Relative volatility pseudo

For single separation duty, Diwekar et al. (1989) considered the multiperiod optimisation problem and for each individual mixture selected the column size (number of plates) and the optimal amounts of each fraction by maximising a profit function, with a predefined conventional reflux policy. For multicomponent mixtures, both single and multiple product options were considered. The authors used a simple model with the assumptions of equimolal overflow, constant relative volatility and negligible column holdup, then applied an extended shortcut method commonly used for continuous distillation and based on the assumption that the batch distillation column can be considered as a continuous column with changing feed (see Type II model in Chapter 4). In other words, the bottom product of one time step forms the feed of the next time step. The pseudo-continuous distillation model thus obtained was then solved using a modified Fenske-Underwood-Gilliland method (see Type II model in Chapter 4) with no plate-to-plate calculations. The... 

It has become international practice to employ the mixtures n-heptane-inethyl-uyclohexane, 1.2-dichloroethane-benzene, benzene-carbon tetrachloride und benzene-ethylene dichloride (for plate numbers up to 50 or 60) and benzene-carbon tetrachloride (for plate numbers up to 30) for tests at atmospheric pressure. Brandt and Rock [196] examined the system n-heptane-methylcyclohexane as regards its ideality of behaviour. It was found that the mixture must be classed as a separate typo, termed pseudo-ideal , because the heats of mixing are not negligible in spite of the constancy of the relative volatility. The system is also very suitable for testing under reduced pressure. A further advantage is that the molar heats of evaporation of the components are almost the same (7.575 kcal/mole). For plate numbers from 100 to 500 heavy water is suitable as a test substance [214]. The system... 

Chapter 5, we can find the minimum reflux for this pseudo simple column uang the parameters in Table 6.1. For the simplified sharp split, constant relative volatility problem this means that the TTs of both CSs have to just touch one another, effectively an algebraic colinearity condition. This is shown in figure 6.34 for arbitrary product specifications using the TT technique. 

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