Environmentally Friendly Techniques
- Low temperature oxidation of hydrogen off-gas from fuel cells by using atmospheric pulsed plasma.
Background ＆ Objectives
Modern transportation systems rely on petroleum as an energy source, which causes serious environmental problems. The emission of carbon dioxide gas also produces a greenhouse-gas effect causing a global warming of the earth. Fuel-cell operated vehicles (FCVs) are expected to reduce drastically emissions of carbon dioxide gas and environmental pollutants.
However, there are still problems concerning cost reduction in production, fuel storage in commercial-based situations, and treatment of off-gas from fuel cells. In order for fuel cells to operate efficiently, the off-gas, which has a hydrogen concentration of more than 90 vol%, has to be regularly purged into the atmosphere. This may lead to dangerous situations involving fires and explosions. Therefore the off-gas should be treated by an onboard facility.
The off-gas treatment with catalytic combustion was first patented in 1991. However, it should be noted that platinum is used as a catalyst in the combustion technology, which is not a cost-effective solution for the off-gas treatment. The off-gas treatment that use plasmas can be said to be safer and more cost-effective technology. The aim of the present research is to find an efficient way using a DBD plasma for hydrogen oxidation. First, the pulsed DBD plasma effects on oxidation characteristics of a H2/O2/N2 gas mixture were investigated. Second, a parametric survey was carried out to find an efficient treatment of hydrogen oxidation. Applied voltages, its repetition rates, and exhaust gas temperatures were varied. Third, a computational study using electron impact kinetics and gas phase reaction kinetics in H/O system was performed in order to be clear the effects of the parameters on hydrogen conversion rate.
Hydrogen oxidation by pulsed plasma at low temp. |
8.0L-H2/min was oxidized at 300W. |
Hydrogen oxidation mechanisms in plusma. |