Nonideal liquid solutions, multicomponent mixtures

The BP and SR methods for vapor-liquid contacting converge only with difficulty or not at all for separations involving very nonideal liquid mixtures (e.g., in extractive distillation) or for cases where the separator is like an absorber or stripper in one section and a fractionator in another section (e.g., a reboiled absorber). Furthermore, BP and SR methods are generally restricted to the very limited specifications stated above. More general procedures capable of solving ail types of multicomponent, multistage separation problems are based on the solution of all the MESH equations, or combinations thereof, by simultaneous correction (SC) techniques. 

While chemical theories are often useful for describing strongly nonideal liquid mixtures, they are necessarily specific, limited to a particular type of solution. It is difficult to construct a general theory, applicable to a wide variety of components, without introducing complicated algebra and, what is worse, a prohibitively large number of parameters. This difficulty also makes chemical theory impractical for multicomponent mixtures and indeed, while the... 

These advantages ean be compromised for multicomponent liquid mixtures. There, the nonideal solutions require a somewhat different form... 

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