Balance of Plant

The balance of plant (BoP) is required to integrate an MCFC to form a complete, stand-alone power plant 

Depending on the fuel and the configuration, the BoP may include one or more of the following components  

Similarly to turbocharged internal combustion engines and to large-scale steam turbines within combined cycle power plants, MCFCs also can be integrated with turbines. 

Different types of MCFC-gas turbine (GT) integration are possible. The configuration proposed by Ansaldo Fuel Cells (AFCo) uses the compressor to pressurize the air fed to the FC the FC exhaust is burnt with additional methane in the turbine burner and expanded. This configuration couples the Brayton cycle top pressure and the MCFC pressure, and is most suited for integration with microturbines or in any case with low compression ratios. 

Fuel ceU energy (FCE) proposes integration with an externally fired turbine, in the sense that the heat is supplied by the MCFC. In this way, the Brayton cycle and the MCFC pressure are decoupled. 

Except for the stack, the remaining portion of a fuel cell system is referred to as the balance of plant (BOP). Several major items will be discussed here. 

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While comparison of the absolute capital costs and costs of electricity among different power systems is difficult and uncertain, the structure of these costs is rather typical, and the costs of component units are usually within known ranges. For an oxygen-blown IGCC power system, the breakdown of the capital cost for the four component units is air separation plant (11 to 17 percent), fuel gas plant (33 to 42 percent), combined-cycle unit (32 to 39 percent), and balance of plant (2 to 21 percent). The breakdown of the cost of elec tricity is capital charge (52 to 56 percent), operating and maintenance (14 to 17 percent), and fuel (28 to 32 percent). 

Heat recovery water heater and the saturated air preheater. Balance-of-plant equipment and systems, including interconnecting piping, valves, controls, etc. 

Key features of the 1,300 MWe System 80+ (Bagnal, 1992) are 15% improvement in thermal margin, slower response to upset conditions, no fuel damage up to a 6-in. break, and the ability to withstand an 8-hour station blackout. System 80+ integrates the nuclear island, turbine island, and balance of plant. 

BALANCE OF PLANT 3110-3199. Condensln 5 System 3110-3119. .Condenser Tubes... 

Closed Cooling W.ater Systems. Auxiliary Steam. Service Air. . Instrument Air -Fire Protection System. .Miscellaneous (Auxiliary Systems). Miscellaneous (Balance of Plant)... 

The various balance of plant equipment systems (BOP) consist of a wide range of post-boiler section equipment and associated pipework, including turbines, condensers, condenser cooling systems, and related components. 

Economizers form part of the boiler (heat transfer) surfaces, whereas closed LP/HP heaters and open (deaerating) heaters, although forming part of the overall FW supply system, are often regarded as balance of plant equipment. 

The steam system cycle is a regenerative water heating, steam generation and delivery, and condensed steam recovery cycle. It involves the operation and management of a boiler(s) and some or all of the auxiliaries and balance of plant equipment discussed in Chapters 2 and 3. 

Where problems develop, there is almost always a chain of cause and effect rather than any single cause, so that problems originating, for example, in the pre-boiler FW system may produce additional problems in the boiler itself, or perhaps the post-boiler condensate system, or in any balance of plant equipment such as a turbine. 

AVT Barg BD BDHR BF BOF BOOM BOP BS W BSI BTA Btu/lb BW BWR BX CA CANDUR CDI CFH CFR CHA CHF CHZ Cl CIP CMC CMC CMC COC All-Volatile treatment bar (pressure), gravity blowdown blowdown and heat recovery system blast furnace basic oxygen furnace boiler build, own, operate, maintain balance of plant basic sediment and water British Standards Institution benzotriazole British thermal unit(s) per pound boiler water boiling water reactor base-exchange water softener cellulose acetate Canadian deuterium reactor continuous deionization critical heat flux Code of Federal Regulations cyclohexylamine critical heat-flux carbohydrazide cast iron boiler clean-in-place carboxymethylcellulose (sodium) carboxy-methylcellulose critical miscelle concentration cycle of concentration... 

Mooney, H.A. (1972). The carbon balance of plants. Annual Review of Ecology and Systematics, 3, 315 6. 

