3rd Generation solvent membrane contactor

In this project a membrane contactor is proposed as a viable solution to fully exploit the potential of the highly volatile 3rd generation solvents. Non-porous composite membranes with high CO₂ permeation but limited amine permeation towards the gas phase will be developed and optimized for the membrane contactor. The 3rd generation solvents will be further optimized to improve the separation performance and reduce the energy penalty associated with the amine regeneration step. In view of the smaller footprint and the easier scalability compared to traditional absorption columns, the 3rd generation solvent membrane contactors could have a faster and more accessible commercialization of the CO₂ capture technology for post combustion applications.
Goal of project:
To develop energy efficient solution for CO₂ capture in post-combustion process.
Technical content:
This project deals with the development of membrane contactor process using volatile CO₂ absorbents for CO₂ capture from flue gas coming from power plants.

The research is carried out as six main tasks:
-    Compatibility between solvent and membrane materials;
-    Membrane material development and characterization;
-    Characterization and optimization of compatible solvent systems;
-    Preparation of membrane module and lab scale experimental rig;
-    Further characterization of the chosen solvent;
-    Process modelling and cost analyses;
Technical advantages:
The project should result in a proof of concept for a process for CO₂ capture utilizing a 3rd generation solvent in a membrane contactor achieving:
-    A regeneration energy requirement less than 2 MJ/kg CO₂ captured (for 13 vol% CO₂ in the exhaust gas)
-    Control of solvent and degradation product emissions to levels acceptable by Norwegian and international regulations.
-    Avoidance or drastic reduction of mist formation in gases where this is a problem
-    Reduction of process footprint (and cost) compared to a conventional column based process
R&D challenges:
The two main challenges in this project are:
1)    To select/develop a solvent system that has the potential for low energy demand and at the same time shows long term compatibility with the chosen membrane material;
2)    To develop a membrane material, compatible with the solvent, that has low mass transfer resistance for CO₂ and ensure barrier features towards the amine permeation.
Results to date:
The following results have been achieved during phase I of the project:
(1)    5 different new solvent systems with better energy efficiency compare to the benchmark solvents (i.e., 5M MEA and 5M DEEA 2M MAPA) have been identified through screening tests. The new solvents showed a larger CO₂ partial pressure at high temperature (120 °C), suggesting an easier and more energy efficient regeneration. The selected absorbents also showed a lower heat of absorption compared to 5M MEA on a specific cyclic capacity loading ranges. The lowest energy penalty of 2.3 MJ/kgCO₂ has been estimated in an optimized solvent;
(2)    A polymer family (e.g., AF2400), which is found durable in the 3rd generation solvents and stable in a long term operation, has been identified as the thin coating layer materials for the non-porous membrane contactor. AF2400 composite membranes have high CO₂ permeation rate, and the presence of the liquid phase in the contactor shows a limited effect on the transport properties of the membranes. Pervaporation of various amine mixture (5M MEA and DEEA-MAPA blends) have been tested, and the membranes achieved high selectivity (> 100) in the considered operating conditions (25 – 60 °C);
(3)    A procedure has been determined to coat a thin (1 µm) layer of AF2400 on porous PP hollow fibers. Membrane modules containing up to 45 fibers have been prepared (membrane contactor tests are currently ongoing).