Split-feed treatment

The most frequent application of phase-equilibrium calculations in chemical process design and analysis is probably in treatment of equilibrium separations. In these operations, often called flash processes, a feed stream (or several feed streams) enters a separation stage where it is split into two streams of different composition that are in equilibrium with each other. 

Stack, and a potential difference sufficient to force current through the stack is applied between the two electrodes placed at each end of the stack. For current to pass between the electrodes, ions must be transported through each of the membranes. By arranging the feeds to the various intermembrane compartments, it is possible to force ionic salts to pass from the dilute stream to the concentrated stream. In this way, a salt can also be split into its acid and base components. By combination of several cell pairs that comprise an anion- and a cation-selective membrane sheets in parallel, a stream concentrated in the original salts may be prepared. This configuration is the common method for industrial use, in which electrodialysis gives broadly the same result as reverse osmosis and has found very similar applications to general water treatment. 

In the flotation section, classification units may be used to split the minus 1.0 mm plus 0.1 mm feed into two size fractions for separate treatment. The coarser fraction (minus 1.0 mm to approximately plus 0.4 mm) can be concentrated by gravity (spirals) and froth flotation methods. The finer, minus 0.4 mm plus 0.10 mm, fraction is dewatered to 60%-75% solids. After being condi-... 

Equations 9.26 to 9.28 contain integrals have to be solved iteratively because there are no analytical solutions independent of the distribution function of the feed phase. For 0 = 0, eqs 9.26 to 9.28 are equivalent to eqs 9.21, 9.24 and 9.25. The treatment may be easily generalized to mixtures of several polymers and several solvents. Equations 9.26 to 9.30 play an important role in polymer fractionation. In each fractionation step a feed phase F splits into two coexisting phases I and II. 

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