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This work deals with an efficient two-step thermal upgrading process for converting extra-heavy fuel oil to light olefins (ethylene, propylene, and butenes) and fuels (gasoline and diesel fuel). In the first step, mild thermal pretreatment was implemented at different temperatures (360-440 °C) in the liquid phase to obtain a more suitable feedstock for an olefin production unit. Thanks to this cost-effective pretreatment, the upgraded feedstock demonstrated considerable flowability and crackability compared to the initial fuel oil, making the subsequent vapor-phase operation easier to handle at temperatures as high as 800 °C with no severe operational impediments. The quantitative ¹H and 13C NMR studies shed light on the enhanced features of the thermally treated feedstock toward lighter and more valuable products. As a result, remarkable olefin production (74.7 or 55.1 wt % light olefins based on the upgraded or the original feedstock) was accomplished in this two-step process. The process could be alternatively stopped at the first stage for maximum liquid fuels (69.3 wt %) with gasoline as the larger constituent. The detailed kinetic investigations of the thermal decomposition of the feedstock using several reliable approaches revealed that the activation energy predictions (42.3-272.9 kJ/mol) by the Kissinger-Akahira-Sunose method almost perfectly matched the trend of a reference Starink model over the whole range of conversion. All model-free methods correlated with a coefficient of determination above 97.9%. Avrami's theory was further applied to determine the reaction order, and the values were slightly smaller than those from a five-lump kinetic model of the semibatch operation. However, the apparent activation barrier in the reactor was in good correspondence with the range from the microscale nonisothermal decomposition. [ABSTRACT FROM AUTHOR]

Crude oil is becoming more and more difficult to refine because of increasingly large heavy oil molecules. Increased external surface of catalysts contributes to promoting precracking of heavy or extra-heavy oil molecules. Flowerlike hierarchical Y zeolite with considerably increased external surface was synthesized without using any organic templates by a hydrothermal procedure. Because the isolated nanoparticles are unstable, the primary nanocrystals gather via self-assembly into loose aggregates. The inner crystals, which act as the "pistils", are difficult to grow because of the confined spaces, while the outer crystals in the aggregates can further grow and form the oriented sheet "petals". The increased exterior surface offers the catalysts dramatically elevated conversion when tested in the catalytic cracking of triisopropylbenzene. The result also suggests that the activity of the catalysts in large reactant involved reactions may generally depend on its external surface properties. [ABSTRACT FROM AUTHOR]

To prevent the occurrence of thermal runaway accidents in semibatch reactors (SBRs), it is desirable and practicable to develop criteria that can distinguish between the safe and runaway operating regions. In this article a new safety criterion, namely, the adiabatic criterion, has been developed for SBRs in which liquid homogeneous as well as liquid-liquid heterogeneous reactions with arbitrary reaction orders occur. It states that an SBR is operated in the potential runaway situation if the value of the adiabatic criterion exceeds zero at a segment of the reaction path. Numerical results show that the adiabatic criterion is more conservative than the two other criteria (divergence criterion and target temperature criterion). However, the adiabatic criterion is not suitable to reactions with autocatalytic behaviors. Also knowledge of activation energies and reaction enthalpies is necessary to utilize the adiabatic criterion. [ABSTRACT FROM AUTHOR]

Alloy composition and morphology of the inner wall of steam cracking reactors are well-known key factors that affect their coking tendency. The effect of surface roughness on the coking tendency remains uncharted to date and has been studied here for a 35/25 Ni/Cr wt % alloy in a quartz jet stirred reactor equipped with an electro-balance under coil outlet industrially relevant ethane steam cracking conditions: Tgas phase = 1173 K, Ptot = 0.1 MPa, and XC2H6 = 70%. Up to 6 times higher initial coking rates have been observed during cyclic aging in an Rα surface roughness range of 0.15-7 μm, and cyclic aging proved to have an effect mainly on the catalytic coking behavior. No effect was observed on the asymptotic coking rates. Scanning electron microscopy, energy diffractive X-ray surface analysis, and cross section elemental mappings suggest that the effect of surface roughness and aging on the catalytic coking rate derives mainly from changes in the metal surface composition. The amounts of metallic Ni and Fe show an increasing tendency with increasing surface roughness, explaining the pronounced coke deposition. Using Ekvicalc, thermodynamic calculations were performed proposing that the amount of Cr2O3 gradually decreases followed by an increase of manganese chromite, MnCr2O4. [ABSTRACT FROM AUTHOR]

A molecular-level-process model for a fluidized catalytic cracking process was developed. The work was aimed at the coarseness of the reaction network used in traditional lumping kinetic models. A feed-component matrix containing 14692 molecules was generated using a structure-oriented-lumping (SOL) method. A total of 95 groups of reaction rules were compiled, and 702943 reactions were involved. The SOL reaction kinetic model was combined with the reactor model to calculate the temperature distribution and feedback on the complex reaction network by taking into account the reaction heats in each reaction. The model was validated by the industrial data and predicted that the gasoline yield was >51% and the olefin content in gasoline was <24% at proper operation temperatures and catalyst/oil ratios. With the aid of the molecular-level model for the maximizing-isoparaffin technology, the product distribution and corresponding product quality can be controlled rationally by manipulating the operation conditions. [ABSTRACT FROM AUTHOR]

