Plate and frame modules

Characteristics of plate and frame modules are discussed below. 

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Plate-and-frame modules were one of the earliest types of membrane system. A plate-and-frame design proposed by Stem [110] for early Union Carbide plants to recovery helium from natural gas is shown in Figure 3.38. Membrane, feed spacers, and product spacers are layered together between two end plates. The feed mixture is forced across the surface of the membrane. A portion passes through the membrane, enters the permeate channel, and makes its way to a central permeate collection manifold. 

Plate-and-frame units have been developed for some small-scale applications, but these units are expensive compared to the alternatives, and leaks through the gaskets required for each plate are a serious problem. Plate-and-frame modules are now only used in electrodialysis and pervaporation systems and in a limited number of reverse osmosis and ultrafiltration applications with highly fouling feeds. An example of one of these reverse osmosis units is shown in Figure 3.39 [111],... 

Figure 3.39 Schematic of a plate-and-frame module. Plate-and-frame modules provide good flow control on both the permeate and feed side of the membrane, but the large number of spacer plates and seals lead to high module costs. The feed solution is directed across each plate in series. Permeate enters the membrane envelope and is collected through the central permeate collection channel [111]...

In the early 1960s and 1970s, the in-line plate-and-frame module was the only available microfiltration module. These units contained between 1 and 20 separate membrane envelopes sealed by gaskets. In most operations all the membrane envelopes were changed after each use the labor involved in disassembly and reassembly of the module was a significant drawback. Nonetheless these systems are still widely used to process small volumes of solution. A typical plate-and-frame filtration system is shown in Figure 7.10. 

Figure 9.11 Photograph of a 50-m2 GFT plate-and-frame module and an ethanol dehydration system fitted with this type of module. The module is contained in the large vacuum chamber on the left-hand side of the pervaporation system [44]...

Table 11.1 Comparison between hollow-fiber and plate-and-frame modules...

These and tubular modules offer the low packing density (membrane area per unit volume). Typical packing density is less than about 45 -150 ft2/ft3 for plate-and-frame modules.22... 

The major advantage of the spiral configuration over a plate-and-frame configuration is that there is minimal leakage associated with the spiral configuration. The spiral wound module does not require periodic tightening of nuts and bolts to prevent leaks, unlike plate-and-frame modules. Limitations of the spiral configuration include inferior current and flow distribution relative to plate-and-frame modules, as well as difficulty in assembly and field membrane replacement.17... 

In plate and frame modules, the membranes are placed (with or without spacers) between two plates. The packing density of this configuration varies between 100 and 400 m m, depending on the number of membranes or cassettes used. Andersson et al. [31] have used a plate and frame configuration for desalination purposes, where various cassettes were stacked together, each consisting of injection molded plastic frames of two membranes. Naveen et al. [92] used a plate and frame membrane... 

The irradiated membranes were then tested in a pilot plant with a plate-and-frame module with capacity for two membranes with an effective area of 90 cm each. Permselective results of irradiated membranes were compared to those of nonirradiated membranes [3]. It was observed that the performance of the samples irradiated with electronic or gamma radiation was very similar to that of the nonirradiated membranes. Tables 32.1 and 32.2 show the results of permeate flux and retention index for gamma- and electron-irradiated membranes, respectively. 

Typical Membrane Modules 6.2.1. Plate-and-Frame Module... 

A schematic drawing of a plate-and-frame module is given in Fig. 9. This type of module appeared in the earliest stage of industrial membrane applications. The structure is simple and the membrane replacement is easy. As illustrated, sets of two membranes are placed in a sandwich-like fashion with their feed sides facing each other. In each... 

Fig. 1 Membrane modules (from left to right at top row plate and frame module schematic, plate and frame module, spiral wound module schematic, spiral wound module at bottom row monoliths, tubular membranes, capillary membranes, hollow fibers. (Photos courtesy of http //www.niroinc.com/html/filtration/ftechsys.html.) (View this art in color at www. dekker.com.)...

A new type of configuration, the flowing liquid membrane (FLM) was studied by Teramoto et al. [20]. In this case, the membrane liquid phase is in motion as the feed and strip phase. In this type of system a plate-and-frame and spiral-wound configuration with flat membrane was used. The scheme of the FLM configuration is drawn in Fig. 7.3A. The hquid phase flows (FLM) between two hydrophobic microporous membranes. The two membranes separate the hquid membrane phase from feed and strip phases. In Fig. 7.3B, it is reported the classical plate-and-frame module employed for the separation of ethylene from ethane [20]. The liquid membrane convection increased the membrane transport coefficient in gas separation. However, the membrane surface packing density (membrane surface area/ equipment volume) is much lower in spiral-wound system than in hollow fiber. 

Figure 7.3 (A) Section of the membrane module and (B) plate-and-frame module of...

Seperation Unit. The elements of a separation process. Separation units of a separation process could be, for example, a gas centrifuge, a membrane module, a tray of distillation column or the evaporator of a multiple effect plant. It should be kept in mind, however, that in plate-and-frame modules as well as in modules of the spiral-wound-type usually every block or pressure-vessel contains more than one separation unit ... 

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