Abstract
It is very likely that gas separation processes will be of increased importance in future, as they are a crucial element in the world’s changing energy and raw material supply scenario. Furthermore, they are required for minimisation of greenhouse gas emissions. Gas permeation is one of the processes that is especially well suited to address the resulting separation tasks. It is versatile with respect to application sizes as well as operating temperatures and pressures. Key elements are the availability of a membrane material suited for the desired separation and the possibility to apply it to a support structure stable under the envisaged operating conditions as well as mounting the resulting technical membrane into a suitable membrane module. These aspects are of special importance for the use of membrane gas separation at elevated pressures.
This contribution will concentrate on possible applications in the fields of natural gas conditioning and the processing of liquefied natural gas as well as the integration of gas permeation stages in novel and established production routes in the chemical industries. Examples that will be introduced are the conditioning of natural gas with respect to the removal of carbon dioxide, higher hydrocarbons and water vapour or the management of hydrogen and carbon dioxide streams in power to X applications. These examples will be discussed considering the process design as well as the suitable polymeric membranes. A special focus will be put on high flux thin film composite membranes.
The demanding operating conditions require a careful consideration of the phenomena influencing the permeation process. These include the real gas behaviour of the gas phases, swelling phenomena of polymer layers, temperature dependency as well compaction issues. Furthermore does concentration polarisation play an important role, especially when high flux membranes used in high pressure applications are considered in combination with condensable gases. An additional issue important at high pressure gas processing by membranes is the Joule-Thomson effect, typically causing a cooling down of gases when they are throttled to a lower pressure due to the permeation through the membrane material. The impacts of these effects have to be accounted for when designing membrane modules suitable for transferring the membrane materials’ intrinsic properties to the actual separation process.
