Refinery Hydrogen Network Research Articles

Synthesis of refinery hydrogen networks based on compressor performance models

Synthesis of refinery hydrogen network contributes to reductions in hydrogen consumption, production cost, and emissions. Hydrogen compressors are drivers for hydrogen distribution, which has a direct effect on the performance of hydrogen networks. The existing works focus on the hydrogen network synthesis and often use simple compressor models for easy modelling and solving, which may lead to overly ideal results. This work proposes a novel mathematical method for refinery hydrogen network synthesis considering compressor performances, incorporating both centrifugal and reciprocating compressors. The compression power vs. volumetric flowrate curves and the compression ratio vs. volumetric flowrate curves are considered for a centrifugal compressor, while the efficiency of a reciprocating compressor is correlated with the compression ratio. A mixed integer nonlinear programming model (MINLP) is formulated to minimize the total annualized cost. The developed MINLP model is examined based on two hydrogen network cases reported in literature. The results show that the minimum total annualized cost is a co-optimization of compressor type, operating points, compressor placement, and hydrogen network structure. In the two cases, compression efficiencies of centrifugal compressors range from 0.760 to 0.795 and that of reciprocating compressors are between 0.539 and 0.807. The consideration of centrifugal compressors rather than just reciprocating compressors not only improves the compression efficiencies but also simplify the hydrogen network structures. Moreover, it also brings reductions in the compression power by 2.23% and 1.97%, and decreases in the compressor investment by 7.12% and 6.87%.

Efficient hybrid strategy for simultaneous design of refinery hydrogen networks and pressure swing adsorption unit

Refineries face increasing hydrogen demand due to the consumption of heavy and sour crude oil. This study presents a novel hybrid method to optimize hydrogen network configurations with a rigorous pressure swing adsorption (PSA) process model. This method utilizes Bayesian optimization to address the upper-level unknown constraints black-box optimization problem while employing deterministic algorithms to manage the lower-level nonlinear programming problem. Furthermore, infeasible regions are transformed into feasible ones by introducing a dummy stream, and the costs incurred during the transformation process are accurately calculated. The proposed method is validated using two literature cases. In Case 1, Bayesian optimization outperformed the Kriging model, resulting in a 7.84% reduction in total annual cost (TAC). In Case 2, a comparison of four search strategies revealed the developed two-phase strategy as the most effective one. This method offers a powerful and practical tool for optimizing real-world hydrogen networks with PSA processes.

Synthesis of refinery hydrogen network considering compressor selection and interstage suction/discharge

In refinery hydrogen networks, the optimal arrangement of hydrogen compressors is important to hydrogen reuse and cost reduction. The share of hydrogen compressors can not only reduce the number of compressors, but also provide the economy of scale. However, the previous studies only consider the whole share of compressors and mostly treat the compressor model as reciprocating compressors by default, which limits the optimization of hydrogen networks and does not correspond well with the practice. This paper presents a novel method for hydrogen network synthesis considering the hydrogen compressor type selection and the interstage suction/discharge of multi-stage compressors. In the developed superstructure, hydrogen sources are allowed to be suctioned and discharged via all possible stages of multi-stage compressors. Meanwhile, hydrogen sources can select centrifugal compressors or reciprocating compressors according to the working ranges. A mixed integer nonlinear programming model is developed to minimize the total annualized cost. The proposed method is suitable for both retrofit problems and new design problems, which is demonstrated by a refinery case and a literature case. For the refinery case, the zero-investment retrofit based on the existing compressors can reduce the fresh hydrogen demand by 1.73%, and the new hydrogen network design requires fewer compressors. In terms of the literature case, the hydrogen network design obtained in this paper can reduce the number of compressors by 5 or 3 through interstage suction/discharge of multi-stage compressors.

Optimal Design of Refinery Hydrogen Networks: Reduced Superstructure and Effective Algorithm

In refinery hydrogen networks, the cost related to hydrogen compressors is the second largest contributor to the total annualized cost (TAC). The optimal synthesis of hydrogen networks considering compressor arrangement is a computationally difficult optimization problem because of the highly nonlinear terms caused by hydrogen compression. In this study, a reduced superstructure for optimal design of hydrogen networks is first developed based on several heuristics. This reduced superstructure includes all possible connections among hydrogen sources, hydrogen sinks, and compressors. The maximum number of compressors is reduced dramatically, and the inlet and outlet pressures of all compressors can be preassigned, which notably reduces the bilinear terms and completely eliminates the linear fractional terms in the mathematical model. A mixed-integer nonlinear programming (MINLP) model is formulated, and a tailored algorithm that incorporates successive piecewise linear approximation of concave terms and linear relaxation of bilinear terms is proposed. The case studies show that the proposed model and algorithm can give better hydrogen network designs with only 2.9 and 4.9% of the computational time in the existing publication.

