanism was revised to accurately reproduce the detailed reaction paths of steam reforming of methane over a Ni/Al2O3 catalyst. A steady-state fixed-bed reactor experiment and a 1D reactor catalyst model were utilized for this task. The distinctive feature of this experiment is the possibility to measure the axially resolved temperature profile of the catalyst bed, which makes the reaction kinetics inside the reactor visible. This allows for understanding the actual influence of the reaction kinetics on the system; while pure gas concentration measurements at the catalytic reactor outlet show near-equilibrium conditions, the inhere presented temperature profile shows that it is insufficient to base a reaction mechanism development on close equilibrium data. The new experimental data allow for achieving much higher quality in the modeling efforts. Additionally, by carefully controlling the available active surface via dilution in the experiment, it was possible to slow down the catalyst conversion rate, which helped during the adjustment of the reaction kinetics. To assess the accuracy of the revised mechanism, a monolith experiment from the literature was simulated. The results show that the fitted reaction mechanism was able to accurately predict the experimental outcomes for various inlet mass flows, temperatures, and steam-to-carbon ratios.

Municipal solid waste is a pool of various solid wastes by towns and cities from different types of household activities. All over the world, municipal solid wastes are dumped in permitted landfills. Landfill gas is a mixture of methane and carbon dioxide which is emitted from the dumping sites of municipal wastes. Methane is a flammable toxic greenhouse gas more damaging to the climate than carbon dioxide. Instead of discharging into the atmosphere and becoming a greenhouse gas which is harmful to the environment, methane can be collected in every landfill and used to produce useful energy. This paper outlines the basic procedure for estimation of methane from landfill site. The Landfill Gas Emissions Model (Landgem) is an automated estimation tool with a Microsoft Excel interface which is available from the EPA's Clean Air Technology Center. It can be used to estimate emissions rate of methane from municipal solid waste landfills. Based on the methane emission rate obtained from Landgem output and the heating value of methane, the net heat input available and hence the potential for generation of electric power can be computed. A typical case study on the evaluation of methane emission rate from a landfill site at Namibia and its potential for generation of electric power as well as the cost estimates are presented. It is found that the power plant would be able to provide 142 streetlights in the city with electrical energy every day.