Pinch Analysis in Optimising Energy Consumption on a Naphtha Hydrotreating Unit in a Refinery

Energy consumption plays a significant role in process profitability. This is particularly important for energy intensive business such as petrochemical industries, cement factories, oil refineries and other plants that involve thermos-chemical processes. One of the efficient ways to reduce energy consumption is through energy integration, especially for the process where numerous heat sources and sinks exist. Pinch analysis is one of globally recognized and well-proven methods in identifying the most economical ways of maximizing heat recovery and minimising the demand for external utilities (e.g., steam and cooling water). This paper discusses the application of pinch analysis in optimising energy consumption of a heat exchanger network based on a Naphtha Hydrotreating Unit (NHU) in a refinery based in Nigeria.
Realistic process streams data were used as input in the NHU simulation using Aspen Plus to extract necessary thermodynamic data. Using Aspen Pinch, the Heat Exchanger Network (HEN) for the NHU plant was designed, followed
by strict application of pinch analysis and its principle to the process plant. The minimum temperature approach was optimised to obtain the optimum ∆푇푚푖푛 of 15 ℃ for the minimum total annualised cost. The final heat exchanger network
designed, based on this optimum ∆푇푚푖푛, is also presented along with its composite curve, grand composite curve and total annualized cost. With the analysis of the NHU plant, an improved heat exchanger network (HEN) was obtained. Nineteen heat exchangers with the surface area of 2113.6m2 were used to obtain a minimum annual capital cost (ACC) of $17,301.46/yr, annual operating cost (AOC) of $561,994.20/yr and total annualized cost (TAC) of $579,295.66/yr.