Fuel processing subsystem

Because the components and design of a fuel processing subsystems depend on the raw fuel type, the discussion after Table 9-1 is organized by the fuel being processed. 

A process flow schematic of the demonstration unit1 installed at the Tokyo Electric Power facility at Goi. Japan and in operation since 1983 is shown in Fig. 4, Fuel cell generalors have three unique major subsystems that are unfamiliar to electric utilities (1) A fuel processing subsystem, (2) a fuel cell power section, and (3) a power conditioning subsystem. Sec Fig. 5. 

Natural gas feedstock enters the fuel processing subsystem at about 63 psig (4,5 atm). The fuel is first processed in hydrodesulfurizing unit (HDS) and zinc-oxide (ZnO) beds lo remove any sulfur compounds. The desulfurized fuel is mixed with process steam and preheated to about 850°F (454cC) before entering the reformer, which consists of reactor tubes containing a... 

The output of each CSA is approximately 280 V at 850 A (dc). In order to deliver a desired voltage of approximately 2800 V at 1700 A of 4.8 MW dc at full power, the CSAs are connected electrically to each other. The CSAs are cooled individually by circulating water through cooler plates. Heat from the electrochemical reaction produces steam within the cooler plates, which is used in the fuel-processing subsystem. 

Figure 1 provides a schematic of the gasoline fuel cell power plant. The major subsystems include the Fuel Processing Subsystem, the Power Subsystem and the Balance of Plant. The Balance of Plant includes the Thermal Management Subsystem, the Air and Water Subsystems and the Controller and associated electrical equipment. 

Fuel processing subsystem This subsystem is composed of a reformer (if the system design includes external reformation for fuels other than hydrogen) and other equipment for fuel cleanup, if any. 

Figure 33.36 is an example of a 300 kW aircraft SOFC APU design [70]. In this system design, the power generation subsystem consists of twin 150 kW hybrid SOFCs and the fuel processing subsystem consists of an ATR FR and a DS. A fuel heat exchanger (HEX) is used to cool the reformate gas stream. A portion of exhaust gases from the SOFC are recycled via the CGR and AGR blowers. 

Of interest is the view that the majority of the cost is dominated by the fuel cell stack and the fuel processing subsystems. Further, the primary cost reduction for smaller SOFC units will stem from improvements to the fuel cell subsystem, whilst cost reductions for the fuel processing system will be difficult balance of plant component costs reduction opportunities, such as compressors, pumps, sensors and heat exchangers, are considered to be fairly small. Similarly, other subsystems such as power electronics are considered fairly stable cost wise. 

Panasonic, with Tokyo Gas, announced in January 2013 that it had reduced the price (excluding installation) of its domestic PEM fuel cell system to 1,995,000 by approximately 760,000, a reduction of 27.5 % from its 2011 model. This itself was a reduction from its 2009 model (selhng at 3,465,000 [104]) of 20 %. A year or so earlier in January 2012 Toshiba, with Osaka Gas, announced that it had reduced the price of its domestic fuel cell system by 650,000- 2,604,000, a 25 % reduction in cost [105]. In both cases sales increases were anticipated and further cost reductions expected. The Panasonic announcement also included further information on the performance and other aspects of the unit. The cost reduction was associated with an improvement of lifetime from 50,000 to 60,000 h a reduction in components by 20 % reduced weight by 10 % and reduced size overall. Of significance was a reduction in noble metals in the fuel processing subsystem by 50 % and platinum catalyst by 50 %. Total efficiency, both heat and power, was calculated at 95 % LHV. 

Selected methodologies for fuel cell process engineering were introduced in this chapter. The use of the DOE theory was discussed as a powerfiil tool for system verification using examples from fuel cell subsystems. Measurement uncertainty... 

A fuel subsystem that manages the fuel supply to the power section. This subsystem can range from simple flow controls to a complex fuel-processing facility. This subsystem processes fuel to the type required for use in the fuel cell (power section). 

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