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Title: Effects of fuel cell anode recycle on catalytic fuel reforming

Abstract

The presence of steam in the reactant gas of a catalytic fuel reformer decreases the formation of carbon, minimizing catalyst deactivation. However, the operation of the reformer without supplemental water reduces the size, weight, cost, and overall complexity of the system. The work presented here examines experimentally two options for adding steam to the reformer inlet: (I) recycle of a simulated fuel cell anode exit gas (comprised of mainly CO2, H2O, and N2 and some H2 and CO) and (II) recycle of the reformate from the reformer exit back to the reformer inlet (mainly comprised of H2, CO, and N2 and some H2O and CO2). As expected, anode gas recycle reduced the carbon formation and increased the hydrogen concentration in the reformate. However, reformer recycle was not as effective due principally to the lower water content in the reformate compared to the anode gas. In fact, reformate recycle showed slightly increased carbon formation compared to no recycle. In an attempt to understand the effects of individual gases in these recycle streams (H2, CO, CO2, N2, and H2O), individual gas species were independently introduced to the reformer feed. Published by Elsevier B.V.

Authors:
; ; ; ;
Publication Date:
Research Org.:
National Energy Technology Lab. (NETL), Pittsburgh, PA, and Morgantown, WV (United States). In-house Research; National Energy Technology Lab. (NETL), Pittsburgh, PA, and Morgantown, WV (United States)
Sponsoring Org.:
USDOE Assistant Secretary for Fossil Energy (FE)
OSTI Identifier:
1013553
Report Number(s):
NETL-TPR-1704
Journal ID: ISSN 0378-7753
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Power Sources; Journal Volume: 168; Journal Issue: 2
Country of Publication:
United States
Language:
English
Subject:
29 ENERGY PLANNING, POLICY, AND ECONOMY; Solid oxide fuel cell, Anode recycle, Reformer recycle, Carbon formation, Auxiliary power unit, Diesel reforming