Light cycle oil (LCO) from fluid catalytic cracking (FCC) was treated by selective hydrogenation and then cracked in a FCC apparatus. Compared with LCO, hydrogenated LCO (hydro-LCO) exhibited remarkable FCC performance, recording with that 50.83 wt % hydro-LCO was converted into gasoline fraction. This is attributed to the reduction of aromatics in hydro-LCO, especially for the multiring aromatics. After hydrogenation, the amount of multiring aromatics significantly decreased from 63.2 to 9.5 wt %, while naphthenoaromatics (including indans, tetralin, and indenes) increased from 8.8 to 34.2 wt %. In accordance with the experimental results and theoretical analysis of LCO reaction characteristics, a synergistic process for LCO efficient conversion to high octane number gasoline was proposed, and simulation experiments were carried out. The results show that, compared with routine FCC, 20 wt % higher conversion and 16 wt % more gasoline could be obtained. Moreover, gasoline from synergistic process exhibited decreased sulfur and olefins, but increased aromatics, and thereby improved octane number. These findings indicate that the proposed synergistic process could be an effective option for producing gasoline with high octane number. [ABSTRACT FROM AUTHOR]

The catalytic cracking of a blend of raw bio-oil (20 wt %) from black poplar sawdust fast pyrolysis and vacuum gasoil (VGO, 80 wt %) has been studied. The runs have been performed in a riser simulator reactor (RSR) under fluid catalytic cracking (FCC) conditions; that is, 500-560 °C, catalyst tofeed mass ratio of 6 gcat (gfeed)-1 on a dry basis, reaction times of 3-10 s and a equilibrated commercial FCC catalyst. The cofeeding effect has been quantified by comparing the yields of product lumps and individual components in the gaseous fraction and gasoline lump in the cracking of VGO, raw bio-oil, and their blend (20% bio-oil/80% VGO), at the same conversion values (60-70 wt %). The cofeeding has a favorable synergy because it promotes the formation of C3-C4 and gasoline (C5-C12) hydrocarbon lumps, attenuating the formation of CO2, CO, and also coke formation. In the cracking of the blend (80% VGO/20% bio-oil) at 70 wt % conversion, a deoxygenation degree of 95 wt % has been obtained, with a total liquid fuel yield of 52.8 wt % and a gasoline yield of 31.6 wt %, with a low oxygenate fraction (<4 wt %) containing carboxylic acids, aldehydes, ketones, and phenols. [ABSTRACT FROM AUTHOR]

A number of catalystsmade of Ni particles of different size distributionssupported on a hierarchical beta zeolite (Ni/h-beta) were preparedand tested in the hydroreforming of low-density polyethylene (LDPE)thermal cracking oils. The materials were prepared by identical impregnationmethod but using different nickel precursors: chloride, nitrate, acetylacetonate,and tris(ethylenediamine) nickel(II) chloride (TEDAN). A variationin the Ni particles size distribution was obtained depending on themetal precursor, whereas no significant differences in the acidicproperties were detected. Ni nitrate and acetylacetonate resultedin smaller and more dispersed particles, thus closer to the acid sites,driving to higher hydrogenation and hydrocracking activities. In contrast,Ni TEDAN and chloride led toward larger nickel particles which preventedintermediate species to be rapidly hydrogenated and so favored theproduction of aromatic and branched hydrocarbons. Hence, the catalystcoming from Ni nitrate produced 25 wt % iso-paraffins and 71% lightproducts (C1–C12), while the materialprepared with Ni chloride produced 35% iso-paraffins and 60% lightproducts. [ABSTRACT FROM AUTHOR]

The conventional PID control hasbeen proven insufficient and incapablefor this particular petro-chemical process. This paper proposes anonlinear adaptive predictive functional control (NAPFC) algorithmbased on the Takagi–Sugeno (T-S) model for average crackingoutlet temperature (ACOT) of the ethylene cracking furnace. In thisalgorithm, in order to overcome the effect on system performance undermodel mismatch, the structure parameters of the T-S fuzzy model areconfirmed, and the model consequent parameters are identified onlineusing the forgetting factor least-square method. Prediction outputis calculated according to the identified parameters instead of computingthe Diophantine equation, thereby obtaining directly the predictivecontrol law and avoiding the complex computation of the inverse ofthe matrix. Application results on ACOT of the ethylene cracking furnaceshow the proposed control strategy has strong tracking ability androbustness. [ABSTRACT FROM AUTHOR]

Iron-containingphosphorus-modified HZSM-5 catalysts were preparedand used for the coupling cracking of butene and pentene (mole ratioof butene to pentene = 4:1). The impact of iron content on the structureand acidity of catalysts was studied by XRD, N2adsorption,UV–vis spectroscopy, NMR, and FTIR of adsorbed pyridine. Theresults revealed that iron interacted with phosphorus and increasedthe content of tetrahedral framework aluminum after impregnating ironinto P/HZSM-5. Such interaction recovered partial Brønsted acidsites which were previously neutralized by phosphorus modification,and introducing iron created some Lewis acid sites, significantlypromoting the concentration and strength of acid sites. In the couplingcracking of butene and pentene, the addition of iron into phosphorus-modifiedHZSM-5 significantly increased the conversions of butene and pentene.As iron loading increased from 0 to 2 wt %, butene conversion andpentene conversion increased by 26.8% and 45.8% at 550 °C, weighthourly space velocity = 6 h–1, steam ratio = 0.36g/g, and time-on-stream = 4 h. With increasing iron loading in phosphorusmodified HZSM-5, ethylene selectivity increased while propylene selectivitydecreased. The catalytic performance of catalyst was strongly influencedby reaction conditions in the cracking. Proper reaction conditionscould inhibit the secondary reactions and enhance propylene selectivity. [ABSTRACT FROM AUTHOR]

