IMPROVING THE EFFICIENCY OF NIGERIAN REFINERIES USING PINCH TECHNOLOGY A CASE STUDY OF THE CRUDE DISTILLATION UNIT OF PORT HARCOURT REFINERY, ALESA ELEME

Abstract

The crude distillation unit (CDU) of the New Port Harcourt Refinery, with a processing capacity of 150,000
barrels per day, was adopted as the case study for this project. The research was motivated by measurable
production and energy losses arising from frequent plant downtime, inefficient energy utilization, and
inadequacies in process network dynamics and control. Pinch Analysis was applied to the heat exchanger
network (HEN) of the CDU using Aspen Pinch 11.1, a commercial process integration software. The study
involved the collection of relevant process data, including the CDU process flow diagram, energy balance
flow sheets, plant operating records, plant information system (PI) data, and heat exchanger operational
data obtained from the PI system. From these sources, the required data for pinch analysis were extracted
and converted into pinch-compatible thermal data. The analysis procedure included the development of
problem tables, construction of composite and grand composite curves, determination of the pinch point,
energy and area targets, and grid representation of the heat exchanger networks. This approach enabled
the identification of heat exchangers that crossed the pinch, violated pinch design rules, and contributed to
energy penalties. The total computational time for the analysis was 141,039 CPU seconds, executed on a
3.2 GHz Intel® Core™2 T5200 laptop with 1024 MB RAM. The analysis was conducted at minimum
temperature differences (ΔTmin) ranging from 20 to 40 °C, consistent with values established for the oil
refining industry. A flowsheet comprising 23 heat exchangers distributed across three networks formed the
basis of the study: HEN-1 with 7 exchangers and 25 nodes, HEN-2 with 12 exchangers and 36 nodes, and
HEN-3 with 4 exchangers and 18 nodes. Results showed that HEN-1 exhibited poor and unclear grid
representation, leading to uncertainties in pinch location, cross-pinch effects, penalties, and stream
matching. HEN-2 demonstrated a clearer grid structure, allowing accurate identification of pinch location,
cross-pinch effects, and exchangers violating pinch rules. At ΔTmin = 20 °C, HEN-2 achieved heat balance, optimal stream matching, and zero cross-pinch effect, requiring only minimal retrofitting. Conversely, HEN 3 produced unsatisfactory results across all ΔTmin values, indicating the need for complete retrofitting. Even then, optimal performance may not be achievable due to its low potential for process-to-process heat recovery. Overall, the study revealed heat imbalance, poor stream matching, and moderate cross-pinch
effects across the CDU HEN, confirming the need for total network retrofitting. The findings further demonstrate that the design of an energy-efficient HEN is highly dependent on the selected ΔTmin, with  each network exhibiting unique performance characteristics under different conditions.