Natural gas reforming

Reforming natural gas is a sophisticated and well-established production method that works upon the existing natural gas pipeline delivery infrastructure. Currently, 95 percent of hydrogen generated in the United States is produced by reforming natural gas in huge central facilities. This is an essential technological approach for hydrogen generation in the near future.

HOW DOES IT FUNCTION?

Natural gas includes methane (CH4), which may be converted into hydrogen by thermal processes such as steam-methane reformation and partial oxidation.

A refinery where hydrogen is created by reforming natural gas.
Despite the fact that the majority of hydrogen is currently generated from natural gas, the Hydrogen and Fuel Cell Technologies Office is investigating many methods for producing hydrogen from renewable resources.

REFORMING USING STEAM METHANE

Steam-methane reforming is a mature industrial method that uses high-temperature steam (700°C–1,000°C) to create hydrogen from a methane source such as natural gas. In steam-methane reforming, methane interacts with steam at pressures ranging from 3 to 25 bar (1 bar = 14.5 psi) in the presence of a catalyst to create hydrogen, carbon monoxide, and a tiny quantity of carbon dioxide. The reforming of steam is endothermic, meaning that heat is required for the reaction to continue.

Carbon monoxide and steam are then reacted with a catalyst in what is known as the “water-gas shift reaction” to create carbon dioxide and more hydrogen. In a final phase referred to as “pressure-swing adsorption,” carbon dioxide and other impurities are removed from the gas stream, leaving hydrogen that is basically pure. In addition to producing hydrogen from ethanol, propane, and gasoline, steam reforming may also be used to manufacture hydrogen from other fuels, such as methanol, propane, and gasoline.

Reforming of methane using steam
CH4 with H2O (plus heat) yields CO and 3H2

Water and gas transformation
CO and H2O are converted into CO2 and H2 together with a tiny quantity of heat.

LIMITED OXIDATION

In partial oxidation, methane and other hydrocarbons in natural gas react with a little quantity of oxygen (usually from air) that is insufficient to convert the hydrocarbons to carbon dioxide and water. Using less than the stoichiometric quantity of oxygen available, the reaction products consist mostly of hydrogen and carbon monoxide (and nitrogen, if the reaction is conducted with air rather than pure oxygen) and a negligible amount of carbon dioxide and other molecules. Carbon monoxide combines with water in a water-gas shift process to produce carbon dioxide and more hydrogen.

Exerting heat, partial oxidation is an exothermic process. The process is often more quicker and needs a smaller reactor vessel than steam reforming. As seen in chemical reactions of partial oxidation, this method yields initially less hydrogen per unit of input fuel than steam reforming of the same fuel.

Reaction involving partial oxidation of methane
CH4 and 12O2 produce CO and 2H2 (plus heat)

Water-gas transformation
CO and H2O are converted into CO2 and H2 together with a tiny quantity of heat.