Magnetic separation of CO₂ through sorption on magnetic hybrid nanoparticles

-    Goal of the Project:
o    To develop a new, economically and ecologically superior concept for CO₂ separation based on magnetic separation of magnetic hybrid nanoparticles with tailored sorption thermodynamics and kinetics
-    Technical content:
o    The concept of magnetic separation of CO₂ is quite novel. It is based on a conventional amine absorption process, but the solvent consist of functionalized magnetic particles dispersed in the aqueous phase and it is mainly the regeneration part, which differ from the conventional process. The CO₂ rich absorbent phase is passed through a magnetic field outside the absorber where the CO₂ rich magnetic particles are collected out of the bulk liquid while the water flows through. This small fraction of the bulk liquid is regenerated and remixed into the bulk liquid before return to the absorber top.
-    Technical advantages:
o    The regeneration step will necessitate some use of thermal energy, but since the volume is small, the energy demand is likewise smaller compared to conventional amine based solvent systems. However, the nanosolvent is not limited to energy economy alone. A durable nanosolvent will not decompose to the same extent as the presently used amines, conserving resources and limiting release of potentially harmful species to the atmosphere. Its low vapour pressure will further reduce pollution. Foaming and corrosion are other challenges in the application of conventional amine technology that may be met by using nanosolvents.
-    R&D challenges:
The major challenge is regarded the development of the functionalized magnetic particles with appropriate properties for efficient CO₂ absorption and desorption. Also the design of a proper regeneration process is a challenge especially with respect to large-scale application of magnetic separation.
-    Results to date:
Computational studies has shown that direct interaction with CO₂ and amine functionalities at the end of carbon chains attached to a T8O12-silicacube is independent of chain length. However, energetics may change drastically depending on intramolecular hydrogen-bonds and to water. As the complexity and size of the carbon chains increases, mapping all possible conformations and choosing the most probable one for energetic calculations is not feasible with standard quantum mechanics. Thus a methodology to study these specific systems with molecular dynamics is has been developed in collaboration with a group at Penn State University (USA), lead by Prof. Adri van Duin. A molecular model ReaxFF is developed, which is parametrized for bond breaking and bond making and can be tailored to a specific system. The required DFT studies have been completed and a ReaxFF force field tailored to our POSS-sorbents is now available. The model is used now to investigate reaction and activation energies for a range of POSS-based sorbents in order to recommend most promising systems for synthesis in CARBOMAG and to predict properties of the synthesized systems..
In the solvent synthesis and charactirezation, in the first stage of the project, the development effort has been focused on the development of nanofluid capable of competing with MEA in term of CO₂ capture. A systemic study of different nanofluids has been conducted and promising candidate has been selected. Each nanofluids were synthetized from the hybrid platform technology develop by SINTEF MK, FunzioNano®, based on silicon central structure and nitrogen-rich organic chain.
The development has entered a second phase with the incorporation of the magnetic particles into nanofluids. As all nanofluids are based on silicon cage structures, the challenge is to enlarge those structures to integrate magnetic particle into the network. A systematic study is being run to optimize each parameter to achieve a high incorporation of the magnetic particle into the nanofluid.
A simplified model of the magnetic separation unit has been implemented in the in-house tool CO₂SIM and an initial study of the heat requirement in the total process has been done. Based on assumptions that solvent performance is similar to 30 wt% MEA, simulations of CARBOMAG process shows potential of energy reduction by 29%. An interesting and important finding is that flow split ratio after the absorber seems to have larger effect on energy consumption than concentration of active sites in the solution. This gives an important feedback for the solvent development.