Energy requirements in multicomponent distillation trains
This thesis is concerned with feasibility of reducing the energy requirement for mtilticomponent distillation processes. Four systems of four component ideal mixtures are considered, using for each system two degrees of recovery (95% and 99.5%) and two configurations I and lI. A mathematical model has been developed to predict the minimum energy sequence for four component mixtures. Because of the difficulties in solving the equations a graphical method is devised to deal with the problem. To develop this method the concept of pseudo-components is invoked, where a 'pseudo-component' is defined as one having predetermined values of the properties required for the design analysis, e.g. K-values, vapour and liquid enthalpies. A prediction design method has been developed for four component ideal systems which enables the optimal sequence to be related for any type of feed, different degree of recoveries and a set of relative volatilities. Energy integration is considered between reboilers and condensers only and then between intermediate heaters and coolers at the pinch points below and above the feed plate, respectively. The concept of non-ideality is introduced. Nonideal systems often occur e.g.industrially significant mixture for such as Ethanol/Water. Their non-ideality makes them energy intensive usually because of the high reflux ratio required. No general solution is possible but two real mixtures are considered, Acetone/Cumene /Phenol and Ethanol/Water. It is shown that the engineering techniques discussed earlier can be used to produce significant savings in energy requirement for the two systems. These techniques are also applied to an industrial system. The first is the separation of light hydrocarbons, in a stabilizer, C3/C4 splitter and Gasoline Splitter. The mixture is nearly ideal in its vapour-liquid equilibrium relationships and again it is shown that considerable energy savings are possible. The conclusions of the work are summarised and suggestions for further studies in this field are provided.