A New Cryogenic Recovery Technology for Low Price, High Purity, and Readily Transportable Liquid CO2 and for Zero-Emission of Methane
Authors: Hirai Y. , Takamura M. , Ichinose I. 
Published: November 2024

We have developed a new economically available CO2 recovery and liquification technology that facilitates CO2 transfer, shipping, and the following injection at offshore. The leakage of CO2 and methane has been a significant problem in the development of natural gas, as well as in the production of biogas. Especially, latter leakage significantly contributes the acceleration of global warming. However, large energy consumption of the present CO2 recovery processes also limits the application range. Our low-cost technology can separate CO2 and methane without GHG leakage, and it will be applied for natural gas containing high concentration of CO2 (~70%) in Southeast Asia and for anaerobic biogas reactors of 40~45% CO2 concentration.

Our technology features a cryogenic CO2 liquification system combined with CO2 sorption columns containing soft and tough polymeric materials. We developed an elastic sorbent of cross-linked PDMS (polydimethylsiloxane). This sorbent can capture CO2 up to 800 mg/g at low temperature and high pressure. PDMS has a significantly low glass transition temperature (ca. −120℃) and does not deteriorate for many years even under existence of BTX, VFA, H2S, and other gases. The cryogenic CO2 liquefication system with CO2 sorption columns is operated at the temperature near -50℃ and at the pressure near 5 MPa. CO2 and methane separated by the sorption columns and the purification unit, respectively, are returned to CO2 liquefication system, then any gases are not emitted to the outside.

We realized (1) recovery of high purity liquid CO2, (2) lower energy consumption, (3) significantly space-saving facility, and (4) no leakage of CO2 and methane though the process. Soft PDMS elastomer with extremely large CO2 sorption capacity readily desorbs the sorbed CO2 only by decreasing the pressure. The large CO2/CH4 sorption selectivity enables to produce high purity methane. As for durability, we have confirmed that the performance does not deteriorate even after repeated testing of 500,000 times (equivalent to over 5 years of use). The footprint of CO2 sorption columns required for a small natural gas field of 10,000 m3/h is only 10 m2, providing a considerable space-saving manner. Our technology shows the highest energy efficiency and can reduce overall GHG emissions. Furthermore, recovered CO2 is obtained as liquid state, suitable for the following transfer and storage. We will establish a startup and develop new business models for biogas production and natural gas development.

In 2024, a significant improvement has been made in the system to meet customer requests for high purity CO2. The new system can increase CO2 purity to a maximum of 99.99%, so CO2 can be used not only for CCS but also as a raw material for chemical reactions as well as food additives. Based on the simulation results, our technique requires about 30% less energy than conventional membrane separation systems, and we achieve the lowest CO2 recovery cost of less than 1,000 JPY/t-CO2 (6.4 US$/t-CO2 as of 2024.7.22) at natural gas fields of certain conditions.