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Women's participation in the tourism workforce is growing intensely in response to Saudi Vision 2030. Notwithstanding this, Saudi women still have limited access to senior management positions. This study explores the barriers that Saudi women face to reach top managerial positions in the tourism industry and explores how Saudi women could crack the glass ceiling. For these reasons, this study undertook a phenomenological approach using in-depth interviews with Saudi women who were able to reach senior management. The purpose of the interviews is to explore their lived experience and their accessibility to senior management positions. The results of a thematic analysis showed that there were four overlapped barriers for the glass ceiling among Saudi women: cultural and social barriers, regulatory barriers, organizational barriers, and personal barriers. These main barriers have sub-barriers that contribute to the glass ceiling and prevent many women from reaching senior positions. This study shows that overcoming these barriers, particularly cultural and social barriers, could help Saudi women to crack the glass ceiling and achieve their dream of leadership. This study discusses the implications for policy makers, academics, and practitioners on the effective contribution of Saudi women to the tourism labor market, which contributes to sustainable tourism development and, ultimately, to Saudi Vision 2030. [ABSTRACT FROM AUTHOR]

Hydrogen-Bonded organic frameworks (HOFs) are a type of emerging porous materials. At present, little research has been conducted on their solution state. This work demonstrates that HOFs fragment into small particles while maintaining their original assemblies upon dispersing in solvents, as confirmed by Cryo-electron microscopy coupled with 3D electron diffraction technology. 1D and 2D-Nuclear Magnetic Resonance (NMR) and zeta potential analyses indicate the HOF-based colloid solution and the isolated molecular solution have significant differences in intermolecular interactions and aggregation behavior. Such unique solution processibility allows for fabricating diverse continuous HOF membranes with high crystallinity and porosity through solution-casting approach on various substrates. Among them, HOF-BTB@AAO membranes show high C3H6 permeance (1.979 × 10−7 mol·s−1·m−2·Pa−1) and excellent separation performance toward C3H6 and C3H8 (SF = 14). This continuous membrane presents a green, low-cost, and efficient separation technology with potential applications in petroleum cracking and purification. Hydrogen-bonded organic frameworks (HOFs) attract increasing attention as porous materials. Despite the widely studied solid-state properties, little research has been done on the solution state. Here, the authors demonstrate that HOFs fragment into small particles while maintaining their original assemblies upon dispersing in solvents. [ABSTRACT FROM AUTHOR]

Introduction: The occurrence of mixed fracture mechanisms in mechanical elements is frequent, due to the action of multiple factors that intervene during their design, manufacturing and operation. Objective: To establish the causes of failures in tripod columns on trucks, based on the characterization of the base metal and the welded joints in the failure region. Materials and Methods: Visual inspection of the failures, chemical and microstructural characterization by optical microscopy of the columns, as well as tensible test of the base material were carried out. Results and Discussion: The integrated visual inspection analysis and the results of chemical and metallographic characterization reveal that the material of the columns is not recommended for welded structures and that measures such as preheating and thermal treatment after welding were not taken. Due to the characteristics of the steel and the location of the detected cracks, they may be associated with diffusible hydrogen cracking. Conclusions: The failure of the columns was the result of a combination of several factors, highlighting design and manufacturing errors in the selection of a non-recommended material and the non-execution of attenuation measures during the execution of the welding, also linked to factors such as, possible overloads or improper operation of the equipment. [ABSTRACT FROM AUTHOR]

Conducting a study on this topic becomes relevant due to the great importance of the safety of critical infrastructure facilities and the presence of operational defects in equipment elements and pipelines, which poses serious threats, including the possibility of equipment destruction and negative environmental impact. The purpose of this work is to study the possibility of using the diffraction-time technique of ultrasonic non-destructive testing together with a deep convolutional neural network to accurately determine the numerical value of the height of an operational crack. The methods used include the analytical method, classification method, functional method, statistical method, synthesis method, and others. The study found that an automated approach to measuring crack height, based on diffraction signals and the use of neural networks, significantly improved the quality and accuracy of non-destructive testing. Ultrasonic testing is one of the most common inspection methods for detecting service cracks and is considered to be the most effective. It allows for reliable detection of defects and determination of their size without destroying the product. The results of the study emphasize the high potential and efficiency of the method in analysing the data obtained and provide confirmation of its applicability for determining the condition of objects during ultrasonic inspection. The paper emphasizes that these technologies are particularly important and effective. It is noted that their widespread use in various industries, such as medicine, aviation, and machine learning, demonstrates their power in solving complex problems. The practical significance of the work lies in the development of advanced approaches that provide new insights and methods to improve the efficiency of analysing the results, which can be applied in industry to improve the quality of control and reliability of technical facilities. [ABSTRACT FROM AUTHOR]

Fine cracks are easy to occur in the processing of monocrystalline silicon, which affects the surface processing quality. Laser assisted machining (LAM) can soften the substitute machining area, effectively reduce the cutting force, extend the tool life and improve the surface quality. In this paper, a thermo mechanical coupled smooth particle model is established to simulate the laser assisted turning process of single crystal silicon. Under different temperature conditions, crack propagation damage and cutting stress are explored. The influence of speed and cutting depth on surface roughness. Finally, the accuracy of simulation results is verified by laser assisted cutting experiments. The results show that increasing the temperature is beneficial to the plastic cutting of monocrystalline silicon. With the increase of the cutting zone temperature, the tool stress gradually decreases. The tool stress at 300 °C is about 50% lower than that at room temperature, and the surface processing quality is significantly improved. At 600 °C, the chip is a plastic flow sawtooth line, and the plasticity is greatly improved. During cutting, a smaller cutting depth shall be selected, the rotating speed shall be lower than 4 500 r/min, and the surface roughness Sa of monocrystalline silicon can be less than 1 nm. [ABSTRACT FROM AUTHOR]

