Hollow-fiber separator pressure drop

Hollow-fiber separator comp os it ion-dependent permeab ility feed composition feed pressure fiber dimensions multistage pressure drop Horizontal decanters HTU... 

Show how the water flux and salt rejection would change with upstream pressure for a perfect cellulose acetate asymmetric membrane and a feed with an osmotic pressure of 20 atm. Use the dilfusivity and solubility values for NaCL (fl) Calculate the internal pressure drop for an oxygen-nitrogen hollow-fiber separator that has 600 pm outside diameter and 400 pm inside diameter fibers 1.0 m long. When = 751by/in. abs and = 15Iby/in. abs, the permeate flux is... 

Spiral-wound modules are much more commonly used in low pressure or vacuum gas separation appHcations, such as the production of oxygen-enriched air, or the separation of organic vapors from air. In these appHcations, the feed gas is at close to ambient pressure, and a vacuum is drawn on the permeate side of the membrane. Parasitic pressure drops on the permeate side of the membrane and the difficulty in making high performance hollow-fine fiber membranes from the mbbery polymers used to make these membranes both work against hollow-fine fiber modules for this appHcation. 

Parallel-plate hemodialyzers using flat membranes, with several compartments in parallel, separated by plastic plates, are now only available from Hospal Co (Crystal and Hemospal models). Blood circulates between two membranes and the dialysate between the other side of membrane and the plastic plate. These parallel-plate dialyzers have a smaller blood-pressure drop than hollow-fiber ones and require less anticoagulants as flat channels are less exposed to thrombus formation than fibers, but they are heavier and bulkier and thus less popular. A recent survey of the state-of-the-art in hemodialyzers is given in [13]. 

In gas permeation, a gas species is separated based mainly on its permeability in hollow fiber and spiral wound membranes. The hollow fiber systems can have an inside diameter up to 200 xm and hence very large surface-to-volume ratios, but high pressure drops inside the tubes. The basic flow equation for a species / is... 

For analytical LC, standard packed columns (4-8 mm I.D.), capillary packed colunms (50-100 pm I.D.), and microbore packed colunms (0.5-1.5 mm I.D.) are used widely. Colunm sizes depend on the application, e.g., analytical, preparative, or commercial separations. Special configurations also exist, including membrane chromatography modules (stacks and hollow fibers) that offer lower pressure drops and easier scale-up than packed beds. 

The use of membrane reactors offers several advantages, including (1) a high specific surface area, (2) instantaneous reaction and separation of substrate and product, (3) reusing the lipase, and (4) continuous operation. Immobilization of lipase onto a membrane offers many advantages, such as a low drop in pressure when continuously operated, and high operational stability with low external and internal diffusional resistance (Giorno and Drioli, 2000). In these bioreactors, the lipase is immobilized on a membrane, which may be either a flat sheet (FSMR) or hollow fiber (HFMR). 

Spiral-wound modules are used where pressure drop has to be considered and when counter eurrent flow is not needed to maximize separation efficiency. Higher pressure applieations involving eostly pressure vessels and piping make the hollow fiber modules more favorable because this reduces the component costs of the system by as mueh as a faetor of ten in some cases. An overview of the features and applications of the different module types is given in Table 5.2. 

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