A steam cracking furnace plays animportant role in the naphthapyrolysis process that produces ethylene and propylene. These twoproducts are the key monomers in the petrochemical industry. Thisarticle investigates the multiobjective operation optimization ofthe naphtha pyrolysis process to maximize the yields of ethylene andpropylene. To solve this problem efficiently, multiobjective paralleldifferential evolution with competitive evolution strategies (MOPDE-CES)is employed. In MOPDE-CES, the population is divided into four parts,each part having its own evolution strategy. During evolution, thefour parts of the population compete with each other to survive andevolve. At the same time, they share search information with eachother by communicating with an external archive that stores the obtainednondominated solutions. The MOPDE-CES approach is compared to otherpowerful multiobjective algorithms, and the computational resultsshow that MOPDE-CES is superior based on benchmarking and practicalproblems. In addition, the computational results of MOPDE-CES indicatethat the operation of an ethylene plant can be improved by increasingthe yields of ethylene and propylene. [ABSTRACT FROM AUTHOR]

The continuous deterioration of feedstocks, the increasingdemandof diesel, and the increasingly strict environmental regulations ongasoline call for the development of fluid catalytic cracking (FCC)technology. To increase the feed conversion and the diesel yield aswell as produce low-olefin gasoline, the multifunctional two-stageriser (MFT) FCC process was proposed. Experiments were carried outin a pilot-scale riser FCC apparatus. Results show that a higher reactiontemperature is appropriate for heavy cycle oil (HCO) conversion, andthe semispent catalyst can also be used to upgrade light FCC gasoline(LCG). The synergistic process of cracking HCO and upgrading LCG inthe second-stage riser can significantly enhance the conversion ofHCO while reducing the olefin content of gasoline at less expenseof gasoline yield. Furthermore, the novel structure riser reactorcan increase the conversion of olefins in gasoline. Because of thesignificant increase of HCO conversion, the fresh feedstock can becracked under mild conditions for producing more diesel without negativeeffects on the feed conversion. Compared with the TSR FCC process,in the MFT FCC process, the increased feed conversion, diesel andlight oil yields can be achieved, at the same time, the olefin contentof gasoline decreased by approximately 17 wt %. [ABSTRACT FROM AUTHOR]

The synthesis process and production of forms of theY zeolite (i.e., NaY, NH4Y, HY, and USY) have been studiedin depth, in order to investigate the thermal stability of the Y structurethroughout calcination, steaming, and cracking processes. The resultsindicate that an increase in the cation content within the Y frameworkduring calcination and/or steaming processes led to an increase inthe catalyst stability and a reduction in the rate of any associateddehydroxylation reactions. It was also found that the presence ofsodium ions hindered the extraction of Al atoms from the crystal latticestructure during the steaming treatment, which minimized partial and/orentire structural collapse at high temperatures. Finally, enhancementsin the distribution of the acid sites, and an increase in the activityand selectivity of the produced USY catalysts during n-C7cracking reactions, have also been observed. [ABSTRACT FROM AUTHOR]

Sieve tray internals are a well-known method for reducing liquid phase backmixing in bubble columns. In the soaker mode of visbreaking, cracked hydrocarbon vapors increase in volume as we move up in a soaker drum because of more vapor generation due to cracking as well as reducing hydrostatic head on the gas bubbles. The free flow area in sieve trays is gradually increased as we move up in the soaker drum because of this increase in volume. A CFD analysis is presented on a soaker drum with two set of sieve tray internals with same free flow area on corresponding sieve trays, but different configuration of holes. The liquid and vapor properties have been taken identical to the hot short residue and hydrocarbon vapors, respectively. The size of flow domain for simulation has been taken equivalent to a real soaker drum, for realistic simulations. It was found that increasing of flow area in sieve trays by increasing the size of holes is more effective way for reducing liquid phase back mixing, as compared to increasing number of holes. [ABSTRACT FROM AUTHOR]

This paper focuses on the fluid catalytic cracking (FCC) process and reviews recent developments in its modeling, monitoring, control, and optimization. This challenging process exhibits complex behavior, requiring detailed models to express the nonlinear effects and extensive interactions between input and control variables that are observed in industrial practice. The FCC models currently available differ enormously in terms of their scope, level of detail, modeling hypothesis, and solution approaches used. Nevertheless, significant benefits from their effective use in various routine tasks are starting to be widely recognized by the industry. To help improve the existing modeling approaches, this review describes and compares the different mathematical frameworks that have been applied in the modeling, simulation, control, and optimization of this key downstream unit. Given the effects that perturbations in the feedstock quality and other unit disturbances might have, especially when associated with frequent changes in market demand, this paper also demonstrates the importance of understanding the nonlinear behavior of the FCC process. The incentives associated with the use of advanced model-based supervision strategies, such as nonlinear model predictive control and real-time optimization techniques, are also presented and discussed. [ABSTRACT FROM AUTHOR]