Citation Formats

shekhawat, D., Berry, D., Gardner, T., Haynes, D., and Spivey, J. Effects of fuel cell anode recycle on catalytic fuel reforming. United States: N. p., 2007. Web. doi:10.1016/j.jpowsour.2007.03.031.
shekhawat, D., Berry, D., Gardner, T., Haynes, D., & Spivey, J. Effects of fuel cell anode recycle on catalytic fuel reforming. United States. doi:10.1016/j.jpowsour.2007.03.031.
shekhawat, D., Berry, D., Gardner, T., Haynes, D., and Spivey, J. Mon . "Effects of fuel cell anode recycle on catalytic fuel reforming". United States. doi:10.1016/j.jpowsour.2007.03.031.
@article{osti_1013553,
title = {Effects of fuel cell anode recycle on catalytic fuel reforming},
author = {shekhawat, D. and Berry, D. and Gardner, T. and Haynes, D. and Spivey, J.},
abstractNote = {The presence of steam in the reactant gas of a catalytic fuel reformer decreases the formation of carbon, minimizing catalyst deactivation. However, the operation of the reformer without supplemental water reduces the size, weight, cost, and overall complexity of the system. The work presented here examines experimentally two options for adding steam to the reformer inlet: (I) recycle of a simulated fuel cell anode exit gas (comprised of mainly CO2, H2O, and N2 and some H2 and CO) and (II) recycle of the reformate from the reformer exit back to the reformer inlet (mainly comprised of H2, CO, and N2 and some H2O and CO2). As expected, anode gas recycle reduced the carbon formation and increased the hydrogen concentration in the reformate. However, reformer recycle was not as effective due principally to the lower water content in the reformate compared to the anode gas. In fact, reformate recycle showed slightly increased carbon formation compared to no recycle. In an attempt to understand the effects of individual gases in these recycle streams (H2, CO, CO2, N2, and H2O), individual gas species were independently introduced to the reformer feed. Published by Elsevier B.V.},
doi = {10.1016/j.jpowsour.2007.03.031},
journal = {Journal of Power Sources},
number = 2,
volume = 168,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The presence of steam in the reactant gas of a catalytic fuel reformer decreases the formation of carbon, minimizing catalyst deactivation. However, the operation of the reformer without supplemental water reduces the size, weight, cost, and overall complexity of the system. The work presented here examines experimentally two options for adding steam to the reformer inlet: (I) recycle of a simulated fuel cell anode exit gas (comprised of mainly CO2, H2O, and N2 and some H2 and CO) and (II) recycle of the reformate from the reformer exit back to the reformer inlet (mainly comprised of H2, CO, and N2more » and some H2O and CO2). As expected, anode gas recycle reduced the carbon formation and increased the hydrogen concentration in the reformate. However, reformer recycle was not as effective due principally to the lower water content in the reformate compared to the anode gas. In fact, reformate recycle showed slightly increased carbon formation compared to no recycle. In an attempt to understand the effects of individual gases in these recycle streams (H2, CO, CO2, N2, and H2O), individual gas species were independently introduced to the reformer feed.« less
  • Solid oxide fuel cells (SOFC) are currently being developed for a wide variety of applications because of their high efficiency at multiple power levels. Applications for SOFCs encompass a large range of power levels including 1-2 kW residential combined heat and power applications, 100-250 kW sized systems for distributed generation and grid extension, and MW-scale power plants utilizing coal. This paper reports on the development of a highly efficient, small-scale SOFC power system operating on methane. The system uses adiabatic steam reforming of methane and anode gas recirculation to achieve high net electrical efficiency. The anode exit gas is recirculatedmore » and all of the heat and water required for the endothermic reforming reaction are provided by the anode gas emerging from the SOFC stack. Although the single-pass fuel utilization is only about 55%, because of the anode gas recirculation the overall fuel utilization is up to 93%. The demonstrated system achieved gross power output of 1650 to 2150 watts with a maximum net LHV efficiency of 56.7% at 1720 watts. Overall system efficiency could be further improved to over 60% with use of properly sized blowers.« less
  • To give a better understanding of autothermal reforming (ATR), a process which offers an advantageous alternative to steam reforming for H/sub 2/ production for fuel cells because of the wider range of fuels which can be converted, the conversion of individual fuel components was studied. Attempts have been made to characterize the chemical reactions of light and heavy paraffins and aromatics in ATR. Results of studies to determine the effects of operating parameters on the carbon-forming tendency of each hydrocarbon type are reported. The catalyst used for the ATR process was three-layers of supported nickel catalysts, Norton NC-100 spheres inmore » the top zone, cylindrical G-56B tablets in the bottom one, and either ICI 46-I or ICI 46-4 Raschig rings in the middle zone. A summary of the experimental studies of the ATR of n-hexane, n-tetradecane, benzene, and benzene solutions of naphthalene is presented. (BLM)« less
  • Experimental results are presented for the autothermal reforming (ATR) of n-hexane, n-tetradecane, benzene and benzene solutions of naphthalene. The tests were run at atmospheric pressure and at moderately high reactant preheat temperatures in the 800-900 K range. Carbon formation lines were determined for paraffinic and aromatic liquids. Profiles were determined for axial bed temperature and composition. Space velocity efforts were assessed, and the locations and types of carbon were recorded. Significant reactive differences between hydrocarbons were identified. Carbon formation characteristics were hydrocarbon specific. The differing behavior of paraffinic and aromatic fuels with respect to their carbon formation may be importantmore » in explaining the narrow range of carbon-free operating conditions found in the ATR of number two fuel oil.« less
  • We present density-functional theory calculations of the chemisorption of atomic species O, S, C, H and reaction intermediates OH, SH, and CHn (n = 1, 2, and 3) on M/Ni alloy model catalysts (M= Bi, Mo, Fe, Co, and Cu). The activity of the Ni alloy catalysts for solid-oxide fuel cell (SOFC) anode oxidation reactions is predicted, based on a simple descriptor, i.e., the binding energy of oxygen. First, we find that the binding of undesirable intermediates, such as C and S, can be inhibited and the catalytic activity of planar Ni-based anodes can be tuned towards oxidation by selectivelymore » forming a bimetallic surface alloy. In particular, Cu/Ni, Fe/Ni, and Co/Ni anode catalysts are found to be most active towards anode oxidation. On the other hand, the Mo/Ni alloy surface is predicted to be the most effective catalyst in terms of inhibiting the deposition of C and S (while still preserving relatively high catalytic activity). The formation of a surface alloy, which has the alloy element enriched on the topmost surface, was found to be critical to the activity of the Ni alloy catalysts.« less