Reforming reactors

Catalytic reformer—reactor effluent gas (24-Inch stack) Dehydrogenation unit (12-inch stack) Hydrogen (31-inch stack) Hydrogen (30-inch stack) ... 

Traditionally, the steam reforming reactor has a tubular design in which vertical tubes, loaded with catalyst, are surrounded by furnaces to supply the heat required for the strongly endothermic process, see Fig. 8.2. Combustion of natural gas supplies the heat to the tubes. 

Ereeman, H. D., Marco, J. L., Roberts, G. L., VanderWiel, D. P., A compact steam reforming reactor for use in an automotive fuel processor, in Proceedings of the 4th International Conference on Microreaction Technology, IMRET 4, pp. 358-363 (5-9 March 2000), AIChE Topical Conf. Proc., Atlanta, USA. 

Also a simulation of the flow field in the methanol-reforming reactor of Figure 2.21 by means of the finite-volume method shows that recirculation zones are formed in the flow distribution chamber (see Figure 2.22). One of the goals of the work focused on the development of a micro reformer was to design the flow manifold in such a way that the volume flows in the different reaction channels are approximately the same [113]. In spite of the recirculation zones found, for the chosen design a flow variation of about 2% between different channels was predicted from the CFD simulations. In the application under study a washcoat cata-... 

Pretreated NG feedstock is mixed with steam (2.6 MPa), the resulting mixture is preheated to 500°C and introduced to the catalytic reforming reactor. In the reforming reactor, the steam-methane mixture is passed through externally heated reformer tubes filled with Ni catalyst, where it is converted to CO and H2 at 850-900°C according to the following equation ... 

Another cause of activity loss is carbon deposition, which can be avoided if a high steam to carbon (S/C) ratio is employed [45, 46], However, economic evaluations indicate that the optimum S/ C ratio tends to be low. The presence of tars in the reforming reactor enhances coking and it is the main cause of carbon formation in reforming a gas from biomass thermal conversion [29]. 

An intrinsic, exothermic water-gas shift reaction occurs in the steam reformer reactor. The combined reaction, steam reforming and water gas shift, is endothermic. As such, an indirect high temperature heat source is needed to operate the reactor. This heat source usually takes the shape of an immediately adjacent high temperature furnace that combusts a small portion of the raw fuel or the fuel effluent from the fuel cell. Efficiency improves by using rejected heat from other parts of the system. Note that the intrinsic water-gas shift in the reactor may not lower the... 

The CH4 in the natural gas is usually converted to H2 and CO in a SR reactor. Steam reforming reactors yield the highest percentage of hydrogen of any reformer type. The basic SR reactions for methane and a generic hydrocarbon are ... 

The reformer reactor performance as an ammonia cracker was evaluated. The experiments were conducted using a reformer feed composed of 6 seem ammonia. The reactor was heated with the electric heaters to determine the heater power required to achieve high conversion. In these experiments, approximately 97% of the ammonia feed was converted to hydrogen at 900 °C (approximately 1.8 W) when operating at atmospheric pressure. - °... 

Methanol Reforming Reactors for a 200 1/14 Fuel Cell Power System... 

Pfiefer et al. are developing a methanol fuel processor system using steam reforming for a 200 Wg fuel cell based power supply. The researchers are currently working on the methanol reformer reactors, heat exchangers, combustors, and preferential oxidation reactors (Figure 23) for the system. The reactor bodies are either stainless steel or copper. 

The next step in the processor development will be to integrate the palladium alloy membrane with the methanol steam reformer reactor. The researchers anticipate that the addition of the palladium membrane will improve the reactor performance due to in-situ hydrogen removal. 

The pyrolytic reforming reactor was a packed bed in a quartz tube reactor. Quartz was selected to reduce the effect of the reactor construction material on the hydrocarbon decomposition rate. ° The reactor was packed with 5.0 0.1 g of AC (Darco KB-B) or CB (BP2000) carbon-based catalyst. The reactor was heated electrically and operated at 850—950 °C, and the reactants had a residence time of 20—50 s, depending on the fuel. The reactor was tested with propane, natural gas, and gasoline as the fuels. Experiments showed that a flow of 80% hydrogen, with the remainder being methane, was produced for over 180 min of continuous operation.The carbon produced was fine particles that could be blown out... 

Table 5. Methanol Steam Reforming Reactor Performance ...

Carbonaceous compounds can also form in the absence of a catalyst by free-radical, gas-phase condensation reactions. The formation of this pyrolytic carbon is known in steam-reforming reactors where it can be controlled to some extent by minimizing the free volume within the reactor chamber. This type of carbon does not form readily with methane but can be severe with larger hydrocarbons. The compounds formed by free-radical reactions tend to be quite different from the graphitic carbon formed by metal catalysts. For example, Lee et al. showed that the compounds formed by passing pure, undi-... 

The first reaction is the isomerization from a zero-octane molecule to an alkane with 100 octane the second is the dehydrocyclization of heptane to toluene with 120 octane, while the third is the rmdesired formation of coke. To reduce the rate of cracking and coke formation, the reactor is run with a high partial pressure of H2 that promotes the reverse reactions, especially the coke removal reaction. Modem catalytic reforming reactors operate at 500 to 550°C in typically a 20 1 mole excess of H2 at pressures of 20-50 atm. These reactions are fairly endothermic, and interstage heating between fixed-bed reactors or periodic withdrawal and heating of feed are used to maintain the desired temperatures as reaction proceeds. These reactors are sketched in Figure 2-16. 

Thus steam reforming is typically done in two or three staged chemical reactors, the first a reforming reactor operated at 850°C, and then one or two WGS reactors operated at temperatures as low as 200°C, where the equihhrium conversion to H2 is higher because the WGS reaction is exothermic. 

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