Membranes class distillation

Refinery product separation falls into a number of common classes namely Main fractionators gas plants classical distillation, extraction (liquid-liquid), precipitation (solvent deasphalting), solid facilitated (Parex(TM), PSA), and Membrane (PRSIM(TM)). This list has been ordered from most common to least common. Main fractionators are required in every refinery. Nearly every refinery has some type of gas plant. Most refineries have classical distillation columns. Liquid-liquid extraction is in a few places. Precipitation, solid facilitated and membrane separations are used in specific applications. 

Ion-selective membrane electrodes as amperometric and potentiometric biosensors cannot be successfully used for ion monitoring in water. Their main characteristic is detection of an ion in the sample continuously and without any prior separation. The sampling process for a solid sample is reduced at its dissolution in distilled water. Due to the complexity of the matrix for wastewater or for seawater samples, there are a number of interfering inorganic and organic ions. Using biosensors for water analysis, one can obtain the total quantity of organic substances that are contained in a class it is practically impossible to discriminate the content of every compound from within the same class. 

Another class of applications are aqueous solutions containing low concentrations of a volatile component such as occur in mixtures of ethanoi/waier or trichloroethylene/water. Here also a vacuum can be applied instead of water on the permeate side, resulting in a high driving force (p2 => 0). Becau.se the separation is based on a vapour-liquid equilibrium, the permeate is enriched in the volatile component. Although this process is sometimes referred to as pervaporation it is in fact a membrane distillation process. Membrane distillation can have a distinct advantage over distillation, especially for small-scale applications, because of the large surface area per volume as can be found in hoUow fiber and capillary modules. 

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