Nitrogen+Syngas 384 Jul-Aug 2023
31 July 2023
Hydrogen production with >99% CO2 recovery
BLUE HYDROGEN
Hydrogen production with >99% CO2 recovery
The world’s transition toward the use of hydrogen and ammonia as clean energy and fuel sources will depend upon production technologies that are affordable, scalable, and meet net zero carbon targets. 8 Rivers recently introduced8 RH2 , a groundbreaking solution that offers world-leading efficiency in hydrogen production and captures over 99% of CO2 emissions. Maulik Shelat of 8 Rivers provides an overview of the technology with a comparison to other low-carbon hydrogen production technologies.
Hydrogen and ammonia are widely expected to play key roles in the global energy transition. McKinsey & Company forecasts that the ability of clean hydrogen and ammonia to reduce emissions from hard-to-abate sectors would enable it to eliminate 80 Gt of cumulative CO2 emissions by 2050, accounting for 20% of annual emissions abatement in the year of 2050 (Hydrogen Council 2022). As shown in Fig. 1, the most anticipated applications for clean hydrogen include heavy-duty transportation (e.g., long-haul trucking, maritime shipping, and aviation), provision of high-grade and intensity industrial heat, power generation and storage, and industrial feedstocks for materials like steel and cement. Clean ammonia, on the other hand, will be used in fertilizer production, and is expected to play a large role in transporting clean hydrogen. Because of its higher boiling point, it can be transported in liquid form more cost-efficiently than hydrogen and then be converted back to hydrogen (a process called “cracking”) upon arrival at its destination. The transportation of ammonia by ship offers a practical decarbonisation solution for countries that face geographical limitations in scaling up renewable power generation or clean hydrogen production, such as Japan, where LNG import terminal conversion into ammonia import facilities are in evaluation (Atchison 2023).
A question of scale and speed
The IEA estimates that hydrogen use will need to increase from 94 Mt in 2021 to 200 Mt in 2030 to be on track for net zero emissions by 2050, 100 Mt of which will need to come from low-emission production (International Energy Agency 2022). To meet this increase in demand for clean hydrogen, production technology deployment will be dependent on carbon intensity (CI), technical readiness, and infrastructure scalability. Two leading technology contenders are hydrogen formed via renewable energy, such as electrolysis, and hydrogen formed via natural gas reformation with post-combustion carbon capture. Unfortunately, the first cannot currently scale at the speed, price point, and volume needed to meet forecasted demand and, while the second offers scalability, it only captures ~90-95% of carbon.
Recently, however, 8 Rivers announced the commercialisation of its second generation8 RH2 technology – a new process that provides the scalability and deployment speed of established blue hydrogen processes plus greater than 99% carbon capture.
Limitations on existing hydrogen production technologies
Two conventional large-scale hydrogen production methods are steam methane reforming (SMR) and autothermal reforming (ATR). Both are suitable for combination with carbon capture and sequestration (CCS), but both struggle to break the 95% carbon capture threshold put forth by think tanks such as the Rocky Mountain Institute (RMI) as the minimum for viable long-term investment (Weiss, et al. 2022). SMR currently tops out at 90% capture, and ATR at around 95%.
In both SMR and ATR, hydrogen is formed from natural gas (or methane) through chemical reactions in the presence of a catalyst. SMR reacts methane with steam, with heat delivered by an external combustion process. Thus, two gaseous flow streams exiting the reformer are isolated – dilute combustion flue gas and pressurized syngas (H2 , CO, CO2 , H2 O, and unreacted CH4 ) from which H2 is later separated. Alternatively, ATR has only one flow stream and no external heat source, as the methane is partially oxidised with oxygen in the presence of steam to drive the reaction. The single flow stream exiting the ATR reformer is high-pressure syngas.
For both of these processes, recovering CO2 requires back-end carbon capture. Conventional technologies use absorption and stripping, often with amine-based systems, which requires significant equipment and energy demand – driving up capex and opex. Amine liquids absorb CO2 from the gases that pass through the column. The amine with absorbed CO2 is then sent to a stripper column where it is lowered in pressure and heated to liberate and capture the CO2 . Due to the low concentrations from two main sources of CO2 generation in these conventional processes, back-end CO2 separation processes are energy-intensive and lack the means to efficiently capture 100% of CO2 . Therefore, some of the CO2 is released to the atmosphere along with the nitrogen, oxygen, and other gases rather than captured for sequestration. The high pressure of the ATR process enables a higher recovery of up to 95% of CO2 whereas the low-pressure flue gas stream of the SMR process reduces overall SMR capture efficiency to 90%.
