Membrane Distillation (MD) is a very promising new technology which can be coupled with renewableenergies and/or waste heat to produce pure water at a low-cost. MD is extremely dependent upon theperformance of the membrane, as it dictates the mass transfer, the heat transfer and the long-termapplication. Unfortunately, there are no commercially produced MD-specific membranes at this point intime. This project aims at finding correlations between membrane characteristics and their performancesin order to define the optimal morphologies and operating conditions for a MD-specific membrane. Todo so, the characteristics of 3 PTFE membranes initially designed for MF were determined throughporosity measurements and microscopic imaging, while their performances were evaluated by measuringthe air permeability and by testing them on an AGMD bench-scale unit.It was found that the most desirable characteristics for a membrane with a high flux are a film with largeporosity, low tortuosity, a small thickness with a resistance to compaction and that has not been subjectedto thickness altering processes. Moreover, the surface pore sizes need to be small enough to avoid surfacewetting, and the backing layer should not restrict the vapor flow in a significant way and should possesslarge open areas.As the feed water temperature and/or the flow rate rises, the flux increases and the energy requirementdecreases, this means that one should ideally aim for the highest possible operating conditions whichrequires larger costs. Therefore it is necessary to find a cost effective solution for each application.The results show that, for comparative purposes, Gurley values are good indicators of a membrane’soverall performance in MD, despite the fact that it does not always accurately predict it. It has also beenfound that membrane specifications provided by manufacturers are generally only approximations, andshould therefore not be used as very precise data for comparing membranes.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kth-31959 |
| Date | January 2011 |
| Creators | Baaklini, Daniel |
| Publisher | KTH, Kraft- och värmeteknologi |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
Page generated in 0.0117 seconds