Fuel processing steps

Several fuel-processing steps such as reforming and clean up are figure out in Figure 2. The reforming section can contain the reforming reactors... 

The different fuel processing steps are carried out at different temperatures and range from strongly endothermic to strongly exothermic. Hence proper heat management is indispensable for efficient hydrogen production. 

Since the proton exchange membrane fuel cell (PEMFC) anode catalyst can be poisoned by CO at ppm levels of concentration, it is necessary to estimate how much CO will exist at each of the fuel processing steps. Let us use the steam reforming As an example to do some analyses. Table 3.2 lists the molar Gibbs free energy of formation of the species involved, plus values for CO2 and O2 for later analysis. 

Next, let us figure out the actual concentrations of all the species involved in the fuel processing steps. The following analysis neglects the impact of Reaction 3.6 on Reaction 3.2 during the reforming step. For Reaction 3.2, if we assume that there are initially 0.5 moles of CH4,0.5 moles of H2O (i.e., the initial total number of moles of reactants is 1), and n moles and 3n moles of CO and H2 formed, respectively, then at thermodynamic equilibrium, the amounts (equivalent to the molar or volumetric concentration, and the partial pressure) of CH4, H2O, CO, and H2 are 0.5 - n, 0.5 - n, n, and 3n, respectively. Therefore,... 

And thus the poisoning is not recoverable when switching to S-fee H2. Fortunately, H2S and all the S-containing compoimds should have been removed prior to the fuel processing steps and thus the fuel stream is not expected to contain any of it before entering the fuel cell. 

Figure 8-2 Representative Fuel Processing Steps Temperatures...

The fuel to be chosen in the context of endurance depends not only on the gravimetric energy density of the storage system but also on the characteristics of each individual subsequent fuel processing step. In particular, the reforming... 

Used to present the heat and material balance of a process. This may be in broad block form with specific key points delineated, or in more detailed form identifying essentially every flow, temperature and pressure for each basic piece of process equipment or processing step. This may and usually does include auxiliary services to the process, such as steam, water, air, fuel gas, refrigeration, circulating oil, etc. This type of sheet is not necessarily distributed to the same groups as would receive and need the piping flowsheet described next, because it may contain detailed confidential process data. 

The function of the carbon coating is to contain the byproducts of the fission reaction, thereby reducing the shielding requirements. It also protects the nuclear fuel from embrittlement and corrosive attack and from hydrolysis during subsequent processing steps. CVD coatings of alumina deposited at 1000°C and beryllia deposited at 1400°C have also been studied for that purpose.P l... 

Texaco gasification is based on a combination of two process steps, a liquefaction step and an entrained bed gasifier. In the liquefaction step the plastic waste is cracked under relatively mild thermal conditions. This depolymerisation results in a synthetic heavy oil and a gas fraction, which in part is condensable. The noncondensable fraction is used as a fuel in the process. The process is very comparable to the cracking of vacuum residues that originate from oil recycling processes. 

In a petroleum refinery a large number of different products are produced, and the demand for some of these products is seasonal. For instance, there is not much need for residential fuel oil in the summer. The price of products also varies from day to day. To optimize the company s profit, it is therefore necessary periodically to vary the amount of each product produced. This can be done by changing the amounts of material sent to cracking units and reformers and by changing the conditions in these and other process steps. Some petroleum companies provide a computer with the data on market prices, current inventories, and crude oil compositions. The computer output then specifies the operating conditions that will yield the greatest profit for the company. The computer could then make the changes in these conditions directly, or this could be done manually. 

As in all long-chain fuel processes, this initiation step does not appear to contribute significantly to the product distribution and, indeed, no formaldehyde is observed experimentally as a reaction intermediate. 

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