Methane reformer

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A methane refomer is a device used in chemical engineering, which can produce pure hydrogen gas from natural gas using a catalyst. There are two natural gas reformer technologies — autothermal reforming (ATR) and steam methane reforming (SMR). Both methods work by exposing natural gas to a catalyst (usually nickel) at high temperature and pressure.

1 Steam reforming
2 Autothermal reforming
3 Advantages and disadvantages
4 See also
5 References
6 External links

[edit] Steam reforming

SMR uses an external source of hot gas to heat tubes in which a catalytic reaction takes place that converts steam and lighter hydrocarbons such as natural gas (methane) or refinery feedstock into hydrogen and carbon monoxide (syngas). Syngas reacts further to give more hydrogen and carbon dioxide in the reactor. The carbon oxides are removed before use by means of pressure swing adsorption (PSA) with molecular sieves for the final purification. The PSA works by absorbing all impurities from the syngas stream to leave a pure hydrogen gas.

[edit] Autothermal reforming

Autothermal reforming (ATR) uses oxygen and carbon dioxide or steam in a reaction with methane to form syngas. The reaction takes place in a single chamber where the methane is partially oxidized. The reaction is exothermic due to the oxidation. When the ATR uses carbon dioxide the H₂:CO ratio produced is 1:1; when the ATR uses steam the H₂:CO ratio produced is 2.5:1

The reactions can be described in the following equations, using CO₂:

2CH₄ + O₂ + CO₂ $\rightarrow$ 3H₂ + 3CO + H₂O + Heat

And using steam:

2CH₄ + O₂ + H₂O $\rightarrow$ 5H₂ + 2CO

The outlet temperature of the syngas is between 950-1100 C and outlet pressure can be as high as 100 bar.^[1]

The main difference between SMR and ATR is that SMR uses no oxygen. The advantage of ATR is that the H₂:CO can be varied, this is particularly useful for producing certain second generation biofuels, such as DME which requires a 1:1 H₂:CO ratio.

[edit] Advantages and disadvantages

The capital cost of steam reforming plants is prohibitive for small to medium size applications because the technology does not scale down well. Conventional steam reforming plants operate at pressures between 200 and 600 psi with outlet temperatures in the range of 815 to 925 C. However, analyses have shown that even though it is more costly to construct, a well-designed SMR can produce hydrogen more cost-effectively than an ATR.^[2]