C2+ hydrocarbons, especially C2+ olefins, as important basic chemical raw materials, mainly come from petroleum cracking. With the increasing scarcity of petroleum resources, the search for new olefins production routes has become the focus of research, and the production of olefins by the oxidative coupling of methane (OCM) process has attracted extensive attention. The OCM route is an important alternative to the production of olefins from petroleum resources and is also an important direction for the development of efficient and clean utilization of natural gas. In this paper, the mechanism, catalysts, and other key factors for the production of olefins by methane oxidative coupling are reviewed. The mechanism of OCM, including the reaction pathway and the formation of intermediate products, is introduced. Then, commonly used catalysts, such as alkali metal/alkaline earth metal oxides, rare earth metal oxides, composite metal oxides with special structures, and classical catalysts Mn/Na2WO4/SiO2, and their mechanisms of action in the reaction are discussed. In addition, the application of chemical looping oxidative coupling of methane (CLOCM) in olefin production is also investigated, which is a promising alternative way due to the high selectivity of olefins and the low cost of catalysts owing to the excellent performance of the catalyst recycling. These studies will help to further understand the mechanism of OCM for olefin production and provide guidance and support for applications in related fields. [ABSTRACT FROM AUTHOR]

The concrete deck at the negative bending moment region of a continuous steel-concrete composite girder bridge is the weakest part of the structure. Introducing ultra-high performance concrete (UHPC) to the hogging region may overcome the shortage and break through the bottleneck. This paper explores the cracking performance of steel-concrete composite girders with concrete slabs topped by a thin layer of UHPC subjected to a negative bending moment. A real continuous composite girder bridge is briefly introduced as the engineering background, and the cracking characteristic of the concrete deck over the middle piers of the bridge is numerically modeled. Approaches to strengthen the cracking performance of the concrete deck at the hogging region through topping UHPC overlays are proposed. The effectiveness of the approaches is examined by conducting a series of numerical and experimental tests. Numerical results indicate that the normal concrete (NC) deck near the middle forums of the bridge would crack due to the large tensile stress from negative bending moments. Replacing the top concrete with an identical-thick UHPC overlay can increase the cracking resistance of the deck under the moment. As the thickness of the UHPC overlay increased from 6.0 cm to 12.0 cm, the maximum shear stress at the UHPC overlay-to-NC substrate interface under different load combinations was decreased by 56.3%-65.3%. Experimental results show that the first-cracking load of the composite beam using an NC-UHPC overlaid slab was 2.1 times that using an NC slab. The application of a UHPC overlaid deck can significantly improve the crack performance of the steel-concrete composite girder bridge. [ABSTRACT FROM AUTHOR]

Flexible strain sensors are capable to detect external force induced strain change owing to their unique ability to convert deformation into electrical signals. Generally, micro/nano patterning of conductive layer in strain sensor is an effective method to improve its sensitivity, however the sophisticated manipulation process is limited only in laboratory scale. In this report, a simple and scalable fabrication strategy was used to create micro-cracking conductive layer as an alternative patterning method to achieve high performance of strain sensor. In details, the sensor was fabricated using leather as the substrate to filtrated acidified multi-walled carbon nanotubes (a-MWCNTs)/layered double hydroxides (LDHs) suspension. During stretching process, micro-cracking structure emerged on the percolated a-MWCNTs/LDHs layer, causing a rise up of resistance according to increasing strain and generated a detectable electrical signal. The prepared sensor had a large detecting range (60%), high sensitivity (GF of 7238.92 at strain 30–60%), fast response (tensile response time of 270 ms), good stability and repeatability. The sensor also inherited the advantages of leather, such as biodegradability and good air permeability, and the introduction of a-MWCNTs/LDHs further enhanced its fire retardancy properties. These features ensured the sensor as an eco-friendly, comfortable and safe electronic device for human motion detection. [ABSTRACT FROM AUTHOR]

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Anuario do Instituto de Geociencias is the property of Universidade Federal do Rio de Janeiro, Instituto de Geociencias and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In view of the difficulty of kerosene-air detonation faced by the application of rotating detonation to aviation engines, in order to improve the kerosene detonation activity, the atmospheric pressure gliding arc plasma is used to conduct secondary adjustment of the pre-combustion cracking products. The results show that the components with larger molecular weight in the pre-combustion cracking products, such as ethylene and methane, can be cracked into highly active species of hydrogen and acetylene by gliding arc plasma. With the increase of the fuel ratio of pre-combustion cracking, the plasma has a more significant effect on the adjustment of high active components. However, as the flow rate of the cracking gas treated by plasma increases, the adjustment effect is obviously reduced. [ABSTRACT FROM AUTHOR]

The article talks about novel sensor and material technologies designed to help identify bridges most at risk of failure or collapse so they can be repaired and strengthened. Topics covered include the aging bridge infrastructure in both the U.S. and Europe, automated versions in monitoring bridges for crack formation that are being developed by researchers, and a flexible strain-sensing sheet for monitoring bridges developed by a team led by Branko Glisic at Princeton University.

Introduction: The finite element method has become popular to determine fracture mechanics parameters, but this type of numerical analysis may or not lead to accurate results, depending on the model quality and the implementation of the established methods. Objective: Implement and validate the calculation of the stress intensity factor and the J integral through the displacement extrapolation, domain integral and interaction integral methods, through finite element modeling of cracked part problems in 2D and 3D. Materials and methods: The stress intensity factor and the integral J were calculated in a compact cracked specimen and a plate with a semi-circumferential surface crack, by means of 2D and 3D finite element models, and these results were verified with those obtained by means of published analytical expressions. Results and Discussion: The error of the results provided by the finite element models does not exceed 3% for the two-dimensional models and 7% for the three-dimensional ones, which demonstrates their quality and precision. Conclusions: The implementation of the calculation of the fracture mechanics parameters is considered validated, which makes it possible to extend its use in the future for constructions and equipment that present cracking in service. [ABSTRACT FROM AUTHOR]

Hot tearing is one of the most serious defects during the casting solidification process. In this study, a new type of multichannel "cross" hot tearing device was designed. The hot cracks initiation and propagation were predicted by the relationship between temperature, shrinkage force and solidification time during the casting solidification process. The reliability and practicability of the multichannel "cross" hot tearing device were verified by casting experiments and numerical simulations. The theoretical calculation based on Clyne-Davies model and numerical simulation results show that the hot tearing tendency decreases in the order: 2024 Al alloy>Al-Cu alloy>Al-Si alloy at a pouring temperature of 670 °C and a mold temperature of 25 °C. Feeding of liquid films at the end of solidification plays an important role in the propagation process of hot tearing. The decrease of hot tearing tendency is attributed to the feeding of liquid film and intergranular bridging. [ABSTRACT FROM AUTHOR]

