Reformer micro-channel

In this work, the MeOH kinetic model of Lee et al. [9] is adopted for the micro-channel fluid dynamics analysis. Pressure and concentration distributions are investigated and represented to provide the physico-chemical insight on the transport phenomena in the microscale flow chamber. The mass, momentum, and species equations were employed with kinetic equations that describe the chemical reaction characteristics to solve flow-field, methanol conversion rate, and species concentration variations along the micro-reformer channel. 

The catalytic combustor provides heat for the endothermic reforming reaction and the vaporization of liquid fuel. The endothermic reforming reaction is carried out in a parallel flow-type micro-channel of the reformer unit. It is well known that the methanol steam reforming reaction for hydrogen production over the Cu/ZnO/AbOs catalyst involves the following reactions [10]. Eq. (1) is the algebraic summation of Eqs. (2) and (3). 

Fig. 2 Schematic diagram of a micro-channel of reformer (a) and meshes in 2-D model (b)...

Fig. 2 shows a schematic diagram of a micro-channel of reformer section to be examined in this study. A multi-physics computer-aided numerical model framework integrating kinetics, mass transport, and flow dynamics in micro-channel reactors has been established. 

A growing number of research groups are active in the field. The activity of reforming catalysts has been improved and a number of test reactors for fuel partial oxidation, reforming, water-gas shift, and selective oxidation reactions were described however, hardly any commercial micro-channel reformers have been reported. Obviously, the developments are still inhibited by a multitude of technical problems, before coming to commercialization. Concerning reformer developments with small-scale, but not micro-channel-based reformers, the first companies have been formed in the meantime (see, e.g., ) and reformers of large capacity for non-stationary household applications are on the market. 

Development of Catalyst Coatings for Methanol Steam Reforming in Micro Channels... 

Two reaction mechanisms for partial propane oxidation exist in the literature. One of them proposes that the reaction starts with catalytic combustion followed by reactions of a lower rate, namely steam reforming, C02 reforming and water-gas shift [54], Aartun et al. [55] investigated both reactions. The other mechanism proposes that the partial oxidation reaction occurs directly at very short residence times [56], which are easier to achieve in the micro channels. 

Figure 2.46 Effect of coolant temperature on CO conversion for the water-gas shift reaction in a micro channel reactor at constant reformate feed inlet temperature of 350 °C. Coolant temperature ( ) 125 ( ) 200 ( ) 225 °C.

Bravo et al. [29] dealt with the coating of a commercial CuO/ZnO catalyst on quartz and fused-silica capillaries for future application in micro channels. The catalyst was mixed with boehmite as binder and water at a mass ratio of44 11 100. The boehmite was treated with hydrochloric or nitric acid before. The capillaries were pretreated with a hot sulfuric acid/solid oxidation step before coating. The capillaries were filled with the catalyst/binder suspension and then cleared with air. In this way, catalyst coatings up to 25 pm thick were obtained. The coatings were applied to methanol steam reforming (see Section 2.4.1). 

Pfeifer et al. [45] deposited CuO/ZnO and PdO/ZnO nanoparticles on micro channels by wash coating. A stable dispersion of the nanoparticles was achieved when polymers such as hydroxylpropylcellulose were added to the solvent 2-propa-nol. The wash coating was performed on both single micro structured foils and stacked foils (post-coating, see Figure 2.97). These coatings were applied to methanol steam reforming [22]. 

G. P., Datye, A., Wall coating of a CuO/ Zn0/Al203 methanol steam reforming catalyst for micro channel reformers, Chem. Eng.J. 2004, 101, 113-121. 

Kolb, G., Zapf, R., Hessel,V., Lowe, H., Propane steam reforming in micro channels, Appl. Catal. A 2004, submitted for publication. 

Homogeneous combustion in micro-channels Hydrocarbon reforming Averaged signal height... 

II.C.4 Novel Catalytic Fuel Processing Using Micro-Channel Steam Reforming and Advanced Separations Technology... 

Llorca et developed a micro-channel reactor where ethanol steam reforming is performed on one side of the plate while ethanol combustion is performed on the with 14 microchannels. The results revealed that Rh-based catalysts exhibited the highest catalytic activity, when compared to Co and Ni. The Rh-Ni-Ce catalyst was operated for 100 h without any noticeable degradation in activity and selectivity. Full conversion was achieved for the entire period and the Hg selectivity was 86%. The CO content in reformate remained constant ca. 8.2%. 

Hao, Y, Du, X, Yang, L, Shen, Y, Yang, Y. Numerical simulation of configuration and catalyst-layer effects on micro-channel steam reforming of methanol. InL J. Hydrog. Energy 2011 36 15611-15621. 

Y.G., and Han, H.S. (2008) Process intensification by micro-channel reactor for steam reforming of methanol. 

Kundu and colleagues, working at Samsung Electromechanics in Korea, developed the silicon-based micro-channel reactor shown in Figure 11.13. Here a Cu/Zn0/Al203 Johnson Matthey catalyst was used. In the experiments a serpentine patterned micro-reformer proved superior in tenns of activity to a parallel-patterned unit. Nevertheless, dates for commercialisation, conclude the authors in the review, remain uncertain. 

The interest in fuel cells for automotive applications has resulted in a large number of investigations of reforming of methanol [286] [501] for on-board reforming or for distributed units for hydrogen production. Compact units have been studied [183] using micro-channel or plate reformers [94] [340] [442] or a combination with selective hydrogen membranes [26] [40]. 

The reformer is the key element of the fuel processing system. The special requirements have led to new concepts for steam reforming and partial oxidation [282] [488]. One example is micro-channel reactors... 

The micro-channel reformers used show high heat transfer rates and the design achieves a high productivity per volume [295]. However, there is little economy of scale and the feasibility is limited to small- to medium-size capacities. 

In order to avoid carbon deposition, the steam-to-carbon ratio is normally higher than 2 (Ni, 2012). However, a high steam concentration could decrease the SOFC s performance. A common practice for methane fueled SOFCs is to pre-reform methane fuel to obtain a gas mixture with sufficient hydrogen concentration. In this chapter, a commonly used 30% pre-reformed methane fuel mixture is employed (Ni and Leung, 2008). In operation, the fuel mixture is fed to the anode micro-channel while air is supplied to the cathode micro-channel. MSR and WGSR occur in the porous anode, as shown in Equations (6.1) and (6.2), respectively ... 

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