Catalytic upgrading of pyrolysis vapors derived from oak was carried out using a fixed-bed catalytic column at 425 °C. The vapors were drawn by splitting a fraction from the full stream of vapors produced at 500 °C in a 5 kg/h bench-scale fast pyrolysis reactor system downstream from the cyclone separator. The placement of the fixed-bed column was varied within the condenser train to determine the effect of temperature, residual water, solids, and oxygenated components of the approach vapor stream on the upgraded product quality. The upgraded liquid was collected by immediate contact with a dry ice acetone bath, complimented by a secondary collection system comprised of a methanol spray condenser. Quantitative gas chromatography/mass spectroscopy (GC/MS) analysis of the recovered liquid showed a substantial decrease of oxygen-containing species with a significant increase in carbon-rich (≥C6) aromatic hydrocarbons. The extent of deoxygenation was location-specific and dependent upon temperature and the relative concentrations of water, oxygenates, and residual solids in the approach vapor. The study provides the engineering practicality to catalytic vapor upgrading and offers the necessary data for the design and optimization of a full-stream upgrading of pyrolysis oils via in situ vapor cracking. [ABSTRACT FROM AUTHOR]

To investigate a sulfur-emission-free process of molybdenum carbide synthesis from molybdenite, the reaction pathways of MoS2reduction with methane in the presence of lime (CaO) have been studied. A mixture of MoS2 2CaO was reduced isothermally with CH4in a microreactor, and the composition of effluent gases and the reduced fraction were determined as a function of reaction time. Analysis of the solid phase at different reaction times at 800 °C showed the formation of CaMoO4as an intermediate phase. Hence, the reaction pathways proposed for reduction of MoS2 CaO with CH4involves the direct reduction of MoS2with CH4to form Mo2C and sulfur-containing gases. The sulfur-containing gases are captured by CaO to form CaS, CO(g), CO2(g), and H2O(g). The unreacted MoS2is oxidized by CO2(g) and H2O(g) to form MoO3(g), which reacted with CaO to form CaMoO4on CaO particles. Finally, CaMoO4and remaining MoS2are further reduced with CH4. Characterization of solid samples was carried out by XRD, CHN, and FE-SEM equipped with EDS, providing results consistent with the proposed reaction pathways. Carbon content of solid sample increased with reduction time, and in fully reduced sample at 800 °C it was well above the stoichiometric amount indicating considerable excess carbon deposition due to CH4cracking. [ABSTRACT FROM AUTHOR]

Spouted beds are used in chemical vapor deposition as they provide good solid mixing, thereby enhancing high mass and heat transfer rates. In the present study, investigations on the kinetics of a coating process by chemical vapor deposition were carried out in a spouted-bed reactor. Pyrolytic carbon coatings were studied by thermal cracking of acetylene mixed with carrier gas argon at 1350 °C. A theoretical model was proposed based on the mass balance of the precursor in the spout and annulus zones at isothermal condition, and the model equations were solved using MATLAB (version 7.1) software. The effect of the operating gas velocity, initial static bed height, and acetylene concentration on the coating rate was examined experimentally and also by simulation results. The simulated results agreed well with the experimental results. Model equations used for simulation were utilized to evaluate the reaction rate constant and radial gas diffusion coefficient and then to study the effect of spout diameter, operating gas velocity, and precursor concentration on the overall conversion of the precursor. [ABSTRACT FROM AUTHOR]

Fluidized-bed catalytic cracking of heavy petroleum distillates is one of the most important processes in petroleum refining; because of its large scale, estimation of the kinetic rate constants is performed at the laboratory level. Several experimental devices are commonly used, including fixed-bed reactors, fluidized-bed reactors, and riser emulator reactors. Despite the different hydrodynamics of the reactors mentioned, when compared to the industrial unit, the production of the main products (gasoline, gases, and coke) can be predicted and emulated accurately in the laboratory. Taking advantage of this fact, prediction of the kinetic rate constants and catalyst activity parameters has been performed at the laboratory level; however, frequency factors are larger than those necessary to simulate the industrial unit. This situation could arise because of the lack of fundamental modeling of transport phenomena and catalyst activity decay due to coke deposition; these phenomena have been modeled using side functions associated with “time-on-stream”, “coke-on-catalyst”, or “feedstock conversion”. The objective of this work is to improve accuracy during estimation of the frequency factors at the laboratory level, via the estimation of catalyst activity, based on the effectiveness factor; which has been included in the mathematical model of a fixed-bed laboratory bench-scale reactor. It is shown that following activity evolution along the experiment time helps to calculate frequency factors that are very similar to those needed to simulate industrial units; moreover, this model estimates different catalyst activity for each reactant and each reaction, and, therefore, it is selective. Frequency factors for a lumped kinetic scheme obtained at the laboratory level are used to simulate an industrial unit, showing good agreement during prediction of the product yields. [ABSTRACT FROM AUTHOR]

A new concept of reactora prototype of transported-loop reactor that reduces residence time for the cracking of a light naphtha streamenhances commercial, low-value, light streams with an alternative process to applying these fractions to light olefins (ethylene and propylene). In particular, a prototype of a transported-loop reactor was developed to reduce the resistance time in the cracking of a light naphtha stream to produce olefins. In particular, a prototype of a transported-loop reactor has been developed to reduce resistance time in the cracking of a light naphtha stream to produce olefins. It is currently used to study the gas−solid fluid-dynamic. The novel device includes a uniflow-type reactor and a partial gasification downer riser circulating reactor. The novelty lies in converting the light naphtha at a very high temperature and ultrashort residence time by contacting a hot solid with the naphtha to immediately separate the olefins to avoid further reactions. The solid is then partially gasified to provide autothermal operation of the reactors. The design of the equipment provides information about the gas/solid contact to develop several prototypes of the pyrolysis and the carbon gasification reactor. The cold model will derive suitable hydrodynamic relationships and performance constraints for high solid loading not available in the literature. The main result obtained is the need to provide an initial high solid contact to ensure the heat transfer and then proceed to separate the gas and solid. The other result is the effect of the hydrocyclone in the clustering behavior of the circulation reactor. Knowledge of the fluid dynamic in both reactors and kinetic information already developed will facilitate design and scale-up of a new process for cracked naphtha valorization. [ABSTRACT FROM AUTHOR]

