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[Display omitted] • Real time monitoring of magnesite formation at 90 °C by Raman spectroscopy. • Hydromagnesite and eitelite as main transient phases prior to magnesite formation. • Counterions and competitive divalent cations play a significant role. The production of engineered magnesite (MgCO 3) under mild conditions remains an important fundamental challenge in order to store permanently the industrial captured CO 2. Because, the magnesite is the more-known-stable carbonate at the Earth surface conditions and it is ready-to-use as profitable construction materials. In the present study, time-resolved Raman spectroscopy experiments have been conducted to characterize magnesite formation from nesquehonite slurry at 90 °C in an ionic carbonate alkaline medium (CO 3 2–/HCO 3 – close to 1) using four different soluble Mg salts (acetate, sulphate, nitrate and chloride of magnesium). The investigated experimental conditions have revealed that only nesquehonite (MgCO 3 ·3H 2 O) via un amorphous phase transformation is produced at room temperature. However, magnesite was systematically formed from nesquehonite slurry when temperature increase to 90 °C (heat-ageing step). Here, hydromagnesite (Mg 5 (CO 3) 4 (OH) 2 ·4H 2 O) and eitelite (Na 2 Mg(CO 3) 2) with long lifetimes were the main characterized transient phases prior to magnesite formation depending of the counterions. Moreover, eitelite rare mineral has not been reported as transient phase during magnesite formation. In summary, the imposed carbonate concentration, carbonate speciation, counterions, competitive divalent cations and pH have played a critical role on the magnesite formation at 90 °C. The discovered experimental mild conditions are promising; however, 2–3 days were required in single Mg system, except when dissolved calcium is added (Ca/Mg≈0.15) in the chloride counterion system; for such case only one hour is required to produce Ca-magnesite and protodolomite at 90 °C, i.e., the production of anhydrous Mg-Ca carbonates phases in very reduced time. In this latter case, the monohydrocalcite (CaCO 3 ·H 2 O) and the nesquehonite precursors produced at room temperature were rapidly transformed via concurrent dissolution into Ca-magnesite (Ca x Mg 1-x CO 3) and protodolomite (Ca 0.5 Mg 0.5 CO 3). In conclusion, these novel insights are relevant for fundamental (direct monitoring of multi-nucleation events in complex ionic and/or slurries systems) and applied (permanent storage of CO 2) research on the formation of anhydrous Mg carbonates (e.g., magnesite and dolomite) debated in the last two centuries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Model based design of a novel polymerization process is performed. • The process is applicable to solution and slurry polymerization with phase change. • The process can efficiently control product properties and reactor heat load. • Cooled evaporation streams affect concentration gradients and heat transfer rates. • The feature of ethylene/1-octene copolymerization system is studied as an example. This work aims on developing a novel process that is applicable to solution and slurry polymerization, which can efficiently control production efficiency, product properties and reactor thermal load through changing the flow ratios of cooled evaporation streams between different reactors. Furthermore, various process routes can be created by varying the destinations of cooled evaporation streams, markedly enhancing the process flexibility. To provide a thorough insight into the characteristics of the developed process, numerical simulations based on coupling the constructed models of polymerization reaction kinetics, thermodynamic properties and reactors are conducted to comprehensively study the impact of various factors (e.g. , process routes, pressure, monomer and catalyst concentration, flow rates of cooled evaporation streams in different reactors) on the ethylene/1-octene solution copolymerization system with several stirred reactors connected in series. Some strategies for regulating production efficiency, product properties and reactor heat load of different process routes are obtained. [ABSTRACT FROM AUTHOR]

• Flow characteristics of erythritol slurry was experimentally investigated. • Linear regression analysis was used for the flow pattern determination. • Effect of gravity on rheological characteristics of the slurry were examined. • Erythritol slurry can be treated as a power law fluid in homogeneous flow. • Non-Newtonian behavior became greater in horizontal flow than in vertical flow. Erythritol slurry has shown great potential as a heat transport medium. We investigated the versatility of the flow pattern determination method and the effect of gravity on the rheological characteristics of erythritol slurry, with a focus on homogeneous flow. In vertical flow, the flow pattern was always homogeneous, whereas in horizontal flow, it depended on the flow velocity. Thus, the plots obtained from the horizontal flow were divided into two parts using linear regression analysis, and the discussion focused on the homogeneous part, which is the high-velocity region. Erythritol slurry behaved as a power law fluid in a homogeneous flow, regardless of the flow direction. However, the viscosity indices differed in the vertical and horizontal flows. The non-Newtonian behavior became more pronounced in the horizontal flow than in vertical flow. These findings may be valuable for the design and optimization of heat transport systems that use high-density PCM slurry. [ABSTRACT FROM AUTHOR]

