Investigation of Naphtha Hydrotreating (NHT) Unit Exergy Utilization: A Case Study of a Petrochemical Industry in A developing Country

The need for efficient energy use in refinery operations is the proffered solution to the poor management of energy resources which has resulted in the instability in oil products prices, irregular plant shutdowns experienced in refineries of developing countries and increased carbon emission to the atmosphere. This research work aims to carry out exergy analysis on major energy consuming units which will aid in determining sites and causes of primary energy losses and proffer solutions to maximizing energy utilization. The Naphtha Hydro-treating (NHT) unit of the case model refinery was successfully simulated using Aspen Hysys. The analysis revealed more than half (51.9 %) of the input exergy was lost to the environment and an irreversibility of 32.7% occurred in the Stripper column. Comparison was also made with the same unit at Kaduna refinery and petrochemical plant and the results showed a conversion efficiency of about 91.28% when compared to 44.35% from the old refinery though this could be attributed to factors like age of plant, inadequate maintenance etc. The positive value of the amount of heat recovered from that of the flue gas in the boiler and furnace gave an opportunity to recover the energy lost and integrated back to the system for economic viability of the plant which result in a payback period that is less than a year.