Search Results (5)

Natural gas is an important and fast-growing energy resource in the world and its purification is important in order to reduce environmental hazards and to meet the required quality standards set down by notable pipeline transmission, as well as distribution companies. Therefore, membrane technology has received great attention as it is considered an attractive option for the purification of natural gas in order to remove impurities such as carbon dioxide (CO₂) and hydrogen sulphide (H₂S) to meet the usage and transportation requirements. It is also recognized as an appealing alternative to other natural gas purification technologies such as adsorption and cryogenic processes due to its low cost, low energy requirement, easy membrane fabrication process and less requirement for supervision. During the past few decades, membrane-based gas separation technology employing hollow fibers (HF) has emerged as a leading technology and underwent rapid growth. Moreover, hollow fiber (HF) membranes have many advantages including high specific surface area, fewer requirements for maintenance and pre-treatment. However, applications of hollow fiber membranes are sometimes restricted by problems related to their low tensile strength as they are likely to get damaged in high-pressure applications. In this context, braid reinforced hollow fiber membranes offer a solution to this problem and can enhance the mechanical strength and lifespan of hollow fiber membranes. The present review includes a discussion about different materials used to fabricate gas separation membranes such as inorganic, organic and mixed matrix membranes (MMM). This review also includes a discussion about braid reinforced hollow fiber (BRHF) membranes and their ability to be used in natural gas purification as they can tackle high feed pressure and aggressive feeds without getting damaged or broken. A BRHF membrane possesses high tensile strength as compared to a self-supported membrane and if there is good interfacial bonding between the braid and the separation layer, high tensile strength, i.e., upto 170Mpa can be achieved, and due to these factors, it is expected that BRHF membranes could give promising results when used for the purification of natural gas. Full article

Designing hollow fiber (HF) membrane modules occupies one of the key positions in the development of efficient membrane processes for various purposes. In developing HF membrane modules, it is very important to have a uniform HF distribution and flow mixing in the shell side to significantly improve mass transfer and efficiency. This work suggests the application of different textile 3D HF structures (braided hoses and woven tape fabrics). The 3D structures consist of melt-spun, dense HFs based on poly(4-methyl-1-pentene) (PMP). Since the textile processing of HFs can damage the wall of the fiber or close the fiber bore, the membrane properties of the obtained structures are tested with a CO₂/CH₄ mixture in the temperature range of 0 to 40 °C. It is shown that HFs within the textile structure keep the same transport and separation characteristics compared to initial HFs. The mechanical properties of the PMP-based HFs allow their use in typical textile processes for the production of various membrane structures, even at a larger scale. PMP-based membranes can find application in separation processes, where other polymeric membranes are not stable. For example, they can be used for the separation of hydrocarbons or gas mixtures with volatile organic compounds. Full article

Hollow fiber membranes (HFMs) possess desired properties such as high surface area, desirable filtration efficiency, high packing density relative to other configurations. Nevertheless, they are often possible to break or damage during the high-pressure cleaning and aeration process. Recently, using the braid reinforcing as support is recommended to improve the mechanical strength of HFMs. The braid hollow fiber membrane (BHFM) is capable apply under higher pressure conditions. This review investigates the fabrication parameters and the methods for the improvement of BHFM performance. Full article

Radiation-induced graft polymerization provides industrially superior functionalization schemes by selection of existing polymer substrates and design of graft chains. In this review, by a pre-irradiation method of the radiation-induced graft polymerization and subsequent chemical modifications, charged polymer chains grafted onto various components and shapes of the polymer substrates are described. The charged graft chains immobilized onto a porous hollow-fiber membrane captured proteins in multilayers via multipoint binding. A membrane onto which positively charged graft chains are immobilized, i.e., an anion-exchange porous hollow-fiber membrane, was commercialized in 2011 for the removal of undesirable proteins in the purification of pharmaceuticals. On the other hand, a membrane onto which negatively charged graft chains are immobilized, i.e., a cation-exchange porous hollow-fiber membrane, exhibited a low permeation flux for pure water; however, the prepermeation of an aqueous solution of magnesium chloride through the membrane restored the permeation flux because of ionic crosslinking of graft chains with magnesium ions. The charged graft chains provide a precipitation field for inorganic compounds such as insoluble cobalt ferrocyanide. The graft chains entangle or penetrate a precipitate owing to electrostatic interactions with the surface charge on the precipitate. Braids and wound filters composed of insoluble-cobalt-ferrocyanide-impregnated fibers are used for the removal of radiocesium from contaminated water at Tokyo Electric Power Co. (TEPCO) Fukushima Daiichi Nuclear Power Plant. Full article

Novel poly(tetrafluoroethylene) (PTFE) hollow fiber membranes were successfully fabricated by electrospinning, with ultrafine fibrous PTFE membranes as separation layers, while a porous glassfiber braided tube served as the supporting matrix. During this process, PTFE/poly(vinylalcohol) (PVA) ultrafine fibrous membranes were electrospun while covering the porous glassfiber braided tube; then, the nascent PTFE/PVA hollow fiber membrane was obtained. In the following sintering process, the spinning carrier PVA decomposed; meanwhile, the ultrafine fibrous PTFE membrane shrank inward so as to further integrate with the supporting matrix. Therefore, the ultrafine fibrous PTFE membranes had excellent interface bonding strength with the supporting matrix. Moreover, the obtained ultrafine fibrous PTFE hollow fiber membrane exhibited superior performances in terms of strong hydrophobicity (CA > 140°), high porosity (>70%), and sharp pore size distribution. The comprehensive properties indicated that the ultrafine fibrous PTFE hollow fiber membranes could have potentially useful applications in membrane contactors (MC), especially membrane distillation (MD) in harsh water environments. Full article