Mixed oxides (Al−Si, Zr−Si, Mg−Si) were synthesized by the sol−gel method at different gelation times. The synthesized supports were impregnated by the incipient wetness method to obtain Ni−Mo, Co−Mo, and Ni−W supported catalysts. Both the supports and catalysts were characterized by N2physisorption for determining textural properties, and their catalytic activities were tested with isopropyl alcohol (2-propanol) and cumene decomposition in order to evaluate their acid−base properties. According to the obtained products, it was possible to assess qualitatively that Al−Si and Zr−Si supports and their respective catalysts were mainly acidic. In the case of NiMo/AlSi catalyst, high conversion during cumene cracking particularly at higher temperatures was observed. Cracking activity results indicated that surface acidity predominated due to Brønsted acid sites, which are mainly dependent on the support composition as well as their preparation methods. Conversion of isopropyl alcohol leads to the dehydration products, typically propylene with a very low amount of di-isopropyl ether or acetone. NiMo/AlSi catalyst was evaluated for cumene cracking and its kinetic parameters were obtained by applying the Langmuir−Hinshelwood model. The activation energy was found to be 27.75 kcal mol−1while the heat of adsorption calculated with the Van’t Hoff equation was −14.15 kcal mol−1taking into account a single-site surface reaction. [ABSTRACT FROM AUTHOR]

A continuing challenge in materials design is the achievement of greater operational efficiency through improvements in performance criterion, particularly, high strength and service lifetime characteristics. In this study, we report on the effect of heat treatment (annealing) on the stress corrosion cracking (SCC) behavior of α-brass (71Cu−28Zn) in aqueous electrolytes containing some aggressive anions (Cl−, ClO3−, NO2−, and SO42−). The annealed specimens suffered from SCC in all tested electrolytes under the anodic polarization conditions while they were susceptible to SCC only in NaNO2and Na2SO4solutions under the open circuit condition. The susceptibility toward SCC was found to decrease considerably in NaCl, KClO3, and Na2SO4solutions and very slightly in NaNO2solutions upon annealing the specimens. [ABSTRACT FROM AUTHOR]

A kinetic model of lumps has been established for n-butane cracking over HZSM-5 zeolite catalyst (SiO2/Al2O3= 30) in the 400−550 °C range, based on the results obtained in a fixed bed reactor (space time, up to 2.4 (g of catalyst) h (mol CH2)−1; He/n-butane molar ratio in the feed, up to 6/1; time on stream, 5 h). The model allows quantifying the distribution of the lumps of products (C2−C4olefins, C2−C4paraffins, methane, and C5−C10components) in a wide range of temperatures, partial pressures of hydrocarbons in the reaction medium, and space times. The kinetic model steps for the transformation of n-butane into olefins and of olefins into paraffins and C5−C10are second order with respect to the reactant, whereas the remaining steps are first order with respect to each reactant. When the target is the production of C2−C4olefins, the yield is limited to 12%, at 550 °C. [ABSTRACT FROM AUTHOR]

The presence of liquid hydrocarbon droplets in the convection section of a steam cracker may cause serious fouling problems due to coke formation, especially in high temperature zones. In order to investigate these fouling problems, a model has been developed and implemented in a CFD code to accurately simulate the behavior of a hydrocarbon droplet impinging on a hot surface. The impact energy of the droplet and the hot surface temperature are found to determine the impact behavior. On the basis of the newly developed model, the positions where droplets preferentially collide with the convection section tube walls and liquid material is deposited are determined. Furthermore, a kinetic model describing coke formation out of liquid hydrocarbon droplets in the temperature range of 450−700 K has been developed to calculate the rate of coke formation in each zone of the convection section tube. The calculated coke layer thickness on the most vulnerable tube locations and the industrially available values correspond remarkably well. [ABSTRACT FROM AUTHOR]

Cracking furnaces of ethylene plants are capable of processing multiple feeds to produce smaller hydrocarbon molecules, such as ethylene, propylene, and ethane. The best practice for handling the produced ethane is to recycle it as an internal feed and conduct the secondary cracking in a specific furnace. As cracking furnaces have to be periodically shut down for decoking, when multiple furnaces processing different feeds under various product values and manufacturing costs are considered, the operational scheduling for the entire furnace system should be optimized to achieve the best economic performance. In this paper, a new MINLP (mixed-integer nonlinear programming) model has been developed to optimize the operation of cracking furnace systems with the consideration of secondary ethane cracking. This model is more practical than the previous study and can simultaneously identify the allocation of feeds with their quantity, time, and sequence information for each cracking furnace. A case study has demonstrated the efficacy of the developed scheduling model. [ABSTRACT FROM AUTHOR]

