Heat Exchanger Network Thermal Analysis Using Hybrid Pinch Technology

Abstract

This research employs hybrid pinch analysis method to evaluate the heat exchanger network (HEN) of an existing refining plant for thermal design bottlenecks. The pinch rules and thermodynamic models were used to analyze the existing network design using available heat flow data to and from each cascade to determine the pinch temperature on incremental heat changes. The pinch point was discovered at the 6 th and 7 th temperature interval corresponding to a process pinch of 188°C with temperature above and below pinch at 193°C and 183°C respectively. The temperature profile showed two distinct regimes: exponential and linear trend lines within 0°C and 110°C which indicated an initial uneven temperature rise that later stabilized with increment proportional to the heat flow quantity within the heat exchanger with time. Furthermore, the temperature of the crude after it passed through the preheat exchanger network in the base case was found to be 242°C but through the retrofit method 275°C was achieved resulting in 33°C temperature differential. By this approach, the base case number of heat exchangers and trains were reduced from 36 and 20 to 30 and 10 respectively and an energy saving of about 19255KJ was achieved for each second the plan was operated.