Development of Energy-Efficient Fiber Sorbents for Direct Air Capture
Koh’s group at the Saudi Aramco-KAIST CO2 Management Center developed a fiber-type adsorbent module that can be produced at low cost and in high capacity based on high-performance porous organic frameworks. The present work is significant because the fiber-type adsorbent can be applied to highly efficient adsorption and desorption technologies for the capturing of atmospheric carbon dioxide included in the exhaust gases from power plants and many chemical processes.
Previous carbon capture was performed by using an aqueous amine solution that can be easily contacted with carbon dioxide. After carbon dioxide is dissolved in the aqueous solution and then evaporated, it is again liquefied and the resulting liquid is stored in the ground. However, the regeneration of the waste aqueous solution requires huge cost and facilities, and the efficiency is low. The previous technology may be used to reduce the carbon dioxide in the exhaust gas from power plants by 30%, but 20% of the generated power should be used to heat the aqueous solution for regeneration. That’s why Professor Koh says that the existing caron reduction technology has a very low profitability and causes many penalties.
|Technological Accomplishments Contributing to the Realization of Genuine Carbon Neutrality|
A groundbreaking improvement in the method for reducing carbon dioxide
To overcome the limitations of the conventional carbon capture method, the research group developed a fiber-type adsorbent based on porous organic frameworks. The researchers needed a method for giving porosity to metal organic frameworks (MOF) consisting of nanoparticles, because MOF has a low porosity despite the easy adsorption with gaseous substances.
If the porosity is low, the MOF is unable to tolerate the high flow rate of the exhaust gas. Just as a face mask filter with a low air permeability makes the breathing difficult, when MOF with a low porosity is used to capture the exhaust gas from a power plant, the power generation facilities will be over-loaded. Hence, the research group designed a porous polymeric absorption module that can reduce the pressure of the gas flow, and combined the module with an MOF that has the function of amine, developing a fibrous adsorbent with high carbon dioxide absorption capacity. Professor Koh compare it to thread.
“We produced polymeric threads that are 3 to 4 times as thick as our hairs, and then we filled them with solid adsorbent particles. In this way, we increased the porosity. Imagine a face mask including a filter of excellent performance. When you are breathing, you can freely breathe out without any resistance. Our new adsorbent allows for the processing of an exhaust gas at a very high flow rate. Another advantage of our technology is that we can significantly downscale the volume of the adsorption system, compared with the conventional system based on the amine solution.”
Capturing carbon in both the exhaust gas and the air
The present work is expected to make great contributions to carbon neutrality by drastically reducing the energy cost that is needed for the reduction of carbon emission. In particular, the fiber-type adsorbent developed by the research group has the advantage that it can easily capture the carbon dioxide included in both the exhaust gas and the air. The carbon dioxide concentration in the air is just 0.04%, while it is about 10% in the exhaust gas. “The affinity of an adsorbent should be much higher in order to capture the carbon dioxide in the ait. Our fiber-type adsorbent shows good performance in both areas.” Professor Koh predicts that the innovative technology may be commercialized in 3 to 5 years. “My goal is to utilize the over-produced renewable energy from islands and mountainous areas in carbon capture, and then convert the concentrated carbon dioxide to highly value-added materials. That is genuine carbon neutrality, isn’t it?”
2021 Annual Report