Ethylene is an essential platform chemical with a conjugated double bond, which can produce many secondary chemical products through copolymerisation. At present, ethylene production is mainly from petroleum fractionation and cracking, which are unsustainable in the long term, and harmful to our environment. Therefore, a hot research field is seeking a cleaner method for ethylene production. Based on the model ethylene-forming enzyme (Efe) AAD16440.1 (6vp4.1.A) from Pseudomonas syringae pv. phaseolicol, we evaluated five putative Efe protein sequences using the data derived from phylogenetic analyses and the conservation of their catalytic structures. Then, pBAD expression frameworks were constructed, and relevant enzymes were expressed in E. coli BL21. Finally, enzymatic activity in vitro and in vivo was detected to demonstrate their catalytic activity. Our results show that the activity in vitro measured by the conversion of α-ketoglutarate was from 0.21–0.72 μmol ethylene/mg/min, which varied across the temperatures. In cells, the activity of the new Efes was 12.28–147.43 μmol/gDCW/h (DCW, dry cellular weight). Both results prove that all the five putative Efes could produce ethylene. [ABSTRACT FROM AUTHOR]

• EU-1 zeolite crystal sizes are shortened to nanoscale with the presence of TPOAC. • EU-1 nano zeolite aggregates expose more external acid sites and accessible volume. • Refining of EU-1 crystal sizes improves the accessibility and utilization degree of acid sites. • EU-1 nano zeolite aggregates show higher n-hexane cracking activity than parent EU-1. One-dimensional microporous zeolite, EU-1, exhibits more favorable selectivity of propylene in cracking of petroleum components. However, it faced the problem of low catalytic activity for the poor utilization of active sites. In this work, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (TPOAC) was used to functionalize protozeolitic units and inhibit the excessive growth of crystals by the long hydrophobic alkyl chain. The introduction of TPOAC decreased the crystal sizes into nanoscale, enhanced the mesoporous volume of EU-1 zeolite, and exposed more external acid sites. Moreover, TPOAC could interact with Al species, and in this case, fewer Al atoms were incorporated into the zeolite framework, reducing the acid strength and amount. Intelligent gravitation analyzer test indicated that the zeolite prepared with the presence of 0.30 g TPOAC exhibited the largest accessible volumes in n-hexane adsorption, and the highest accessibility of acid sites, which synergistically promoted cracking of n-hexane for the production of light olefins. [ABSTRACT FROM AUTHOR]

Unfilled elastomers often suffer from poor fracture resistance at high temperature where viscoelastic dissipation is low. A molecular design based on multiple interpenetrating networks composed of a brittle filler network isotropically prestretched to a value λ0 by swelling it in an extensible matrix leads to a dramatic increase of fracture energy Γc, typically attributed to sacrificial bond scission creating a dissipative damage zone ahead of the propagating crack. However, the molecular mechanisms controlling the size of the damage zone when the crack propagates are currently unknown. Here, we combine fluorogenic mechanochemistry with quantitative confocal mapping and mechanical testing to characterize both and the extent of bond scission in the sacrificial network detected on the fracture surfaces for different stretch rates and temperatures. We find that increasing the prestretch λ0 of the filler network leads to a large increase in Γc mainly at temperatures well above the glass transition temperature of the elastomers, where viscoelasticity is inactive, but also at lower temperatures where both mechanisms are coupled. Yet, we show that there is no direct linear relation between the extent of filler network scission and Γc. We mainly attribute the large increase in Γc to the dilution of highly stretched strands in the entangled and unstretched matrix, which delocalizes stress upon bond scission and effectively protects the matrix network from scission and the material from crack growth. Delaying the localization of bond scission by network design is a promising strategy that will guide molecular designs able to toughen elastomers even in the absence of viscoelastic dissipation. [ABSTRACT FROM AUTHOR]

The hot-tearing susceptibility (HTS) of Mg-6Zn-xGd (x=0.5, 1, 2, 3, 4, 6) alloys was evaluated using a constrained rod casting (CRC) method. The results show that the HTS curve follows a typical "Λ" shape with the increase of Gd content. The Mg-6Zn-2Gd alloy has the highest while Mg-6Zn-6Gd alloy has the lowest HTS value. The hot-tearing behavior characteristics of Mg-6Zn-xGd alloys were further studied through a multifunctional hot-tearing test device. According to the dendrite contact point inferred from the stress curve, the Clyne-Davies criterion was modified and found to be accurate in predicting the HTS of Mg-6Zn-xGd alloys. Microstructure observation reveals that the grain size and the volume of eutectic liquid are the two key factors affecting HTS of Mg-6Zn-xGd alloys. The large grain with columnar structure can easily promote initiation and propagation of hot-tearing due to the poor feeding and coordinating deformation capability, which have a harmful effect on HTS. A higher volume fraction of eutectic phase can refill the cracking and provide continuous feeding channels by dendrite bridge and thicker liquid film, thus increase the hot-tearing resistance. [ABSTRACT FROM AUTHOR]

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Because thermowells are prone to fatigue damage in petroleum cracking gas pipelines, in this paper, the LES method is used to simulate the flow around thermowells through two-way thermal-fluid-solid coupling, the internal causes of thermowell damage are explored, and measures for improving the thermowell safety are proposed. According to this study, when high-speed, high-temperature gas passes the thermocouple bushing, the main factors affecting the structural safety of the thermocouple bushing are the alternating stress caused by the vortex falling off, the thermal stress cycle due to the temperature gradient, and the pressure gradient impacted by the gas. Furthermore, this paper proposes improving the thermowell safety by installing the interference devices and optimizing the installation angle. The improvement measures were studied by conducting a two-way thermal fluid-structure coupling simulation. The results of this study show that after installing the interference device and optimizing the installation angle the displacement deformation of the thermowell and the equivalent stress is reduced by 57.2% and 72.1%, respectively, which indicates the safety improvement of the thermowell structure and the effectiveness of the method. The research contents of this paper can provide guidance for the installation and use of thermocouple bushing. [ABSTRACT FROM AUTHOR]

The article discusses issues associated with science industry. Topics discussed include antivirals as another promising route to decrease risk of Covid-19 pandemic risks alongside vaccination; joint venture technology firm created by Reaction Engines in Oxfordshire; new approach to treat Alzheimer's disease by using an engineered form of a protein associated with the disease.