• Heterogeneous slurry flows in inclined pipes. • Pressure drop prediction. • Turbulent particle diffusivity correlation. • Static and moving bed predictions. • Concentration profiles predicted. A modified three-layer model for solid-liquid flow in inclined pipes is developed, which overcomes the limitations of previous mechanistic models. The steady-state model predicts the pressure loss, critical velocity, concentration profile in the heterogeneous layer, mean heterogeneous layer and moving bed layer velocities, and bed layer heights for each set of parameters. We propose a new correlation for the turbulent solids diffusivity, and include appropriate closures for forces and stresses attributed to the solids and liquid phases in the different layers. The proposed turbulent solids diffusivity correlation and the steady-state model predictions show a good agreement with experimentally measured results in the literature: for concentration profiles in the heterogeneous layer, pressure losses and critical (deposition) velocity, both over a wide range of parameters and for different regimes. We also define a critical Péclet number based on which, a transition boundary between bed-load and heterogeneous regimes can be found. This boundary implicitly represents the critical velocity. In turbulent flow, the pressure loss vs mean velocity curve shows a characteristic minimum just before the critical velocity is attained, in agreement with published research. [ABSTRACT FROM AUTHOR]

Highlights • Developed and validated the CFD model of a bubble column with vertical internals. • The importance of fluctuations in the gas flow rate in the impulse tracer method. • The presence of internals reduced the gas dispersion. • The presence of internals increased liquid mixing time. • Liquid mixing time affected by the tracer injection position. Abstract Bubble columns are widely equipped with vertical internals for heat removal in slurry/bubble column reactors or providing the light source in photobioreactors. Understanding the effect of internals on the hydrodynamics of a bubble column reactor is crucial for the reactor design and scale-up. The gas dispersion and liquid mixing are two important parameters in design of bubble columns. In this study, the Eulerian-Eulerian simulation coupled with the population balance model was developed for the bubble column with dense vertical internals. The impulse tracer injection was applied to study the gas dispersion. The effect of the gas flow fluctuations, the time span of tracer injection, and the presence of internals was assessed at different superficial gas velocities. The results showed that the presence of internals has a notable effect on gas behavior. A stronger gas velocity gradient with less turbulence and dispersion were observed in the presence of internals. To study the liquid mixing, the tracer technique was applied, and the sensitivity of results to the tracer injection and detector points have been discussed. The presence of internals reduced the fluctuating liquid velocities, which led to a lower mixing performance in the bubble column. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Explores rheology of very high ionic strength and polydispersed slurries. • Develops a Cross rheological model inclusive of yield stress. • Demonstrates that radiological waste follows traditional rheology with adjustments. Abstract This article evaluates the slurry viscosity of radioactive waste. Hanford waste is a motley mixture of particle sizes and densities composed of metal and oxide particles with constituents spanning much of the periodic table stored at high ionic strength and high pH. Hanford wastes have traditionally been represented as simply an ideal Bingham plastic, but this rheological approximation often provides a poor fit from 0 to 200 1/s, precisely the range of interest for engineering design of waste transport and mixing systems. A modified Cross formulation inclusive of a yield stress is used to fit stress-strain rate data for reconstituted Hanford REDOX sludge waste, measured by increasing shear-rate (up-ramp) and decreasing shear-rate (down-ramp) sweeps. This continuous single equation formulation quantitatively matches experimental data better than other rheological models including the Bingham plastic and Herschel-Bulkley approximations. The increase of viscosity and yield stress from up ramp to down ramp suggests the formation of particle microstructure during shear due to attractive forces. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu-tartrate precursor for the Cu-CNF adsorbent is synthesized in a CFI. • First-time adsorptive desulfurization of thiophene using Cu-CNF slurry in CFI. • Recycling increases adsorption efficiency as well as reduces the numbers of CFI unit. • Adsorption loading is measured to be 103 mg-S/g at 2000 ppmw-S thiophene. • CFI can potentially replace packed bed desulfurization adsorbers. This study presents an alternative to adsorptive desulphurization (ADS) process in packed beds by making use of enhanced radial mixing prevalent in coiled flow inverter (CFI). We describe the synthesis of Cu-tartrate as the precursor for Cu-carbon nanofiber (Cu-CNF) and the application thereof in ADS of liquid fuels in a CFI. Thiophene was removed from n-hexane using a slurry of Cu-CNF in the liquid. The data show the sulfur (S) - loading of 103 mg/g in Cu-CNF at 2000 ppmw-S concentration of thiophene in the liquid at 120 cc/min flowrate using five CFI units connected in series. Recycling was introduced for the first time in CFI, and three CFI units connected in series with the recycle ratio of 2 were sufficient to achieve the same removal efficiency as with five CFI without recycling. The results indicate that CFI is an efficient technology and has potential to replace packed bed adsorbers. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dual control system maintains consistent, reliable heating and atomization. • Hot steam/cold slurry instabilities necessitate continuous controller adjustments. • Controllers operate simultaneously and independently but are linked by process physics. • Slurry pressure and droplet size kept constant during 100x slurry viscosity increase. We introduce proportional integral derivative (PID) controls into transonic pulsatile steam-assisted non-Newtonian slurry heating and disintegration. The purpose is to ensure consistent, reliable atomization during generic process upset scenarios, while this implementation involves a sudden pronounced slurry property shift. The uniquely interrelated physical responses of phase interfacial atomizer instabilities require continuously coupled PID controllers, the first of which automates slurry flow based on slurry pressure drop. The second compensates for the variable phase momentum ratio and sets a new heating steam flow based on the targeted droplet size. Three tests with increasing rigor were conducted to demonstrate successful coupled controller adaptability. During controller compensations, slurry and steam flows were significantly altered and drastically changed atomization characteristics. For a 100-fold increase in slurry viscosity, however, the controllers successfully maintained consistent droplet size and slurry flow resistance. The control methodology was shown to be mesh-independent and to operate across multiple atomization regimes. [ABSTRACT FROM AUTHOR]

