Membranes and membrane modules

Because membranes appHcable to diverse separation problems are often made by the same general techniques, classification by end use appHcation or preparation method is difficult. The first part of this section is, therefore, organized by membrane stmcture preparation methods are described for symmetrical membranes, asymmetric membranes, ceramic and metal membranes, and Hquid membranes. The production of hollow-fine fiber membranes and membrane modules is then covered. Symmetrical membranes have a uniform stmcture throughout such membranes can be either dense films or microporous. 

Several factors contribute to the successful fabrication of a high-performance membrane module. First, membrane materials with the appropriate chemical, mechanical and permeation properties must be selected this choice is very process-specific. However, once the membrane material has been selected, the technology required to fabricate this material into a robust, thin, defect-free membrane and then to package the membrane into an efficient, economical, high-surface-area module is similar for all membrane processes. Therefore, this chapter focuses on methods of forming membranes and membrane modules. The criteria used to select membrane materials for specific processes are described in the chapters covering each application. 

Yoshino, Y., Suzuki, T., Nair, B.N., Taguchi, H., and Itoh, N., Development of tubular substrates, silica based membranes and membrane modules for hydrogen separation at high temperature, Journal of Membrane Science, 267, 8-17, 2005. 

In conclusion, membrane contactor technology has been creating a distinct application base for itself in recent years. The installed base of membrane contactors is stdl small compared to other membrane technologies. However, use of this technology cuts across diverse industries and markets, and in many instances membrane contactors are enabling customers with new oppormnities that did not exist before. Many well-known producers of membrane and membrane modules today offer commercial membrane contactors as part of their product portfolio. It is our belief that new installations of membrane contactors will continue and new applications of this technology wdl be found in coming years. 

Today, annual market membrane of ca. U.S. 4.5 x 10 for membranes and membrane modules (mostly polymeric ones) indicates that separation processes seem to be the largest application field, whereas membrane reactors are just on the verge of being considered as a competitive tool [274]. 

Figure 8.1. Schematic of a hydrogen separation membrane and membrane module.

Tab. 5.1 Coefficients of thermal expansion at 298 K for membrane and membrane module structural materials [6].

Industrial interest in soluble polymer-bound catalysts has been closely linked to the development of ultrafiltration membranes with sufficient long-term stability in organic solvents. Membranes fulfilling these requirements were prepared first in the late 1980s. Today, solvent-stable flat sheet membranes and membrane modules are available from several suppliers. As for the viability of ultrafiltration in organic solvents, rhodium-catalyzed hydroformylation of dicydopentadiene with continuous catalyst recovery and recycling has been demonstrated successfully on a pilot plant scale over an extended period of time [5]. The synthesis of other fine chemicals by asymmetric reduction and other reactions has also been carried out in continuously operated membrane reactors (also cf Section 7.5) [6-9]. The extent of commercial interest in catalysts bound to soluble polymers appears to fluctuate at intervals. Amongst other factors, the price of precious metals can be a driver. 

Moreover, a review of membranes and membrane modules actually available on the market, not comprehensive of all the suppliers, allows focusing on the main costs determinants in the membranes production cycle. 

When hydrophobic membranes, such as those made of silicone rubber material, are used for the separation of an aqueous solution, organic components of the mixture permeate preferentially through the membrane [341]. Thus, it is possible to remove and concentrate organic contaminants in the industrial waste water. This principle was applied by Membrane Technology Rc.scarch Inc., CA, using their membranes and membrane modules similar to those developed for the separation of volatile organic compounds from air (Figure 10.32). One... 

The authors intend to make a historic overview of carbon-related membranes in this book. It will cover the development of carbon related membranes and membrane modules from its onset to the latest research on carbon mixed matrix membranes. After the review of the progress in the field, they also intend to show the future direction of R D. 

The challenges for the membrane manufacturers are to produce membranes and membrane modules with reproducible performance. The performance variability is due to the variability associated with the polymer, membrane and the flow dynamics of the membrane module. Therefore, when more than one module is used in a gas separation system, each module feed flow and back pressure need to be adjusted to get the best performance of the membrane system. This makes module replacement and substitution difficult. Standardization and compatibility of the membrane modules with various membrane skids will make membrane gas separation applications more acceptable. 

Another major deterrent for the advancement of the gas separation membranes is that it requires a special art to make efficient membranes and membrane modules from a given polymer. A better understanding of the role of membrane fabrication processes and module and system design on... 

Most of the publications listed in Figures 12.2 and 12.3 are concerned with theoretical models of MD and experimental studies on the effects of the operating conditions. More than 56% of the MD publications dealt with theoretical models (i.e., 50.7% for DCMD, 62.1% for AGMD, 64.5% for VMD, and 80% for SGMD), whereas less than 8% focused on the preparation of membranes for MD. Few authors have considered the possibility of manufacturing new membranes and membrane module designs specifically for MD... 

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