| dc.description.abstract | The scarcity of fossil fuels and the problems of air pollution draw researchers to search more efficient and clearer energy sources. Syngas/hydrogen may become a vital energy for sustained power consumption with reduced impact on the environment. It can be used in engines or fuel cells with minimal emissions of pollutant gases. But certain problems such as syngas/hydrogen storage and infrastructure.exist for vehicles and fuel cells application The conversion of hydrocarbon to hydrogen is a potential source of hydrogen production and supply to fuel cell and hybrid vehicles. Therefore, a reformer designing to generate syngas on board with the characters of energy-saving, compactness, fast start-up and rapid response is particularly important and essential. This study demonstrates methane and ethanol reforming technologies as well as their possible applications. There are three parts in this study, i.e. methane reforming, ethanol reforming and operating strategy for motorcycle.
The first part demonstrates an economic reforming process that combines arc plasma with catalyst in series for hydrogen production. Hydrogen was generated by means of partial oxidation of methane. Granular Ni catalysts were packed in the post plasma zone. No extra-energy was needed to sustain the temperature of catalyst bed; the elevated temperature was maintained both by the hot gases from plasma region and by the heat of reforming reaction itself. A promising energy efficiency of 1.21 MJ/kg-H2, being together with high hydrogen yield (89.9%) and high methane conversion (90.2%), was experimentally achieved. The energy efficiency is estimated 20% higher compared with a gas turbine system with methane as the fuel. In addition, thermodynamic analysis for partial oxidation of methane was conducted. Experimental data agreed well with the thermodynamic results, indicating that high thermal efficiency can be achieved with the plasma-assisted catalysis process. Methane was also reformed by Pt catalyst in this study. Autothermal reaction was adopted and preheated reactants by recovering the waste heat of high temperature flue gas exhausted form SOFC. The concentration of combustible gas (H2 + CO, dry base) was as high as 80% in the reformate. Catalyst performance was very stable during the 1000-hr durability test.
The second part shows a commercial-scale ethanol reforming system, which converts ethanol into hydrogen-rich gases, via autothermal reaction mechanism. In this study, four kinds of noble metal catalyst were extensively investigated with the ethanol reforming system. Two of the four catalysts, Pt-Pd-Rh/?-Al2O3 and Rh/?-Al2O3-CeO2-ZrO2, had been conducted in a 26-day long-time test. The Pt-Pd-Rh/?-Al2O3 catalyst showed high catalytic activity and achieved an ethanol conversion of 97% in the early stage; but deactivated with reaction time and finally achieved a conversion of only 50% at 26th day. The Rh/?-Al2O3-CeO2-ZrO2 catalyst achieved and maintained high ethanol conversion for the first 14 days, then gradually decreased and achieved a conversion efficiency of 85% at 26th day.
In the last part, we designed a compact plasma-assisted catalysis (PAC) reformer as an onboard device for motorcycle. This PAC reformer was used to convert methane into a hydrogen-rich gas which then mixed with gasoline to fuel motorcycle engine. Performance of the PAC reformer for motorcycle operated in the cold start, low load and normal cruising periods were evaluated experimentally. In the cold start period, with the assistance of plasma the catalyst-bed temperature could rise from 25oC to > 500oC in 14 s. In the normal operation mode, the goal is to achieve either a high power output in the cruising mode or a low energy consumption in the idle mode. At 32.4 W power consumption of plasma, the total thermal power of reformates increased by 2% to 16% at given conditions. Idle engine test showed that the PAC reformer not only reduced CO and HC emission by 42% and 21%, respectively, but also enhanced the engine performance, e.g. the brake power increased by 14% and the gasoline consumption by 33%. This study confirmed that in the low load mode, the plasma can be turned off without sacrificing the PAC’s performance. In brief, the plasma plays a great role in the cold start, be minor in the cruising mode, and trivial in the low load mode.
This study has successfully developed a methane plasma-assisted catalysis reformer and a methane catalyst reformer for motrocycle engine and SOFC, respectively. They could improve the energy utility efficiency, CO2 emission and air quality if these reformer could be applied in the future. This is beneficial to the environment.
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