Hydrocarbon steam autothermal reforming

CO = 25 vol.%, C02 = 12 vol.%) not containing any hydrocarbons and a low tar (200 mg Nm 3) content at 800 °C and S/C (steam over carbon ratio) = 1.5. Problems associated with pyrolysis oil gasification are similar to those of biomass gasification. Gasification of the tar fraction and conversion of methane formed are important challenges. Both require highly active and stable steam/autothermal reforming catalysts. 

Equation 9-4 and related heats of reaction can be manipulated to show that the maximum efficiency is a state point function, regardless of path (steam reforming, partial oxidation, or autothermal reforming), and is achieved at the thermoneutral point. In practice, x is set slightly higher than the thermoneutral point so that additional heat is generated to offset heat losses from the reformer. Table 9-1 presents efficiencies at the thermoneutral point for various hydrocarbon fuels. 

The aim of this study is to convert as much as the hydrogen in the fuel into hydrogen gas while decreasing CO and CH4 formation. Process parameters of fuel preparation steps have been determined considering the limitations set by the catalysts and hydrocarbons involved. Lower S/C (steam to carbon) ratios favor soot and coke formation, which is not desired in catalytic steam and autothermal reforming processes. A considerably wide S/C ratio range has been selected to see the effect on hydrogen yield and CO formation. 

Following sulfur removal (1), the autothermal reformer (2) and reforming exchanger (3), which operate in parallel, convert the hydrocarbon feed into raw synthesis gas in the presence of steam using a nickel catalyst. 

Autothermal reforming is a teim adopted for the process in which a mixture of air and steam serves as the oxidant in the conversion of hydrocarbon fuels to a hydrogen-rich product. This process has also been reported to become more efficient as a result of the use of monolithic catalyst beds [11]. An example of this has been the demonstration of a modified version of the fuel-rich partial oxidation process in which noble metal catalysts were used in place of nickel on ceramic monoliths [2j. In earlier reports where packed catalyst beds were used, the concept to control carbon formation, which was predicted by thermodynamic equilibrium at low air-to-fuel ratios, was demonstrated by introducing steam, in addition to air, as an oxidant. 

Figure 13 Monolith catalyst bed configuration used in demonstration of autothermal reforming of hydrocarbons. The monolith catalyst bed through which the hydrocarbon, oxygen, and steam mixture (A) passes is No. 2, and the pellet steam reforming bed is No. 4. (From Ref. 11.)...

M. Flytzani-Stephanopoulos and G.E. Voecks, Conversion of Hydrocarbons for Fuel Cell Applications Part I Autothermal Reforming of Sulfur-Free and Sulfur-Containing Hydrocarbon Liquids Part II Steam Reforming of n-Hexane on Pellet and Monolithic Catalyst Beds, Final Report DOE/ET-11326-1, Jet Propulsion Laboratory Publication 82-37, pp. 75-120 (1981). 

R.M. Yarrington, I.R. Feins, and H.S. Hwang, Evaluation of steam reforming catalysts for use in autothermal reforming of hydrocarbon feed stocks. Proceedings of National Fuel Cell Seminar, San Diego, CA (1980). 

Autothermal reforming combines partial oxidation and adiabatic steam reforming for conversion of the hydrocarbon feedstock into synthesis gas free of soot and higher hydrocarbons. The ATR reactor design consists of burner, combustion chamber, and catalyst bed placed in a refractory lined vessel, as illustrated in Fig. 10. The hydrocarbon feedstock with steam is reacted with oxygen in a substoichiometric flame, often... 

Autothermal reforming with oxygen and steam (ref. 6) is an alternative to the SPARG process. By combined partial oxidation and steam reforming of the hydrocarbon, it is possible to achieve low H2/C0 ratios without the addition of C02. 

Autothermal reformers combine some of the best features of steam reforming and partial oxidation systems. A hydrocarbon feedstock (methane or a liquid fuel) is reacted with both steam and air (or oxygen) to produce a hydrogen-rich gas, i.e.. 

Autothermal reforming is a combination of partial oxidation and steam reforming carried out in a single reactor. The endothermic heat of reaction for the steam methane reforming reaction is supplied by partial oxidation of the hydrocarbon feedstock in the first section of the reactor. 

Precombustion capture. This solution is developed in two phases (1) the conversion of the fuel in a mixture of H2 and CO (syngas mixture) through, for example, partial oxidation, steam reforming, or autothermal reforming of hydrocarbons, followed by water-gas shift (WGS), and (2) the separation of CO2 (at 30%-35%) from the H2 that is then fed as clean fuel to turbines. In these cases, the CO2 separation could happen at very high pressures (up to 80 bar of pressure difference) and high temperatures (300°C-700°C).42... 

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