Two semi-synthetic clay-based catalysts were prepared. These catalysts were obtained by incorporating lanthanum oxide (Cat1) and chromium oxide (Cat2). They were then tested for catalytic cracking of a heavy petroleum residue (fuel). The two formulations were carried out in the presence of silica to improve their acidity then underwent an acid activation. The catalysts obtained were characterized by various methods (XRD, FTIR, ICP-OES, SEM). The results showed that the incorporation of oxides and the addition of silica improves the structural characteristics of the final products. The support used was a kaolinite rich clay, having a specific surface area of 15.26 m2/g and acidity of 14 meq/g. These values increase, respectively, to 456.14 m2/g and 50 meq/g for Cat1 and to 475.12 m2/g and 57 meq/g for Cat2. The influence of the type of oxide incorporated, the specific surface area, the porosity and the acidity of the catalysts on their catalytic activity was studied. The nature of the oxide used proved to be decisive on the quality of the catalyst. Thus Cat1, prepared with lanthanum oxide, showed the best performance in cracking the petroleum residue achieving a conversion rate of 74.13% compared to 66.53% for cat2. [ABSTRACT FROM AUTHOR]

Steel ingot with a large height-to-diameter ratio is utilized to produce multiple products by one stock in practice. Water cooling is a usual way to enhance production efficiency. However, the combination of the two factors will generate internal defects, such as shrinkage porosity and hot crack. The characteristic of internal shrinkage crack in a 10 t water-cooled steel ingot with a large height-to-diameter ratio was examined by an ultrasonic test. A slice was sectioned from the ingot middle part where billets containing star-like crack were further extracted. The billets were examined by X-ray high energy industrial CT, and the compactness was reconstructed in three dimensions. Microstructure near the crack was observed using scanning electron microscopy, and the solidification process and grain size were studied by high temperature confocal microscopy. Moreover, thermomechanical simulation and post-processing were carried out to analyze the formation of shrinkage porosity and hot crack. A new criterion considering mushy zone mechanical behavior in brittle temperature as well as grain size distribution was proposed to evaluate hot cracking potential in the ingot. The results show that a deep shrinkage porosity band easily forms in the center line of such an ingot with a large height-to-diameter ratio, and water-cooling further generates excessive tensile stress tearing the liquid films around the porosities. Then, hot cracks begin to propagate along grain boundaries. The grain size in the upper and center of the ingot is large, which leads to an inverted cone shape defects zone in the ingot center. [ABSTRACT FROM AUTHOR]

High Nb-TiAl (Ti-44Al-8Nb-0.2W-0.2B-0.5Y, at.%) ingot was fabricated by vacuum arc remelting (VAR). The as-cast ingot was hot-isostatic pressed (HIP) and homogenizing annealing processed. The influence of heat treatment temperature and thermomechanical processing on the microstructure and tensile property of the alloy was investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and tensile tests. It was found that the high Nb-TiAl alloy after HIP and annealing was mainly composed of coarse α2/γ lamellae, β/B2 phase and γ phase and the solidification path of this alloy was: L→L+β→β→α+β→α→α+β+γ→α2+β+γ. The water quenching results showed that the alloy was in α single phase region at 1,340 °C. After heating at 1,340 °C for 30 min followed by furnace cooling, the alloy showed a full lamellar microstructure and its ultimate tensile strength was about 538 MPa, with an elongation of 0.3% at room temperature. Free-crack forged pancakes with fine-grained fully lamellar structure (FFLS) were obtained with an initial deformation temperature of 1,340 °C and the ultimate tensile strength of forged alloy was about 820 MPa, with an elongation of 0.9% at room temperature, which was much higher than that of alloy after HIP and annealing because of microstructural refinement. [ABSTRACT FROM AUTHOR]

Copyright of Iraq Journal of Market Research & Consumer Protection / Al-Mağallaẗ al-ʿIrāqiyyaẗ li-Buḥūṯ al-Sūq wa-Ḥimāyaẗ al-Mustahlik is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Understanding the mechanisms of petroleum thermal cracking is critical to develop more efficient and eco-friendly petroleum cracking processes. Asphaltenes are the main component of petroleum subjected to cracking processes. Thermal cracking mechanisms of petroleum were explored by computational methods using 1,2-diphenylethane (DPE) as a model molecule in this study. The overall mechanisms were divided into four steps including initiation, H-transfer reaction, H-ipso reaction, and termination represented by seven reactions. We carried out extensive quantum chemistry calculations at high levels of theory to accurately explore the minimum energy pathways as the mechanisms of the proposed reactions. The reaction energy and barriers in terms of enthalpy and free energy and their temperature dependence were calculated in the vacuum and in both polar and nonpolar solvents using the polarizable continuum model (PCM) method. The temperature dependence of the target reaction barriers are characterized in different environments and provides computational guidance for future development for petroleum thermal cracking. As the first reported systematic investigation of petroleum cracking mechanisms, this study provided a comprehensive theoretical description of petroleum cracking processes with valuable information about temperature and solvent dependence. [ABSTRACT FROM AUTHOR]

Body text Keywords Body text Review policy Body text Reader comments Body text Prestressed hollow-core slabs are generally precast concrete elements manufactured using an extrusion machine. Although prestressed hollow-core slabs are designed as uncracked members under service loads, cracking is unavoidable under excessive loading. The postcracking behavior of hollow-core slabs can be improved at very low cost by adding structural macrosynthetic fibers during the casting process with no modifications to the mixture proportions of zero-slump concrete. This paper examines the behavior of structural macrosynthetic fiber-reinforced hollow-core slabs at three different shear span-to-depth ratios a/d. Six full-scale tests were conducted on hollow-core slabs, of which three had no fiber additives and three had a polyolefin fiber dosage of 0.33%. The a/d values of 2.5, 3.75, and 7.5 were considered to evaluate the effect of macrofibers on the performance of hollow-core slabs. The test results indicate that the addition of macrosynthetic fibers increased the ultimate strength up to 19% with an increase in ductility. The contribution of fibers in improving the postcracking stiffness was better at higher a/d values under flexure-dominant behavior. Existing analytical models were suitably modified to predict the theoretical capacity of slabs with and without fibers. [ABSTRACT FROM AUTHOR]

