Porous support tubes

An electrochemical vapor deposition (EVD) technique has been developed that produces thin layers of refractory oxides that are suitable for the electrolyte and cell interconnection in SOFCs (9). In this technique, the appropriate metal chloride (MeCl ) vapor is introduced on one side of a porous support tube, and H2/H2O gas is introduced on the other side. The gas environments on both sides of the support tube act to form two galvanic couples, ie. 

Similarly, impervious yttria-stabilized zirconia membranes doped with titania have been prepared by the electrochemical vapor deposition method [Hazbun, 1988]. Zirconium, yttrium and titanium chlorides in vapor form react with oxygen on the heated surface of a porous support tube in a reaction chamber at 1,100 to 1,300 C under controlled conditions. Membranes with a thickness of 2 to 60 pm have been made this way. The dopant, titania, is added to increase electron How of the resultant membrane and can be tailored to achieve the desired balance between ionic and electronic conductivity. Brinkman and Burggraaf [1995] also used electrochemical vapor deposition to grow thin, dense layers of zirconia/yttria/terbia membranes on porous ceramic supports. Depending on the deposition temperature, the growth of the membrane layer is limited by the bulk electrochemical transport or pore diffusion. 

To better control the thickness and densification of each layer, a technique utilizing the osmotic pressure can be applied. Here, while the membrane layer is being deposited onto the inside surface of a porous support tube, the support tube is immersed in a... 

Kusakabe K, Kuroda T, and Morooka S. Separation of carbon dioxide from nitrogen using ion-exchanged faujasite-type zeolite membranes formed on porous support tubes. J Membr Sci 1998 148(l) 13-23. 

In this type of module, a number of membranes of tubular shape are encased in a container. A schematic diagram is given in Fig. 12. The feed solution always flows through the center of the tubes while the permeate flows through the porous supporting tube into... 

Supported, multilayered (as5onmetric) - dense oxide or metal - porous ceramic membranes alumina, zirconia, titania, carbon - composite ceramic-metal, ceramic-ceramic layers on porous support tube, disk multilayers on porous support plate, disk, tube, monolith... 

Figure 5. Gelman pleated crossflow filter cartridge. Cartridge components (A) a porous pleated support screen to provide mechanical support under applied pressure (B) the pleated microporous filtration element (C) the pleated spacer which creates the thin flow channel and promotes turbulent flow (D) the impermeable film which creates the flow channel (E) a porous support tube to provide an exit for permeate (F) open-end cap which provides for exit of product flow (G) closed-end cap completely which seals one end of module (H) outer seal ring which creates the seal between the impermeable film in the module and the interior of the housing. The back pressure support tube is not pictured. The ends of the cartridge are potted and sealed. A space between the ends of Film D and the end seals is provided to allow the entrance and exit of the flow-channel fluid.

The externally wound membranes were developed by Universal Water Corp., San Diego, California. In this design, the membrane element consists of a porous supporting tube on which are simultaneously wound, in helical fashion, a strip of permeable fabric overlaid with a helical wound strip of semlpermeable membrane film. Adjacent turns of the membrane overlap in winding, and these overlaps are sealed by a bonding solvent so that, the membrane Itself... 

The biggest disadvantage of tubes is their cost. The porous support tube (often fiberglass reinforced epoxy) is the dominant cost factor and the membrane area per foot of tube is low. When the membrane is spent, usually the whole tube must be replaced. PCI utilizes a "paper" insert on which the membrane is cast as the replaceable element. Others have developed epoxy bonded consolidated sand as the porous support in an attempt to reduce costs. 

Conceptually, hollow fibers are the ideal membrane configuration. There is no "parasite drag" and no expensive porous support tube. The fibers may be pressurized on the inside (up to 30 psig) permitting "thin-channel" fluid management of the feed stream (refer to Figure 3.13). 

A different tubular design is pursued by Mitsubishi Heavy Industries (MHI/Japan, Fig. 2). The single cells are positioned on a central porous support tube and connected electrically in series via ceramic interconnector rings, which leads to an increased voltage at the terminals of a single tube. In... 

MHI (Mitsubishi Heavy Industries) with EPDC tubular (porous support tube, serial connection") materials, cells, stack, manufacturing, system... 

The tubular design is probably the best-known design. It has been developed by Westinghouse (now Siemens Power generation) [8]. The first concept that was pursued by Westinghouse consisted of an air electrode supported fuel cell tube. In earlier days the tubes were made from calcium-stabilized zirconia on which the active cell components were sprayed. Nowadays this porous supported tube (PST) is replaced by a doped lanthanum manganite (LaMn) air electrode tube (AES) that increases the power density by about 35 %. The LaMn tubes are extruded and sintered and serve as the air electrode. The other cell components are deposited on this construction by plasma spraying. 

In parallel with the development of the membrane reformer system, a new concept membrane module, which has a palladium alloy membrane coated on the porous support tube with catalytic activity has been developed (Nishii, 2009). This membrane module is expected to provide a more compact reactor because the reactor does not require a separate catalyst. It is also expected that this module can be manufactured at low cost by applying the industrially-established mass production process used to make oxygen sensors for combustion control in vehicles with internal combustion engines. 

Fig. 21.24 Active tube and extruded porous support tube [76, 77]...

Yamamoto M, Kusakabe K, Hayashi J, Morooka S (1997) Carbon molecular sieve membrane formed by oxidative carbonization of a copolyimide film coated on a porous support tube. J Membr Sci 133 (2) 195-205... 

Soffer A, Azariah A, Amar A, Cohen H, Golub D, Saguee S (1997) Method of improving the selectivity of carbon membranes by chemical vapor deposition. US patent 5695618 Vu DQ, Koros WJ, Miller SJ (2002) High pressure CO /CH separation using carbon molecular sieve hollow fiber membranes. Ind Eng Chem Res 41 (3) 367-380 Ogawa M, Nakano Y (1999) Gas permeation through carbonized hollow fiber membranes prepared by gel modification of polyamic acid. J Membr Sci 162 (1-2) 189-198 Yamamoto M, Kusakabe K, Hayashi J, Morooka S (1997) Carbon molecular sieve membrane formed by oxidative carbonization of a copolyimide film coated on a porous support tube. J Membr Sci 133 (2) 195-205... 

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