Pre- Reformer

Methane can be reformed into hydrogen in several ways. One method is steam reforming, which is based on methane decomposition to carbon monoxide and hydrogen, and the water gas shift process which is based on the further decomposition of the water molecule and the composition of carbon dioxide  

Fuel type Factor name and reference Definition (by molar fractions) Value assumed during calculations 

Overall, steam methane reforming reactions (5.38 and 5.39) are endothermic in summary with the heat process dependent on the reaction temperature AH = 165-247 kJ/mol (see 4.2 and 4.3 for details). It means that thermal energy is converted into the form of fuel (mainly water molecule decomposition into hydrogen). 

Carbon deposition is a harmful process that causes very rapid degradation of fuel cells and the reformer. For safe fuel cell operation, steam is added to carbon-containing fuels to prevent carbon deposition on the cell surfaces. Various kinds of factors are used to describe adequate steam content in hydrocarbon fuel to avoid carbon deposition. For gaseous hydrocarbon fuel, the most commonly used factor is the steam-to-carbon ratio (s/c ratio). Mostly, the s/c ratio is set at about 2 and above this value no carbon deposition takes place. Boundary values of the s/c ratio are dependent on temperature. Drawn from a review of the literature, typical factors and their definitions for various fuels are listed in Table 5.4. 

The s/c ratio at which no carbon deposition occurs is temperature dependent, as shown in Fig. 5.36. 

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Pre-Keformer A pre-reformer is based on the concept of shifting reforming duty away from the direct-fired reformer, thereby reducing the duty of the latter. The pre-reformer usually occurs at about 500°C inlet over an adiabatic fixed bed of special reforming catalyst, such as sulfated nickel, and uses heat recovered from the convection section of the reformer. The process may be attractive in case of plant retrofits to increase reforming capacity or in cases where the feedsock contains heavier components. 

Auernheimer, Richard and Frank Baron, eds. Johannes Trithemius humanism and magic in pre-Reformation Germany. Bad Kreutznacher Symposien, no. 1. 

Willard, Thomas S. Review of Johannes Trithemius humanism and magic in pre-Reformation Germany (Bad Kreutznacher Symposien, Vol 1), by Richard Auernheimer and Frank Baron. In Cauda Pavonis 11, no. 2 (Fall 1992) 14.. ... 

Walsh, James Joseph. Basil Valentine, a great pre-reformation chemist. Amer CathQ Rev 31, no. 122 (Apr 1906) 342-358. 

FCE tested a lab-scale carbonate fuel cell stack on a model diesel-like fuel (Exxsol) using an adiabatic pre-reformer to convert the liquid fuel to methane in 1991 to 1993. In 1995 and 1996, FCE verified a 32 kW MCFC stack operation on jet fuel (JP-8) and diesel (DF-2) in system inte-... 

Figure 1-14. Simplified System process flow diagram of pre-reformer/SOFC system... 

M. M. Piwetz, J.S. Larsen, T.S. Christensen, "Hydrodesulfurization and Pre-reforming of Logistic Fuels for Use in Fuel Cell Applications," Fuel Cell Seminar Program and Abstracts, Courtesy Associates, Inc., November 1996. 

The SOFC module is set (sized) to operate at 0.69 volts per cell. The spent fuel and air effluents of the SOFC are combusted within the module to supply heat for oxidant preheating. Unlike the natural gas case, the fuel does not require a pre-reformer with only 0.3% methane along with 36% hydrogen and 43% carbon monoxide. The carbon monoxide will be either water gas shifted to hydrogen or utilized directly within the fuel cell. A gas recirculation loop for the... 

Steam pre-reforming of propane to a methane-rich fuel for internal reforming in solid oxide fuel cells," K. Ahmed and K. 176ger, Ceramic Fuel Cells Ltd., 4th EUROSOFC, Luceme/Switzerland July 2000... 

Typically, the prereforming process is performed in an adiabatic fixed-bed reactor upstream of the main reformer. In the pre-reformer, higher... 

Traces of sulfur can be eliminated prior to entering the main reformer, due to the lower operating temperatures of the prereformer, which favors the deposition of sulfur on the Ni-based pre-reforming catalyst. 

Next, as other examples of the simulations for the calculating conditions in Table 10.2, the calculated 5 distribution in the interconnector for the pre-reforming and co-flow pattern cases are shown in Figures 10.38a and 10.39a, respectively. In... 

Fig. 10.40 The simulated distribution in the La0.9Sr0.1Cr0.98Co0.02O3 interconnector for (a) the standard, (b) pre-reforming, and (c) co-flow cases.

Fig. 10.42 The calculated distribution of the principal stress in the Lao.8Sro.2Cro.95Nio.o5C>3 j interconnector for the pre-reforming case 2 in Table 10.2 (a) the stress is calculated considering both the temperature and distributions in the interconnector, (b) the stress is only the thermal stress. The model geometry with 16-channels is used, and half the model is drawn in the figure.

A - Syngas cooling D - Flue gas cooling G - Multi-stage combustion EHD Reform ing/pre-reforming f> Steam/water... 

Figure 2.81 Network of 27 catalyst beds (five for pre-reforming, nine for reforming, nine for catalytic combustion to supply the heat, two for water-gas shift and two for preferential oxidation) and of 20 heat exchangers [128]...

The plant consists of a pre-reforming step which converts C2+ into methane, which also reduces the coking risk downstream (Figure 4.50). The actual reforming step, the water gas shift reaction, follows and also a step for the selective oxidation of carbon monoxide before the hydrogen-rich gas enters the fuel cell. A steam evaporator is also included in the set-up. 

In some cases a plant may have a pre-reformer. A pre-former is an adiabatic, fixed-bed reactor upstream of the primary reformer. It provides an operation with increased flexibility in the choice of feed stock it increases the life of the steam reforming catalyst and tubes it provides the option to increase the overall plant capacity and it allows the reformer to operate at lower steam-to-carbon ratios166. The hot flue gas from the reformer convection section provides the heat required for this endothermic reaction. 

In addition to the capital cost for a new reactor, the pre-reformer does add complexity to the system - particularly in the requirements for startup and shutdown. It is most attractive in cases 1) where more capacity is needed without increased firing and 2) where the feedstock contains a significant amount of C3 or higher hydrocarbons, which could crack and form coke in the preheat coil86. 

The Catalytic Rich Gas (CRG) technology from Kvaerner is an example of pre-reformer technology that can be licensed. This technology was developed by British Gas and was first used in 1964. In 2001 over 25 CRG pre-reformers were in operation. If desired, a pre-reduced CRG catalyst is available. ... 

Proportional Same Medium Pre- Reformer Catalyst Cost... 

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