Membrane design concepts

Several test runs have been carried out using 1.5 dm2 laboratory cells with the F-8934 at 8kA m-2. The current efficiency at 8kA m-2 was about 1% lower than that at 5kAnT2, and no further decline was observed. F-8934 has also had a similar evaluation result in full-scale pilot cells at 8 kA m-2. AGC has been obtaining slightly lower current efficiencies than its desired target of 97% at the beginning of the membrane lifetime. This has led AGC to ensure that the other stepped-up design concept should be applied to the membrane for 8 kA m-2 operation. 

Results to date also include the development of detailed process models of SMR and purification systems. These models served as the baseline for the development of the mechanical design concepts. Options such as high/low pressure reforming, natural gas/syngas compression, PSA/membrane purification and various levels of thermal/process integration were modeled. 

Figure 8.6 Figures 6 (A) and 7 (B) from Hazbun, U.S. Patent 4 791 079 [17] showing some of the first concepts for a monoiithic ceramic membrane design for the partiai oxidation of hydrocarbons.

Moritz K, Schiemann L (2008), Structural Design Concept, lecture notes. First Master Program for Membrane Structures, Hochschule Anhalt, Dessau, Germany Schiemann L (2009), TragverhaIten von ETFE-Folien unter biaxialer Beanspruchung, Dissertation, Technische Universitat Munchen... 

Khulbe et ah [20] and Tan et al. [21,22[ both stated that smoother membrane surfaces, formed as a result of the merging of nodules, would enhance the selectivity of membranes when they were used for gas separation. This concept has not been proven by other researchers since few people have apphed the AFM technique to study gas separation membranes. Combined with plasma etching, the AFM technique will provide detailed information on the surface morphology of gas separation membranes, which will definitely influence the future of gas separation membrane design. 

Yamaguchi, T., Miyazaki, Y, Nakao, S., Tsuru, T. and Kimura, S. 1998. Membrane design for pervaporation or vapor permeation separation using a filling-type membrane concept. 

Despite the fact that membrane technology already fulfills the concept of process intensification in some areas, especially in water desalination, fruit juice concentration and the petrochemical industry, effective application of these technology types at an industrial level still needs additional effort addressed at developing and integrating new materials, new design concepts, econonfics and process control, scale-up and realistic assessment of the basic working parameters on real pilot plants. 

Most PEMs require water for proton migration but membrane swelling leads to high solvent permeation. To control membrane swelling and solvent permeation, the pore-filling concept is proposed. A systematic membrane design and development... 

Chapter 16 presents a unique membrane design and development using the concept of pore-filhng. The membranes are used for both polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs). 

EFCs are electrochemical systems that consist of an anode, a cathode, and an electrolyte. Design of EFC prototypes was inspired by conventional batteries and fuel cells, but there are substantial differences that lead to completely new design concepts and requirements. Specifically, in contrast to conventional batteries, the oxidized substance in the EFC is not carried in the electrodes, but instead stored as a fuel. In contrast to conventional fuel cells, EFCs use highly selective enzymes in the anode and cathode reactions and they can operate without any membrane separation, in neutral aqueous electrolyte, and at room temperature and are capable to provide deep, or complete, fuel oxidation. 

Transport Models. Many mechanistic and mathematical models have been proposed to describe reverse osmosis membranes. Some of these descriptions rely on relatively simple concepts others are far more complex and require sophisticated solution techniques. Models that adequately describe the performance of RO membranes are important to the design of RO processes. Models that predict separation characteristics also minimize the number of experiments that must be performed to describe a particular system. Excellent reviews of membrane transport models and mechanisms are available (9,14,25-29). 

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