1. Membranes for gas separation

The Memfo group

The Memfo group currently counts 9 members (5 PhD-students, 2 post docs, 1 senior researcher, and the head of the group, professor May-Britt Hägg) The group has extensive activities both on basic membrane material development, as well as membrane gas separation processes, modelling and simulations. The main focus for the research is CO2 capture by membranes (from flue gas, natural gas sweetening, biogas upgrading) and hydrogen recovery from various mixed gas streams. In addition to these energy focused applications, the research on membranes for chlorine separation continues. The membrane materials in focus are various types of polymers, nanocomposites, carbon membranes, and modified glass membranes. The international network is extensive, with co-operation both within EU-projects, USA, Japan, the Nordic countries and Russia.

Brief description of sample projects

a) EU-project NaturalHy http://www.naturalhy.net
The project counts ~40 partners, and the main idea is to investigate the possibility of using the European gas net work for co-transport of hydrogen with natural gas. Realising that the society only slowly will convert to hydrogen based energy, the idea is that hydrogen may be injected into the gas net at various places where it is produced, and then separated from the natural gas at points along the line where pure hydrogen is needed (for fuel cells or storage). The task into which Memfo is doing research, is development of suitable membrane(s) for hydrogen recovery. Carbon molecular sieve membranes as well as mixed matrix materials are investigated for this purpose. One PhD-student and one post doc is engaged in this research. Very promising results have been documented. The project continues for 3 more years; project co-ordinator is Gas Unie in the Netherlands.

b) Membrane development for selective CO2 capture
The membrane material being developed in this project contains a specific “carrier” which makes it selective for CO2 while other gas components are being retained. The material is based on a polymer containing fixed amine groups as carriers. A significant progress was achieved during 2005, both with respect to CO2-flux and selectivity compared to the other components in a mixed gas. The obtained results have drawn international attention. The membrane is now patented, and there are big expectations for the further development. The project runs for 2 more years; then hopefully the membrane is ready for small scale pilot testing. One senior researcher, one PhD, and one “associated PhD” is working on the project. Next step will be focusing on process development. Project partners are NFR, Statoil and Alstom.

c) Two projects within the Nanomat program / NFR
in cooperation with Sintef and North Carolina State University. In both projects the material development for hydrogen – CO2 separation are in focus. There are two PhD-students on the US-side; one PhD and one Post doc on the NTNU-side, in addition to one “associated PhD” on the NTNU-side. The materials under development here are nano-composites (so called mixed matrix) and block copolymers – very challenging and very promising. Within this project a NASA award was granted during 2005 for a US patent.

d) Development of hybrid membrane for chlorine purification
Memfo is one of very few groups in the world doing research on membranes for the purification of chlorine gas. This is probably for security and safety reasons, and the challenge of handling this poisonous gas. The project is extremely challenging, but if successful, it will be a major step towards simplification of expensive and complicated unit operations for recovery of chlorine from various process streams. Chlorine is one of the major chemicals used in chemical process industry worldwide. The materials in focus are glass and perfluorinated polymers. There is co-operation with Japanese research in this project. Small steps forward have been documented during 2005, and one post doc is currently on the project. There is a major interest from industry in this project.

Applications for projects with Denmark and Russia (Univ. of St. Petersburg) were filed in 2005 – the co-operation is already active.

2. Crystallization
The research within crystallization is focused at kinetics of nucleation, crystal growth, and agglomeration in order to predict and control the particle size distribution and shape of crystalline particulate products for the effect on down-stream processes like solid-liquid separation and powder characteristics.

In 2005 one researcher has been working in a project directly financed by GE Healthcare to analyse the separation and purification in a bottleneck intermediate crystallization step in their production units at Lindesnes, Norway.

Two joint projects have been started up in 2005 employing 2 PhD candidates and 1 Post Doc for the period 2006-2008/2009.

Sample Projects:

a) Optimisation of Glycol Loop Design and Operation
The aim of the project is to develop a simulation tool for glycol loops in processing of natural gas. This necessitates a deep understanding of the precipitation and crystallization behaviour of salts and scale-forming carbonates in ethylene glycol and water mixtures. Kinetics of calcium carbonate precipitation in the glycol injection point off-shore and the crystallization and separation of salts in the on-shore glycol reclamation units will be the main research tasks. The project is in collaboration with Institute of Energy Technology, Norway (IFE) and financed by several international oil and gas companies and the Research Council of Norway (NFR).

b) Industrial Crystallization and Powder Technology
The goal of this project is to relate filtration and washing characteristics and powder properties to the underlying growth and agglomeration phenomena. It involves studies of inorganic salts and pharmaceuticals, and the primary target for the activity at NTNU is to link the parameter choices in the crystallisation process to the subsequent filtration step by focusing on common mechanisms for these selected systems. The project is in collaboration with POSTEC at Tel-Tek and is financed by the Research Council of Norway (NFR) and Norwegian industry partners.

3. Membrane separation of liquids: Sample project: Developing Pressure Retarded Osmosis (PRO) for power production.
Membrane separations in liquid media are well established in many processes and expected improvement may often be small and incremental, but still there are many open problems.

Reverse osmosis is today one of the major methods for desalting ocean water into freshwater. Osmotic effects demands that a high pressure on the saltwater side of the membrane modules must be applied to override the osmotic pressure difference between sea water and freshwater. If the applied pressure in the cells is lower than the osmotic pressure the water flow is reversed and freshwater flows into the saltwater compartment, thus increasing the volume of moderately pressurized saltwater. This is the principle of Pressure Retarded Osmosis (PRO), which may be used to produce electric energy as the surplus water on the saltwater side may be run through turbines for power production. The potential for power production at the outlet of every river that flows into the ocean is very large.

To make this principle to work economically, the membrane and its function is of very large importance.

One of the problems to eliminate or reduce is the gradually fouling of the membranes by different impurities in the water and also the possibility of bacterial and algae growth on the membranes. This will gradually reduce the water flux through the membrane.

In two doctoral projects in our group these problems have been under investigation for the last few years. The studies are performed in experimental membrane rigs, equipped with automatic cleaning cycles and remote data reading. One set of experiments is performed in small cells which are designed to uncover the types of fouling that may occur on contacting Norwegian river water with sea water from a fjord. Cleaning procedures and frequencies of are tested during the experiments which are run continuously for several months. Verifying experiments for comparison are run in a local laboratory.

Another set of experiments on a larger rig is aiming at optimizing membrane modules of a new construction for use in salinity power plants. Included in this part of the project is also computer modelling of the flow through the modules. The experiments are done in cooperation with SINTEF and others, and are partly financed by Statkraft.