Body text Keywords Body text Review policy Body text Reader comments Body text The American Association of State Highway and Transportation Officials' AASHTO LRFD Bridge Design Specifications have a refined method for the calculation of time-dependent losses in prestressing force. This method estimates a gain in the prestressing force due to differential shrinkage between the precast concrete girder and the cast-in-place deck; however, it does not consider the possibility of cracking in the deck. Some state departments of transportation believe that after the deck cracks, the gain in the prestressing force is lost, and they do not include it in the prestress loss calculations. Some other state departments of transportation believe that not all of the prestress gain is lost and allow some percentage of the gain to be retained. This study focuses on the effect of deck cracking on the long-term loss of prestressing force. A finite element software model was used to simulate three different girder lengths with varying deck concrete strengths, differential shrinkage parameters, and girder ages at the time the deck was placed. When the girder age at the time of deck placement is more than 60 days, there is a high probability that the deck will crack, though a deck placed on a girder of any age may crack, depending on the properties of the deck and girder. When the deck cracks, some of the gain of prestressing force is lost, but the percentage lost depends on the extent of cracking in the deck. The older the girder is when the deck is placed, the greater the cracking. The cracked deck still provides some restraint, and even in cracked decks, nearly 50% of the prestress gain due to differential shrinkage was retained. [ABSTRACT FROM AUTHOR]

Highlights • Enhancing cracking process based on synergy improvement among radial field profiles. • Quantitatively analyzing the suitable arrangement of internals based on fluid mechanics principle. • A novel concept of mass transfer synergy angle was derived to explain the mass transfer enhancing mechanism. Abstract A novel insert-hollow cross disk (HCD) combined with twisted tape is embedded in a cracking coil to enhance the propane cracking process by positive constructing of synergetic flowing field. Quantitative analysis of appropriate insert arrangement has been conducted based on contrastive CFD simulation results in the bare and novel coil. The characteristic exchanging flow between the central zone and the near wall area induced by inserts in the novel coil can play an effective role in improving the radial synergy among heat, mass and velocity. This leads to an obvious yield increase of 0.50% and 10.23% of ethylene and propylene comparing with the bare coil. And the average tube skin temperature is declined by 28.45 k. Moreover, the Nu and Sh are increased by 10.96% and 2.98% respectively and the overall PEC factor has a rise of 8.00% in the novel coil. This confirms the effective strengthening effect by the novel coil. Furthermore, the field synergy theory is applied to evaluate the synergy improvement for the heat and mass transfer process. Comparing with the bare coil, the synergy angles for heat as well as mass transfer in the novel coil have a maximum decrease of 21.76% and 23.14% in the downstream of the twisted tape (z/L = 0.23) and HCD insert (z/L = 0.60), respectively. This could explain the enhanced heat and mass transfer as well as the product distribution due to the synergic flow field in the novel coil with the assemble inserts group. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Heat transfer performance is investigated at the presence of hollow-cross disk as a vortex generator for the cracking coil. • The vortical flow induced by HCD couples with CVPs and hairpin-like vortex, efficiently enhancing the heat transfer locally and globally. • The heat transfer mechanism is studied by field synergy theory, which indicates superior synergy near the wall weighs higher for the cracking flow. Abstract A novel comprehensive vortex generator, hollow-cross disk (HCD) which comprises a special sinusoidal wave structure, has been proposed to modify the configuration for cracking coil. The effects of HCD on the turbulent flow patterns, heat transfer characteristics and micro-mixing efficiency of the flow are investigated by CFD modelling in the present work. The numerical results demonstrate that in the test range of flow rates, the vorticial flow induced by HCD couples with CVPs and hairpin-like vortex, efficiently enhancing the convective heat transfer locally and globally. In contrast, although the global swirling flow induced by a twisted-tape can enhance the turbulence intensity, larger pressure drop taking place in the coil leads to relatively poor comprehensive heat transfer performance and lower micro-mixing efficiency. Moreover, the mechanisms of heat transfer enhancement for the cases with inserts have been investigated by the synergy regulation and the synergy between the temperature gradient and velocity has been discussed. The results indicate that better synergy occurring in the vicinity of coil surface is a key factor to enhance heat transfer for the cracking process. The obtained results can be used as a guidance for the design and optimization of the inserts for the cracking process. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Development of a novel cracking catalyst for deoxygenation from earth abundant kaolin. • Characterization of the deoxygenation active sites on catalyst for the first time. • Correlation of the catalyst deoxygenation ability to its density of weak Lewis acids. • Study of the effects of density of Bronsted acids on triglyceride dehydrogenation. • The total amount of Bronsted acids determines the cracking capability of a catalyst. Abstract This work presents a cost-effective abundant kaolin-based cracking catalyst that has high deoxygenation, mild cracking, and low dehydrogenation performances for waste cooking oil (WCO) upgraded into organic liquid products (OLPs). Acid treated kaolin (ATK) exhibited high yield of 74.4% and high quality liquid products with high oxygen removal of 93.8% and low aromatic contents of 22.5%. The reference catalyst, a commercial petroleum catalyst (CC) could eliminate the most of oxygen (90.8%) but produced too many unexpected aromatics (55.8%). The density of weak Lewis acids was related to the deoxygenation capability. The density of Bronsted acids contributed to hydrogen transfer reactions. The total amount of Bronsted acids was correlated to cracking capability. The cracking by CC primarily followed carbonium ion reaction mechanism, whereas those by the kaolin-based catalysts complied more with free radical reaction mechanism. The deoxygenation active sites were characterized by CH 3 COOH-TPD for the first time. [ABSTRACT FROM AUTHOR]

