Two-Level Decoupled Ethylene Cracking Optimization of Batch Operation and Cyclic Scheduling

Self Cite

The global supply chain is experiencing ongoing turmoil after COVID-19, which inevitably affects the supply and demand of the chemical industry. Ethylene plants are regarded as one of the most profitable chemical industry chains, and thus, there is a need to track fluctuations in the supply chain and responsively adjust their operations and scheduling decisions to achieve optimal economic benefits. However, previous studies about ethylene cracking optimization are mostly limited to fixed supply chain parameters and cannot meet the need for real-time updates according to supply chain fluctuations. To address this problem, we propose an ethylene cracking optimization framework which combines parameter prediction and receding horizon optimization (predictive RHO) for real-time optimal operation and scheduling under supply chain fluctuations. This optimization framework uses historical supply chain data (supply quantities, feedstock prices, and product prices) to predict future parameters and uses the predicted parameters to optimize the operation and scheduling of ethylene cracking furnace systems in a receding horizon way. Two industrial case studies were used to validate the efficacy of the proposed optimization framework. In case 1, the predictive-RHO framework achieved comparable economic profits of 147,370 and 146,483 $/day without violating daily inventory constraints (vs 151,204 $/day from the original model violating inventory constraints) and a faster calculation speed of 40 s (vs 32 min) under two fluctuating feed supply modes. In case 2, predictive RHO improves economic profits by 1.8% through integrating operations with scheduling and 1.1% by tracking the feed and product price fluctuations. These two cases show the strong capability of predictive RHO in tracking supply chain fluctuations and improving the inventory management level as well as the economic profits of ethylene cracking plants.

Section: Daily Inventory Constraintsmentioning

confidence: 99%

Section: Case Studiesmentioning

confidence: 99%

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Receding Horizon Optimization of Ethylene Cracking Operation and Scheduling under Supply Chain Fluctuations

Zhang

Qiu

2023

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“…Steam cracking, carried out in high-temperature furnaces, is one of the most important processes for producing foundational chemicals like olefins and aromatics. − Simultaneously, it stands as a relatively energy-intensive technology, with cracking furnaces constituting a significant proportion of energy consumption within a petrochemical plant. , It is clear then that even a slight change in the process can bring attractive economic benefits. Coke is a byproduct during steam cracking that forms and deposits on the inner wall of the reactor coils and has adverse effects on the process.…”

Section: Introductionmentioning

confidence: 99%

Effect of Reactor Alloy Composition on Coke Formation during Butane and Ethane Steam Cracking

Mohamadzadeh Shirazi,

dos Santos Vargette,

Reyniers

et al. 2024

The use of highly specialized alloys in ethane steam cracking environments can lead to reduced coking and alloy aging. However, the fouling resistance of these materials when exposed to heavier feedstocks, such as butane, especially at higher temperatures (950 °C) and toward the end of a cracking run, remained unknown. To address this knowledge gap, this study investigated the coke resistances of presulfided three alloys, Al-Boosted, Spinel-Coated, and 35/45 Cr−Ni, during the steam cracking of both ethane and butane using a quartz Electrobalance setup with a tubular reactor. Under experimental conditions of T gas = 950 °C, P = 1.1 bar, χ Butane ≈ 79%, χ Ethane ≈ 68%, dilution δ = 0.4 kg Hd 2 O /kg HC , and DMDS = 48 ppmw S/HC, the results revealed that butane cracking exhibited higher coking compared to ethane for the Al-Boosted and 35/45 Cr−Ni. This difference was attributed to the generation of larger quantities of coke precursors, such as aromatics, naphthenes, and butadiene, during butane cracking. Notably, the Alcontaining alloy displayed exceptional resistance to aging, in contrast to the non-Alcontaining alloys, which experienced severe carburization and aging effects after multiple cracking cycles. Detailed scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analyses indicated that the presence of a continuous and robust Al 2 O 3 layer on the surface of the Al-containing alloy provided significant protection to the catalytic sites within the material. The average catalytic coking rate for the Al-containing alloy during butane cracking was measured at 5.83 × 10 −6 kg m −2 s −1 , while for the non-Alcontaining alloys, it ranged from 7.26 × 10 −6 to 15.25 × 10 −6 kg m −2 s −1 . Furthermore, this study explored the relative influence of the feedstock and reactor material, revealing that for the Al-Boosted alloy, the feedstock had a greater impact on coking behavior. Conversely, for the 35/45 Cr−Ni alloy, aging had a more pronounced effect compared to that of the specific feedstock used. This research provides valuable insights into the fouling behavior of specialized alloys in the steam cracking of ethane and butane. The study highlights the superior resistance to aging and reduced coking rate exhibited by the Al-containing alloy, underscoring the protective role of the Al 2 O 3 layer. Additionally, it emphasizes the relative significance of both feedstock composition and reactor material on coking tendencies, thereby contributing to a better understanding of fouling mechanisms in the steam cracking process.

“…The uncertainty and dynamic variation of raw materials as well as markets impart challenges to petrochemical enterprises. Molecular management is a feasible approach for optimizing, refining, and enhancing the utilization efficiency of crude oil resources. − Additionally, it would help countries such as China commit to peak carbon dioxide emissions before 2030 and achieve carbon neutrality before 2060. − …”

Section: Introductionmentioning

confidence: 99%

Molecular Reconstruction of Crude Oil: Novel Structure-Oriented Homologous Series Lumping with a Cloud Model

Zhang

Qiu

2022

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It is crucial to provide the detailed composition of crude oil for molecular management in refineries. Molecular reconstruction methods have been widely investigated for converting bulk properties to the detailed composition of feedstock by optimization calculations. In this work, a novel structureoriented homologous series lumping with a cloud model (SOHSL-CM) is proposed for the molecular reconstruction of crude oil to achieve a molecular-level representation of crude oil. A twodimensional homologous series distribution was applied to construct a molecular library with a clear structure, and a CM was designed to introduce fluctuations in the molecular distribution. Molecular reconstruction was demonstrated by industrial datasets containing 42 sets of crude oil data, with a mean absolute relative error <0.7%. In addition, the computational efficiency of the optimization was acceptable, with a time consumption of <1000 s. The accuracy, reliability, and efficiency of the proposed method indicate substantial potential for practical industrial applications.