A new cheaper, highly-efficient process of producing hydrogen from fossil gas has been unveiled that is said to be able to capture more than 99% of CO2 emissions by recycling carbon dioxide within the technology.
8 Rivers, a company originally set up to commercialise its chief inventor Rodney Allam’s design for zero-emission gas power plants, has designed a similar approach to blue hydrogen production with its new 8RH2 technology.
The Allam cycle that he co-invented combusts natural gas with oxygen, producing a high-pressure “supercritical” CO2 stream that can be used to drive power generation within the system — while the small amount of CO2 that exits the cycle during each run can be easily captured owing to its pressure and purity.
8 Rivers’ “8RH2” process similarly uses and recycles CO2 via an “oxy-fired combustor”, where oxygen is added, and a “CO2 convective reformer” that takes the natural gas, and hot carbon dioxide and steam from the combustor to form a syngas — a mixture of carbon monoxide and hydrogen that is later separated.
The hot CO2 is extracted “using a proprietary refrigeration based CO2 separation system”, according to the North Carolina company’s website.
8 Rivers says its technology “is cheaper and cleaner than traditional steam methane reforming [SMR] approaches that also release all their carbon dioxide”.
And it explains that it “has optimised thermal efficiency for improved conversion rates, minimal power requirements and high CO2 capture rate at high concentration and pipeline pressure” compared to other methods of producing H2 from gas such as steam methane reforming and autothermal reforming (ATR).
Most blue-hydrogen carbon capture technologies target capture rates in the range of 90-96% depending on the hydrogen production method, with ATR considered best-in-class for producing concentrated, high-pressure CO2 streams that can be easily separated from H2.
It is harder to capture carbon dioxide from the more efficient SMR process because while 60% of the CO2 can be easily captured from the process stream, the remaining 40% is contained in flue gas, which comes out under low pressure at high temperature and contains other gases such as oxygen, making its CO2 difficult to capture without further expensive energy-demanding post-combustion processes.
8 Rivers tells Hydrogen Insight that in addition to confirming its 99% carbon capture rate, the 8RH2 process also has an overall efficiency of more than 80% in terms of the potential gas-to-hydrogen ratio, compared to around 65-75% for SMR.
The company is now progressing design for a pilot commercial-scale plant, with a site expected to be chosen by the end of this year, and won a $100m investment from South Korea’s SK Group in March.
The Allam Cycle technology has already been validated for gas-fired power production at a 50MW test facility in La Porte, Texas, which was commissioned in 2018 by a company called NET Power that is co-owned by 8 Rivers, utility Constellation Energy, Occidental Petroleum and energy services company Baker Hughes.