To convert methane into a hydrogen and carbon monoxide rich product gas a reforming step is needed. There are different process options available that can produce product gasses with different H₂/CO ratios:

Steam methane reforming

• Catalytic (nickel-based catalysts), endotherm process
• Bio-methan is mixed with steam under pressure of 20-25 bar
• Thermal energy (820-880°C) has to be provided from an external source
• Results in very high H₂/CO ratios (4-7:1)

 

Partial oxidation

• Bio-methan is partially oxidized at high temperatures (1300-1400°C) and pressures of 25-40 bar
• Results in H₂/CO ratios from 1.6-1.9 (e.g. not sufficient for further processing via FT synthesis)
  
  

Autothermal reforming

• Bio-methane is fed into the reactor together with steam and oxygen, where a part is burned (patially oxidized) to provide thermal energy
• The gas is passed over a catalyst and reacts to product gas
• Requires temperatures from 1020-1065°C and pressures of 25-29 bar
• Results in H₂/CO ratios of 2.2-2.3
  
  

After reforming, cleaning and upgrading steps are needed to receive the desired syngas for further use, e.g. in FT synthesis. In particular, CO₂ must be removed and the H₂ content adjusted (see water gas shift reaction). In general, the product gas from reforming is much cleaner than the product gases from thermo-chemical processes (like gasificationor pyrolysis, which are described in the previous lesson on synthesis gas production from lignocellulosic biomass). Unlike the product gases from these processes, product gas from reforming does not contain any tar or dust particles that need to be removed.