Practical fuels

Although the principle was first proposed in 1839, making a practical fuel cell eluded scientists for a centuiy and a half The concept is simple, but the chemistry is difficult. A hydrogen fuel cell must cleanly convert H2 into H3 O at one electrode and cleanly convert O2 into OH at the other electrode. In addition, the fuel cell must contain a medium that allows these ions to diffuse and combine stoichiometrically. 

The use of available fuels will allow fuel cells on the market more quickly. Hydrogen could be processed from gasoline onboard vehicles until hydrogen becomes a more practical fuel choice. DaimlerChrysler has been working with an onboard sensor that would tell what kind of fuel is being pumped in and then adjust the reformer on the fly. This system would allow different fuels to be reformed at different temperatures using varying proportions of steam and air. 

In Albany, NY, the state government started leasing Honda FCX hydrogen fuel cell cars on a cold November morning. Previous fuel cell vehicle demonstration programs have occurred in warmer areas to ensure that the fuel cell stacks would not freeze up. Subzero temperatures can change any liquid water present into expanding ice crystals that can puncture thin membranes or crack water lines. Honda has demonstrated that their fuel cell units can operate under winter conditions, this was an important achievement for practical fuel cell cars. 

Low tolerance to sulfur compounds that are present in every practical fuel, requiring gas cleanup to below 1 ppm. 

Useful work (electrical energy) is obtained from a fuel cell only when a reasonable current is drawn, but the actual cell potential is decreased from its equilibrium potential because of irreversible losses as shown in Figure 2-2". Several sources contribute to irreversible losses in a practical fuel cell. The losses, which are often called polarization, overpotential, or overvoltage (ri), originate primarily from three sources (1) activation polarization (r act), (2) ohmic polarization (rjohm), and (3) concentration polarization (ricoiic)- These losses result in a cell voltage (V) for a fuel cell that is less than its ideal potential, E (V = E - Losses). 

Also in the operation of a practical fuel cell, some unbumed fuel must remain in the combustion products leaving the cell in order to maintain a significant generated voltage throughout the cell. 

In contrast, stability is a key aspect of any practical fuel cell, and biofuel cells must have lifetimes ranging from months to years to justify implanted, highly distributed, or consumer portable applications. Such stability is often difficult to achieve in redox enzymes, although introduction of thermophilic species and the use of mutagenic techniques might provide future... 

With continued improvement, fuel cells having stable and relatively inexpensive electrodes will enable the development of practical fuel cell vehicles. If the fuel is hydrogen, obtained by some clean process, these will be zero-emission, environmentally friendly vehicles. 

British engineer Francis Thomas Bacon demonstrates the first practical fuel cell. 

Honda, a Japanese manufacturer, develops a practical fuel cell vehicle. 

Effect of Petroleum Fuel Properties. Three primary requirements must be met by practical fuels for aircraft turbojets. These requirements are They must be available in large quantities at low cost, they must produce satisfactory performance in all types of engines, and they must be suitable for aircraft fuel systems. Petroleum fuels vary in volatility, chemical composition, and concentrations of minor nonhydrocarbon compo-... 

The thermodynamically possible conversion efficiency, however, is only partly realized in a practical fuel cell. Two basic losses are encountered (I) the ohmic loss and (2) the electrode polarization, that is. Ihe deviation of... 

Methanol has a very low freezing point which is essential for a practical fuel, and indeed, methanol was once used as an engine coolant antifreeze before better antifreeze compounds were found. While methanol s freezing point is much lower than gasoline and diesel fuel, this is no particular advantage to methanol since gasoline s freezing point is sufficiently low to prevent problems in vehicle fuel systems. 

Fuel cell (Bacon) The first practical fuel cell developed by British engineer... 

Although Equation [5] suggests that aqueous NaBH4 solutions can store sufficient H2 to make a practical fuel, the rate at which H2 can be extracted or produced is very important. Experiments with NaBH, solutions have been conducted in two modes the static NaBH solution and the flowing NaBH solution. 

In order to provide information which may be useful in the specification of emission control techniques, it is important to understand those parameters which influence particulate formation in practical fuel oil combustion systems. Carbonaceous emissions from liquid fuel spray flames burning synthetic and petroleum... 

Alkaline fuel cells (AFC) — The first practical -+fuel cell (FC) was introduced by -> Bacon [i]. This was an alkaline fuel cell using a nickel anode, a nickel oxide cathode, and an alkaline aqueous electrolyte solution. The alkaline fuel cell (AFC) is classified among the low-temperature FCs. As such, it is advantageous over the protonic fuel cells, namely the -> polymer-electrolyte-membrane fuel cells (PEM) and the - phosphoric acid fuel cells, which require a large amount of platinum, making them too expensive. The fast oxygen reduction kinetics and the non-platinum cathode catalyst make the alkaline cell attractive. 

Industry experts today suggest conversions of 40-50 percent and selectivities above 80 percent based on methane and oxygen as the minimum needed for commercial consideration after fixed and variable costs are added. Nonetheless, methane oxidative coupling holds the most promising combination of process simplicity, product slate versatility and low cost, and worldwide raw material availability not offered now by practiced fuel and chemical feedstock technologies. 

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