Diesel partial oxidation

Conventional Transportation Fuels. Synthesis gas produced from coal gasification or from natural gas by partial oxidation or steam reforming can be converted into a variety of transportation fuels, such as gasoline, aviation turbine fuel (see Aviation and other gas turbine fuels), and diesel fuel. A widely known process used for this appHcation is the Eischer-Tropsch process which converts synthesis gas into largely aHphatic hydrocarbons over an iron or cobalt catalyst. The process was operated successfully in Germany during World War II and is being used commercially at the Sasol plants in South Africa. 

As an alternate to LNG, natural gas can be chemically converted to methanol, chemical feedstocks (such as ethylene), gasoline, or diesel fuel. Most processes start with the conversion of methane to synthesis gas, a mixture of carbon monoxide and hydrogen. This can be done partial oxidation, an exothermic reaction ... 

In the case of synthesis gasoline or diesel fuel from natural gas (GTL), synthesis gas is produced by a combination of steam reforming and partial oxidation processes (combined reforming) to achieve a H2 CO ratio of generally 2.1 1. This means that the overall process energy demand can be reduced to its minimum. The individual reactions are ... 

Liquid fuels such as distillate, naphtha, diesel oils, and heavy fuel oil can be reformed in partial oxidation reformers. All commercial POX reactors employ noncatalytic POX of the feed stream by oxygen in the presence of steam with reaction temperatures of approximately 1,300 to 1,500°C (2,370 to 2,730°F) (18). For illustration, the overall POX reaction for pentane is... 

The minimum fuel/air ratio for ignition is analogous to the lower limit of flammability. It is important in Diesel fuel combustion because partial oxidation will occur in local regions in which the concentration of fuel is less than the minimum or lower limit, but these regions will not ignite or inflame. Consequently, products of partial oxidation giving rise to odor, and possibly deposits, will appear in the exhaust. This is discussed in a subsequent section. 

Aldehydes are usually present in part-per-million concentrations (44> 62 y 138) and are partially responsible for the odorous and irritating properties of Diesel exhaust gas (33y 138). Removal of aldehydes (33) produces significant reduction in odor and irritation. Aldehydes are products of partial oxidation, and their concentration in the ex-... 

It is fair to state that by and large the most important application of structured reactors is in environmental catalysis. The major applications are in automotive emission reduction. For diesel exhaust gases a complication is that it is overall oxidizing and contains soot. The three-way catalyst does not work under the conditions of the diesel exhaust gas. The cleaning of exhaust gas from stationary sources is also done in structured catalytic reactors. Important areas are reduction of NOv from power plants and the oxidation of volatile organic compounds (VOCs). Structured reactors also suggest themselves in synthesis gas production, for instance, in catalytic partial oxidation (CPO) of methane. 

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. 

Partial oxidation processes rank next to steam-hydrocarbon processes in the amount of hydrogen made. They can use natural gas, refinery gas, or other hydrocarbon gas mixtures as feedstocks, but their chief advantage is that they can also accept liquid hydrocarbon feedstocks such as gas oil, diesel oil, and even heavy fuel oil. All processes employ noncatalytic partial combustion of the hydrocarbon feed with oxygen in the presence of steam in a combustion chamber at flame temperatures between 1300 and 1500°C. For example, with methane as the principal component of the feedstock ... 

COPox [CObalt Partial oxidation] A three-stage GTL process. The first stage produces syngas by partial oxidation. The second stage converts this to a mixture of hydrocarbons by the FT process, using a cobalt catalyst in a fluidized bed reactor. The third stage converts this mixture to the required products diesel, naphtha, and LPG. Designed by ConocoPhillips and demonstrated in Ponca City, OK, in 2003. 

Natural gas, by direct partial oxidation, can provide olefins suitable for oligomerisation using the Mobil Olefin to Gasoline and Diesel process. Alternatively, synthesis gas routes to olefins can be via methanol or Fischer-Tropsch synthesis. In the Fischer-Tropsch option, the hydrogen-rich nature of the synthesis gas requires that the catalyst should have poor shift activity and produce a narrow range of lower olefins. 

Systems Analysis Figure 1 shows a concept identified by NETL for a integrated fuel processor/ fuel cell system targeted for diesel APUs. There are several favorable attributes of this system. For example, startup occurs by firing an internal combustor in the dual reactor reformer. This provides heat to the ATR reformer (via conduction) as well as supplying heat to the fuel cell cathode via direct exhaust from the combustor or preheated air from the heat exchanger (optional). If necessary, the ATR is fired in a partial oxidation mode to aid in heatup and to provide heat to the anode side of the... 

A 50 kW multi-fuel partial oxidation processor coupled to an SPFC stack has been presented in October 1997 by Arthur D. Little Inc., USA, and test-operated in the meantime for more than 3000 h. The fuels that can be applied are gasoline, methanol, and ethanol in a later stage, also diesel, oil, methane and propane processing will be possible [27]. In the UK, a bench-scale steam reformer system processing gasoline and diesel was successfully demonstrated for over 50 hours each. The H2 concentration in the reformate was typically... 

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