A Multiperiod Optimization Model for Hydrogen System Scheduling in Refinery

Abstract

In a refinery, hydrogen, as a valuable resource, is also a byproduct and a significant raw material source of the petroleum refining and petrochemical hydrogenation process. To reduce costs and save energy for the petrochemical industry, the hydrogen system in a refinery should be operated under the optimal scheme to meet the varying hydrogen demands of hydrogen consumers. Optimal scheduling of the hydrogen system can help a refinery to achieve cost reduction and cleaner production. In this paper, a discrete-time mixed-integer nonlinear programming (MINLP) model that considers the penalties for abnormal situations in the hydrogen pipe network (HPN), compressors start–stop, and changes in hydrogen sources for hydrogen consumers is proposed for the optimal scheduling of the hydrogen system under multiperiod operation. The solution of the scheduling problem is obtained based on an iterative method between that of a mixed-integer linear programming (MILP) problem and that of a nonlinear programming (NLP) problem, avoiding the solution of the MINLP problem directly and the occurrence of composition discrepancy. A case study based on the data from a real refinery is presented to illustrate the effectiveness and feasibility of the proposed methodology.

MILP Formulation for Solving and Initializing MINLP Problems Applied to Retrofit and Synthesis of Hydrogen Networks

“…Therefore, it is necessary to have greater control in the sources and consumers of hydrogen through network management as a whole, because it is not economically feasible to produce and burn the product with an excellent added value [5]. It is known that the cost of hydrogen is the second-highest cost in a refinery, behind only the cost of crude oil [6]. Therefore, savings in terms of the amount of hydrogen consumed and the operating cost of the network have great economic appeal.…”

Retrofit Design of Hydrogen Network in Refineries: Mathematical Model and Global Optimization

“…Hydrogen network designs capable of functioning under multiple modes of refinery operation were proposed by Ahmad et al and Jiao et al A mathematical model for hydrogen network design under uncertain operating conditions, mainly in the uncertainty in the hydrogen requirement at the process units, were developed by several authors. − An interplant hydrogen network model, for network integration among multiple refineries, between oil refineries and petrochemical plants and in petrochemical complexes, were also developed in the literature. − Many mathematical models for hydrogen network design were developed in the literature including integration with hydrogen sulfide removal; integration with rigorous models of process units in a refinery; , models with fuel cells and hydrogen plant; , hydrogen system scheduling studies; , consideration of sustainability and greenhouse gas (GHG) emissions; targeting of compressors and compressor works; − those based on exergy and thermodynamic analysis; constraints on the hydrogen-to-oil ratio at the hydrogen consumer; superstructure having hydrogen headers; models which involved more sophisticated design equations and rigorous procedure for the incorporation of purification units; − using mixing potential concept; , and comparison of different investigative network designs concerning hydrogen utility flow with connections in the network, with the placement of compressors and purifiers and with different economic performance criterions . Apart from these, a more comprehensive review on the state-of-the-art practices used in the field of hydrogen network design and management were given in the works of Elshreif et al and Marques et al…”

“…Hydrogen network designs capable of functioning under multiple modes of refinery operation were proposed by Ahmad et al 17 and Jiao et al 18 A mathematical model for hydrogen network design under uncertain operating conditions, mainly in the uncertainty in the hydrogen requirement at the process units, were developed by several authors. 19−22 An interplant hydrogen network model, for network integration among multiple refineries, between oil refineries and petrochemical plants and in petrochemical complexes, were also developed in the literature.…”

A mathematical model for optimal compression costs in the hydrogen networks for the petroleum refineries

“…Shariati et al introduced a new automated targeting procedure for conserving hydrogen in petrochemical plants. Hydrogen network design with pressure constraints applicable for hydrogen scheduling was proposed by Jiao et al Jhaveri et al developed different models for the optimization of hydrogen distribution in a refinery. They considered different types of compressor (centrifugal, reciprocating, and screw compressor) in their work along with their costs.…”