Autothermal reforming reactor

In the thermal zone, above the catalyst bed, further conversion occurs by homogeneous gas-phase reactions. The main reactions in the thermal zone are homogeneous gas-phase 

Schematic diagram of the reactor for ATR of hydrocarbons. 1 = Autothermal reformer, 2 = burner section, 3 = combustion chamber, 4 = catalyst, and 5 = heater. 

SMR (reaction 2.4) and shift (reaction 2.6) reactions. Reactions between N2 and hydrocarbon radicals leading to the formation of such by-products as NH3 and HCN can also take place in the thermal zone. By proper adjustment of 02/CH4 and H20/CH4 ratios, the partial combustion in the thermal zone provides the heat for the subsequent endothermic steam reforming reaction taking place in the catalytic zone [40]. Thus, simplistically, ATR of methane at temperature T can be represented as follows  

The key elements of the ATR technology are the burner and the catalyst. The burner provides proper mixing of the feed streams, and the fuel-rich combustion is taking place 

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Autothermal reforming reactor (ATR) is maintained under adiabatic conditions. There is no heat transfer from or to the reactor section during the reaction. The effect of S/C and O/C ratios on the net electric efficiency of the system with fuel cell has been calculated. The results are illustrated for different inlet temperatures (700° and 400°C) in Figures 7 and 8. A decrease of the S/C ratio decreases the efficiency. On the other hand, an... 

Fig. 10 Autothermal reforming reactor. (View this art in color at WWW. dekker. com.)...

The reactions taking place in the combustion zone of the autothermal reformer reactor are... 

The autothermal reformer reactor is a refractory lined cylindrical vessel swaged to a smaller diameter at the top to provide a combustion zone. A specially designed oxygen burner is installed in this section. The bottom, a larger diameter section, contains the catalyst. A schematic is shown in Figure 9. 

Few studies are reported in literature dealing with the integration of an autothermal reforming reactor with a membrane for hydrogen separation, and most of them are simulation studies. 

The laboratory plant employed for the catalytic activity tests in the presence of a membrane integrated in the autothermal reforming reactor is reported in Fig. 6.1. 

It is under development for various fuels such as methanol, ethanol, LPG and gasoline. The complete fuel processor was composed of a catalytic autothermal reformer reactor, a heat exchanger for cooling the reformate downstream of the CAR,... 

Kolb et al. performed catalyst development in microchannel reactors for auto-thermal reforming of isooctane. Rhodium, nickel, ruthenium and palladium catalysts supported by zirconia and alumina were tested [73]. Rhodium on alumina turned out to be the most active catalyst, which also showed lowest selectivity towards methane. The rhodium content was then varied from 0.1 to 2 wt.% 1 wt.% rhodium on alumina was considered to be the optimum catalyst formulation with respect to both performance, stability and cost. A minimum S/C ratio of 3.3 was required to prevent coke formation. The catalyst was incorporated into an autothermal reforming reactor of kilowatt size (see Section 7.1.2). 

Springmann et al. [152] performed dynamic simulations of a combination of a monolithic autothermal reformer reactor with a tubular heat-exchanger for feed preheating and a high temperature water-gas shift reactor (diameter 70 mm 1600 cells per square inch or about 630-p,m chaimel size) [389]. Both reactors were metallic monoliths. The reformer has already been described in Section 5.1.3. During normal operation, air and steam were fed at 200 °C to the heat-exchanger and heated therein to approximately 650 °C. The reformate leaving the reformer was cooled in the... 

CAR [Combined autothermal reforming] A "reforming process for making "syngas from light hydrocarbons, in which the heat is provided by partial oxidation in a section of the reactor. Developed by Uhde and commercialized at an oil refinery at Strazske, Slovakia, in 1991. 

The coupling of SR with POX is termed autothermal reforming (ATR). The exact definition varies. Some define ATR as an SR reaction and a POX reaction that take place over microscopic distances at the same catalytic site thus avoiding complex heat exchanging (16). Others have the less restrictive definition that ATR occurs when there is no wall between a combined SR reaction and catalytic POX reaction. ATR is carried out in the presence of a catalyst that controls the reaction pathways and thereby determines the relative extents of the POX and SR reactions. The SR reaction absorbs part of the heat generated by the POX process reaction, limiting the maximum temperature in the reactor. The net result is a slightly exothermic process. 

McDermott has operated non-catalytic POX reformers as large as 35 kWe and catalytic autothermal reformers as large as 30 kWe, the latter on high-sulfur marine diesel. McDermott has over 1,000 hours experience utilizing a POX reactor and about 400 hours on the autothermal unit. The longest continuous run of the autothermal reformer has been 175 hours (30,31). 

Researchers at the Chinese Academy of Sciences are developing a scalable methanol autothermal reforming (ATR) reactor. The microchannel reactor will be composed of multiple reactor chips (Figure 21). with each chip able to process enough methanol for approximately 100 We hydrogen. Both aluminum and stainless steel were evaluated for use as the chip... 

Experimental results concerning the development of a small-scale 1 kW autothermal reformer of propane were reported by Rampe et al. [76]. In the proposed reactor, two reactions occur on a metal honeycomb structure coated with platinum. Air and water are mixed before they are fed to the reactor in counterflow to the product gas outside the reactor wall, where the water is vaporized and the steam and air are heated up. Then, they are mixed with propane at the bottom of the reactor. It was verified that the preheating operation mode led to about a 4% higher efficiency, since the higher inlet air temperature causes a higher temperature level in the reaction zone, resulting in improved kinetics of the reforming reaction. 

Heinzel et al. [77] compared the performance of a natural gas autothermal reformer with that of a steam reformer. The ATR reactor was loaded with a Pt catalyst on a metallic substrate followed by a fixed bed of Pt catalyst. In the start-up phase, the metallic substrate was electrically heated until the catalytic combustion of a stoichiometric methane-air mixture occurred. The reactor temperature was increased by the heat of the combustion reaction and later water was added to limit the temperature rise in the catalyst, while the air flow was reduced to sub-stoichiometric settings. With respect to the steam reformer, the behavior of the ATR reactor was more flexible regarding the start-up time and the load change, thus being more suitable for small-scale stationary applications. 

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. 

A stand-alone IkW integrated fuel processor for gasoline, incorporating an autothermal reformer followed by high- and low-temperature WGS reactors, was reported by Qi et al. [85]. The start-up of the ATR reformer lasted less than 5 min and stabilized in around 50 min for the whole system. 

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