An industrial case study application in synthesising a feasible heat exchanger network

Abstract

Heat exchanger network synthesis (HENS) is an important part in the overall chemical process. HENS links the process flowsheet with the utility system and generally involves a large fraction of both the overall plant capital cost, operating costs in terms of energy requirements, which is a key factor for a profitable process. The aims of the synthesis consist of finding a network design that minimises the total annualised cost, i.e. the investment cost in units and the operating cost in terms of utility consumption. In HENS, the feasibility of the HEN design does not take into consideration. As a consequence, the HEN design may not be able to be implemented into industrial applications. It is essential to check the feasibility of a design before it is being implemented into the industry. The objective of this paper is to present the application of a new flexible and operable heat exchanger network (FNO HEN) methodology in synthesising a feasible heat exchanger network (F-HEN) using an industrial case study. The aim of this work is to verify the existing industrial HEN design in terms of the process design point of view as well as the process feasibility. The existing industrial HEN design is verified in terms of ΔTmin value that gives minimum external energy requirement (EER) and heat exchanger area (HEA) as well as simultaneously analyse the feasibility of the HEN design. Using the new developed FNO HEN methodology framework, HEN design target, which is the value of ΔTmin is determined in order to obtain the F-HEN design. From process design point of view, ΔTmin value determines the size of heat exchanger in the network as well as energy saving. A process simulator is used to check the process feasibility of the HEN designs. With the use of the F-HEN trade-off plot, which is a plot of EER and HEA at different value of ΔTmin. with additional of feasibility area, the optimal feasible HEN design which satisfies external energy requirement (operability), heat exchanger area (capital) and process feasibility has been successfully determined in an easy, systematic and efficient manner.