Process hydration, opportunities

The cool-down process of the cold-start experiment also provides an opportunity to obtain the membrane proton conductivity as a function of temperature at a known water content. Note that the temperature dependence of proton conductivity with low membrane water content is of particular interest here as PEFC cold start rarely involves fully hydrated membranes after gas purge. In addition, unlike PEFCs operated under normal temperatures, the membrane resistance under low water content and low temperature typical of cold start conditions is much greater than the contact resistance, making in-situ measurements of the membrane proton conductivity in a PEFC a simple but accurate method. 

The majority of studies on drugs and excipients involving TGA have used the technique as a means of identifying and characterizing pharmaceutical hydrates. The method presents several opportunities in this respect. In the first instance, the presence of a hydrate (as opposed to sorbed water) is usually easily discerned by the sharpness of the instrumental response corresponding to the water loss process. More specifically, loss of water of hydration usually occurs for pharmaceuticals over a range of approximately 5 to 20°C, depending on the experimental conditions used,... 

In the 1980 s the opportunity for using hydrated lime to remove acid gases from processes such as incinerators and small boilers was recognised. However, trials showed that relatively large excess of commercially available hydrate had to be added to reduce the acid gas concentrations to the required levels. It was postulated that increasing the effective surface area would increase absorption efficiencies. The challenge was how to produce a hydrate with significantly improved properties. 

In surfactant-nonpolar solvent systems where the sense of the micelle is reversed, the polar interactions of the head groups provide not only a driving force for the aggregation process but also an opportune location for the solubilization of polar additives. Water is, of course, one of the most important potential polar additives to nonaqueous systems, and it is located primarily in the core. The nature of such solubilized water is not fixed, however. The initial water added Ukely becomes closely associated with the polar head group of the surfactant (as waters of hydration), while subsequent additions appear to have the character of free bulk water. Other polar additives, such as carbox-yhc acids, which may have some solubility in the organic phase, are probably associated with the micelle in a manner analogous to that for similar materials in aqueous systems. 

Water is a common impurity in natural gas that must be removed to prevent hydrate formation. This is a good opportunity for the apphcation of membrane technology, but to be competitive, the membrane system must minimize the loss of methane with the permeate water [5], This loss can be reduced, on the one hand, by choosing membranes with desired selectivity, but, on the other hand, by the process parameters, because this separation is pressure ratio-limited [5]. 

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