Ethylene Cracking Research Articles

Analysis of Flow-induced Noise Characteristics of Ethylene Cracking Furnace Tubes before and after Coking

Analysis of Flow-induced Noise Characteristics of Ethylene Cracking Furnace Tubes before and after Coking

B-COPNA resin formation from ethylene tar light fractions: Process development and mechanical exploration by molecular simulation

Efficient utilization strategy of ethylene tar (ET), the main by-product of ethylene cracking unit, is urgently required to meet demands for modern petrochemical industry. On the other hand, condensed polynuclear aromatic resin of moderate condensation degree (B-COPNA) is a widely used carbon material due to its superb processability, the production of which is however seriously limited by high cost of raw materials. Under such context, an interesting strategy was proposed in this study for producing B-COPNA resin using crosslinked light fractions of ethylene tar (ETLF, boiling point < 260 °C) facilitated by molecular simulation. 1,4-Benzenedimethanol (PXG) was first selected as the crosslinking agent according to the findings of molecular simulation. The effects of operating conditions, including reaction temperature, crosslinking agent and catalyst content, on the softening point and yield of B-COPNA resin products were then investigated to optimize the process. The reaction mechanism of resin production was studied by analyzing the molecular structure and transition state of ETLF and crosslinking agent. It was shown that PXG exhibited a superior capacity of withdrawing electrons and higher electrophilic reactivity than other crosslinking agents. In addition to the highest yield and greatest heat properties, PXG-prepared resin contained most condensed aromatics. The corresponding optimized conditions of resin preparation were 180 °C, 1:1.9 (PXG:ETLF) and 3% (mass) of catalyst content with a resin yield of 78.57%. It was the electrophilic substitution reaction occurred between the ETLF and crosslinking agent molecules that was responsible for the resin formation according to the experimental characterization and molecular simulation. Hence, it was confirmed that the proposed strategy and demonstrated process can achieve a clean and high value-added utilization of ETLF via B-COPNA resin preparation, bringing huge economic value to the current petrochemical industry.

Partners start electric ethylene cracking system

Partners start electric ethylene cracking system

The dominant role of surface chemistry on coking resistance of passivating coating

Passivation coatings with excellent coking inhibition performance play an important role in active cooling technology and ethylene cracking furnace. However, different coating types possess different coking resistance, and the dominant factor remains unclear. Herein, a novel strategy of isolative analysis for coke in coating underwent RP-3 supercritical cracking is proposed to account for the role of carburization and surface chemistry. The carburization amount of TiN coating after cracking experiment was obtained from the model constructed by artificial carburization of standard TiN-coated samples. Introduced TiN/SiO2 coating owned different surface chemistry contrast to the TiN coating, additive of density-functional-theory calculations to reveal the correlation between surface chemistry and coke amount. The results indicated that carburization contributed little to the total coke amount of TiN coating, and non-negligibly, the coke diffused rapidly along the grain boundaries, threatened the integrity of coating. More importantly, the main coke belonged to the part that adhered to the coating surface. The strongly adsorbed 3d-4σ*/2π*bonded coking precursors (C2H2), were presented on the TiN surface, while the great flexibility of amorphous SiO2 made it non-adsorbent to C2H2, leading to weak coke adhesion on the TiN/SiO2 surface and strongly adherent coke on TiN surface. These results reveal that surface chemistry influenced coke adhesion and dominated coking resistance of coating.

Failure analysis on outer tube breaks of a double-sleeve rapid cooling heat exchanger

Failure analysis of a double-sleeve rapid cooling heat exchanger used for ethylene cracking process is presented in this study. The outer tubes of the heat exchanger break four times in succession. The inner tube and the outer tube materials of the heat exchanger are 13CrMo4-5 and SA106Gr.B, respectively. Based on the analysis of fracture appearance, chemical composition, mechanical properties, oxidation products and metallographic microstructure, it is found that short-time local overheating resulted in the four outer tube breaks. The observed pearlite spheroidization of SA106Gr.B indicate the temperature at the break positions exceed the phase transition critical temperature AC1（735℃）. Based on the analysis of the heat transfer process and boiler water circulation, it is found that the heat transfer deterioration of in a single set of double-sleeve, i.e., water is completely converted into superheated saturated steam, is the root cause of short-time local overheating. In view of the above failure mechanism, several countermeasures were proposed including the verification of the circulation ratio to ensure that the heat absorption per unit volume of cooling water is within the threshold value should be conducted in the design process, considering the uneven distribution of cooling water and cracking gas at the inlet and the influence of shock vibration caused by water and cracked gas, an appropriate safety factor should be considered for the design of gap / water volume during operation, as well as promoting the monitoring of vital parameters (e.g., the temperature during operation).

