Tables, separation process

Many of the impurities are much lower than the values shown in Table 3, but these analytical lower limits are typical and more than sufficient for all but special appHcations. Zirconium content can be from 0.01 to 4.5%, and is typically 0.5—2%, but this is a function of how far the separation process was carried, not a function of the reduction or refining processes. 

An improved solvent extraction process, PUREX, utilizes an organic mixture of tributyl phosphate solvent dissolved in a hydrocarbon diluent, typically dodecane. This was used at Savannah River, Georgia, ca 1955 and Hanford, Washington, ca 1956. Waste volumes were reduced by using recoverable nitric acid as the salting agent. A hybrid REDOX/PUREX process was developed in Idaho Falls, Idaho, ca 1956 to reprocess high bum-up, fuUy enriched (97% u) uranium fuel from naval reactors. Other separations processes have been developed. The desirable features are compared in Table 1. 

The selection of a separation process depends on many factors, not the least of which is the type of gas to be purified. Table 7 gives some... 

These tetrahedra are arranged in a number of ways to give the different zeohtes. The stmctures are unique in that they incorporate pores as part of the regular crystalline stmctures. The pores have dimensions of the order of molecular dimensions so that some molecules fit into the pores and some do not. Hence the zeohtes are molecular sieves (qv), and they are apphed in industrial separations processes to take advantage of this property. Some zeohtes and their pore dimensions are hsted in Table 2. 

Deviations from Raonlt s law in solution behavior have been attributed to many charac teristics such as molecular size and shape, but the strongest deviations appear to be due to hydrogen bonding and electron donor-acceptor interac tions. Robbins [Chem. Eng. Prog., 76(10), 58 (1980)] presented a table of these interactions. Table 15-4, that provides a qualitative guide to solvent selection for hqnid-hqnid extraction, extractive distillation, azeotropic distillation, or even solvent crystallization. The ac tivity coefficient in the liquid phase is common to all these separation processes. 

Table 16.1. Classification of membrane separation processes for liquid systems...

Industrial membrane processes may be classified according to the size range of materials that they are to separate and the driving force used in separation. There is always a degree of arbitrariness about such classifications, and the distinctions that are typically drawn. Table 16.1 presents classification of membrane separation processes for liquid systems. 

Table 16.2. Module designs most commonly used in major separation processes...

Separation processes are based on some difference in the properties of the substances to be separated and may operate kinetically, as in settling and centrifugation, or by establishing an equilibrium, as in absorption and extraction. Typical separation processes are shown in Table 6.1. Better separations follow from higher selectivity or higher rates of transport or transformation. The economics of separation hinges on the required purity of the separated substance or on the extent to which an unwanted impurity must be removed (Figure 6.13). 

Table 11.4 lists reactors used for systems with two fluid phases. The gas-liquid case is typical, but most of these reactors can be used for liquid-liquid systems as well. Stirred tanks and packed columns are also used for three-phase systems where the third phase is a catal5hic solid. The equipment listed in Table 11.4 is also used for separation processes, but our interest is on reactions and on steady-state, continuous flow. 

Applications Membranes create a boundary between different bulk gas or hquid mixtures. Different solutes and solvents flow through membranes at different rates. This enables the use of membranes in separation processes. Membrane processes can be operated at moderate temperatures for sensitive components (e.g., food, pharmaceuticals). Membrane processes also tend to have low relative capital and energy costs. Their modular format permits rehable scale-up and operation. This unit operation has seen widespread commercial adoption since the 1960s for component enrichment, depletion, or equilibration. Estimates of annual membrane module sales in 2005 are shown in Table 20-16. Applications of membranes for diagnostic and bench-scale use are not included. Natural biological systems widely employ membranes to isolate cells, organs, and nuclei. 

Separation processes, as could be seen from Figure 2.1, position themselves at the back end of the sequence in operations in the mineral processing flowsheet. The front-end operations has been found virtually to terminate with the liberation or the size-reduction processes involving crushing and grinding. It is important to limit the amount of size reduction to that at which adequate liberation is accomplished. The term adequacy is related to the cost involved in comminution and to performance of the concentration methods that follows. The concentration is obtained by separation processes which rely on differences in the properties of the particles, the physical and physico-chemical characteristics of minerals. In this context, it will only be relevant to refer to Table 2.5 which presents a summary of the processes along with the properties of the minerals that are exploited. 

Table 2.7 Some characteristics of minerals utilized in separation processes.

A list of separation processes and the properties that are exploited by them is given in Table 4-2. Just as for distillation, for all the processes the greater the difference in the magnitude of the separative property, the easier it is to perform the separation. Of course, various complications can negate this generality. For instance, the formation of an azeotrope or the tendency to foam may eliminate the use of distillation even though there is a reasonable difference in boiling points. 

Table 2 presents the results of tests to measure the calorific power, ash content, and chlorides concentration of some of the materials obtained from the separation process, such as polystyrene, aluminum foil, plastic foam, and other plastics (general, clear, colored, black, and vinyl). Polystyrene and clear plastic have very high calorific power and low levels of chlorides, but polystyrene has very high ash content. Figures 10-17 present the samples of waste components from the separation and composting plant of Cantagalo. 

Since the interaction of the mixture components with the liquid stationary phase plays the key role in the separation process, the nature of the stationary phase is obviously important. Several hundred different liquids useful as stationary phases are known. This means that the analyst has an awesome choice when it comes to selecting a stationary phase for a given separation. It is true, however, that relatively few such liquids are in actual common use. Their composition is frequently not obvious to the analyst because a variety of common abbreviations have come to be popular for the names of some of them. Table 12.3 lists a number of common stationary phases, their abbreviated names, a description of their structures, and the classes of compounds (in terms of polarity) for which each is most useful. 

Table 1. Characteristics of the separation process by pervaporation function of the membrane composition and structure, composition of feed mixture and temperature [18]...

PVA-PAcr.Ac. membranes have been tested also for ethanol separation from ethanol/toluene mixture, by using pervaporation technique. The reported data concerning the separation process characteristics are presented in table 8. 

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