Modeling and simulation of heat balance and internal heat recovery targets through a combination of stream specific minimum temperature difference and polynomial temperature coefficients of specific heat capacities using pinch analysis

Abstract

Existing heat balancing and energy targeting model in Pinch Analysis rely on use of interpolated values of specific heat capacities and global values of minimum temperature difference ∆Tmin, respectively. Even though this model is useful in estimation of the maximum internally recoverable heat recoverable in processing plants, it does not adequately represent the actual state properties of industrial processes. Specific heat capacities of fluids are polynomial functions of temperature of material under processing. The values of ∆Tmin also vary depending on the nature of the process stream under analysis. In this study, improvement to the heat balancing and energy targeting processes of pinch analysis was proposed. The study combined the use of stream specific values of ∆Tmin and polynomial temperature functions of specific heat capacities for heat targeting model. This was coded and executed using a PHP program. The model performance was tested using data from three thermochemical plants, Plant A, B and C, which process linear alkyl benzene sulphonic acid, dairy products and ethanol, respectively. The proposed method for heat balancing computed more heating requirements for plant A, B and C by 0.37%, 0.65% and 0.72% respectively, compared to the traditional method of heat balancing. The cooling loads for Plant A and B were less by 2.23% and 32.52% respectively, while for Plant C, they were more by 0.64%. The computed internally recoverable heat targets were more by 1.5%, 4.5% and 2.2% for Plants A, B and C. Simulations of the proposed model were carried out over a range of temperature targets, for different process streams. For gaseous process streams, heating and cooling load requirements were less. Reverse behavior was observed in liquid and steam containing streams, where the heating and cooling load requirements were more.