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Currently, 95% of the hydrogen produced in the United States is produced via steam methane reforming.[1] This process converts methane and water into hydrogen and carbon dioxide. Hydrogen production typically occurs at centralized facilities. Hydrogen compression or hydrogen liquefaction is commonly used to concentrate hydrogen gas prior to shipment via tube trailer or pipeline.
Tube trailers have an upper pressure limit of approximately 3200 psi. Hydrogen is compressed into the trailer and further compressed on-site in order to provide a 5000–10,000 psi hydrogen fill to vehicles. Transporting liquid hydrogen requires cooling hydrogen below −250°C, and losses during handling are due to hydrogen boil-off. Both hydrogen compression and liquefaction are energy intensive. A hydrogen pipeline network would provide a more efficient way to transport hydrogen by eliminating/reducing distributed compression and storage hardware. However, an extensive hydrogen pipeline network does not currently exist.
Another option for distributed hydrogen is the on-site reformation of liquid feedstock. The EERC reformer system utilizes liquid feedstocks that are pressurized at up to 12,000 psi, introduced into a reactor, and continuously converted to a high-pressure, hydrogen-rich reformate stream that can be purified at pressure and dispensed into vehicles. This design eliminates hydrogen transportation, hydrogen liquefaction and/or compression, and large-volume storage of high-pressure hydrogen. Liquid feedstock would be brought to and stored in tanks at fueling stations and the high-pressure hydrogen reformer would ideally be located out of the way, above hydrogen dispensers.
Laboratory experiments have been performed on methanol, ethanol, glycerol, and S-8 (a Fischer–Tropsch-based jet fuel) with conversion and selectivity that greatly exceed modeled output. Recently, a methanol feedstock fed to the reactor at a rate of 2 lb/hour was converted to a 6800-psig reformate stream comprising 83 volume% (vol%) hydrogen, 11 vol% carbon dioxide, 2 vol% carbon monoxide, 1 vol% methane, and less than 0.5 vol% each of water and light hydrocarbons. A parallel effort is focusing on the high-pressure purification of the reformate gas stream to provide proton exchange membrane fuel cell-quality hydrogen. Results from recent high-pressure reforming experiments will be presented, along with an overview of the on-site liquid reforming approach.
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