A mathematical model for refinery hydrogen network synthesis integrating multi-stage compressors

The synthesis of refinery hydrogen network (HN) is generally performed under the assumption that compressors are single-stage ones. This assumption might overestimate the compression power, leading to deviation from the optimum designs. To tackle this problem, we integrate multi-stage compressors into hydrogen networks synthesis in the present work. The number of compression stages inside each compressor is defined as a variable which is simultaneously optimized with the network configurations. Taking advantage of the discrete nature of the defined stage variable, we linearize the constraint of compression power without losing generality. The proposed mathematical model for HN synthesis is formulated as a mixed-integer nonlinear programming problem. Three instances are conducted and the solution results show that the proposed model could be solved to global optimality. The total annualized costs of globally optimal solutions are 1.4–5.1% lower than those of the base solutions.

Design of Refinery Hydrogen Networks with Pressure Swing Adsorption Unit Configuration under Uncertainty: Economy and Flexibility Aspects

Design of Refinery Hydrogen Networks with Pressure Swing Adsorption Unit Configuration under Uncertainty: Economy and Flexibility Aspects

Total Site Hydrogen Integration with fresh hydrogen of multiple quality and waste hydrogen recovery in refineries

This paper proposes a novel method combining Pinch Methodology and waste hydrogen recovery, aiming to minimise fresh hydrogen consumption and waste hydrogen discharge. The method of multiple-level resource Pinch Analysis is extended to the level of Total Site Hydrogen Integration by considering fresh hydrogen sources with various quality. Waste hydrogen after Total Site Integration is further regenerated. The technical feasibility and economy of the various purification approaches are considered, demonstrated with a case study of a refinery hydrogen network in a petrochemical industrial park. The results showed that fresh hydrogen usage and waste hydrogen discharge could be reduced by 21.3% and 67.6%. The hydrogen recovery ratio is 95.2%. It has significant economic benefits and a short payback period for Total Site Hydrogen Integration with waste hydrogen purification. The proposed method facilitates the reuse of waste hydrogen before the purification process that incurs an additional environmental footprint. In line with the Circular Economy principles, hydrogen resource is retained in the system as long as possible before discharge.

Simulation-based modeling and optimization for refinery hydrogen network integration with light hydrocarbon recovery

Purge gases from hydrocrackers and hydrotreaters and refinery off-gases are important hydrogen sources. Some of these hydrogen sources are also rich in light hydrocarbons that are valuable energy resources and chemical materials. In this work, a systematic method is proposed to integrate hydrogen networks considering light hydrocarbon recovery. This work first develops a hydrogen network superstructure with light hydrocarbon recovery. Aspen HYSYS is employed for rigorous process and thermodynamic modeling of the light hydrocarbon recovery process, and a simulation-optimization model is then developed. To solve the simulation-optimization model efficiently, the genetic algorithm is used as the global solver to determine the feed to light hydrocarbon recovery unit, and the linprog and fmincon solvers are combined to determine the optimal hydrogen network design. The application and effectiveness of the proposed method is validated through a case study. The results show that fresh hydrogen consumption decreases by 13% and the total annualized cost reduces to 72% because of light hydrocarbon recovery. This method could provide useful guides for the management of hydrogen and light hydrocarbons in refineries.

Globally optimal design of refinery hydrogen networks with pressure discretization

The design of refinery hydrogen networks minimizing the total annualized cost is a computationally hard optimization problem. This is mainly due to the highly nonlinear compression power constraint and the nonconvexities of the problem. To decrease the nonlinearities, we propose in this work a concept of pressure discretization, and therein the pressure variables of new makeup compressors make discrete choices among the specified pressures of hydrogen origin and destination units. Based on this concept, the constraint of compression power is linearized without losing rigors. Then, hydrogen networks design is formulated as a mixed integer nonlinear programming model that is applicable to both grass-roots synthesis and retrofit problems. We develop a global optimization algorithm to solve the proposed model to global optimality. Two grass-roots synthesis and three retrofit examples are tested for illustration purposes. The total annualized cost and computing time of our solutions compare favorably to those of literature solutions.

Fuzzy optimization design of multicomponent refinery hydrogen network

Hydrogen and light hydrocarbon components are essential resources of the refinery. The optimization of the refinery hydrogen system and recovery of the light hydrocarbon components contained in the gas streams are key strategies to reduce the operating costs for sustainable development. Many research efforts have been focused on the optimization of single impurity hydrogen network, and the flowrates of the hydrogen sources and sinks are assumed to be constant. However, their flowrates vary along with the quality of crude oil and refinery processing plans. A general superstructure of multicomponent refinery hydrogen network is proposed, which considers four components, namely H 2 , H 2 S, CH 4 and C 2 + , as well as the flowrate variations of hydrogen source and hydrogen sink. The mathematical model based on the superstructure is developed with objective functions, including the minimization of total annualized cost and the maximization of overall satisfaction of the hydrogen network. Moreover, the model considers the removal of hydrogen sulfide and the recovery of light hydrocarbon components ( i . e ., C 2 + ) in the optimization. To verify the applicability of the proposed mathematical model, a simplified industrial case study with four scenarios is solved. The optimization results show that the economic benefit can be maximized by considering both the direct reuse of gas streams from high-pressure separator (HP gas stream) and from low-pressure separator (LP gas stream) and the recovery of the light hydrocarbon streams. The fuzzy optimization method can be used to guide the optimal design of the refinery hydrogen system with multi-period variable flowrates.

