Heat transfer enhancement to decrease the energy consumption of a Light Naphtha Isomerization unit by means of heat exchanger network retrofitting

Abstract

The Light Naphtha Isomerization (LNI) process increases the quality of gasoline, and the Pinch Design Method (PDM) is a novel method in the field of heat transfer that implements the design of Heat Exchanger Network (HEN) to improve energy efficiency. In this research, the HEN of an LNI unit was retrofitted using PDM to determine the best design to decrease hot and cold utility consumption. Stream selection and data extraction were necessary for PDM, and graphical tools in the form of Composite Curves (CC) and a Grand Composite Curve (GCC) were presented to calculate the minimum and actual hot and cold targets. The base-case results showed minimum hot and cold targets of 37 and 42 MW for ΔTmin = 10 °C, respectively and an energy pocket above the pinch in the interval of between 120 and 180 °C. The pocket enhanced heat recovery because of the large driving forces, decreasing MP steam consumption. Scenarios were suggested for the retrofitting of the LNI unit to enhance heat transfer to decrease energy consumption. In particular, the heat pump intensified heat transfer from the Cooling Water cold utility at 29.5 °C to the MP Steam hot utility at 150 °C.