Thermal cracking of hydrocarbons in the presence of steam is the most important process for the production of ethylene and propylene, which are the raw materials for many petrochemicals. In this work, multiobjective optimization (MOO) of an industrial LPG (liquefied petroleum gas containing mainly propane and butane) thermal cracker is studied using the elitist nondominated sorting genetic algorithm adapted with the jumping gene operator, NSGA-II-aJG. A first principles model based on free radical mechanism for LPG thermal cracking is employed for optimization. Several bi- and triobjective optimization problems are solved; these problems involved maximization of annual ethylene/propylene production, selectivity and run length, and minimization of severity and total heat duty per year. Feed flow rate, steam ratio, inlet temperature, coil outlet temperature, and pressure are the decision variables. MOO of the LPG thermal cracker provides a range of optimal operating conditions and objective values, with the triobjective optimization giving more optimal solutions compared to those from the biobjective optimization for the objectives considered. With this detailed knowledge, a suitable operating point can be selected based on specific requirements in the particular plant. [ABSTRACT FROM AUTHOR]

The crude bio-oil was upgraded in supercritical ethanol under hydrogen atmosphere by using Pd/SO42−/ZrO2/SBA-15 catalyst. This is a novel way to upgrade bio-oil with the combination of hydrotreatment, esterification, and cracking under supercritical conditions. The results indicated that the upgrading process performed effectively and the properties of the upgraded bio-oil were improved significantly. After the upgrading process, a trace amount of tar or coke was produced and most of the organic components were kept in the upgraded bio-oil. No phase separation was observed. The amount of aldehydes and ketones decreased evidently. In particular, aldehydes were almost completely removed. Most acids were converted into corresponding esters, and at the same time many new types of esters were produced. The results of TGA and DTA indicated that macromolecular compounds were decomposed and much more volatile compounds were produced after the upgrading process. The pH value and heating value of the upgraded bio-oil increased; meanwhile, the kinematical viscosity and density decreased compared to those of the crude bio-oil. [ABSTRACT FROM AUTHOR]

Thermal cracking of hydrocarbons converts them into valuable materials in the petrochemical industries. Multiplicity of the reaction routes and complexity of the mathematical approach has led us use a kind of black-box modelingartificial neural networks. Reactor feed type plays an essential role on the product qualities. Feed type is a qualitative character. In this paper, a method is presented to introduce a range of petroleum fractions to the neural network. To introduce petroleum cuts with final boiling points of 865 °F maximum to the neural network, a real component substitute mixture is made from the original mixture. Such substitute mixture is fully defined, it has a chemical character, and physical properties can be simply retrieved from databases. The mixture compositions are defined with the aid of an optimization algorithm−interval method. The obtained TBP curves of substitute mixture are in good agreement with the experimentally obtained curves. Nine single carbon structural increments will be the representative of 93 real component compositions in order to make the topology of the neural network smaller and hence to have a less complex model. [ABSTRACT FROM AUTHOR]

The scheduling of decoking operations in a naphtha cracking furnace system is an important issue to ethylene producers, because excessive coke deposits inside the furnace coils can negatively impact plant safety and productivity. For optimal scheduling, accurate online estimation of the thickness of the deposited coke is essential. In practice, the coke thickness can be estimated from various furnace operating variables, but measurement errors and unexpected changes in the coke growth rate cause significant uncertainties in the estimation. Errors in the coke thickness estimate manifest themselves as gaps between the model prediction and actual measured values of key operating variables such as the pressure drop and the tube temperature. To handle the potential conflicts in an established schedule caused by the uncertainties, we propose to use a “proactive” scheduling strategy. In “reactive” scheduling, rescheduling is performed whenever an unexpected operational problem causes an unscheduled decoking operation, thus making a standing schedule no longer viable. On the other hand, in the “proactive” scheduling strategy, model information, as well as measurement information, are used to determine appropriate rescheduling points before actual operational problems arise. Under the proposed proactive scheduling strategy, the model predictions of the pressure drop and the tube temperature are compared against their measurements while the plant is operating according to a current decoking schedule. Whenever the gap between the model prediction and the measurement is larger than a given threshold value, the model is updated based on the measurements and the scheduling problem is solved again with the updated model information. The new scheduling solution is applied to the operation until the next scheduling point is found. This proactive scheduling procedure is applied to a simulated system of multiple furnaces. The advantages of the proactive scheduling strategy, in terms of productivity and risk management, are shown by comparing it with a reactive scheduling strategy and a heuristic decoking strategy over a large number of scenarios. [ABSTRACT FROM AUTHOR]

The selectivity of the EDC (1,2-dichloroethane) cracking process in vinyl chloride monomer (VCM) manufacturing strongly depends on the cracking severity and the EDC feed quality. A strong decline of selectivity is observed for EDC feed purities below 99.5 wt % or cracking rates above approximately 60%. The selectivity of the cracking process also deteriorates in the course of the plant’s operating time as a result of accelerated coke formation. Reduced selectivity in the process of EDC cracking results in increased marginal costs (additional costs per each additional tonne of VCM). This is especially relevant for a VCM plant running near full load. The marginal costs can be expressed as a function of the cracking rate and the resulting costs for processing the uncracked portion of EDC. With a new and simplified EDC cracking simulation model for the energy input and conversion, together with a simplified reaction model for the definition of the corresponding product spectrum, the cost impact of the aforementioned influences on the cracking process can be estimated in advance based on the current production rate and plant performance. [ABSTRACT FROM AUTHOR]

