Scale Membrane Production

For any membrane to be useful in an industrial process it has to be produced on a large scale and installed into an appropriate device which should be com- 

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Briefly, the authors of this paper claim that they have presented a method to facilitate the orientation of CNTs on the porous support (PTFE) and the method can easily be adopted to the large-scale membrane production. The PS/CNT/PTFE composite membrane showed the same fast gas transport observed by Holt et al. Then-work also showed for the first time the transport of the binary gas mixtures through the CNTs based membrane. 

The earliest concerted effort in the research and development of Nafion perfluorosulfonate ionomers was directed toward their use as a permselective membrane separator in electrochemical cells used in the large scale industrial production of NaOH, KOH, and CI2. In short, the membrane in this application, in addition to keeping CI2 and H2 gases separated, prevents the unfavorable back migration of hydrated OH ions from the catholyte (concentrated aqueous NaOH or KOH) chamber, while allowing for the transport of hydrated Na+ ions from the anolyte chamber in which is aqueous NaCl. 

The use of membranes to separate gases commercially is a relatively new application. Both Du Pont and Union Carbide had ventures in the early 1970s for recovering H2 and He ffom industrial processes, but these projects were never fully commercialized. Recently, however, a combination of improved economics and better technology has resulted in membrane products that signal a new era in the commercial use of membranes for large-scale gas separation. 

However, large-scale commercial production of CVI-membranes is hindered by the complicated equipment needed for their synthesis and the associated high costs. Furthermore the permeance of CVI membranes (1 1 O 7 mol/m2sPa or lower) are still too low. Maybe these low permeances can be increased using different precursors or other reaction conditions, but a large improvement is not to be expected. 

Scaled membranes exhibit lower productivity and lower salt rejection. This lower salt rejection is a function of the concentration polarization phenomenon (see Chapter 3.4). When membranes are scaled, the surface of the membrane has a higher concentration of solutes than in the bulk solution. Since the membrane rejects when the membrane "sees," the passage of salts will be higher, even though the absolute or true rejection stays constant. 

Industrial production of perfluorinated ionomers, Nafion membranes, and all perfluorinated membranes is costly due to several factors first, the monomers used are expensive to manufacture, since the synthesis requires a large number of steps and the monomers are dangerous to handle. The precautions for safe handling are considerable and costly. Secondly, the PSEPVE monomer is not used for other applications, which limits the volume of production. The most significant cost driver is the scale of production. Today, the volume of the Nafion market for chlor-aUcali electrolysis (150,000 m year ) and fuel cells (150,000 m year ) is about 300,000 m year resulting in a production capacity of 65,000 kg year. When compared to large-scale production of polymers like Nylon (1.2 x 10 m year ), the perfluorinated ionomer membrane is a specialty polymer produced in small volumes. 

The development of the membrane production to real large-scale production will increase the realiability of membrane-filtration plants and increase the competitive power of the membrane-filtration process. 

Virus Concentration. In large scale virus production, concentration of the virus or its proteins is frequently necessary to obtain workable volumes for subsequent processing. Often continuous-flow zonal centrifuges are used for this purpose but with a significant loss in biological activity. Most viruses are larger than 0.01 n and can be safely (closed system) concentrated with a 80,000 MWCO membrane without loss of activity. 

In this context, only two polymers have ever been used on a large scale in asymmetric membranes cellulose acetate and Permasep B-9/B-10 aramids. The former polymer predates the era of reverse osmosis membranes. The latter polymer has been used in hollow fiber membranes for 15 years. Attempts to bring other new polymers into asymmetric membrane production have been few (PBIL, PBI, polypiperazineamides), generally without particular success. 

Evaluate the ITM Syngas/ITM H2 processes using PDU data Conduct long-term stability tests of tubular membranes and seals at high pressure Demonstrate performance of pilot-scale membrane modules in PDU Complete membrane module design and select catalysts for the SEP Commission the ceramic Production Development Facility and fabricate SEP membranes Design and fabricate the SEP reactor... 

ITM S mgas Membrane and Module Design and Fabrication," membrane reactors will be designed for the ITM S mgas/ITM H2 processes at the PDU, SEP and commercial scales. Pilot-scale membrane modules will be fabricated for testing in the PDU. Fabrication of the membrane reactor modules will be scaled up in a Production Development Facility to supply the requirements of the SEP. 

Membrane electrolysis technology is well established and appropriate for smaller scale facilities. One application is its use as an oxygen generator in submarines, where the hydrogen is considered only a byproduct. Drawback is the high-cost membrane production [14]. 

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