8 Rivers’ 8RH2 process
In contrast to SMR and ATR, the8 RH2 process attains greater than 99% CO2 capture at lower capital and operating costs than its peers by employing 8 Rivers’ new CO2 Convective Reformer (CCR) technology. While the8 RH2 reformation process leverages much of the same equipment and process flow of established SMR processes, the CCR enables a pure stream of high pressure and temperature CO2 to deliver the heat to the reformation reaction. The result is two separate flow streams of flue gas and syngas, similar to SMR, but at high pressures, similar to ATR. However, unlike either of the existing processes,8 RH2 ’s use of CO2 as the working fluid enables inherent capture of pipeline-ready CO2 without post-combustion carbon capture – saving cost and energy consumption while increasing capture. Furthermore, the CCR is a prefabricated, compact tube-in-tube (bayonet) design with catalyst filled in an annular space and the product stream exiting from a central tube. This enables the hydrogen production process to operate more efficiently by exchanging heat between the product gas stream and the reforming gas stream. Additionally, as the CCR tubes are not exposed to direct flame, they can be packed in a much tighter configuration. This design allows the CCR to have a smaller footprint and to be prefabricated for faster and cheaper installation.
8RH2 process description
To start,8 RH2 reforms the hydrocarbon feed – which is natural gas combined with steam – in a device called the CO2 Convective Reformer, or CCR. A traditional convective reformer, its bayonet design contains tubes filled with catalyst that enable the conversion of natural gas and steam into syngas (H2 , CO, unconverted CH4 , and some CO2 leftover from the chemical reaction). The heat of reaction is provided by a high temperature and pressure CO2 stream produced by combusting hydrocarbon fuel (natural gas + process tail gas) in presence of pure oxygen using recycled CO2 as a diluent (as opposed to nitrogen in the case of air fired combustion).
The generated syngas from the CCR goes to the waste heat boiler, where it is quenched to around 650°F (342°C). Once cooled, the syngas goes through the water gas shift process, where the CO combines with more steam to produce additional hydrogen and CO2 . After another cool down, the mixture goes through the hydrogen pressure swing adsorption (PSA) process, which separates the hydrogen from everything else, including the CO2 . The residual tail gas has the CO2 generated on the process side, plus any unconverted methane and CO.
Once separated from the hydrogen, the tail gas is cycled to the Oxy-fired Combustor – a device that burns the tail gas with pure oxygen, additional methane fuel, and recycled CO2 as a dilutant. This combustion produces two components: hot CO2 and steam which pass through the CCR. At the same time, process feed gas (CH4 and steam) travels through the CCR via separate tubes filled with catalyst. Thus, the hot CO2 from the Oxy-fired Combustor remains physically isolated but delivers the heat necessary to reform the process gas into syngas.
Exiting the CCR, the now cooler but still high-pressure CO2 from the Oxy-fired Combustor, is further cooled in a direct contact cooler and then sent for sequestration while a portion is recycled to the oxy-combustor. Meanwhile, the pure hydrogen is extracted and the remaining tail gas is sent to the oxy-combustor. The result is a process that looks similar to SMR, and uses existing equipment, but that inherently delivers hydrogen and pipeline quality CO2 .
“… a groundbreaking solution that offers world-leading efficiency in hydrogen production and captures over 99% of CO2 emissions.”
Ultra-low carbon hydrogen
Investment and commercialisation of ultralow-carbon hydrogen and ammonia at significant volumes and at rapid speeds is needed now to bridge the decarbonisation gap as other technologies continue their development pathways. The focus of 8 Rivers is on speed, feasibility, and cost-effectiveness, all while keeping emissions reduction at the forefront of efforts.
The8RH2 process inherently captures CO2 for sequestration without a back-end CO2 separation process. This unique aspect enables8 RH2 Gen 2 to produce low cost, ultra-low CI hydrogen. Levelised cost of hydrogen produced via8 RH2 Gen 2 technology is expected to be 5-10% lower than traditional hydrogen production technologies while capturing nearly all of the CO2 . It is the most economical, efficient, and effective method compared to its low-carbon, natural-gas-powered hydrogen peers, and when combined with responsibly sourced natural gas, its lifetime emissions intensity can be as low as hydrogen production via renewables, depending on the method’s technology, on-site power generation, and other setup details.8 RH2 Gen 2 technology is available for commercialisation today to enable deployment of affordable and large-scale hydrogen and ammonia to meet the world’s increasing demand for clean fuels, energy and other industrial uses.
Key take-aways
- Clean hydrogen and ammonia are critical to the net-zero transition but renewable energy powered methods likely cannot scale quickly enough and existing SMR/ ATR reformation with CCS misses capturing 5-10% or more of CO2 emissions.
- 8 Rivers’ new8 RH2 Gen 2 technology leverages existing equipment and infrastructure in a novel process to inherently capture pipeline quality CO2 without requiring backend carbon capture.
- 8 RH2 delivers greater than 99% carbon capture at lower costs than competing technologies.
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