Optimal scheduling of ethylene plants under uncertainty: An unsupervised learning-based data-driven strategy

Ethylene cracking furnaces are core units that determine the yield of key products, and its cycle scheduling optimization is of great significance to improve the efficiency of the whole plant. However, uncertainties in cracking batch durations may lead to sub-optimal or ineffective scheduling arrangements. This paper develops a novel data-driven stochastic robust optimization strategy to achieve the optimal scheduling of cracking furnaces under uncertainty. The proposed stochastic robust optimization model applies machine learning methods to extract data information and is represented as a bilevel problem: the outer layer is a two-stage stochastic programming, where typical scenarios are clustered by a three-level data mining approach; the inner layer is robust optimization, whose uncertainty set is constructed by an efficient kernel-based approach. An actual ethylene cracking system is investigated and the results show that the proposed method achieves the highest daily profit, performing well in data coverage (92.3%) and change rate (0.826%). Moreover, the sensitivity analysis for the number of clusters and regularization parameter values is performed.

Borealis charters tanker for feedstocks

The petrochemical maker Borealis has signed a long-term charter agreement with IINO Kaiun Kaisha for the Oceanus Aurora , classified as a very large gas carrier vessel. The ship will carry propane and butane from North America to Borealis’s ethylene crackers and propane dehydrogenation plants in Kallo, Belgium; Stenungsund, Sweden; and Porvoo, Finland. The vessel will be powered by low sulfur fuels and liquefied petroleum gas. It will eventually also be equipped with rotor sails.

Slurry-Phase Hydrogenation of Different Asphaltenes to Liquid Fuels on Dispersed MoS2 Nanocatalysts.

Asphaltene, the most complex and recalcitrant fraction of heavy oil, was investigated in this study to gain new insights into its structure and reactivity. Two types of asphaltenes, ECT-As and COB-As, were extracted from ethylene cracking tar (ECT) and Canada's oil sands bitumen (COB), respectively, and used as reactants for slurry-phase hydrogenation. Characterization of ECT-As and COB-As was carried out by a combination of techniques, including XRD, elemental analysis, simulated distillation, SEM, TEM, NMR, and FT-IR, to gain insights into their composition and structure. A dispersed MoS2 nanocatalyst was used to study the reactivity of ECT-As and COB-As under hydrogenation conditions. The results showed that under optimal catalytic conditions, the vacuum residue content of hydrogenation products could be reduced to less than 20%, and the products contained over 50% light components (gasoline and diesel oil), indicating that ECT-As and COB-As were effectively upgraded. The characterization results indicated that ECT-As contained a higher aromatic carbon content, shorter alkyl side chains, fewer heteroatoms, and less highly condensed aromatics than COB-As. The light components (gasoline and diesel oil) of ECT-As hydrogenation products mainly consisted of aromatic compounds with 1-4 rings, with the alkyl chains mainly composed of C1-C2, while light components of COB-As hydrogenation products were mainly composed of aromatic compounds with 1-2 rings and C11-C22 paraffins. The characterization of ECT-As and COB-As and their hydrogenation products revealed that ECT-As was an "archipelago type" asphaltene, composed of multiple small aromatic nuclei interconnected through short alkyl chains, while COB-As was an "island type" asphaltene, with long alkyl chains connected to aromatic nuclei. It is suggested that the structure of asphaltene has a significant impact on both its reactivity and product distribution.

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

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.

Science‐guided data analytics for selecting ionic liquid solvents for aromatic extraction

AbstractIonic liquids (ILs) are promising solvents for the aromatic extraction process. An attractive characteristic is the existence of hundreds of ILs that exhibit different properties. To identify key properties of IL solvents for an energy‐optimum aromatic extraction, we use process simulation to generate the process datasets for multivariate data analytics with partial least squares, and use science‐guided fundamentals to develop an IL heat load variable (HLV). We consider 16 well‐studied ILs and correlate process steam duty and process variables affecting equipment size to the HLV for ethylene cracker feeds of low aromatic content. For such feeds in an IL aromatic extraction process, 11 of 16 ILs show energy advantage compared with sulfolane solvent with the lowest energy IL process requiring 57% of total energy required for an equivalent sulfolane process. Our results facilitate the IL solvent selection for pilot tests and subsequent commercialization of an IL aromatic extraction process.

