MSA

The integral equation approach has also been explored in detail for electrolyte solutions, with the PY equation proving less usefiil than the HNC equation. This is partly because the latter model reduces cleanly to the MSA model for small h 2) since... 

In principle, simulation teclmiques can be used, and Monte Carlo simulations of the primitive model of electrolyte solutions have appeared since the 1960s. Results for the osmotic coefficients are given for comparison in table A2.4.4 together with results from the MSA, PY and HNC approaches. The primitive model is clearly deficient for values of r. close to the closest distance of approach of the ions. Many years ago, Gurney [H] noted that when two ions are close enough together for their solvation sheaths to overlap, some solvent molecules become freed from ionic attraction and are effectively returned to the bulk [12]. 

The GAM ESS program webpage http //www.msa.ameslab.aov/GAMESS/GAMESS.html... 

Exploratory Study of Potassium and Sodium Superoxides forOuygen Control in Manned Space Vehicles, Contract No. NASW-90, MSA Research Corp., Evans City, Pa., Mar. 1962. 

Mine Safety AppHances Company, USA (MSA) developed a reduction process usiag sodium and KCl to produce potassium metal ia the 1950s (4) ... 

The supply and demand for mbidium compounds has grown steadily since the 1970s. In 1979 the U.S. demand was ca 1040 kg of contained mbidium (16), and total world demand was estimated at approximately twice that of the United States. Reserves of mbidium in North America are estimated at 2 X 10 kg the United States is - 100% import-reliant for mbidium, and Canada is the principal source of the raw material (16). The demand for mbidium metal is small compared to the demand for mbidium compounds. Table 2 fists approximate prices of mbidium metal and mbidium compounds. Primary producers of mbidium are Cabot Performance Chemicals (Boyerstown, Pennsylvania), MSA Research Corporation (Callery, Pennsylvania), and CM Chemical Products, Inc. (Berkeley Heights, New Jersey). Research quantities of mbidium in standard and specialized ampuls are available from Strem Chemicals, Inc. (Newburyport, Massachusetts). 

Determine identity of any additional species to be used as mass separating agent (MSA). 

Decision points = product specifications and identity of MSA species... 

Prepare Hst of known critical features which must be dealt with to reach all destinations (products as weU as MSA compositions). 

The thermodynamics and physical properties of the mixture to be separated are examined. VLE nodes and saddles, LLE binodal curves, etc, are labeled. Critical features and compositions of interest are identified. A stream is selected from the source Hst. This stream is either identified as meeting all the composition objectives of a destination, or else as in need of further processing. Once an opportunistic or strategic operation is selected and incorporated into the flow sheet, any new sources or destinations are added to the respective Hsts. If a strategic separation for dealing with a particular critical feature has been implemented, then that critical feature is no longer of concern. Alternatively, additional critical features may arise through the addition of new components such as a MSA. The process is repeated until the source Hst is empty and all destination specifications have been satisfied. 

The more stmcturaHy, chemically similar components are, the less likely that the separation will be improved by azeotropic distillation (if an MSA-key component azeotrope is being used to alter the RCM) any azeotropes formed between one component and another similar component tend to have similar boiling points, compositions. 

Usually not favorable for separation of components that show similar Hquid-phase behavior, ie, steroisomers, homologous series, iso-notmA—neo isomers components to be separated must have some different functional group for MSA to affect Hquid-phase behavior differently. 

Eor drown-out, look for MSA in which the component to be crystallised has low solubihty, while other components have high solubihty (MSA should be completely miscible with feed mixture). 

Consider component already ia mixture for MSA if system exhibits appropriate Hquid-Hquid behavior. 

D/B = distillate-to-bottoms ratio, RCM = residue curve map, DRD = distillation region diagram, and MSA = mass separating agent. 

When two or more sections of the flow sheet perform similar functions, ie, both produce the same product using the same or similar unit operations, one section often can be eliminated by recycling the stream to the input of the remaining section. An MSA contaminated by other components in the mixture often functions as effectively as a pure MSA without the need for additional purification operations. 

Different MSAs may lead to completely different separation systems designs. The systematic generation procedure given in the separations synthesis algorithm is demonstrated for two potential solvents, hexane and methylene chloride. 

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