Reformer diesel autothermal

Table 6) indicate that the fuel-processing efficiencies decrease in the order of steam reforming > autothermal reforming > partial oxidation for both gasoline and diesel fuels. 

Kinetic Measurements Preliminary studies have been conducted for the kinetic model development for the autothermal reforming of diesel fuel. Three... 

Cheekatamarla PK, Lane AM (2005) Catalytic autothermal reforming of diesel fuel for hydrogen generation in fuel cells I. Activity tests and sulfur poisoning. J Power Sources 152 256-263... 

Fast preheating is possible in case of ceramic monoliths are applied for autothermal reforming. Lindstrom et al. [43] reported 6 min start-up time demand of their autothermal diesel reformer, which was preheated by a homogeneous diesel burner through a heat exchanger via air (Figure 14.9). 

Greaser et al. [76] modeled autothermal diesel reforming in a ceramic monolithic reactor and verified the modeling results with experimental data as shown in Figure 14.10. The model revealed that axial heat conduction plays an important role even in ceramic monoliths. The catalyst temperature was found to be 25°C hotter than the gas phase at the reactor inlet according to the calculations. At the positions of highest reaction rates, the catalyst utilization was as low as 20%. Transport limitations in the washcoat were assumed to be the root cause. The... 

Figure 14.10 Species concentration versus O/C ratio (here expressed as O2/C) for an autothermal diesel reformer at S/C = 2.3. Symbols represent experimental data, the lines represent simulation results [76].

Karatzas, X, Nilsson, M, Dawody, J, Lindstrom, B, Petterson, LJ. Characterization and optimization of an autothermal diesel and jet fuel reformer for 5 kWe mobile fuel cell applications. Chem. Eng. J. 2010 156 366-379. 

Cheekatamarla and Lane [8] observed a temperature rise from 400 °C to less than 800 °C in an adiabatic testing reactor for autothermal reforming of diesel fuel. 

Aicher et al. [72] measured the temperature profile in their autothermal diesel reformer reactor (see Figure 4.4). Temperatures up to 900 °C were detected upstream of the catalyst honeycomb, while the reformate temperature never exceeded 700 °C at the reactor exit... 

Rosa et al. [251] investigated catalysts for autothermal reforming of diesel. Numerous systems were tested. Firstly, platinum, ruthenium, cobalt and nickel catalysts on an alumina carrier promoted with magnesium and lanthanides to improve thermal stability were investigated. The second set of samples was composed of cobalt perovsldte catalysts. In addition, Rosa et al. investigated ruthenium and platinum catalysts on lanthanum/cobalt perovsldtes. The samples were tested at gas hourly space velocities of between 20 000 and 80 000 h and S/C ratios from 3 to 5. The O/C ratio was set to between 0.4 and 1.4 and the temperature to 650-900 °C. Amongst the first set of samples, platinum stabilised by a dual set of lanthanum stabilisers, that were not disclosed, showed improved performance over nickel and ruthenium. The optimum conditions were 750 °C reaction temperature,... 

To study the effect of increasing sulfur content in the reformate, sulfur dioxide was added in small amounts of between 100 and 400 ppm to the feed mixture of the autothermal diesel reformer. Sulfur dioxide was chosen because under the conditions of autothermal reforming most sulfur components are converted into sulfur dioxide (see Section 3.5). Activity measured as hydrogen yield showed a drastic decrease from 75 to 40%, when 200 ppm sulfur dioxide were added to the feed. However, no further detrimental effects were recorded when more sulfur dioxide was added. A similar behaviour was observed when hydrogen sulfide was added. This is because the plateau had already been reached at 75 ppm hydrogen sulfide addition. 

Figure 7.6 Dry gas hydrogen and carbon oxide concentrations as determined experimentally for different O/C ratios (here shown as the O2/C ratio) for an autothermal diesel reformer thermodynamic equilibrium compositions are provided as lines solid line, hydrogen dotted line, carbon dioxide dotted-dashed line, carbon monoxide [491],...

Aicher et al. [72] developed an autothermal reformer for diesel fuel dedicated to supplying a molten carbonate fuel cell system from Ansaldo Fuel Cells S.p.A., Italy. The diesel fuel (which contained less than 10 ppm sulfur for the pilot plant application) was injected into the steam and air flows, which were pre-heated by a diesel burner to 3 50 °C. The reactor itself was operated at 4 bar, a S/C ratio of 1.5 and high O/C ratio of 0.98, which makes the reactor into a steam supported partial oxidation device. Consequently, the dry hydrogen content of the reformate was rather low with less than 35 vol.%. The operating temperature of the honeycomb had to be kept well above 800 °C to prevent coke formation and the presence of light hydrocarbons such as ethylene and propylene in the reformate. The reactor was operated for 300 h, which led to a slight deterioration in the catalyst performance. 

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). 

The main individual reactions that take place in the reformer (e.g., reactions (1), (2) and (5)) will be considered separately from the overall autothermal reaction for two reasons. First, in ATR the reactor can be considered as two plug-flow reactors in series (1) a very fast POX reaction occurs at the top of the catalyst bed and utilizes a small portion of the bed and (2) a slow SR utilizes the remainder of the reactor bed. Therefore, an optimal ATR catalyst must have excellent SR eatalytic properties. Second, there may be situations in which liquid fuels are reformed using only these individual reactions e.g., diesel fuel may be reformed using only SR (reaction (2)) or only by POX (reaction (1)). 

Autothermal reformers and CPO are being developed by a number of groups, mostly for fuel processors of gasoline, diesel, and JP-8 fuels and for natural gas-fueled proton exchange membrane fuel cell (PEMFC) cogeneration systems. A few examples are the following ... 

Ultimately, develop a kinetic rate methodology for diesel autothermal reforming catalyst systems... 

Kinetic modeling of diesel autothermal reforming is extremely complicated. Diesel fuel consists of a complex variable mixture of hundreds of hydrocarbon compounds containing paraffins, isoparaffins, naphthenes, aromatics, and olefins. To simplify the model, a steady-state power law rate expression for the diesel reforming over each type of catalyst used in this study was developed. A linearized least-squares method of data analysis was used to determine the power law parameters from a series of diesel ATR experiments. The power law rate model for diesel autothermal reaction may be written as ... 

Autothermal reforming of single components such as n-hexadecane and toluene was also performed at the same reaction conditions as the diesel ATR to understand the reaction mechanisms and pathways for the ATR system. 

Kaila RK, Gutierrez A, Krause AOI (2008) Autothermal reforming of simulated and commercial diesel The performance of zirconia-supported RhPt catalyst in the presence of sulphur. Appl Catal B 84 324-331... 

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