Autothermal reforming syngas composition

Natural gas is reacted with steam on an Ni-based catalyst in a primary reformer to produce syngas at a residence time of several seconds, with an H2 CO ratio of 3 according to reaction (9.1). Reformed gas is obtained at about 930 °C and pressures of 15-30 bar. The CH4 conversion is typically 90-92% and the composition of the primary reformer outlet stream approaches that predicted by thermodynamic equilibrium for a CH4 H20 = 1 3 feed. A secondary autothermal reformer is placed just at the exit of the primary reformer in which the unconverted CH4 is reacted with O2 at the top of a refractory lined tube. The mixture is then equilibrated on an Ni catalyst located below the oxidation zone [21]. The main limit of the SR reaction is thermodynamics, which determines very high conversions only at temperatures above 900 °C. The catalyst activity is important but not decisive, with the heat transfer coefficient of the internal tube wall being the rate-limiting parameter [19, 20]. 

The autothermal reforming operation can be used without COj recycle to produce a syngas with H2/CO ratios of between 2.3 to 3.5. However, recycled or imported CO2 extends the range of possible syngas compositions to include H2/CO ratios as low as 0.8. 

Table 7 shows a summary of the operating conditions and the product syngas compositions for several autothermal reforming plant designs [15]. 

Table 7 Raw Syngas Composition with Autothermal Reforming...

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