Fuel autothermal methane

Beil, A. and Seume, J. (2006) Unsteady performance of a PEMFC system including autothermal methane reforming, in Proceedings of the 4th International ASME Conference on Fuel Cell Science, Engineering and Technology, June 19-21, Irvine, CA. 

Hoang DL, Chan SH (2004) Modeling of a catalytic autothermal methane reformer for fuel cell applications. Appl Catal A 268 207-216... 

Lenz et al. [73] described the development of a 3 kW monolithic steam-supported partial oxidation reactor for jet fuel, which was developed to supply a solid oxide fuel cell (SOFC). The prototype reactor was composed of a ceramic honeycomb monolith (400 cpsi) operated between 950 C at the reactor inlet and 700°C at the reactor outlet [74]. The radial temperature gradient amoimted to 50 K which was attributed to inhomogeneous mixing at the reactor inlet. The feed composition corresponded to S/C ratio of 1.75 and O/C ratio of 1.0 at 50 000 h GHSV. Under these conditions, about 12 vol.% of each carbon monoxide and carbon dioxide were detected in the reformate, while methane was below the detection limit. Later, Lenz et al. [74] described a combination of three monolithic reactors coated with platinum/rhodium catalyst switched in series for jet fuel autothermal reforming. An optimum S/C ratio of 1.5 and an optimum O/C ratio of 0.83 were determined. Under these conditions 78.5% efficiency at 50 000 h GHSV was achieved. The conversion did not exceed 92.5%. In the product of these... 

Table 5.10 Effect ofthe S/C ratio on system parameters and water balance of an autothermal methane fuel processor [435].

Ahmed et al. [435] performed calculations to highlight the effect of the various operating parameters of an autothermal methane fuel processor on the overall water balance. The system considered by Ahmed et al. included an afterburner, which combusted the anode off-gas by cathode off-gas oxygen. Water was then recovered from the burner off-gas. As shown in Table 5.10, Section 5.4.1, the water balance improved when the S/C ratio was increased. 

Hydrogen production from carbonaceous feedstocks requires multiple catalytic reaction steps For the production of high-purity hydrogen, the reforming of fuels is followed by two water-gas shift reaction steps, a final carbon monoxide purification and carbon dioxide removal. Steam reforming, partial oxidation and autothermal reforming of methane are well-developed processes for the production of hydro-... 

An experimental study by Lee et al. [72] reported the development and testing of a natural gas fuel processor, which incorporates a catalytic autothermal reformer, a sulfur trap and a WGS reactor. The fuel processor was successfully run over 2300 h of continuous operation. The ATR reactor gave over 40% H2 (dry basis) in the ATR reformate and 96-99.9% methane conversion over the entire test duration. 

The carbon deficit observed in methane steam nsforming does not occur if naphtha feedstock is converted. In autothermal processes using fuel oil as a feedstock, sufficient quantities of excess carbon dioxicte are available within the instailation itself. This gas is recycled from a scrubbing unit... 

With the right mixture of input fuel, air, and steam, the POX reaction supplies all the heat needed to drive the endothermic catalytic steam reforming reaction. Unlike the steam methane reformer, the autothermal reformer requires no external heat source and no indirect heat exchangers. These features make autothermal reformers simpler and more compact than steam reformers and thus can be built for a relatively low capital cost. 

Generally, a pre-reforming ofthe fuel is carried out, whereby part of hydrocarbon is reformed in an external reactor and the remainder is internally reformed. Methane and other hydrocarbons can also be converted to hydrogen by partial oxidation (POX) this is an exothermic process which is often combined with endothermic steam reforming, and leads to an autothermic conversion of methane. 

Autothermal reformers combine some of the best features of steam reforming and partial oxidation systems. A hydrocarbon feedstock (methane or a liquid fuel) is reacted with both steam and air (or oxygen) to produce a hydrogen-rich gas, i.e.. 

Partial oxidation is able to convert methane and other hydrocarbons, catalyzed or non-catalyzed, at temperatures between 1100 and 1500 °C. Despite its lower efficiency compared with steam reforming, partial oxidation provides, on the other hand, exothermicity and a greater selectivity for synthesis gas production as well as advantages for certain applications such as compactness, rapid startup or load change, lower overall cost. If steam is added to the fuel and the oxidant, it is possible to heat balance the exothermal partial oxidation reaction with the endothermal reforming reaction, meaning that no external heat source (autothermal) is required. 

Cao L, Pan L, Ni C, Yuan Z, Wang S (2010) Autothermal reforming of methane over Rh/ Ceo5Zros02 catalyst effects of the crystal structure of the supports. Fuel Process Technol 91 306-312... 

Synthesis gas can be produced by the steam reforming process or by the autothermal process. Hydrocarbons are catalytically cracked in the presence of steam and applied heat in the steam reforming process. Hydrocarbons from methane up to the C4-C7 fractions of light petroleum can be used as raw materials. In contrast, the energy required for cracking is obtained by the partial combustion of the hydrocarbons themselves in the autothermal process. This latter process works without catalysts using steam-oxygen mixtures and hydrocarbons from methane to heavy fuel oils. 

---