Fuel utilization

With respect to fuels utilized as heating fuels for industrial furnaces, or as motor fuels for large diesel engines such as those in ships or power generation sets, the characteristics of primary importance are viscosity, sulfur content and the content of extremely heavy materials (asphaltenes) whose combustion can cause high emissions of particulates which are incompatible with antipollution legislation. 

Land purchases and many of the costs associated with faciUty development can be accompHshed with long-term loans of 15 to 30 years. Equipment such as pumps and tmcks are usually depreciated over a few years and are funded with shorter-term loans. Operating expenses for such items as feed, chemicals, fuel, utilities, salaries, taxes, and insurance may require periodic short-term loans to keep the business solvent. The projected income should be based on a reaUstic estimate of farmgate value of the product and an accurate assessment of anticipated production. Each business plan should project income and expenses projected over the term of all loans in order to demonstrate to the lending agency or venture capitaUst that there is a high probabiUty the investment will be repaid. 

The interval between more thorough inspections will depend on the operating conditions of the gas turbine. Manufacturers generally provide guidelines for determining inspection intervals based on exhaust gas temperatures, type and quality of fuel utilized, and number of starts. 

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 addition, manufacturers boiler operational manuals provide hardcopy data ratings for heat transfer coefficients, local heat flux, fuel utilization, furnace heat release rates, maximum continuous rating... 

Very large, modem WT boilers with sophisticated heat-recovery auxiliaries may attain efficiencies approaching 88 to 90%. However, the overall efficiency of a fossil fuel utility power generation plant system falls to only 32 to 38% when the efficiency of electricity generation and condenser cooling is included. Nevertheless, it only requires 10% more in fuel costs to operate a boiler at 1,250 psig than... 

Options typically include a wide range of pressure ranges and steam outputs, fully automatic operation, full modulation (variable FW or steam supply, rather than on-off operation), low NOx burners, and high tumdown-ratio burners to reduce cycling and improve fuel utilization. 

Fig. 1. Performance evaluation of prepared electro-catalysts as an electrode of PEMFC. Cell temperature 70 C, active area 50cm, platinum loading anode(0.3mgPt/cm )/cathode(0.45mg Pt/cm ), fuel utilization H2/O2 = 80%/50%, RH 100% RFl, pressure H2/O2 = 0 psig/0 psig.

The fuel utilized in the fuel cell is mainly hydrogen since its electrochemical reaction rate is much faster than other fuels. Methanol and formic add can directly partidpate in the electrochemical reaction, but their reaction rates are an order of magnitude lower than hydrogen. Therefore, hydrogen is usually produced from other fuels by using a separate fiiel proeessor and subsequently supplied to the fuel cell. 

One may conclude from all these studies that the loss in fuel utilization and Coulombic efficiency in a DMFC due to methanol crossover is still a major barrier in the development of such types of electrochemical power sources. 

Gorte RJ, Vohs JM, and McIntosh S. Recent developments on anodes for direct fuel utilization in SOFC. Solid State Ionics 2004 175 1-6. 

Similarly, in the development of solid oxide fuel cells (SOFCs), it is well recognized that the microstructures of the component layers of the fuel cells have a tremendous influence on the properties of the components and on the performance of the fuel cells, beyond the influence of the component material compositions alone. For example, large electrochemically active surface areas are required to obtain a high performance from fuel cell electrodes, while a dense, defect-free electrolyte layer is needed to achieve high efficiency of fuel utilization and to prevent crossover and combustion of fuel. 

Fuel utilization by muscle adaptation to exercise and training... 

FUEL UTILIZATION BY MUSCLE ADAPTATION TO EXERCISE AND TRAINING... 

Figure 1-16. Projected cost structure of a SkWnet APU SOFC system. Gasoline fueled POX reformer, Fuel cell operating at 300mW/cm, 0.7 V, 90 % fuel utilization, 500,000...

Utilization (U) refers to the fraction of the total fuel or oxidant introduced into a fuel cell that reacts electrochemically. In low-temperature fuel cells, determining the fuel utilization is relatively straightforward when H2 is the fuel, because it is the only reactant involved in the electrochemical reaction, i.e. 

Cell performance for any fuel cell is a function of pressure, temperature, reactant gas composition and fuel utilization. In addition, performance can be adversely affected by impurities in both the fuel and oxidant gases. 

The addition of H2O and CO2 to the fuel gas modifies the equilibrium gas composition so that the formation of CH4 is not favored. Carbon deposition can be reduced by increasing the partial pressure of H2O in the gas stream. The measurements (20) on 10 cm x 10 cm cells at 650°C using simulated gasified coal GF-1 (38% H2/56% CO/6% CO2) at 10 atm showed that only a small amount of CH4 is formed. At open circuit, 1.4 vol% CH4 (dry gas basis) was detected, and at fuel utilizations of 50 to 85%, 1.2 to 0.5% CH4 was measured. The experiments with a high CO fuel gas (GF-1) at 10 atmospheres and humidified at 163°C showed no indication of carbon deposition in a subscale MCFC. These studies indicated that CH4 formation and carbon deposition at the anodes in an MCFC operating on coal-derived fuels can be controlled, and under these conditions, the side reactions would have little influence on power plant efficiency. 

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