RETROFIT BY INSPECTION USING THERMODYNAMIC PROCESS VISUALIZATION

Although grassroots Heat Exchanger Network (HEN) Synthesis has receive d much attention in the literature, relatively little research has foc used on the retrofit problem, which comprises the vast majority of rea l industrial cases. Attempts at rigorous automation (Ciric and Floudas , 1989; Yee and Grossmann, 1991) have met with limited success primari ly because of the excessive computational costs associated with this p roblem when formulated as a Mixed-integer Nonlinear Program (MINLP). O ther approaches (Briones and Kokossis 1995; Tjoe, 1986; and Asante, 19 96) make simplifying assumptions which are only appropriate for restri cted classes of problems. The research described here has focused on t he development of a visualisation tool, the Retrofit Thermodynamic Dia gram (RTD), and a set of guidelines for developing retrofit solutions by inspection. The method relies heavily on the ingenuity of the desig ner, but has proved to be very flexible - handling a wide variety of p roblem formulations. It has produced designs that are significantly su perior to published solutions, ranging from 85% additional energy savi ng - for the same payback period - (Lakshmanan and Banares-Alcantara, 1996) to a 70% reduction in capital cost (for the same level of energy saving). (C) 1998 Elsevier Science Ltd. All rights reserved.