Surrogate-assisted optimization of refinery hydrogen networks with hydrogen sulfide removal

Hydrogen management is very important for the production of clean fuels such as low-sulfur gasoline and diesel. As a key contaminant in the hydrogen network, hydrogen sulfide not only deactivates catalysts but also corrodes equipments. Hence, it is necessary to integrate hydrogen sulfide removal process model into the optimization of hydrogen allocation network. However, a desulfurization process model with simplifications and assumptions may yield suboptimal results and a model based on rigorous process mechanism may require high computational cost. To solve this problem, this paper proposes a novel approach for simultaneous optimization of refinery hydrogen allocation network and hydrogen sulfide removal processes. The optimization is realized in two steps. First, surrogate models are developed as approximations to the rigorous process and thermodynamic model for the desulfurization processes. Second, the surrogate model is embedded into the mathematical programming model for hydrogen network optimization. The effectiveness of the proposed approach is illustrated by its application to a case study taken from a real refinery. Result comparison between the proposed method and a literature model based on simplified desulfurization models is carried out, proving that, with the proposed method, more practical optimization result can be obtained with much less computational effort.

Thermodynamic principle based work exchanger network integration for cost-effective refinery hydrogen networks

Work exchanger network (WEN) integration is crucial way to conserve energy for gas networks. Refinery hydrogen allocation network (HAN) determines its work sources and sinks of hydrogen streams and even WEN. Hydrogen gas streams are always non-ideal and there is also energy loss in their pressurization and depressurization processes through direct work exchangers. Based on thermodynamic principles for gas property and work exchange through compressors, expanders and direct work exchangers, this paper proposes a novel methodology for cost-effective refinery hydrogen networks. A stage-wise superstructure consisting of hydrogen allocation network (HAN) and work exchanger network (WEN) is built as problem illustration and the corresponding mixed integer nonlinear programming (MINLP) models for HAN and WEN are formulated to successively perform mass and work networks integration for total annualized cost (TAC) minimization. A refinery case is studied and results show that WEN can conserve 27.4% power utility consumption and reduce 50.9% investment cost. Case study results comparison demonstrates that the consideration of thermodynamic principles is of great significance to real-world energy conservation and investment cost reduction of WEN.

Exergy analysis of petroleum refinery hydrogen network integration based on reaction system

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.

Optimization for refinery hydrogen networks with detailed reactor-separator-purifier modeling

Hydrogen network integration is an effective way to reduce the cost of refineries, and a number of graphical and mathematical methods have been proposed. Parameters of reactors, separators and purifier have a great effect on hydrogen consumption, while only simple models of these equipment are considered. This paper proposed a method to optimize the hydrogen network of a refinery with multiple components and detailed reactor, separator, purifier modeling considered. For all hydrotreating units, models of reactor are built and considered, as well as separators and purifier. The effect of their operation parameters (temperature, pressure et al.) on hydrogen flowrate and concentration is analyzed. An integration model is built with hydrogen network, all reactors and separators, and purifier interconnected. It performs a simultaneous optimization for hydrogen related equipment according to the requirement of refinery, and can minimize the fresh hydrogen consumption with multiple components considered. Based on the developed optimization framework, the hydrogen network of a refinery is optimized and its utility consumption is reduced by 17.70%. The optimal temperatures of reactors and separators, and the pressure in purifier are determined, as well as the corresponding optimal hydrogen distribution network.

Simulation and Modeling-Based Refinery Hydrogen Network Integration with Process Risk Analysis

Hydrogen network integration is a crucial way to achieve resource conservation and cost reduction of refinery and it is performed on quantitative and thermodynamic properties of hydrogen streams su...

