Carbon Membranes for CO2 Removal from High Pressure Natural Gas in Subsea Process

membrane systems possess many advantages such as small footprint, low capital and operating costs, being environmentally friendly, and exhibiting process flexibility. However, there are some challenges for the commercial polymeric membranes used for high pressure natural gas sweetening especially in subsea process due the membrane compaction and plasticization issues, which points to the need of the development of novel, high performance membrane materials and processes. Thus, in the CO2Hing project, we aim to develop mechanically strong, high performance asymmetric carbon membranes from the cheap cellulose materials for natural gas sweetening. The technology and economic feasibility as well as the social and environmental impacts will be analyzed based on process simulation and life cycle assessment to evaluate the novel carbon membrane system for high pressure natural gas sweetening in subsea process.

The scientific results generated in this project will contribute to national and international knowledge within the field of natural gas processing and CO2 capture. the filed patent will attract great attention from oil/gas industries, and potentially to bring this energy-efficient technology for commercial natural gas sweetening to reduce greenhouse gas emission during gas production. Education of engineers and scientists will contribute in maintaining a strong research and education base in Norway, one PhD and one Master thesis generated from this project. more than 15 articles published in high-level peer-review journals, 6 oral presentations and 2 Posters were disseminated in the international conferences.

Developing novel environmentally friendly and energy efficient technology for CO2 removal from natural gas is essential to improve the competition of natural gas processing plants. Although chemical absorption is still the state-of-the-art technology in this area, membrane technology posses many advantages such as small footprint, low capital and operating costs, being environmentally friendly, and exhibiting process flexibility shows great potential. The challenging on natural gas sweetening membranes in the market today are the membrane compaction and plasticization, which points to the need of development on novel membranes materials for high pressure application in subsea process. Thus, in the CO2Hing project, we aim at developing mechanically strong, high performance asymmetric hollow fiber carbon membranes that can exceed CO2/CH4 Robeson upper bound (CO2 permeance >0.3 m3(STP)/(m2.h.bar) and CO2/CH4 selectivity >100) from cheap cellulose materials for natural gas sweetening. In order to achieve this objective, 1) Suitable ionic liquids with appropriate physicochemical property will be designed by molecular dynamic simulation, and synthesized for dissolution of cellulose at room temperature (<50C); 2) Asymmetric cellulose hollow fibers with desired structure and morphology will be spun from cellulose/ionic liquids dope solution by controlling liquid-liquid demixing mechanism based on equilibrium thermodynamics of ternary phase diagram; 3) Asymmetric, defect-free and straight hollow fiber carbon membranes will be prepared by controlling carbonization protocol, and employing post-oxidation and post-reduction; 4) determining the optimal operating condition by experimental design and statistical analysis to achieve high CO2/CH4 separation performance of the carbon membranes. 5) Employing process simulation and life cycle assessment to evaluate the technology advance of a closed-loop two-stage carbon membrane system for natural gas sweetening in subsea process.