Abstract The paper examines the proposed approach of using T-matrix model to convert dynamic moduli (Young's modulus and Poisson's ratio) determined by sonic well logging to values equivalent to values of static moduli (called effective moduli). The chosen approach is particularly suitable for rock masses consisting of solid rocks with irregular local cracking. The proposed approach is based on the fact that for intact rock with Young's modulus values on the order of several tens of GPa and strength σ c on the order of several tens of MPa, the values of static and dynamic moduli are equivalent. Any fractures in the rock will cause the elastic behaviour to cease being linear and a difference will appear between the values of static and dynamic moduli. It is possible to approximate this difference using the T-matrix model. The starting point for creating a T-matrix model is a simplified layered geological model of a borehole profile. Added to this are values of static moduli determined by a uniaxial compression test on representative samples of the borehole core. Additional input data for calculating the T-matrix model include porosity determined from well logging measurements, and the presence of cracks as interpreted from an acoustic scan of the borehole wall. The given approach is demonstrated in the experimental measurement of a borehole in Silurian limestone. The procedure was verified by comparing the calculated effective moduli with values of static moduli, measured on control samples prepared from borehole core outside the collection intervals of samples used as input for calculation of the T-matrix model. This comparison showed that for majority of samples there was a decrease in the difference from nearly 40% (dynamic moduli) to under 10% (effective moduli). Highlights • Use of a T-matrix model made it possible to approximate static moduli from dynamic moduli. • The curves calculated by the model are significantly more detailed than the original well logging. • The calculated effective values can be used for calculations instead of the static values. [ABSTRACT FROM AUTHOR]

Highlights • Large number of scenarios (10) shows impact of various practical variations. • Broad bandwidth of production cost; choice of vegetable oil being the most decisive. • Power-to-gas adds 26–34% to costs compared to conventional hydrogen provision. • High cracking rate for jet leads to high production of low-value hydrocarbons. • Diesel-mode is 30% cheaper than jet-mode. Abstract A techno-economic assessment of a novel biorefinery concept is carried out. It combines the hydrotreatment of vegetable oils (HEFA) with a power-to-gas (PTG) unit that provides the required hydrogen. Several scenarios are examined: the electricity supply for the PTG unit is varied from a grid-based supply to a renewable island solution; the hydrogen supply is varied from a PTG unit to conventional steam reforming; the utilised vegetable oil is varied from jatropha to rapeseed, palm and used cooking oil; the main product is varied from jet fuel to diesel. The HEFA-plant is assumed to process 500 kt of vegetable oil annually. In the reference scenario, jatropha oil is used as feedstock producing 227 kt a−1 of jet fuel. Per ton of processed oil, 1910 kWh el are used to produce 35.7 kg of hydrogen required for its treatment. By using different vegetable oils, both hydrogen demand and fuel output vary in a range of about ±10%. The overall energetic efficiency towards jet fuel is 41.6%. With a bandwidth between 1295 and 1800 EUR t−1 of jet fuel, the specific production costs are three to four times higher than the market price for fossil jet fuel. Operating the refinery in diesel-mode could lower the production costs by ca. 30%. More high-value, long-chained fuels are produced this way due to a lower cracking rate compared to the jet-mode. Investments of around 132 million EUR are required for the HEFA-plant in all scenarios. Investments for the PTG-plant lie around 82 million EUR if there is a constant electricity supply from the grid. They reach 246 million EUR if electricity is supplied in an island-solution based on fluctuating renewables demanding much higher hydrogen production and storage capacities. Total investments in the biorefinery reach 378 million EUR in this case. Despite high capital costs, the largest cost item is vegetable oil – similarly to a conventional HEFA plant. Supporting policy instruments such as subsidies or quotas for renewable jet fuel seem indispensable for an introduction of the PTG-HEFA technology in the short to medium term. [ABSTRACT FROM AUTHOR]

A new approach to improve the gasification process was studied through the development of an automatic shaking grate mechanism in a single stage downdraft gasifier. Tar and ash build-up are problems commonly encountered during the gasification process. This study was conducted to mechanically induce tar cracking, to prevent blockages of biomass materials at the hopper as well as to ease the removal of ashes during the gasification process. It applies the principle of increasing the effective area for tar cracking at elevated temperatures to improve the amount of combustible producer gas as well as the conditions for thermal tar cracking. Experiments were done at varying air flow rates to evaluate different gasification parameters in comparison to conventional downdraft gasifier. The study resulted to 74% reduction in tar content, 30% improvement in high heating value and 27% increase in efficiency compared to the conventional downdraft gasification at 160 Lpm air flow rate. [ABSTRACT FROM AUTHOR]

It is important to develop new promoters of fluid catalytic cracking (FCC) catalyst to increase iso-paraffin yield and avoid the decrease of research octane number (RON) caused by olefin saturation in gasoline hydrofining. SAPO-11 and LaAPO-11 molecular sieves were used as promoters to FCC catalyst to increase gasoline RON and were tested in the cracking reaction of n-dodecane on FCC conditions. LaAPO-11 molecular sieve has less and weaker acidity than SAPO-11 molecular sieve. LaAPO-11’s metallic sites polarize the C H bonds to form carbenium ions for isomerization reaction and weak acid sites make less contributions to the cracking of iso-paraffin. LaAPO-11 promoter increases the yield of iso-paraffin (C 5-9 ) from 6.4% to 10.2%. Besides that, a high yield of arene (2.0%) is caused by the dehydrogenation activity of LaAPO-11 promoter. The new contributions of this paper are the synthesis of a hydrothermal stable LaAPO-11 molecular sieve with isomerization activity and proposing the reaction routes of iso-paraffin. These new contributions are important for developing more effective RON promoters of FCC catalyst. [ABSTRACT FROM AUTHOR]

Currently, the manual method using hand-held infrared temperature measurement instruments for measuring temperatures on the external surfaces of ethylene cracking furnace tubes is highly subjective and is affected by a number of prominent issues, such as the high temperature working environments, which leads to low efficiency and poor measurement accuracy. Hence, an automatic temperature measurement system based on infrared light is designed and realized. In the system, a dual-phase drive synchronization method is proposed to rotate the thermodetector during horizontal movements, thus realizing automatic batch temperature measurements of the furnace tubes. Moreover, a temperature processing algorithm is developed to automatically identify furnace wall and tube surface temperatures, filter out abnormal temperatures and select only high-quality temperature measurements prior to calculating the final result. Real temperature measurement experiments demonstrated that the dual-phase drive temperature measurement system and temperature processing method are effective and efficient. Compared with the traditional manual way, temperatures obtained using the proposed system are more stable and accurate. [ABSTRACT FROM AUTHOR]

