Heat exchanger network retrofit considering physical distance, pressure drop and available equipment space

Abstract

Heat integration has played an important role in maximising heat recovery, improving energy efficiency and reducing environmental emissions of industrial processes. However, practical aspects of heat integration such as physical distances between pipelines and space constraints must be considered especially during retrofit of heat exchanger networks (HEN). During HEN retrofit, process streams are matched based on their thermodynamic profiles to achieve energy targets. The physical distances between process streams and the space available for heat integration are usually not considered during HEN retrofit even though these issues could offset the cost savings from heat recovery. Matching of process streams across long distances may impose extra piping and pumping costs in order to overcome pressure drop. Pumping cost is also affected by elevation apart from pipeline distance. This work proposes a new graphical tool for visualising the location of process streams as well as the available space within an existing process plant, based on a proposed graphical coordinate representation. With the aid of this graphical tool, process streams can be matched not only based on their thermodynamic profiles, but also by considering the nearest physical distance and elevation of process streams. Designers can also identify the physical locations of additional equipment such as heat exchangers and pumps using the coordinate representation based on a proposed set of heuristics for equipment placement. Pumping and piping costs are included in the capital-energy trade-off analysis. Results of the study show that the coordinate representation of the existing plant can help generate a more practical HEN retrofit design for actual implementation.