(303r) Development of a Design Algorithm for Petlyuk Columns Using a Process Simulator

The use of distillation sequences, as separation process, is the most used in the industry, in addition of being the most studied unit operation. The use of simple columns sequences (direct or indirect) allows to achieve the separation of the components in a mixture with relative ease. Nevertheless, the inefficiency of traditional columns and their high energy consumption have motivated the search of alternative separation systems. Following the line of distillation, the complex columns arise with the promise of energy saving. The use of complex thermally coupled columns in the industry is not common due to two serious problems: the lack of reliable design methods and the difficulty in the control and operation of these columns. Amongst the proposed schemes of complex columns, the Petlyuk type was selected for this study, since several authors have demonstrated energy savings of 30% in heat duties of condensers and reboilers. A design algorithm for Petlyuk columns is proposed based on the decomposition of the system into three simple columns and performing the design/optimization of these, to get a final design. The Aspen Plus 2004.1 simulator was used as the fundamental tool for the design/optimization of the columns using shortcut and rigorous methods to obtain the final design. The case of study proposed by Jiménez-Castro (2002) was used, which consist in an equimolar mixture of three hydrocarbons and the Redlich - Kwong ? Soave equation was selected as the property method. With the developed algorithm, the final design had significant savings with respect to the traditional sequences. Savings in heat duties were 40% in condenser and 30% in reboiler and columns of similar size to the traditional sequences were obtained. Comparing these results to those of Jiménez ? Castro, similar designs were achieved, with slightly larger columns but smaller reflux ratios, which would mean a greater fixed cost but a decrease in operation costs.