A thermal cracking experimental equipment of hydrocarbon fuels was built to study n-heptane pyrolysis and the effect of reaction conditions on this reaction process. The main species were measured and the change rules were analyzed on the range of temperature 873–1073 K and pressure 0.1–3.5 MPa. The total content of alkenes products was more than alkanes on this pyrolysis process. Compared to alkenes with same number carbons, the alkanes were more easy to decompose with temperature but more conducive to formation with pressure increasing. The content of ethylene is usually the most on above reaction conditions, but its descent is also the fastest with pressure increasing. A mechanism model of n-heptane pyrolysis (44 species and 166 reactions) was constructed and validated by experiments on different conditions. Compared with n-heptane oxidation detailed model of Version 3.1 from Lawrence Livermore National Laboratory (LLNL), the pyrolysis model present a better accordant with experiment results on a range of temperature and pressure. The kinetic reaction of n-heptane pyrolysis was analyzed with present pyrolysis model, and the pyrolysis reaction pathway for the main products was obtained. The formation of alkenes are mainly through C C bond dissociation reaction, especiallyβ-C dissociation, and small alkanes are formed mainly by radical metathetical or synthesis reaction, the former are endothermic reactions, but the latter are mostly exothermal reactions. The properties of some main reactions have a critical role for the change of product content with temperature and pressure, which is the main reason for the variety of products selectivity under different conditions. Pressure increased the pyrolysis residence time and mass density but it does not significantly affect the reaction energy, so its contribution to conversion rate of fuels thermal cracking is limited, although it changes the reaction pathway greatly. However, the temperature can increase obviously the reaction activation energy, even though the residence time and concentration is decreased, the conversion rate of n-heptane pyrolysis still increased. [ABSTRACT FROM AUTHOR]

The present manuscript reviews state-of-the art models of hydrogen-assisted cracking (HAC) with potential for application to remaining life prediction of oil and gas components susceptible to various forms of hydrogen embrittlement (HE), namely, hydrogen-induced cracking (HIC), sulfide stress cracking (SSC), and HE-controlled stress corrosion cracking (SCC). Existing continuum models are compared in terms of their ability to predict the threshold stress intensity factor and crack growth rate accounting for the complex couplings between hydrogen transport and accumulation at the fracture process zone, local embrittlement, and subsequent fracture. Emerging multiscale approaches are also discussed, and studies relative to HE in metals and especially steels are presented. Finally, the challenges that hinder the application of existing models to component integrity assessment and remaining life prediction are discussed with respect to identification of model parameters and limitations of the fracture similitude, which paves the way to new directions for further research. [ABSTRACT FROM AUTHOR]

Internal pores and fractures inside oil shale undergo complex changes during pyrolysis in superheated steam. After a simulated in-situ pyrolysis in superheated steam, the pore characteristics of 30 oil shale samples from different zones between the injection and production wells were investigated using mercury intrusion porosimetry (MIP). The results showed that the porosity of oil shale exceeded 27.65% in each position of horizontal fractures. In different types of pores, the proportions of mesopore (0.1 µm < d ≤ 1 µm) and micropore (d ≤ 0.015 µm) were the largest and the smallest, respectively. Moreover, mesopores outnumbered micropores. The pore structure of pyrolyzed oil shale after convection heating was complex. After the pyrolysis in superheated steam, the proportion of the oil shale ore body with a porosity ranging from 23 to 31% was 74.95% of total. This finding proved that oil shale was transformed from dense rock to a porous medium under the effect of superheated steam. [ABSTRACT FROM AUTHOR]

Acidic bentonite clay was obtained through surface modification of bentonite clay using hydrochloric acid as acidic precursor to increase the acidity of the bentonite. The modified catalyst was examined via X-ray fluorescence (XRF), XRD analysis, Brunauer Emmett and Teller surface area (BET), FTIR analysis and temperature-programmed desorption (TPD) analysis. XRF analysis showed that the acid modification of bentonite clay results in an increase in the silica content and lower abundance of metal oxides, due to the dissolve of Fe 2 O 3 , MnO, CaO, Na 2 O. Ca 2+ , Na + cations from the interlayer and octahedral sheets. FTIR spectroscopy showed that the acid activation decreased the intensity of the absorption bands at 915, 875 and 836 cm −1 which arise from the binding modes of OH groups. NH 3 -TPD analysis showed a considerable increase in the moderate and strong Bronosted acid cites on the modified bentonite compared to the native clay. The modified bentonite was evaluated as economic and efficient heterogeneous catalyst in catalytic cracking process of two nonedible vegetable oils to obtain the corresponding biofuels at moderate processing temperature of 250–280 °C. It was observed that the catalytic conversion was preceded under mild temperature and obtained efficient biofuels with approved physical and fuel properties according to ASTM specifications. The role of the catalyst ratio was considerable on the yield percent and the properties of the obtained biofuels. The catalytic activity-reaction mechanism was discussed based on NH 3 -TPD analysis. [ABSTRACT FROM AUTHOR]

We determine the chemical changes associated with viscosity reduction when heavy oil is cracked in subcritical water. The viscosity reduction has a temperature threshold for onset of 290 °C-this suggests an enhanced acid cracking regime associated with the maximisation of water dissociation at these conditions aided by the already increased solubility. The mean molecular weight is reduced by nearly 50%. Oxygen and sulphur are reduced by about half of this-either by expelled gas effluent (H2S) or by conversion into mono-aromatic base sulphur-containing structures. The amount of lower branched paraffins is increased. [ABSTRACT FROM AUTHOR]

Nowadays, the time is coming for development of oil deposits with the so-called hard-to-recover reserves (HRR). Particularly relevant and important at this time are the fundamental issues of the formation of hydrocarbon deposits. To understand how the most cost-effective way to extract heavy oil from clay-bituminous sediments, it is necessary to know the nature of the process of the formation of hydrocarbons. In the present work, experimental studies confirming the influence of electromagnetic fields on the change in the fractional composition of oil and fraction of heavy naphthenic hydrocarbon fractions are considered, as well as examples of natural phenomena that could affect the rapid, jumping formation of light oil deposits by changing the electromagnetic field of our planet. The object of research is the change in the fractional composition of oil under the influence of an electromagnetic field of frequency 50 Hz and magnetic induction of about 0, 81 T, as the subject of research is oil Bazhenov horizon, which according to many scientists is oil generating in Western Siberia. The purpose of the study was to evaluate the change in heavy oil fractions under the influence of an electromagnetic field. [ABSTRACT FROM AUTHOR]

