Title: Retrofit and optimisation for a vacuum gas oil hydrotreating system based on exergy load distribution analysis

Authors: Xiaoqiang Liang; Yongzhong Liu; Lixia Kang

Addresses: Department of Chemical Engineering, Xi'an Jiaotong University, Xi'an Shaanxi, 710049, China ' Department of Chemical Engineering, Xi'an Jiaotong University, Xi'an Shaanxi, 710049, China ' Department of Chemical Engineering, Xi'an Jiaotong University, Xi'an Shaanxi, 710049, China

Abstract: The energy-intensive hydrotreating processes, which operate at high pressure and high temperature, are widely adopted in refineries to improve the quality of oil products. In this paper, the energy and emission performance of a vacuum gas oil hydrotreating unit is investigated by the exergy load distribution analysis incorporated with process simulations. The quantitative relationship among the exergy loads, exergy efficiencies of the subsystems and the exergy efficiency of the entire system is obtained. Two operational optimisation strategies and one retrofit scheme for the entire system are proposed by adjusting the exergy loads and exergy efficiencies of the subsystems. Results show that the exergy efficiency of the entire system increases by 1.23% through the proposed operational optimisation strategies, and the CO₂ emission of the entire system can be reduced by 56.45% through the proposed retrofit scheme.

Keywords: hydrotreating process; exergy load distribution; operational optimisation; retrofit; vacuum gas oil hydrotreating; oil refineries; product quality; exergy analysis; process simulation; exergy efficiency; carbon emissions; CO2; carbon dioxide.

DOI: 10.1504/IJEX.2016.080066

International Journal of Exergy, 2016 Vol.21 No.4, pp.347 - 368

Received: 03 Dec 2015
Accepted: 09 May 2016
Published online: 31 Oct 2016 *

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