Utilization Fuel 67 percent

Figure 7-17 Cell Performance at 1,000 °C with Pure Oxygen (o) and Air (A) Both at 25 percent Utilization (Fuel (67 percent Hi/ll percent CO/11 percent HiO) Utilization is 85... 

The total cost of utilities (fuel, electricity, steam, water, etc.) equals 5 percent of the total cost of producing the formaldehyde. 

Figure 6-5 Voltage and Power Output of a 1.0/m 19 cell MCFC Stack after 960 Hours at 965 °C and 1 atm, Fuel Utilization, 75 percent (50)...

Sulfur It is well established that sulfur compounds in low parts per million concentrations in fuel gas are detrimental to MCFCs (74, 75, 76, 77, 78). The tolerance of MCFCs to sulfur compounds (74) is strongly dependent on temperature, pressure, gas composition, cell components, and system operation (i.e., recycle, venting, gas cleanup). The principal sulfur compound that has an adverse effect on cell performance is H2S. At atmospheric pressure and high gas utilization ( 75 percent), <10 ppm H2S in the fuel can be tolerated at the anode (tolerance level depends on anode gas composition and partial pressure of H2), and <1 ppm SO2 is acceptable in the oxidant (74). These concentration limits increase when the temperature increases, but they decrease at increasing pressures. 

Since each system achieves the same total fuel utilization (90 percent) across the same total area, each stack has the same average current density. Irreversible voltage loss is mainly a function of current density and stack temperature. Since these parameters are equivalent in each stack, it is assumed that the Nemst potential of each stack would be reduced by the same amount. 

Fuel switch. The choice of fuel used in furnaces and steam boilers has a major effect on the gaseous utility waste from products of combustion. For example, a switch from coal to natural gas in a steam boiler can lead to a reduction in carbon dioxide emissions of typically 40 percent for the same heat released. This results from the lower carbon content of natural gas. In addition, it is likely that a switch from coal to natural gas also will lead to a considerable reduction in both SO, and NO, emissions, as we shall discuss later. 

Nonfood Uses. Vegetable oils are utilized in a variety of nonedible applications, but only a few percent of the U.S. soybean oil production is used for such products (see Table 13). Soybean oil is converted into alkyd resins (qv) for protective coatings, plasticizers, dimer acids, surfactants (qv), printing inks, SoyDiesel fuel (methyl esters used to replace petroleum-based diesel fuel) and other products (76). 

The fuel value of most solid wastes is usually sufficient to enable self-supporting combustion, leaving only the incombustible residue and redlicing the volume of waste eventually consigned to sanitaiy landfills to only 10 to 15 percent of the original volume. The heat released by the combustion of waste can be recovered and utilized, although the cost of the recoveiy equipment or the distance to a suitable point of use for the heat may make its recoveiy economically infeasible. 

Use of excess air levels of 5 percent or less has been shown to reduce fuel ash corrosion in furnaces, most likely by stabilizing the vanadium as a refractory suboxide, VO2 or V2O3. Utility plants have had some success using this method to control vanadium ash corrosion. However, practical application of excess air control in refinery and chemical plant operations is difficult, and has not been particularly successful. Problems with particulates, smoke, pollution, and flame control are encountered unless the necessary expensive control systems and operator attention are constantly available. 

Historically, under both federal and state regulations, the demand for gas to heat homes and to meet needs of business and industiy took priority over utility use to generate electricity. These restrictions have been eased by amendments to the Fuel Use Act in 1987, and, as a result, new gas-fired generation units are being constructed. However, coal-fired units continue to provide over 50 percent of the total utility generation of electricity. 

Furnaces and boilers sold today must by law have annual fuel utilization efficiency of at least 78 to 80 percent. Gas water heaters operating this way as space heaters are equivalent to the efficiency of pre-1992 furnaces and boilers which had space heating efficiencies typically in the mid-60 percent range. However, the combined efficiency for space and... 

Most new gas and oil-fueled furnaces and boilers have similar efficiencies. The range of efficiency has narrowed with the introduction of minimum efficiency standards for new products sold since 1992. New gas and oil heating equipment currently available in the marketplace have /knnual Fuel Utilization Efficiency (AFUE) ratings of at least 78 to 80 percent. /VFUE is a measure of how efficient a furnace operates on an annual basis and takes into account cycling losses of the furnace or boiler. It does not include the... 

In that case, protests caused delays that contributed to large cost overruns. But Seabrook was an exception most nuclear utilities got into financial trouble with little help from protesters. Although oil prices rose dramatically in the 1970s—a spur to nuclear development—the stagflation of the times drove down demand for electricity from 7 percent to 2 percent per annum and drove up interest rates into the double digits. Between 1971 and 1978, nuclear capital costs rose 142 percent, making them more expensive to build per kilowatt-hour of capacity than new fossil fuel plants. 

Beyond the ATS program, the DOE is looking at several new initiatives to work on -with industry. One, Vision 21, aims to virtually eliminate environmental concerns associated with coal and fossil systems while achieving 60 percent efficiency for coal-based plants, 75 percent efficiency for gas-based plants, and 85 percent for coproduction facilities. Two additional fossil cycles have been proposed that can achieve 60 percent efficiency. One incorporates a gasifier and solid oxide fuel into a combined cycle the other adds a pyrolyzer with a pressurized fluidized bed combustor. Also under consideration is the development of a flexible midsize gas turbine. This initiative would reduce the gap between the utility-size turbines and industrial turbines that occurred during the DOE ATS program. 

Gulf intended to produce chiefly distillate fuel oil in the West Virginia plant. This is a low sulfur (less than 0.3 percent) nonpolluting fuel for the production of electrical power and steam in the eastern United States, where utilities and industry presently use natural petroleum fuel oil. Gulf claimed that a larger commercial-size plant processing 30,000 tons of coal daily would yield 60,000 barrels of distillate fuel oil or enough to meet the electrical demands of a city with one million inhabitants. 

Component enthalpies are readily available on a per mass basis from data such as JANAF (4). Product enthalpy usually includes the heat of formation in published tables. A typical energy balance calculation is the determination of the cell exit temperature knowing the reactant composition, the temperatures, H2 and O2 utilization, the expected power produced, and a percent heat loss. The exit constituents are calculated from the fuel cell reactions as illustrated in Example 10-3, Section 10. 

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