Abstract
High-purity hydrogen is a crucial input in a crude oil refinery to upgrade several products. For this reason, the effective hydrogen management is necessary to satisfy hydrogen requirements. On the other hand, adding exergy analysis to the hydrogen pinch analysis especially for refinery plants, where hydrogen reacts under high temperature and pressure, helps improve the efficiency of unit by overcoming the lack of pinch analysis. The aim of this study is the simulation and exergy analysis of reactors within hydrogen network integration of a petroleum refinery retrofitted by pinch analysis before. Two hydrogen production and four consumption units were considered and simulated by Aspen Plus, and then the exergy efficiencies were calculated. Low exergy efficiencies were determined in the hydrogen production and hydrodesulfurization units, whereas the separation of excess hydrogen from the desired product considerably effected on the efficiency. The results also show that not only the hydrogen demand of reactors has to be reduced, but also the hydrogen recovery and purification is very important for the increase in efficiency. Although the processes are carried out at the high operating conditions, the reactions significantly affect the total exergy flow rate.
Highlights
In a petroleum refining process, crude oil is separated, converted and turned into salable valuable products by using hydrogen
Even though the processes were carried out at the moderate and high operating conditions, the physical exergy flow rates of whole streams were significantly lower than chemical exergy rates
In this study the reactor simulations and the reactions were considered by using exergy analysis
Summary
In a petroleum refining process, crude oil is separated, converted and turned into salable valuable products by using hydrogen. While the main products are white products like gasoline and heavy products like fuel oil, naphtha is an intermediate product of the refinery and used to produce high quality gasoline. Each refinery that processes unique composition of crude oil produces its own naphtha composition, which separates as light and heavy naphtha [1]. Separation and recovery of the unconverted normal paraffins from their isomers play another major role in isomerate octane quality [3]. For this process, the sulfur, oxygen and nitrogen compounds in the structure of the naphtha are first removed in the naphtha hydrotreating (NHT) units with the help of a suitable catalyst in a hydrogen environment [4]
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