Natural Gas Fuel Processors

Reinkingh et al. from Johnson Matthqr reported on a 5-kWd HotSpot natural gas fuel processor [576]. The multi-step unit produced reformate containing 43 vol.% hydrogen, 1 vol.% methane and less than 10 ppm carbon monoxide. The reformer itself produced between only 1 and 2 vol.% carbon monoxide. The natural gas conversion exceeded 90%. 

Numerous natural gas fuel cell/fuel processor systems are under development for residential applications. Because off-heat could well be used for heating purposes and hot water generation in residential applications, the overall system efficiency is usually high for such systems. 

In the first half of2005,175 fuel cell systems were installed in Japan, 67 of them by Tokyo Gas. 

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An experimental study by Lee et al. [72] reported the development and testing of a natural gas fuel processor, which incorporates a catalytic autothermal reformer, a sulfur trap and a WGS reactor. The fuel processor was successfully run over 2300 h of continuous operation. The ATR reactor gave over 40% H2 (dry basis) in the ATR reformate and 96-99.9% methane conversion over the entire test duration. 

Design, construct and evaluate a compact, responsive, natural gas fuel processor, scaleable between - 1 kW and - 50 kW, and hence suitable for residential through to small commercial CHP systems. The system should achieve a power density of > 1 kW/litre, a performance degradation of < 0.5% in 1,000 hours, < 10 ppm CO output, and a 10,000 hour operating life 2005... 

Phase II Demonstration and delivery of a high efficiency reformate tolerant 7-kWf,gt fuel cell stack and power plant utilizing molded bipolar plates and natural gas fuel processor to Argonne National Laboratory for independent testing and verification. 

Develop a T-kW gt fuel cell system with integrated natural gas fuel processor. 

A 10-kW natural gas fuel processor will be integrated into the power plant. The processor is capable of starting up and producing fuel cell quality reformate in less than 60 minutes. Furthermore, it is able to transition from minimum power to full power (2 kW to 10 kW) in less than 60 seconds. The reformer is a larger version of the unit used in the 3-kW et stationary plant, which has demonstrated good transient response and low CO output (less than 50 ppm throughout its operating envelope). 

Adachi et al. [168] developed a model for a natural gas fuel processor composed of an ATR designed as metallic foam monolith coated with catalyst and two-stage WGS reactors also designed as foam monoliths followed by two-stage ceramic monoliths for the preferential oxidation of carbon monoxide as shown in Figure 14.27. Figure 14.28 shows the course of temperature and gas composition of feed and reformate as calculated for... 

Figure 14.29 Start-up energy demand of the different components of the natural gas fuel processor/fuel cell system [168], (Source Adachi et al. [168], Reproduced with permission of Elsevier.)...

Lee, D, Lee, HC, Lee, KH, Kim, S. A compact and highly efficient natural gas fuel processor for 1-kW residential polymer electrolyte membrane fuel cells. J. Power Sources 2007 165 337-341. 

Adachi, H, Ahmed, S, Lee, SHD, Papadias, D, Ahluwalia, RK, Bendert, JC, Kanner, SA, Yamazaki, Y. A natural gas fuel processor for a residential fuel cell system. J. Power Sources 2009 188 244-255. 

Dalle Nogare et al. compared two natural gas fuel processors working with pressure swing adsorption and preferential oxidation for small-scale stationary apphcations [423]. They found a shghtly higher efficiency for the pressure swing adsorption. 

A methane or natural gas fuel processor with 2.5-kW thermal energy output was described by Heinzel et al. [17]. It consisted of a pre-reformer, which made future multi-fuel operation possible, the reformer itself, which carried a nickel catalyst [433], it was operated between 750 and 800 ° C, and had catalytic carbon monoxide clean-up. The preferential oxidation reactor was operated at an O/CO ratio of 3.5 [433]. A carbon monoxide content of between 20 and 50 ppm could be achieved during steady state operation. An external burner suppUed the steam reforming reaction with energy. The natural gas was desulfiirised by a fixed bed of impregnated charcoal. Figure 9.21... 

The Japanese combined heat and power systems are usually smaller. As one prominent example, from numerous systems under development in the Japanese and Asian markets. Figure 9.30 shows the combined heat and power system working with a natural gas fuel processor and a PEM fuel cell, which was developed by Ballard for Tokyo gas [606]. The system achieved an efficiency of 38% at an electrical power output of 800 Wei. 

Seo ct al. reported on the development and operation of a 100-kW natural gas fuel processor, tvhich tvas developed for a molten carbonate fuel cell [609]. The molten carbonate fuel cell does not require any carbon monoxide clean-up (see Section 2.3.2), and thus the system consisted merely of a burner to supply the steam reformer, a compressor, heat-exchangers, the desulfurisation stage and the reformer itself. The reformer was built by relying on conventional technology with tubular reactors top-fired externally from the natural gas burner. The 16 steam reformer tubes shown in Figure 9.33 were operated at a S/C ratio of 2.6 and 3-bar pressure, while the design operating temperature was 700 °C. Seo et al. reported that the efficiency of their system was still too low. Therefore, an improved version of the fuel processor is under development. 

Echigo, M., Shinke, N., Takami, S. and Tabata, T. (2004) Performance of a natural gas fuel processor for residential PEFC system using novel CO preferential oxidation catalyst. J. Power Sources, 132, 29-35. 

Adachi H, Ahmed S, Lee SHD, Papadias D, Ahluwaia RK, Bendert JC, Kanner SA, Yamazaki Y (2009) A natural gas fuel processor for a residential fuel cell systsem. J Power Sources... 

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