Practical Online Characterization of the Properties of Hydrocracking Bottom Oil via Near-Infrared Spectroscopy

Providing real-time information on the chemical properties of hydrocracking bottom oil (HBO) as the feedstock for ethylene cracker while minimizing processing time, is important to improve the real-time optimization of ethylene production. In this study, a novel approach for estimating the properties of HBO samples was developed on the basis of near-infrared (NIR) spectra. The main noise and extreme samples in the spectral data were removed by combining discrete wavelet transform with principal component analysis and Hotelling’s T2 test. Kernel partial least squares (KPLS) regression was utilized to account for the nonlinearities between NIR data and the chemical properties of HBO. Compared with the principal component regression, partial least squares regression, and artificial neural network, the KPLS model had a better performance of obtaining acceptable values of root mean square error of prediction (RMSEP) and mean absolute relative error (MARE). All RMSEP and MARE values of density, Bureau of Mines correlation index, paraffins, isoparaffins, and naphthenes were less than 1.0 and 3.0, respectively. The accuracy of the industrial NIR online measurement system during consecutive running periods in predicting the chemical properties of HBO was satisfactory. The yield of high value-added products increased by 0.26 percentage points and coil outlet temperature decreased by 0.25 °C, which promoted economic benefits of the ethylene cracking process and boosted industrial reform from automation to digitization and intelligence.

Pyridine Ionic Liquid-Based Deep Eutectic Solvents Selectively Separating Toluene from Alkanes

Naphtha is an important raw material for ethylene cracking, and the aromatics in it can affect the ethylene yield due to the easy coking during the cracking process. Therefore, it is important to separate the aromatics from naphtha to increase the alkane content and improve the ethylene cracking production. Liquid–liquid extraction separation of the aromatic/alkane mixture is one of the effective pathways, and the key is the design and synthesis of new efficient extractants. In this work, a novel pyridine ionic liquid-based deep eutectic solvent (DES) for the separation of aromatics from alkanes was proposed and successfully synthesized. 1-Ethylpyridinium chloride (EpyCl) was used as the hydrogen bond acceptor and levulinic acid (LA) as the hydrogen bond donor. Among them, the π–π interactions between pyridine ring, C═O, and aromatic ring can enhance the interactions with aromatic compounds. In contrast, the introduction of acidic groups can increase the polarity of DES, enhance the induced polarization of unsaturated bonds in aromatic rings by DES, and thus increase the non-bonding force with aromatics. Toluene/n-heptane and toluene/cyclohexane were used as simulated oil systems. The optimal ratio of EpyCl/LA is 2:1, which has the best extraction efficiency, stability, and reusability; the selectivity of toluene was up to 69.57 for the toluene-n-heptane system, while it was 24.41 for the toluene-cyclohexane system. The reliability of the liquid–liquid equilibrium data was verified by using the Othmer–Tobias correlation equations, and the basic system physical property data were obtained by fitting with the NRTL thermodynamic model. The interaction mechanism between DES and toluene/alkanes was revealed by AIM topology analysis, IGMH analysis, and symmetry-adapted perturbation theory energy decomposition. The interaction between DES and toluene/alkanes is a van der Waals force, dominated by dispersion forces.

Analysis Methodology of C4 olefins by ethanol coupling based on correlation analysis

C4 olefins are widely used to produce various chemical products and pharmaceuticals. Besides, Ethanol is a good raw material for the production of C4 olefins instead of petroleum cracking and ethylene cracking. First, the optimal choice of catalyst combination and temperature for C4 olefins preparation has been studied, and the process conditions forC4 olefins preparation by catalytic coupling of Ethanol are of great significance and value for promoting industrial production. Besides, a simple scoring method is also proposed to evaluate the differences in the catalytic effects of different experimental groups. We first analyzed the correlation with the R language and found that the temperature was positively correlated with the C4 olefin selectivity and ethanol conversion rate. Then, we fitted 21 curves sets of ethanol conversion rate and C4 olefin selectivity with temperature. Second, R language is used to perform correlation analysis to screen out variables that are significantly related to ethanol conversion and C4 olefin selectivity, then obtain a stepwise regression equation to quantitatively describe the effects of different catalyst combinations and temperatures on ethanol conversion and C4 olefin selectivity. Thirdly, we used the stepwise regression method to obtain the optimal local solution at each temperature, and the optimal combination of temperature and catalyst was 0.5wt% Co loading at 400℃, 200mgCo/SiO2-200mgHAP, ethanol concentration is 0.3ml/min. If the temperature is required to be controlled below 350 degrees, the optimal combination of temperature and catalyst is 2.145wt% of Co loading, 200mgCo/SiO2-200mgHAP, and ethanol concentration of 2.1ml/min at 350℃.

