Hollow fibre membranes for gas separation

During the last century and a half, the development of membranes has resulted in a voluminous amount of literature on the subject. 

One review of membranes by Lonsdale still contained over 400 references, even though the author claimed to have covered only the most relevant references in the article. This review also does not therefore intend to be a comprehensive review of the development of membrane technology rather it is a short account of the interesting developments that have taken place along with the milestones in membranology that have led to the development of hollow fibres for industrial gas separations. 

In order to prove his hypothesis, Pick used two different diffusional-shaped cells containing water and placed a crystalline salt at the bottom of the cells. In case A, the cell was a cylindrical shape and in case B, the cell was a conical shape narrowing at the top. 

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The third part contains five chapters, with a focus on integrating processes and integrated structures. Chapter 10 provides an overview of the developments and key issues in fibre-optic smart textile composites. Chapter 11 presents hollow fibre membranes for gas separation. Chapter 12 describes embroidery as one way of integrating fibre-formed components into textile structures. Chapters 13 and 14 are on wearable electronic and photonic technologies. Chapter 13 provides insights on adaptive and responsive textile structures (ARTS). Chapter 14 describes the development of an intelligent snowmobile suit. 

Brown P J, The modification of polysulphone hollow fibre membranes for gas separation , PhD Thesis, University of I,eeds, 1991. 

Smid, J., J.H.M.Albers and A.P.M. Kusters, The Formation of Asymmetric Hollow Fibre Membranes for Gas Separation, using PPE of Different Intrinsic Viscosities , J. Membr. Sci., 64, 121-128, (1991). 

Peters TA, Fontalvo J, Vorstman MAG et al. 2005. Hollow fibre microporous silica membranes for gas separation and pervaporation Synthesis, performance and stability. J. Membr. Sci. 248 73-80. 

A very rapid development has taken place in the use of membranes for gas separation. Reviews are given in [664-666]. The most popular process for purge gas recovery using membranes is based on the use of hollow fibres, although other types such as spiral wound membranes and stacks of flat elements have also been used. 

Liu,S.,Teo,W. K.,Tan,X. and Li,K. (2005) Preparation of PDMSvi-AljOj composite hollow fibre membranes for VOC recovery from waste gas streams. Separation and Purification Technology, 46,110-117. 

Membrane gas absorption (MGA) is a gas-Hquid (G—L) contacting device that uses a microporous hydrophobic hollow fibre membrane element similar to the membrane contactors discussed earfter. The hydrophobic membrane barrier separates the gas phase from the absorption Hquid phase. The gas to be separated diffuses through the gas-fiUed pores of the membrane and is absorbed in the Hquid. Absorption is based on physical absorption or by a chemical reaction. Both phases should not mix in order for the operation to be efficient. 

Shell Global Solutions is another company which has studied membranes for conditioning of natural gas (Rijkens, 2000 Rijkens et al., 2001). Among the membrane types which can be used for gas separation/drying are hollow fibre units. Membranes have been used by Shell Oil, who applied a Kvaemer-designed... 

Supported liquid membranes offer excellent selectivity for use in gas separation. The transport of CO2 through an aqueous diethanolamine solution held within a hollow fibre membrane is modelled in this paper. When compared with flat-sheet models, the results demonstrated that radial geometry has to be taken into account in a hollow fibre model. The model was used to simulate the CO2 separation in membrane contactors and the results were compared with experimental data. The discrepancy between the results and the experimental data is thought to be due to the conditions within the membrane contactors, which are far from ideal. 

The efficiency of membrane separation increases with the permeability and the selectivity. Thin membranes are economic, since according to Equation (2.1) the gas flow is inverse proportional to the layer thickness. However thin polymeric films, which have favorable permeability and selectivity, are too weak to withstand the high pressure difference between permeate and retentate side. The economic breakthrough set in with the production of ultrathin compound polymeric membranes. These are designed as hollow fibres with a thick porous back-up layer for mechanical stability and a thin dense non porous membrane layer for gas separation. The porous layer only has a slight influence on gas separation. These hollow fibres are combined in a bundle, which is arranged in a cylindrical container [2.13]. Several of these bundles, also called modules, can be added to... 

Li Y, Chung T (2008) Exploratory development of dual-layer carbon-zeolite nanocomposite hollow fibre membranes with high performance for oxygen enrichment and natural gas separation. Microporous Mesoporous Mater 113(l-3) 315-324. doi 10.1016/j.micromeso. 2007.11.038... 

Gas separation Hollow-fibre for high-volume applications with low-flux, low-selectivity membranes in which concentration polarisation is easily controlled (nitrogen from air) Spiral-wound when fluxes are higher, feed gases more contaminated, and concentration polarisation a problem (natural gas separations, vapour permeation). 

Although there are a number of materials with the desired pore structure, for instance silicone rubbers, hydrocarbon rubbers, polyesters, polycarbonates and others, their use for industrial applications is limited to polysulfones and cellulose acetates. While the latt have been used with good success for dehydration, technical gas separation relies exclusively on polysulfones which can be used up to approximately 70 °C (their melting point is around 200 °C) and at pressures between IS and 140 bar. The lowest pressure differential between the feed gas side and the permeate gas side is 3 1 and this differential pressure determines the wall thickness of the membranes. Figure 2.8 shows the design of a membrane element developed by Monsanto Company, USA and marketed by the name of Prism separator. Each of these elements or modules contains thousands of hollow fibres packed to a density of approximately 1(X) per cm. ... 

For commercial applications, flat sheet membranes are rarely used due to poor space efficiency. Many industrial systems make use of hollow fibre devices in order to maximise the surface area per unit volume. In this work, a model is developed to predict the separation of CO2 from a feed gas stream by a hollow fibre SLM. 

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