Efficiency factor reforming

It is reasonable to conclude from these results that for steam reformers operating close to thermodynamic equilibrium it is sufficient for the precise modelling to use a relatively simple model for the computation of the catalyst pellets effectiveness factors. Model H is certainly the simplest and should be used under these conditions. However, for more efficient steam reformers operating far from... 

We recommend the use of overall column efficiency factors. Overall column efficiency refers to the ratio of ideal (or theoretical) trays and actual physical trays. This is a single value that can range from 30-90%. If we consider the case of a distillation column having 20 physical trays and overall efficiency of 0.5, we would model it as a column with 10 ideal trays. With this approach, every tray remains in thermodynamic equUibrium and predictions away from the base operating scenario are reasonable. In the present work, we model the DA301, a reformate... 

A slow rate of p-scission also means that the main cage recombination process will be cage return to reform the peroxydicarbonate. Dialkyl peroxides are typically not found amongst the products of peroxydicarbonate decomposition. In these circumstances, cage recombination is unlikely to be a factor in reducing initiator efficiency. 

In dibenzothiophene-S,S-dioxide the S atom is in a ring, and hence more constrained. The yield of SOz in the radiolysis is linear with the dose to about 13 Mrad after which it levels off as in p,p -ditolyI sulfone. However, the yield of S02 in this case is much lower (a factor of 25) than in the case of p,p -ditolyl sulfone (G = 0.002 compared to G = 0.05). This stability of the dibenzothiophene sulfone could be partially due to back reaction to reform the parent sulfone and partially due to more efficient energy delocalization. The expected biphenylene product was not detected due to limitations of the analytical method. Bowmer and O Donnell70 studied the volatile products in y-radiolysis of dialkyl, alkyl aryl and diaryl sulfones. Table 2 gives the radiolytic yields of S02 and of the hydrocarbon products of the alkyl or aryl radicals. The hydrocarbon products are those obtained either by H atom abstraction or by radical combination. The authors69 suggested the mechanism... 

For the example of methane steam reforming, Eq. (8) yields an acceleration factor of 4. Accordingly, the axial displacement of the reaction zone is a multiple of the axial displacement of thermal fronts. The difference of the axial displacement between the reaction front and the thermal front determines the axial profile of heat demand during the subsequent exothermic semicycle. Efficient heat recovery requires equal heat capacities of the process streams during both semicycles. The initial state can be restored by discrete heat sources distributed at equal distances along the catalytic part of the reactor. Each point source initiates a thermal wave that covers the distance to the next heating point (Fig. 1.13, right). This concept features... 

A fixed-bed reactor often suffers from a substantially small effectiveness factor (e.g., 10 to 10 for a fixed-bed steam reformer according to Soliman et al. [1988]) due to severe diffusional limitations unless very small particles are used. The associated high pressure drop with the use of small particles can be prohibitive. A feasible alternative is to employ a fluidized bed of catalyst powders. The effectiveness factor in the fluidized bed configuration approaches unity. The fluidization system also provides a thermally stable operation without localized hot spots. The large solid (catalyst) surface area for gas contact promotes effective catalytic reactions. For certain reactions such as ethylbenzene dehydrogenation, however, a fluidized bed operation may not be superior to a fixed bed operation. To further improve the efficiency and compactness of a fluidized-bed reactor, a permselective membrane has been introduced by Adris et al. [1991] for steam reforming of methane and Abdalla and Elnashaie [1995] for catalytic dehydrogenation of ethylbenzene to styrene. 

The thermodynamic calculations on the basis of Equations 5.6-5.8 indicate that ZnO might be unable to reduce the sulfur in the reformate to the level for PEMFC applications when the fuel gas contains a large amount of H20, CO, and C02 due to the thermodynamic factor. ZnO is not efficient for removing COS. It needs to catch more close attention to the effects of the coexisting H20, CO, and C02 on the H2S removal from the reformate in the design of a post-desulfurization process in a hydrocarbon fuel processor, especially at high temperature. 

The efficiency of the fuel processor is defined as the ratio of the lower heating value (LHV) of the hydrogen produced to the LHV of the fuel consumed by the fuel processor. The major factors affecting the efficiency are 1) the conversion in the reformer and shift reactors, 2) the recovery of hydrogen in the PSA, 3) the recovery of the process heat, and 4) the minimization of heat losses and parasitic requirements in compressors. 

Within the Production section, there are hyperlinks to detailed analyses of the six hydrogen production options included in H2Sim. Figure 9.3 illustrates the natural gas reformation option. This screen also illustrates the default model results. Key assumptions on each production page include capital, operation and maintenance, and fuel costs, thermal efficiency of the process, interest and discount rates, construction time, plant life, and capacity factor. While some of the assumptions are specific to that production option, changes to assumed interest or discount rates apply to the entire model. Any shaded boxes, such as capital recovery factor, cannot be changed by the user, but will change as other variables (in this case discount rate) do. With the exception of... 

Pension reforms in Europe will be the main factor driving the development of the Eurozone market for inflation derivatives and for real assets in general beyond their current niche market state. As the natural demand for real assets grows in parallel with the development of a private pensions market, corporate payers will emerge, with associated issuance and swaps, that is, analogous to the current state in the UK market. However, the presence of a larger number of players (payers, receivers, and market makers) means that the market will likely be more liquid and more efficient than the current UK IL swap market. 

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