Fuel processors for automotive fuel cell systems: a parametric analysis E. Danial Doss * , R. Kumar, R.K. Ahluwalia, M. Krumpelt Argonne National Laboratory, Argonne, IL 60439, USA Received 12 February 2001; accepted 12 March 2001 Abstract An autothermally-reformed, gasoline-fueled automotive polymer electrolyte fuel cell PEFC) system has been modeled and analyzed for the fuel processor and total system performance. The purpose of the study is to identify the in¯uence of various operating parameters on the system performance and to investigate related tradeoff scenarios. Results of steady-state analyses at the design rated power level are presented and discussed. The effects of the following parameters are included in the analysis: operating pressure 3 and 1 atm), reforming temperature 1000±1300 K), water-to-fuel and air-to-fuel reactant feed ratios, electrochemical fuel utilization, and thermal integration of the fuel processor and the fuel cell stack subsystems. The analyses are also used to evaluate the impact of those parameters on the concentrations of methane and carbon monoxide in the processed reformate. Both of these gases can be reduced to low levels with adequate water-to-carbon used in the fuel processor. Since these two species represent corresponding amounts of hydrogen that would not be available for electrochemical oxidation in the fuel cell stack, it is important to maintain them at low levels. Subject to the assumptions used in the analyses, particularly that of thermodynamic equilibrium, it was determined that reforming temperatures of 1100 K, a water-to- carbon mole ratio of 1.5±2.5, and the use of fuel cell exhaust energy in the fuel processor subsystem can yield fuel processor ef®ciencies of 82±84%, and total system ef®ciencies of 40±42% can be achieved. For the atmospheric pressure system, if the exhaust energy is not used in the fuel processor subsystem, the fuel processor ef®ciency would drop to 75±82% and the total system ef®ciency would drop below 40%. At higher reforming temperatures, say 1300 K, the fuel processor ef®ciency would decrease to 78%, and the total system ef®ciency would drop below 39%, even with the use of the fuel cell stack exhaust energy. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Fuel processing; Fuel cell systems; System modeling; System ef®ciency 1. Introduction Fuel cell systems are being developed for powering clean, ef®cient automobiles of the future. Several prototype fuel cell vehicles have been demonstrated that operate on hydro- gen or methanol as the on-board fuel. The polymer electro- lyte fuel cell PEFC) systems being developed for such use require a fuel gas that is either pure hydrogen, or a gas mixture that contains a signi®cant concentration of hydro- gen. Thus, the vehicles with methanol as the on-board fuel use a fuel processor, also referred to as a reformer, to convert the methanol to a fuel gas, reformate, that contains hydro- gen, carbon dioxide, water vapor, and nitrogen, with trace levels of other species, such as carbon monoxide and unconverted methanol. There is great interest, however, in developing fuel cell vehicles that can operate on the current transportation fuels, primarily gasoline and diesel fuels. Such vehicles would require a fuel processor for gasoline or diesel) to generate the hydrogen needed by the fuel cell. Several organizations and gasoline or diesel) to generate the hydrogen needed by the fuel cell. Several organizations and teams are developing gasoline fuel processors for automo- tive fuel cell systems [1±5]. Using a computer simulation of the fuel processor and the entire fuel cell system, we have analyzed the performance of a generic gasoline autothermal reformer ATR) for a variety of fuel processor and system designs and values of operating parameters. In an autothermal fuel processor, the fuel in this case gasoline, a blend of various hydrocarbons and speci®c additives), air, and water steam) are fed in controlled proportions to generate a reformate gas mixture. This refor- mate must be processed further to convert all the carbon monoxide to carbon dioxide, remove hydrogen sul®de pro- duced from the organic sulfur typically present in gasoline at 30±300 parts per million, by weight), cool and humidify to the desired fuel cell inlet conditions. Journal of Power Sources 102 2001) 1±15 * Corresponding author. Tel.: 1-630-252-5967; fax: 1-630-252-1774. E-mail address: doss@anl.gov E. Danial Doss). 0378-7753/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0378-775301)00784-4