Membrane modules integration

Lee and co-workers (Lee et al., 2007 Lee, Li, Noike, 2009) describe the continuous H2 production in a continuously stirred tank reactor coupled with a submerged hollow-fibre membrane unit. The presence of the membrane module integrated within the reaction volume allows reducing biomass washout at a high hydraulic retention time with a general improvement of the reactor performance in terms of H2 productivity and yield. 

HoUow fibers are usuaUy on the order of 25 p.m to 2 mm in diameter. They can be made with a homogeneous dense stmcture, or preferably with a microporous stmcture having a dense permselective layer on the outside or inside surface. The dense surface layer can be integral, or separately coated onto a support fiber. The fibers are packed into bundles and potted into tubes to form a membrane module. More than a kilometer of fibers may be requited to... 

An integrated proof-of-concept (POC) size fluidized-bed methane reformer with embedded palladium membrane modules for simultaneous hydrogen separation is being developed for demonstration (Tamhankar et al., 2007). The membrane modules will use two 6 in. X 11 in. Pd-alloy membrane foils, 25-pm thick, supported on a porous support. The developmental fluidized-bed reactor will house a total of five (5) membrane modules with a total membrane area of about 0.43 m2 and is scheduled for demonstration by September 2007. 

The diameter of hollow fibers varies over a wide range, from 50 to 3000 xm. Fibers can be made with a uniformly dense structure, but preferably are formed as a microporous structure having a dense selective layer on either the outside or the inside surface. The dense surface layer can be either integral with the fiber or a separate layer coated onto the porous support fiber. Many fibers must be packed into bundles and potted into tubes to form a membrane module modules with a surface area of even a few square meters require many kilometers of fibers. Because a module must contain no broken or defective fibers, hollow fiber production requires high reproducibility and stringent quality control. 

One of the major advantages of membrane chromatography, similarly to EBA, is the possibility for direct processing cell suspensions, enabling an integration of the clarification and primary purification steps. However, this is only possible by the use of membrane modules with suitable hydrodynamics, capable of effectively avoiding membrane fouling (Bel-ford, 1988 Castilho and Anspach, 2003). 

If the normalized salt rejection is low or the normalized permeate flow is high, the integrity of the membrane may be in question. The vacuum decay test is a direct test for the integrity of a spiral wound RO membrane module. The test is best used to identify leaks within the membrane modules rather than leaks due to chemical attack. The test requires the isolation of an individual membrane module or the entire pressure vessel. A vacuum is then pulled on the membrane(s) and the rate of decay in pressure is observed. A decay of greater than 100 millibar per minute is indicative of a leaky membrane. Refer to ASTM Standards D39235 and D69086 for a more detailed review of the technique. 

It is understandable that many types of fluid metering, indicating and controlling equipment are an integral part of the membrane system. This is one of the reasons why the investment cost of the membrane module is not a predominant fraction of the total capital costs. 

Figure 2 Flat membrane module with heat integration. Left, whole module structure, right, picture of the heat integration part.

Installation of the PDU system was completed, and the PDU reactor system and PDU membrane modules were commissioned at high temperature and pressure with a s mgas mixture. The PDU integrates the various components of the ITM Syngas/ITM H2 reactor design and will be used to confirm the performance of the planar membrane modules and seals under commercial process conditions. The PDU reactor is shown in Figure 4. 

Apart from being a precursor of bile salts, cholesterol is a major component of cell membranes where it modulates membrane fluidity. Integration of cholesterol into a lipid bilayer renders it less leaky to small solutes and ions. Conversely, it makes very rigid membranes more flexible. 

In contrast, tube-and-shell type membrane modules do not have these engineering challenges with deflection and compromise of seal integrity. For this reason, tubular membrane modules will generally be lighter in construction relative to stacked planar membrane modules of comparable membrane area. However, a drawback to the tubular membrane module is that the packing density of the membrane is often substantially less than that which can be achieved with the stacked planar designs. 

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