Feature Story | 7-Mar-2024

Cuts costs for capturing carbon dioxide, essential for producing blue hydrogen, by half

Minimizing carbon dioxide emissions from hydrogen production contributes to achieving carbon neutrality. CO2 selectivity over methane improved by 4.6 times, maintaining excellent adsorption working capacity

National Research Council of Science & Technology

Dr. Park Jong-ho's research team at the Clean Fuel Research Laboratory of the Korea Institute of Energy Research (KIER) has successfully developed a key material & process technology that significantly reduces the cost of capturing carbon dioxide, which is essential for the production of blue hydrogen*.
* Blue hydrogen: hydrogen produced by reforming fossil fuels, such as liquefied natural gas (LNG), a process that generates gray hydrogen, with the carbon dioxide emissions generated during this process being removed through the use of CCUS (Carbon Capture, Utilization, and Storage) technology.

The focus on clean energy has primarily been on Hydrogen (H2), however, the majority of hydrogen production (over 90%) is derived from fossil fuels, resulting in 10kg of carbon dioxide for every 1kg of hydrogen produced. The ultimate objective is to use green hydrogen*, which has zero carbon emissions. However, until economic and technical constraints are addressed, a bridging technology is necessary.
* Green hydrogen: hydrogen obtained by electrolyzing water using renewable electricity, a process that does not emit carbon dioxide during production, making it an environmentally friendly hydrogen.

The most realistic alternative is blue hydrogen, a method of hydrogen production that captures carbon dioxide emitted during the production process and stores it underground or utilizes it as a raw material for petrochemical products, thereby preventing release of carbon dioxide into the atmosphere. According to the International Energy Agency, the supply of blue hydrogen is expected to reach 200 million tons by 2050, resulting in a reduction of 1.3 billion tons of carbon dioxide emissions annually.
* The government is set to launch the world's first clean hydrogen power generation bidding market in June 2024, where all types of clean hydrogen, from green hydrogen to blue hydrogen, can participate, in an effort to activate the clean hydrogen industry. SK E&S plans to establish a blue hydrogen production plant near the Boryeong LNG terminal and aims to produce 250,000 tons of blue hydrogen annually.

The KIER research team improved the overall efficiency of the process by enhancing the selectivity for capturing carbon dioxide from exhaust gases and the low adsorption capacity of adsorbents used in conventional carbon dioxide capture processes. By using the developed adsorbent in the process, it is possible to precisely capture carbon dioxide with a selectivity more than 4.6 times higher than commercial adsorbents, while maintaining an adsorption capacity comparable to that of commercial adsorbents.

Commercial adsorbents used in conventional carbon dioxide capture processes had trade-off drawback; CO2 selectivity over other gas components, particularly CH4 in hydrogen production processes, and adsorption working capacity. Conventional adsorbents having high CO2 selectivity exhibited low adsorption working capacity, and vice versa. Owing to these disadvantages, it was necessary to enlarge the capture facilities to increase the amount of carbon dioxide captured, making it difficult to expect efficiency improvements such as operational cost savings according to the downsizing of the equipment.

To overcome these challenges, the KIER research team developed an adsorbent with polar surface characteristics, while optimizing the binding energy for carbon dioxide to maximize effective adsorption working capacity. The adsorbent attracts and captures molecules through electrostatic attraction. The developed adsorbent is designed to be polar, therby minimizing attraction to methane, which has a quadrupole moment close to zero, while maintaining affinity for carbon dioxide.

The research team also developed a Vacuum Pressure Swing Adsorption (VPSA) process technology using the developed adsorbent. Carbon dioxide was successfully captured and produced over 99% purity with 92% recovery through continuous operation at optimized condition. In contrast, conventional adsorbents could only recover 67% of carbon dioxide at a 96% purity, whereas the developed adsorbent significantly improves both purity and recovery, greatly contributing to the efficiency of the process.
* Vacuum Pressure Swing Adsorption: Gas separation technology using the difference in adsorption amount according to pressure change

Especially, the power consumption required for capturing and producing high-purity carbon dioxide has significantly decreased. According to numerical simulation results, approximately 40 kilowatt-hours per ton of CO2 (40 kWh/ton-CO2) would be required. This is a reduction to half the power usage compared to the technology of leading company Air Products in the United States, which requires 83 kWh/ton-CO2. As a result, the cost of capture can also be halved.

Dr. Park Jong-ho, the lead researcher, stated, "By combining the adsorbent developed this time with the hydrogen plant design technology and process development experience possessed by our researchers, it will be possible to produce blue hydrogen at a scale of one million tons per year, with a low capture cost of less than 30 dollars per ton of CO2. We aim to lead the blue hydrogen production market by securing domestic technology that surpasses advanced technologies, and we will strive to contribute to achieving carbon neutrality by 2050."

Meanwhile, this research was conducted with the support of the Ministry of Science and ICT's CCU 3050 project.

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