Membrane and Desalination Technologies - TCE Moodle Website

Membrane Technology: Past, Present and Future 35
Air Separation
O 2 Separation
N 2 Separation
Gas Separation
Hydrogen Separation
Natural Gas Separation Vapor/Gas Separation
CO 2 Removal
Hydrocarbons Recovery
Dehydration
N 2 Removal
challenges in scale-up, cost and energy minimization. Figure 1.15 summarizes various
applications of GS membranes (136).
4.3. Challenges for the Membrane Industry
Vapor/Vapor Separation
Ethylene/Ethane
Propylene/Propane
n-butane/Isobutane
Olefin/Paraffin
Recovery of
Hydrocarbons & Processing Solvent
From petrochemical Purge Gas
Fig. 1.15. Applications of gas separation membranes (adapted from ref. (136)).
Despite the successes and advancements, there is a clear need for further improvements of
both membranes and processes. Current applications of membrane technology for liquid
separation and purification are almost entirely restricted to the processing of relatively benign
water-based systems. Although an increasing variety of membranes are available for water
production and wastewater treatment, there are very few membranes that are able to tolerate
harsh conditions posed by oils, solvents and organics. A similar challenge also exists in
the case of gas/vapor separations. The diversity and operating range of actual large-scale
membrane-based separations remain limited, as the selectivity of current membrane materials
cannot be maintained even under moderately aggressive feed conditions. These challenges
must be overcome to ensure a sustainable industrial growth of existing membrane processes
and to identify opportunities for new applications. The technical barriers include fouling,
instability, low flux, low separation factors and poor durability. Advancements on new generations
of organic, inorganic and ceramic membranes, and mixed matrix polymer–inorganic
and polymer–carbon composite membranes are urgently needed. In addition, economical
processes to form large modules are important and innovative ways to incorporate membranes
in industrial processes are also required. The other major challenge and driver for change and
innovation is the need to reduce the energy used in separation processes, such as membrane
technology. For example, in 2007, RO desalination world wide consumes 50% separations) on a “business-as-usual” basis. Clearly, RO desalination faces
a major energy challenge. An assessment of the challenges and applications for membrane
technology has been provided by Fane (142).