The article presents the results of processing heavy oil residues initiated by atmospheric oxygen. We found that the introduction of a small amount of atmospheric oxygen (2–6%) in the thermo cracking reactor (thermo-oxidative cracking) significantly increases the yields of light fractions. E.g. A thermo cracking of vacuum residue (visbreacking) with the air supply to the soaker camera gives twice more light fractions than traditional visbreacking process (36% of petrol and diesel fractions compared to 10–15% in conventional process). Thermo-oxidative cracking of atmospheric residue gives up to 60% of light fractions. In order to obtain a mathematical description of the process needed for its subsequent industrial implementation we conducted experiments on thermo-oxidative cracking of atmospheric and vacuum residues in a continuous flow reactor with a wide variation of the process parameters. Based on the analysis of the experimental data a common scheme for thermo-oxidative cracking, a mathematical model of the process and its parameters were established. The model adequately describes all the experimental data obtained in the temperature range 430–460 °C, pressure 2–8 atm, retention times 4–33 min and relations oxygen/raw material 0,9–2,5 % wt. Industrial implementation of thermo-oxidative cracking needed just minimal modification of the existing thermal installations through the organization of air supply in the soaker chamber. This modification will increase the output of light fractions in the thermal processing heavy oil residues in 2–3 times with minimal capital investments. [ABSTRACT FROM AUTHOR]

‘Chemical Looping Combustion’ (CLC) is an emerging clean combustion technology which offers an efficient route for fossil fuel combustion with inherent CO 2 capture. Beyond combustion, chemical looping is also applicable to selective oxidation of fuels to synthesis gas or olefins. In all these applications, the main advantage of chemical looping lies in the inherent air separation, which allows conversion of the fuel without nitrogen dilution. In the present work, we extend this inherent separation principle to separation of the product stream by demonstrating the formation of fully separated syngas streams from methane, i.e. the production of separate, high-purity CO and H 2 streams via (non-oxidative) methane cracking. CH 4 is first cracked catalytically over Ni, producing gaseous H 2 and solid carbon. The carrier is then periodically regenerated by burning off the carbon using CO 2 as oxidant, thus enabling the reduction of CO 2 to CO. Importantly, the Ni carrier is never oxidized during this cycle and hence acts as a “carbon carrier” rather than as an oxygen carrier as typical in chemical looping processes to-date. Autothermal process configurations are discussed, which allow reconciling the use of abundant natural gas reserves with the demand for clean, carbon-free energy production. [ABSTRACT FROM AUTHOR]

This study examined the effects of microwave (MW) and ultrasonic (US) waves on an heavy crude oil sample from a reservoir in southwest Iran. The waves irradiated the sample from two to 10 min at two-minute steps. MW caused the temperature of the crude-oil sample to rise by selective heating of polar components and creation of hot zones; under US, heating was accompanied by a cavitation effect. MW at 2 and 4 min reduced the sample’s viscosity by inducing hot zones. At 2 min, the viscosity declined 16% due to cracking of heavy components such as asphaltenes, which have a higher capacity to absorb MW. As the radiation time increased after 4 min, the viscosity increased because light components escaped from the sample. However, US reduced the viscosity of the heavy crude oil sample at all time durations. The greatest reduction of viscosity was around 19%, at 4 min. The viscosity increased with irradiation time and then remained constant. Ultrasonic waves altered the viscosity by creating bubbles, which disintegrated the resin intermolecular bonds and cracked the large molecular particles of the asphaltene. The reduction in sulfur content under US was much greater than under MW. At all time durations, sulfur content fell as radiation time increased. Due to its high potential to absorb MW, creates active sulfur that can be emitted from the crude oil as sulfide and hydrogen sulfide, with the sulfur level falling to 0.39%. Furthermore, US waves also reduced sulfur content to around 0.46% as the asphaltene flocks disintegrated. Reduction of sulfur content from asphaltene agglomerates under MW and US was observed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). In addition to reducing the effect of sulfur by affecting its nitrogen and oxygen elements, irradiation also reduced the polarity of the asphaltene particles and prevented reaggregation of cracked particles. Results of SARA (saturation, aromatic, resin and asphaltene) analysis showed that asphaltene particles have a higher capacity to absorb MW than resin components, as after the amount of asphaltene components declined in the early stages of irradiation, resin components began to change, falling to 34% at 10 min. The decrease in asphaltene content in samples under US was more evident, reaching 34% at 8 min. According to Fourier transform infrared (FTIR) spectra results, MW irradiation caused cracking of large-chain molecules and drove light components from heavy crude sample. These two phenomena are a function of radiation time. The rate of cracking of heavy components was continuously greater than the rate of light components leaving the sample at early time intervals; ultimately, this resulted in an upgraded heavy oil. In some cases, despite cracking of large-chain molecules and creation of light components, the output values of light components were higher. Under US, the cracking of large-chain molecules occurred, but due to the departure of heavy components from the crude oil, peak intensities increased and the resulting crude oil had purer components. [ABSTRACT FROM AUTHOR]

Particle agglomeration can occur in heavy oil upgrading hydroprocessors due to the formation of carbonaceous mesophase, a secondary liquid phase which results from an increased rate of thermal cracking relative to the hydrogenation rate. A cold-flow slurry bubble column operated at atmospheric pressure with an internal diameter of 0.152 m was used to examine particle agglomeration behavior and the overall fluid dynamics in a gas-liquid-liquid-solid system. The experimental system consisted of biodiesel (organic continuous phase), aqueous glycerol solutions (immiscible secondary phase), glass beads and nitrogen. The impacts of the secondary liquid loading, secondary liquid viscosity, and particle diameter on the fluid dynamics were established. Particle agglomeration was studied by measuring the axial solid holdup profiles while varying the superficial gas velocity and secondary liquid loading. Enhanced particle agglomeration was observed when increasing the secondary liquid loading, based on the increased solid holdups at the bottom of the column. Three sparger designs (six-legged spider sparger, perforated plate and conical perforate plate) were compared. Following the glycerol addition, the spider sparger was less effective based on the particle sedimentation at lower liquid/solid ratios when compared to the other sparger designs. A Revolution Powder Analyzer (RPA) was also used for complementary measurements to examine whether operational difficulties due to particle agglomeration can be anticipated using a simplified system. [ABSTRACT FROM AUTHOR]