Partial Oxidation of Heavy

As steam reforming is not applicable to convert hydrocarbons heavier than naphtha to hydrogen, partial oxidation of heavier feedstock is used to produce hydrogen. A simplified flow diagram of the process is shown in Figure B.2. The process basically proceeds at moderately high pressure with or without a catalyst, depending on the raw material and process selected. The catalytic partial oxidation which occurs at 600oC, uses feedstock ranging from methane to naphtha. The non-catalytic partial oxidation operates at 1150-1315oC and can use hydrocarbons ranging from methane, heavy oil to coal. There are three main steps, i.e. synthesis gas generation, water-gas shift reaction, and gas purification. The shift reaction and gas purification either by the conventional wet scrubbing or by the pressure swing adsorption operation are similar to those used in steam reforming. In the synthesis gas generation step, the hydrocarbon feedstock is partially oxidized with oxygen and the carbon monoxide produced is shifted with steam to CO2 and H2. Pure oxygen is used in the process because of the difficulties of separating nitrogen to produce pure hydrogen. The partial oxidation reactions are as follow:

n CO + m/2 H2 + heat n CO + (n+m/2) H2 CO2 + H2 + heat

n CO + m/2 H2 + heat n CO + (n+m/2) H2 CO2 + H2 + heat

Steam Reforming Flow Sheet Study

Figure B.2 Process flow sheet for H2 production from partial oxidation of heavy oil [211].

The hydrocarbon-oxygen reaction is exothermic, the additional energy required for the endothermic hydrocarbon-steam reaction, similar to steam reforming, is supplied by burning additional fuel. The reactions occur mainly in the flame and in an empty brick-lined reactor. The shift reaction occurs along with the oxidation-gasification reactions at temperatures above

1200oC without the presence of catalysts. The product is a very hot mixture of H2 (46%, by vol.), CO (46%, by vol.), CO2 (6%, by vol.), CH4 (1%, by vol.), N2 (1%, by vol).

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Responses

  • Carolyn
    What is partial oxifation in fermentation?
    3 years ago

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