Real-time reconciled simulation as decision support tool for process operation

Decision support tools in the process industry have been gaining relevance, especially for operation under uncertain conditions. This study describes real-time reconciled simulation (RTRS), and analyzes its usefulness as decision-making tool for process operators, especially under unexpected process changes. The proposed methodology is implemented in two case studies in the context of an oil refinery hydrogen network, where both plant and network levels are considered. A what-if analysis is conducted on two case studies, assessing two feasible mitigation actions for each case baseline condition. The focus of the discussion is, nevertheless, on the methodology itself and its general features as decision support tool. The relative error of RTRS for estimation of states and parameters, considering unmeasured disturbances, is satisfactory aligned with industrial standards for online measurements. In terms of mitigation actions, these are assessed with regards to its economic impact on the system in question. It is shown how actions at plant level may be disadvantageous when facing hydrogen demand changes, compared to network-wide mitigation actions. At plant level, it is pointed out the importance of purification units, prevailing over hydrogen make-up for mitigation of demand change. It is highlighted the fact that RTRS complements in a straightforward manner other control operation tools such as model predictive controllers (MPC) and real-time optimizers (RTO). Therefore, it may add to any decision support framework an open-loop component with parameter estimation and forecasting capabilities. Moreover, its potential for training and integration within other tools packages is discussed. Future directions of research are commented such as fully integrated decision support frameworks, including RTRS, MPC and RTO. Additionally, how RTRS may relate to digital twins, including an example of a suitable architecture is introduced, and RTRS role in enterprise-wide decision-making solutions is commented.

Coupling pinch analysis and rigorous process simulation for hydrogen networks with light hydrocarbon recovery

In refineries, some hydrogen-rich streams contain considerable light hydrocarbons that are important raw materials for the chemical industry. Integrating hydrogen networks with light hydrocarbon recovery can enhance the reuse of both hydrogen and light hydrocarbons. This work proposes an automated method for targeting hydrogen networks with light hydrocarbon recovery. A pinch-based algebraic method is improved to determine the minimum fresh hydrogen consumption and hydrogen sources fed into the light hydrocarbon recovery unit automatically. Rigorous process simulation is conducted to determine the mass and energy balances of the light hydrocarbon recovery process. The targeting procedures are developed through combination of the improved pinch method and rigorous process simulation. This hybrid method is realized by coupling the Matlab and Aspen HYSYS platforms. A refinery hydrogen network is analyzed to illustrate application of the proposed method. The integration of hydrogen network with light hydrocarbon recovery further reduces fresh hydrogen requirement by 463.0 m3·h−1 and recovers liquefied petroleum gas and gasoline of 1711.5 kg·h−1 and 643 kg·h−1, respectively. A payback period of 9.2 months indicates that investment in light hydrocarbon recovery is economically attractive.

New superstructure-based model for the globally optimal synthesis of refinery hydrogen networks

Abstract This work presents a new superstructure for refinery hydrogen networks synthesis. The superstructure eliminates the need to have the pressures of compressors as variables, while both dedicated and shared compressors can be included. As a result of considering the pressures as the parameters known a-priori, the constraint of compression power is expressed by using linear equation. Hydrogen networks synthesis is then formulated as a new mixed integer nonlinear model whose nonlinearities are only attributed to the bilinear and concave terms. The proposed model is a simple optimization problem that could be solved to global optimality. Four literature examples and an industrial case are tested for illustration purpose. The obtained solution results exhibit 3.1–4.5 % reduction in the total annualized cost compared with those of literature ones.

Systematic retrofit method for refinery hydrogen network with light hydrocarbons recovery

Retrofit of the refinery hydrogen network is one of the important issues faced by modern refineries. Refinery off-gas streams are rich in hydrogen and valuable light hydrocarbons. Light hydrocarbons recovery (LHR) process can recover the valuable hydrocarbons and generate the hydrogen-rich stream for reuse and recycle. We firstly propose the systematic procedure for the retrofit of refinery hydrogen network integrated with LHR process. The approach combines the pinch analysis technique and process modelling and simulation. The typical pinch analysis technique (i.e. problem table) is used to determine the flowrate targets. Aspen HYSYS is used for the modelling and simulation of LHR process. The retrofit of an industrial refinery hydrogen network is conducted to illustrate the procedure. Results show that the benefit of retrofit scheme (Integrated Scheme 3) with LHR reaches 7.488 million CNY/y, and the investment payback period is only 8 months.

Synthesis of refinery hydrogen network integrated with hydrogen turbines for power recovery

Hydrogen compressors are widely utilized to raise the pressure of hydrogen-rich streams in refineries to satisfy the operating pressure requirements of various hydrogenation units. Pressure relief valves are also placed to reduce the pressure of the hydrogen streams but this leads to a waste of energy. Alternatively, hydrogen turbines may be used in place of pressure relief valves to recover energy. This paper proposes a novel superstructure of a refinery hydrogen network involving hydrogen turbines to recover the expansion work. Such a configuration can be termed a hydrogen/work exchange network. Sequential mathematical models are developed with objective functions including the minimization of the flowrate of hydrogen utility, compression work, total power consumption and total annualized cost. A modified literature case study with five scenarios is solved. Results show that the total power consumption and the total annualized cost can be further reduced by 3.9% and 0.6% by recovering the expansion work of hydrogen-rich streams using hydrogen turbines.