Middle Eastern projects move forward

A pair of big Middle Eastern petrochemical projects have been given the go-ahead. Saudi Aramco and TotalEnergies have made the final decision to invest in a new cracker complex in Jubail, Saudi Arabia. The $11 billion complex will be integrated with the firms’ existing refining joint venture there. The cracker will have capacity to make 1.7 million metric tons (t) of ethylene per year. The project will also include two downstream polyethylene plants and a butadiene extraction unit. It will be majority owned by Aramco and go on line in 2027. Separately, Chevron Phillips Chemical and QatarEnergy have green-lighted a $6 billion project for Ras Laffan, Qatar. It will have a 2.1 million t per year ethylene cracker, the largest in the region, as well as downstream polyethylene plants.

Development and Performance Evaluation of Catalyst for Productive Ethylene Cracking Feedstock in Selective Hydrocracking of Straight Run Diesel Oil

Development and Performance Evaluation of Catalyst for Productive Ethylene Cracking Feedstock in Selective Hydrocracking of Straight Run Diesel Oil

Chevron Phillips gives green light to US cracker

Chevron Phillips Chemical (CPChem) and QatarEnergy say they are going ahead with a previously proposed project to build an $8.5 billion ethylene cracker and polymer facility in Orange, Texas. The complex will include a cracker with 2.1 million metric tons (t) per year of capacity and two 1 million t high-density polyethylene plants. CPChem says it is targeting 25% lower greenhouse gas emissions than such facilities in the US and Europe. CPChem and QatarEnergy are building a similar complex in Qatar.

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

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

Development of energy‐optimum aromatic extraction processes using ionic liquid [EMIM][NTf2

AbstractThere is industrial incentive to extract aromatics from ethylene cracker feeds, but the conventional sulfolane solvent was found not economical by Meindersma and coworkers. Ionic liquids (ILs) have long been considered alternative aromatic extraction solvents. This work develops energy‐optimum aromatic extraction processes for an ethylene cracker feed using IL solvents. We avoid pitfalls of using simplified feeds and a priori thermodynamic property estimates, with the largest set of experimentally regressed UNIQUAC binary parameters for the IL, 1‐ethyl‐3‐methylimidazolium bis([trifluoromethyl]sulfonyl)imide ([EMIM][NTf2]). We screen process energy and operating conditions for [EMIM][NTf2] and sulfolane at varying aromatic feed contents and find [EMIM][NTf2] favorable at low aromatic feed contents. Adding light and heavy components of the ethylene cracker feed necessitates process modifications. Our novel steam‐assisted extractive distillation developed for [EMIM][NTf2] is also suitable for sulfolane. We show that the [EMIM][NTf2] solvent can reduce 10.7% of energy consumption compared to sulfolane using the same novel process.

Shell, Dow test electric cracking

Dow and Shell have started up a small unit in Amsterdam to test their electric steam cracking concept. The companies hope to generate data that will allow them to retrofit gas-fired furnaces. They aim to deploy a larger, multimegawatt pilot plant by 2025. Ultimately, the firms say, powering an ethylene cracker with renewable electricity could reduce the emissions related to the ethylene production process by 90%.

TiN-SiO2 double layer composite coating with enhanced oxidation resistance and reusability in anti-coking applications

The passivation coating has been the main solution to the coking problem in the field of active cooling technology and ethylene cracking furnace. The need for repeated use and essential decoking process poses a great challenge to the single-layer coating. Herein, a new TiN/SiO2 double-layer coating suitable for internal channels has been prepared and characterized, whose results are compared with single-layer TiN coating. The oxidation resistance was revealed by HT-XRD and TGA. The reusability was analyzed from surface roughness, bonding force and coking inhibition performance in the repeated use of the coking-decoking cycle (RP-3 supercritical pyrolysis, on-line decoking technology). Results reveal the synergistic effect of the inner and outer layers of TiN/SiO2 coatings. The outer amorphous SiO2 with high crystallization temperature plays the role of isolating O and C atoms from penetrating, and the inner TiN acts to reduce the mismatch of thermal expansion coefficient between substrate and SiO2. Therefore, excellent oxidation resistance, with a bearable temperature of 1000 °C, can be obtained for the TiN/SiO2 coatings. In addition, during the coking-decoking cycles, the roughness of TiN/SiO2 coatings has been maintained at a low level; the coating has been tightly adhered to the substrate throughout the process; and the coking resistance has not been weakened with an average anti-coking ratio of 93%, higher than that of TiN (31–67%).