To increase the calorific value of the gaseous product from the woody biomass gasification process, a circulating dual-bubbling fluidized-bed gasification system based on the concept of physical separation of the combustion zone from the gasification zone has been proposed. To cope with the difficulty in control of the tar behavior, a catalytic porous γ-alumina has been considered as a bed material for the above process, which circulates between the biomass pyrolysis/steam gasification zone and the char/coke combustion zone, capturing tar vapor as coke on its surface catalytically in the gasifier. Preliminary process simulation clarified the minimum amount of carbonaceous portion (char and coke) in the biomass that must be burnt in the combustor for a thermally self-sustained process operation, suggesting that the coke derived from tar deposited over γ-alumina should be distributed to combustion and gasification zones by controlling the extent of the steam gasification of coke. To develop a method to control the tar conversion during pyrolysis and gasification, we examined the effects of porous γ-alumina on the tar behavior in the secondary reaction in a two-stage bubbling fluidized-bed reactor. Both gasification tests and Brunauer−Emmett−Teller analyses revealed that porous γ-alumina was markedly catalytic toward coking and dehydrogenation of the tar vapor, until a substantial amount of coke had deposited on the catalyst, thus occluding pores. [ABSTRACT FROM AUTHOR]

Data mining techniques can discover experience, knowledge, and operational rules from a large industrial data set to recognize process abnormal situations or faults, further improve production-level, and optimize operational conditions. In this paper, a rough set-based fuzzy rule acquisition approach and a fault diagnosis scheme of industrial process are studied in detail. A new heuristic reduct algorithm is proposed to obtain the optimum reduction set of decision information system. Moreover, a fuzzy discretization model for continuous data based on normal distribution of process variables is put forward to overcome the subjective of selecting fuzzy membership functions and decrease the sensitivity to noise signals. Furthermore, the proposed data mining algorithm and fault diagnosis scheme are applied into a petrochemical process. The validity of the proposed strategy is verified by application of a practical ethylene cracking furnace system, which can discover abnormal process situations and improve plant safety in petrochemical industry. [ABSTRACT FROM AUTHOR]

A two-dimensional reactor model incorporating hydrodynamics, mass balance, energy balance, and a 4-lump/14-lump kinetic model was established to simulate the riser and downer based fluid catalytic cracking (FCC) processes. The kinetic parameters of the 4-lump kinetic model were re-evaluated from the originally published experimental data for a more reliable description of the FCC process. The 14-lump kinetic model based on a molecular description of cracking and hydrogen transfer reactions was to include more details about the feedstock composition, reaction mechanisms, and the products distribution for a better understanding on the reactor performance for FCC process. This comprehensive model captured the key characteristics of the gas−solid reacting flows in the riser and downer, i.e., the uniformity of flow structures, the distinct backmixing behavior in the riser and downer, and the momentum and energy balances during the complex FCC reactions. The model predictions were first validated against industrial data from several literature sources and found to agree with each other reasonably well. Then, the simulations were carried out to fully understand the different reactor performances of riser and downer in the application of FCC refining processes. It can be concluded that the downer benefits from its advantages of the plug-flow nature and uniform flow structures, tending to have more products in the middle distillates, e.g., gasoline and light olefins, especially under high-severity operations. Better control of the reaction extent for increased selectivity to desired intermediate products would allow the use of downer reactors for the larger-scale practical applications in the FCC process, together with the valuable byproduction of light olefins. [ABSTRACT FROM AUTHOR]

The objective of this technical note is to give an alternate explanation of the ring structure behavior for the flow of fluidized catalytic cracking (FCC) particles in a riser recently obtained in L. S. Fan’s laboratory. Their recent explanation of this phenomenon is due to the low velocity at the center. While indeed this is one of the causes of the high concentration near the center, we show that an additional driving force for the higher concentration at the center is the low granular temperature caused by the dissipation of random kinetic energy at the center of the riser. An approximate analytical solution applied to the flow of FCC particles obtained in Fan’s laboratory again produces a dip in the granular temperature in the center and hence a rise in the particle concentration. This phenomenon occurs as a result of the constancy of solids pressure in the developed region of the riser. It is the so-called shear-induced diffusion effect well-known for neutrally buoyant particles in liquids. [ABSTRACT FROM AUTHOR]

Mathematical models and simulations of an integrated downer−regenerator FCC unit are presented. The models describe the steady-state nonisothermal behavior of the interdependent heavy oil cracking downflow reactor and catalyst regeneration fluidized-bed reactor. The models are rooted in four-lump cracking reaction kinetics and complete combustion kinetics for the regenerator reactions. Simulations results for the downer-type unit are partially validated against data collected in a 0.1−0.3 b/day pilot plant that was operated in the high-severitymode. The results are fairly reasonable especially in regard to predicting the performance of the cracking reactor. [ABSTRACT FROM AUTHOR]

A simple procedure is developed to determine the apparent rate constants, reaction orders, and activation energies of various hydrotreating reactions, such as the hydrodesulfurization (HDS), hydrodemetalation (HDM), hydrodenitrogenation (HDN), and asphaltene cracking (HDAsph) of hydrotreating catalysts loaded in multiple-reactor fixed bed units. The procedure is derived from the basic kinetic and engineering principles. The only required input parameters are the sulfur, vanadium, nickel, nitrogen, and asphaltenes contents in the feedstock and products, reaction temperatures, and liquid hourly space velocity (LHSV). These parameters are normally available from laboratories performing the kinetic studies. Since there is no correlation coefficient in the developed kinetic expression, the apparent reaction rate constant and activation energy for various hydrotreating reactions can be determined directly once the optimum value of the reaction order has been identified. To demonstrate how the procedure works, it has been applied to calculate the kinetic values published in the open literature. Excellent agreements are obtained. The procedure is further verified with kinetic parameters from experiments undertaken in our pilot plants. In some cases, kinetic values which were unable to be determined in our pervious studies can now be obtained. The overall absolute average deviation (AAD) is less than 10%. [ABSTRACT FROM AUTHOR]

