Fuel hydrocarbon reforming

Hydrocarbon Fuel Reforming Catalyst and Use Thereof. U.S Non-Provisional Patent Application, Q. Ming, T. Healey, and P. Irving, pending. 

A schematic of the principles behind integrating an OTM-based hydrocarbon fuel reformer with a SOFC for the non-Carnot limited conversion of this feedstock into electricity is shown in Fig. 7.7. 

Even in small amounts, sulfur compounds are extremely harmful to the activity of most catalysts used in fuel cells. The admissible amounts of these impurities are in the ppb (parts per billion) range. In larger amounts, sulfur contaminants will also be harmful to hydrocarbon fuel reforming. 

Natural gas is by far the preferred source of hydrogen. It has been cheap, and its use is more energy efficient than that of other hydrocarbons. The reforming process that is used to produce hydrogen from natural gas is highly developed, environmental controls are simple, and the capital investment is lower than that for any other method. Comparisons of the total energy consumption (fuel and synthesis gas), based on advanced technologies, have been discussed elsewhere (102). 

As a constituent of synthesis gas, hydrogen is a precursor for ammonia, methanol, Oxo alcohols, and hydrocarbons from Fischer Tropsch processes. The direct use of hydrogen as a clean fuel for automobiles and buses is currently being evaluated compared to fuel cell vehicles that use hydrocarbon fuels which are converted through on-board reformers to a hydrogen-rich gas. Direct use of H2 provides greater efficiency and environmental benefits. ... 

Fuel reforming is popular way for hydrogen production for fuel cell use. Hydrocarbons are used for the fuel resource. Methane (CH4) steam reforming process consists of the following two gas phase reactions with various catalysts. 

More complex hydrocarbonaceous fuels might materialize in the long term, depending on the alternative vehicle market. The fuel development programs also include hydro-carbonaceous fuels for both, on-board reformers and for liquid hydrocarbon fuel cells. The introduction of hybrid and FC cars would inevitably reduce the share of gasoline in total fuel consumed. 

The plasma decomposition process is applicable to any hydrocarbon fuel, from methane to heavy hydrocarbons. Similar to oxidative plasma reforming, plasma decomposition processes fall into two major categories thermal and nonthermal plasma systems. 

Ahmed, S. et al., Catalytic partial oxidation reforming of hydrocarbon fuels, Proc. of 1998 Fuel Cell Seminar, Palm Springs, CA, 242,1998. 

In addition to achieving a closed carbon loop, the use of ethanol as a H2 source offers additional advantages of safety and ease of handling, storage, and transportation. Ethanol is non-toxic to humans at trace concentrations in water. Another advantage is that ethanol could be easily reformed catalytically into H2 gas compared to hydrocarbon fuels. 

Onboard reforming for fuel cells depends on catalytic reactions to convert conventional hydrocarbon fuels, such as gasoline or methanol, into hydrogen that fuel cells can then use to produce electricity to power vehicles. 

The fuel processor efficiency is size dependent therefore, small fuel cell power plants using externally reformed hydrocarbon fuels would have a lower overall system efficiency. 

Raw Fuel Conversion - Converting a hydrocarbon fuel to a hydrogen-rich gas reformate. 

Equation 9-4 and related heats of reaction can be manipulated to show that the maximum efficiency is a state point function, regardless of path (steam reforming, partial oxidation, or autothermal reforming), and is achieved at the thermoneutral point. In practice, x is set slightly higher than the thermoneutral point so that additional heat is generated to offset heat losses from the reformer. Table 9-1 presents efficiencies at the thermoneutral point for various hydrocarbon fuels. 

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