Natural Gas Steam Reforming for Hydrogen Production: Basic Knowledge in the Petrochemical Sector

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This post was last edited by Yitailonger on 2016-3-12 at 21:41. Using natural gas as a raw material, a hydrogen-rich mixture is produced through steam reforming; this process makes use of a well-established gas generation technique from the field of ammonia synthesis production. This process consists of two steps: natural gas desulfurization and steam reforming of hydrocarbons. Desulfurization is the process of passing raw natural gas, under certain pressure and temperature conditions, through manganese oxide and zinc oxide desulfurization agents to remove the organic and inorganic sulfur compounds to levels below 0.12 × 10-6, as permitted by the conversion catalyst. The steam conversion of hydrocarbons involves the use of water vapor as an oxidant, and under the action of a nickel catalyst, the following main reactions occur to produce a hydrogen-rich mixed gas: CH4 + H2O → CO + 3H2 – 210 kJ·mol-1; CO + H2O → CO2 + H2 + 431.5 kJ·mol-1. The reaction temperatures are above 800 °C, and the total heat effect of these two reactions is highly endothermic; the heat required is supplied by burning natural gas. Reducing the pressure helps to increase the conversion rate of methane, but in order to meet the requirements of pressure swing adsorption purification and the pressure specifications for pure hydrogen products, as well as to consider the economic viability of the equipment, the reaction pressure is usually maintained at above 115 MPa. Pure hydrogen with a purity of 99.19% to 99.1999% can be obtained using pressure swing adsorption units, and the yield of H2 can exceed 70%. Main consumption quotas (based on 1 Nm3 of hydrogen product with a purity of 99–99%, the same applies hereafter): raw natural gas – 0.148 Nm3, fuel natural gas – 0.112 Nm3, boiler feed water – 11.7 kg, electricity – 0.12 kW·h. The methane content in natural gas is 96.19% (by volume).