Hydrogen production from natural gas mainly adopts the following three different chemical treatment processes.
( 1 ) Steam reforming of methane ( SMR )
Steam reforming is the endothermic conversion of methane and water vapor into H2 and CO.
The chemical reaction process is : CH4 + H2O + heat → CO + 3H2
The heat required for the reaction is supplied by the heat generated by methane combustion. The temperature required for this process is 700 ~ 850 °C, and the reaction products are CO and H2 gas, of which CO gas accounts for about 12 % of the total product. CO is further converted into CO2 and H2 by water vapor transfer reaction, such as chemical reaction process.
( 2 ) Partial oxygen ( POX )
The process of hydrogen production by partial oxidation of natural gas is to release CO and H2 through partial combustion of methane and oxygen. The chemical reaction process is : CH4 + 1 / 2O2 → CO + 2H2 + heat
This process is an exothermic reaction, which requires a rigorous design. The reactor does not require additional heat source, and the outlet temperature of the reactor can reach 950 ~ 1100 °C. The CO produced by the reaction is then converted into H2 by water vapor transfer reaction. The hydrogen produced by the autothermal reforming process needs to be purified, which greatly increases the cost of hydrogen production.
Table 3-2 compares the advantages and disadvantages of the above three hydrogen production methods.
Need low energy ; the process temperature is lower than that of partial oxidation ; the H2 / CO ratio is easily adjusted by the CH4 / O2 ratio.| Hydrogen production technology | Advantages | Disadvantages |
| methane steam reforming | The most widely used ; no oxygen required ; process temperature ; for hydrogen production, the H2 / CO ratio is | Usually need too much steam ; large equipment investment ; high energy demand |
| autothermal reforming | Limited commercial applications ; oxygen is usually required | |
| partial oxidation | Direct desulfurization of feed does not require steam ; a low H2 / CO natural ratio is advantageous for applications with a ratio of less than 20 | Low H2 / CO natural ratio is unfavorable for applications with a demand ratio greater than 20. Very high process operating temperature ; oxygen is usually required |