Industrial gases membrane separation

Industrial separation of hydrocarbons from their mixtures with various gases, including air, is a specific case of a more general objective, separation of organic vapors from various gas/vapor mixtures. Early commercial vapor/gas membrane separation plants installed by Nitto Denko, MTR, GKSS were put into operation in 1988-1990. During the last 20 years, sales... 

The removal of organic solvents from gas streams has been widely developed at the industrial level. The main industrial applications of vapor/gas membrane separation are ... 

Table 20.3 Main industrial applications of vapor/gas membrane separation [57].

Pervaporation is a membrane separation process where the liquid feed mixture is in contact with the membrane in the upstream under atmospheric pressure and permeate is removed from the downstream as vapor by vacuum or a swept inert gas. Most of the research efforts of the pervaporation have concentrated on the separation of alcohol-water system [1-20] but the separation of acetic acid-water mixtures has received relatively little attention [21-34]. Acetic acid is an important basic chemical in the industry ranking among the top 20 organic intermediates. Because of the small differences in the volatility s of water and acetic acid in dilute aqueous solutions, azeotropic distillation is used instead of normal binary distillation so that the process is an energy intensive process. From this point of view, the pervaporation separation of acetic acid-water mixtures can be one of the alternate processes for saving energy. 

Developing industrial membrane separation technologies Gas separation Pervaporation A number of plants have been installed. Market size and number of applications served are expanding... 

Table 1.1 shows two developing industrial membrane separation processes gas separation with polymer membranes (Chapter 8) and pervaporation (Chapter 9). Gas separation with membranes is the more advanced of the two techniques at least 20 companies worldwide offer industrial, membrane-based gas separation systems for a variety of applications. Only a handful of companies currently offer industrial pervaporation systems. In gas separation, a gas mixture at an elevated pressure is passed across the surface of a membrane that is selectively permeable to one component of the feed mixture the membrane permeate is enriched in this species. The basic process is illustrated in Figure 1.4. Major current applications... 

These gas separation processes have also been adapted for use in other industries. For example, the Fetzer Winery in Redwood Valley, California, uses a membrane separator to produce a nitrogen-rich atmosphere for its fermentation tanks to prevent oxygen-driven decomposition of the wine. 

Specialty polymers achieve very high performance and find limited but critical use in aerospace composites, in electronic industries, as membranes for gas and liquid separations, as fire-retardant textile fabrics for firefighters and race-car drivers, and for biomedical applications (as sutures and surgical implants). The most important class of specialty plastics is polyimides. Other specialty polymers include polyetherimide, poly(amide-imide), polybismaleimides, ionic polymers, polyphosphazenes, poly(aryl ether ketones), polyarylates and related aromatic polyesters, and ultrahigh-molecular-weight polyethylene (Fig. 14.9). 

As mentioned earlier, membrane blood oxygenators probably would qualify as the earliest form of membrane contactors. Reference [11] is a good illustration of a hollow fiber device. However, most work on liquid-gas membrane contactor over the years has focused mainly on two categories (1) separation, purification, and treatment of water or aqueous media and (2) absorption of gaseous species from air either for purification or for recovery, which will be discussed separately. Applications in multiple markets and industries have been investigated in each category. 

Masano I, Fumsaki S, and Miyauchi T, Separation of volatile materials by gas membrane. Industrial Engineering Chemistry—Process Design and Development 1982, 21, 421 26. 

Japanese publications report on a large research program which is known as Cj Chemistry Project [ 29 ]. The objective of the study is to substitute gasification carbon for crude-oil carbon (change of feedstock) in organic synthesis.In the processes dealt with there, membrane gas separation has an important place. The information is of significance, since these same techniques may be useful when applied to the membrane separation of industrial gases, waste... 

Membranes play an important role in natural science and for many technical applications. Depending on their purpose, their shape can be very different. For instance, membranes include porous or non-porous films, either supported or non-supported, with two interfaces surrounded by a gas or by a liquid. Important properties of non-porous membranes are their permeability for certain compounds and their stability. In biological cells their main task is to stabilize the cell and to separate the cell plasma from the environment. Furthermore, different cells and cell compartments have to communicate with each other which requires selective permeability of the membranes. For industrial applications membranes are often used for separation of gases, liquids, or ions. Foams and emulsions for instance are macroscopic composite systems consisting of many membranes. They contain the continuous liquid phase surrounded by the dispersed gas phase (foams) or by another liquid (emulsions). Beside these application possibilities membranes give the opportunity to investigate many questions related to basic research, e.g. finite size effects. 

Gas separation membrane technologies are extensively used in industry. Typical applications include carbon dioxide separation from various gas streams, production of oxygen enriched air, hydrogen recovery from a variety of refinery and petrochemical streams, olefin separation such as ethylene-ethane or propylene-propane mixtures. However, membrane separation methods often do not allow reaching needed levels of performance and selectivity. Polymeric membrane materials with relatively high selectivities used so far show generally low permeabilities, which is referred to as trade-off or upper bound relationship for specific gas pairs [1]. 

Liquid membrane separation processes are widely used in biochemical processing, in industrial wastewater treatment, in gas separations, in food and beverage production, and in pharmaceutical apphcations. Below the reader can find some fields where research, development and scale-up efforts are expected ... 

Membrane separation is a relatively new and fast-growing field in supramolecular chemistry. It is not only an important process in biological systems, but becomes a large-scale industrial activity. For industrial applications, many synthetic membranes have been developed. Important conventional membrane technologies are microfiltration, ultrafiltration, electro- and hemodialysis, reverse osmosis, and gas separations. The main advantages are the high separation factors that can be achieved under mild conditions and the low energy requirements. 

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