Defining hydrogen fuel quality specifications is a high priority for the Roadmap. Such specifications must be quantified at the vehicle-station interface and must consider how the presence of small amounts of contaminants affects the performance and durability of fuel cell and balance of plant material compatibility of onboard and stationary hydrogen storage systems and the operation and maintenance of hydrogen production, purification, and delivery systems. Most importantly, fuel quality specification must consider... 

There can be many different cycle configurations for the hybrid fuel cell/turbine plant. In the topping mode described above, the fuel cell serves as the combustor for the gas turbine, while the gas turbine is the balance of plant for the fuel cell, with some generation. In the bottoming mode, the fuel cell uses the gas turbine exhaust as air supply, while the gas turbine is the balance of plant. In indirect systems, high-temperature heat exchangers are used. 

Gas production system Frequency transducer for T-motor Electric motors for balance of plant... 

For both low temperature electrolysers, the biggest gain in efficiency is to be expected from an improvement in Balance of Plant components, taking into account the big gap between cell efficiency (80-90%) and system efficiency (50-60%). In the case of SPE electrolysers, catalytic research should therefore be directed to making the catalysts more tolerant to contaminants. For alkaline electrolysers, in addition to this, more active electrodes could lower capital costs. 

Figure 9. Reactor diagram for balance of plant for a hydrogen generator.

FCE s German partner, MTU Friedrichshafen, is operating a 250 kilowatt molten carbonate fuel cell system in Bielefeld, Germany. The power plant is located on the campus of the University of Bielefeld and provides electric power and byproduct heat. The fuel cells were manufactured by FCE. MTU developed a new power plant configuration for this unit termed a Hot Module that simplifies the balance of plant. The system began operation in November 1999 and logged over 4,200 hours by August, 2000. Electric efficiency is 45% (LHV). 

FCE plans to demonstrate a molten carbonate fuel cell/turbine hybrid system in late 2000. The balance of plant equipment employed in the 250 kilowatt test at ERC s facility will be modified to accommodate a fuel cell and a gas turbine. The turbine is to be powered by waste heat from the fuel cell. The goal of the test is to demonstrate that the hybrid system will realize high efficiencies. This activity is a part of the U.S. DOE Office of Fossil Energy Vision 21 Program. 

Based on the system requirements discussed above, fuel cell APUs will consist of a fuel processor, a stack system and the balance of plant. Figure 1-13 lists the components required in SOFC and PEM based systems. The components needed in a PEM system for APU applications are similar to that needed in residential power. The main issue for components for PEM-based systems is the minimization or elimination of the use of external supplied water. For both PEM and SOFC systems, start-up batteries (either existing or dedicated units) will be needed since external electric power is not available. 

The balance of plant contains all the direct stack support systems, reformer, compressors, pumps, and the recuperating heat exchangers. Its cost is low by comparison to the PEFC because of the simplicity of the reformer. However, the cost of the recuperating heat exchangers partially offsets that. 

While the stack, insulation and stack balance in this simple-cycle system is a key component the balance of plant is also an important factor. The stack cost again mainly depends on the achievable power density. Small systems like these will likely not be operated under high pressure. While this simplifies the design and reduces cost for compressors and expanders (which are not readily available at low cost for this size range in any case) it might also negatively affect the power density achievable. 

The large fraction of cost related to balance of plant issues is mainly due to the very small scale of this system, which results in a significant reverse economy of scale. While design work is still ongoing, it is anticipated that the cost structure of this system will change rapidly to reduce the cost of balance of plant further, and further improve the competitiveness of these systems. 

Balance of Plant - The balance of plant in general should cost less if the stack fuel and oxidant exit temperature is less than 800 C for the same reasons the stack should cost less. 

The results show that, at temperatures below 60 °C and an air feed stoichiometry below three, the cathode exhaust is fully saturated (nearly fully saturated at 60 °C) with water vapor and the exhaust remains saturated after passing through a condenser at a lower temperature. In order to maintain water balance, all of the liquid water and part of the water vapor in the cathode exhaust have to be recovered and returned to the anode side before the cathode exhaust is released to the atmosphere. Because of the low efficiency of a condenser operated with a small temperature gradient between the stack and the environment, a DMFC stack for portable power applications is preferably operated at a low air feed stoichiometry in order to maximize the efficiency of the balance of plant and thus the energy conversion efficiency for the complete DMFC power system. Thermal balance under given operating conditions was calculated here based on the demonstrated stack performance, mass balance and the amount of waste heat to be rejected. 

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