Industrial trials detailed in a riser−downer coupling reactor proposed for the fluid catalytic cracking (FCC) process are presented in this paper. The trials are based on the fundamental research of hydrodynamics, mixing behaviors, and laboratory-scale hot experiments described in our previous investigations. Compared with the riser reactor with the same feeds and catalyst, the LPG and propylene yield increased by 8.15 and 4.30 wt %, respectively. The gasoline octane number likewise reached 94.8 with 28 wt % olefin content. However, dry gas is significantly suppressed, and the coke has little change in yield even with the increased catalyst to oil ratio. With some gasoline recycling, the LPG and propylene yield increased by 11.45 and 5.06 wt %, respectively, and the olefin content in gasoline significantly decreased to 22 wt %; the high octane number (95.4) is maintained. The computational fluid dynamics (CFD) coupled with a 6-lump kinetic model is also applied to simulate the FCC process for the industrial trials. The yield of propylene and butylene and the temperature profile along the axis direction demonstrated consistency between the simulation results and the experimental data. [ABSTRACT FROM AUTHOR]

Application of the Topsoe Aroshift Technology in the Lukoil Neftochim, Bulgaria (LNB), fluid catalytic cracking (FCC) unit was studied in this work. The hydrotreated vacuum gas oil (HTVGO), feed for the LNB FCC unit, was treated in the Topsoe Aroshift pilot plant. The HTVGO and Aroshifted HTVGO were cracked in a laboratory fluid bed catalytic cracking unit (FCC advanced catalytic evaluation unit). The Aroshift treatment of the HTVGO increased the mononuclear aromatics content by 3%, which resulted in 3% higher FCC conversion and higher gasoline selectivity. The octane number of gasoline, produced from the Aroshifted HTVGO, was about 0.5 lower than that of gasoline, obtained by HTVGO cracking. The economic benefit of the Aroshift process application in the LNB FCC unit at a feed rate of 185 t/h was evaluated to be $6.78 million U.S./year. [ABSTRACT FROM AUTHOR]

Thermal cracking of Fischer−Tropsch waxes at mild conditions (430−500 °C) has been reconsidered as a possible refining technology for the production of fuels and chemicals. In this study, the description of paraffin cracking, which was historically developed using material no heavier than C40, was extended to C20−C120wax. In this carbon number range, cracking rate increased with increasing carbon length and thermal cracking resulted in a bimodal product distribution. Using the Rice−Kossiakoff mechanism as a basis, a relationship could be derived between carbon number distribution and conversion that described the observed behavior. The application of thermal cracking to fuels production was evaluated, and it was shown to be less efficient than hydrocracking, although it requires no hydrogen co-feed and has a lower gas make. Thermal cracking is better suited for the production of chemicals such as candle wax and linear -olefins. The study also investigated the formation of deposits during wax cracking. The deposits were inorganic in nature and originated from material produced in the Fischer−Tropsch process. It was found that stripping gases (steam, H2, and N2) were ineffective in reducing these deposits. [ABSTRACT FROM AUTHOR]

Injection of gas hydrate inhibitors at the upstream of oil/gas pipelines is normally based on the calculated/measured hydrate stability zone, worst case scenarios for pressure and temperature conditions, water cut, and the inhibitor loss to the nonaqueous phases. In many cases, high safety margins are used to account for the uncertainties in the above factors and minimize the gas hydrate formation risks as no means of controlling and monitoring are generally available along the pipelines and/or downstream to assess the degree of hydrate inhibition. In this work, the possibility of predicting the hydrate safety margin from specific gravity data of aqueous solutions is investigated using a feed-forward artificial neural network method with a modified Levenberg−Marquardt algorithm. The method, which has been developed for various salts (NaCl, KCl, CaCl2, KBr, NaBr) and organic inhibitors (methanol, ethanol, ethylene glycol, glycerol) aqueous solutions, considers the changes in specific gravity of aqueous solution for estimating the hydrate stability zone. Independent data (not used in training and developing of the neural network) are used to examine the reliability of this tool. The predictions of this method are found to be in acceptable agreement with the independent experimental data, demonstrating the reliability of the artificial neural network method for estimating the hydrate safety margin using specific gravity data of salt or organic inhibitor aqueous solutions. [ABSTRACT FROM AUTHOR]

In this paper, a new multi-objective particle swarm optimization (MOPSO) procedure, based on the Pareto dominance hybrid algorithm, is proposed and applied in a naphtha industrial cracking furnace for the first time. Pareto dominance is incorporated into particle swarm optimization (PSO). Our algorithm takes the Pareto set as a repository of particles that is later used by other particles to guide their own flight. In addition, an MOPSO and artificial neural network (ANN) hybrid model is applied in the operation optimization of a naphtha industrial cracking furnace. Therein, sensitivity analysis is investigated and taken as the basis on which decision variables of multi-objective problem base. From both theoretical computation and practical application, the validity and reliability of proposed algorithm are verified by two test functions studied, and actual application example of the optimization of operation parameter of cracking process. Moreover, the yields of ethylene and propylene are improved. [ABSTRACT FROM AUTHOR]