Study of Ammonia Formation During The Autothermal Reforming of Hydrocarbon Based Fuels
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Study of Ammonia Formation During The Autothermal Reforming of Hydrocarbon Based Fuels A.R. Khan, James Zhao, and O. Y. Polevaya Nuvera Fuel Cells Acorn Park Cambridge, MA 02140, USA ABSTRACT Ammonia formation in autothermal reforming process was studied in Nuvera’s Modular Pressurized Flow Reactor facility. Experiments were conducted to study and compare different catalysts for their ammonia formation characteristics. Different hydrocarbon fuels were reformed and effects of fuel structure and operating conditions on ammonia formation were investigated. Reformate generated was analyzed for ammonia contamination by using FTIR spectroscopy.
INTRODUCTION AND BACKGROUND Recently PEM fuel cell based power systems have gained a lot of focus and attention for their application in stationary and transportation markets. These systems include a reformer that converts hydrocarbon fuel to a hydrogen rich stream of gas. This stream is then fed to a fuel cell that generates electric power. Auto-thermal reforming (ATR) is a widely practiced and accepted process for extracting hydrogen from hydrocarbon based fuels. This type of reforming has been extensively studied in Nuvera Fuel Cells for a variety of fuels including Gasoline [1], Methanol, Ethanol, FT Naphtha , and Bio diesel. Previous studies [2] were mainly focused on the parametric study for syngas production and efficiencies as a function of reforming conditions. For durable fuel cell operation quality of reformate is an important factor, as the reforming process also produces some unwanted trace species (CO, H2S, NH3, HC) that are considered to be poisons for PEM fuel cells. The presence of these contaminants in reformate can adversely effect their performance and functioning. Ammonia is proven to be a fuel cell contaminant and is formed by dissociation of air or fuel based nitrogen in the reforming process. Uribe [3] studied effects of ammonia on PEM fuel cell performance. It was concluded from this study that trace levels of ammonia irreversibly damages the fuel cell over time. These contaminants can be removed from reformate by adding cleanup stages to the process. Depending on the number of contaminants, levels and capacity of clean up material used, these stages can occupy an appreciable volume of the total system and impose pressure drops that penalize efficiencies. Such beds also add another step toward the complexity of the process. Other than the downstream cleanup of such species, catalyst selection could be one way to reduce or eliminate the formation of these contaminants. This study was focused in particular to reduce ammonia formation in auto thermal reformers by choosing the right catalyst and optimizing the process conditions for reforming. The fuels studied included: gasoline, ethanol and natural gas. Ammonia formation characteristic of conventional nickel based catalyst was compared to a precious metal based catalyst.
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EXPERIMENTAL SETUP Figure 1 shows the schematic of the auto-thermal reforming (ATR) process setup used in the current t
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