• m-ARFRs were developed for controllable preparation of FPSQs continuously. • The geometric structure and operating parameters were optimized through CFD simulations. • Taylor vortices in optimized m-ARFRs provides ideal flow and shear conditions. • The particle size and morphology can be flexibly tuned. • m-ARFRs exhibited long-term operation stability for slurry flow. A novel microreaction system based on a miniaturized annular rotating flow reactor (m-ARFR) was developed for the continuous preparation of functionalized polysilsesquioxanes (FPSQs). Compared to conventional batch processes, this new method enables accurate control and flexible adjustment of particle size and morphology of the prepared microspheres. The geometric structure and rotating speed were optimized through CFD simulations and energy analysis. In the optimized m-ARFRs, uniform shear stress and low back-mixing enable the controllable distribution of functional groups and stable slurry flow. By utilizing the flexibility of geometric design, we prepared uniformly functionalized PSQs (FPSQs-NH 2) and surface-functionalized PSQs (PAPSQ@PMSQs). During hourly-level operation of m-ARFRs, the yield of microspheres remained at approximately 90% while maintaining a low internal pressure drop of less than 3 kPa, demonstrating the long-term operating stability of the system. [ABSTRACT FROM AUTHOR]

• A modeling scheme for flows in conveying section of co-rotating twin screw was proposed. • A main application is to design continuous mixing and dispersion for lithium-ion battery slurries. • The scheme was established on the energy-dissipation based flow quantification. • Screw characteristics of fully-filled and narrow pitched conveying element was predicted in a consistent way for various non-Newtonian fluids. In the present work, we propose a new modeling scheme for flows of non-Newtonian fluids in the fully filled narrow-pitched conveying section in a co-rotating twin screw extruder, emphasizing the application to viscoplastic lithium-ion battery slurries for electrode manufacturing. A predictive tool for the relationship between flow rate, screw speed, and pressure build-up was presented for flows with a general class of inelastic non-Newtonian fluids. By introducing the effective viscosity and effective shear rate based on the energy dissipation rate, we showed that the conventional relationship between throughput number and pressure number for various non-Newtonian fluids collapse into a single master curve of a Newtonian fluid, from which the predictive relationship between flow rate, screw speed, and pressure build-up was established. The method was validated numerically with power-law fluids, a Carreau fluid, and a Herschel-Bulkley fluid (anode slurries) for a narrow-pitched conveying element module. [ABSTRACT FROM AUTHOR]

• Line-averaged three-phase holdups were measured using a new hybrid method. • An increase in solid loadings decreases the line-averaged and the gas holdup. • The line-averaged solid holdup is not uniform along the column height. • The SBCR's bottom has greater line-averaged solid holdup concentrations. A new hybrid measurement technique was developed and employed to study line-averaged three-phase holdup distribution in a Slurry Bubble Column Reactor (SBCR) using gamma-ray densitometry (GRD) and point optical fiber probe (OFP) techniques. The OFP technique was used to measure the local gas holdup at 45 nodes in the cross-section area of the SBCR at three different axial levels. Thus, the GRD technique measured the spectrum of the SBCR for two different orientations simultaneously with the OFP technique at the same operating conditions to determine the solid holdup distribution radially and axially. The line-averaged solid holdup for 25% solids loading on the higher measurement level at the column's center decreased compared to the lower level by 45.7%, 43.6%, and 41.7% using superficial gas velocities 0.2, 0.3, and 0.4 m/s, respectively. These results are highly remarkable as it often assumed that the solids exhibit a uniform distribution inside the slurry phase. [ABSTRACT FROM AUTHOR]

Formation of gas hydrates in systems with high water content is one of the major challenges facing the petroleum industry today. Conventional mitigation using thermodynamic inhibitors is expensive due to large water volumes, while the most recent flow management strategies (anti-agglomerants, cold flow, etc.) have not yet been adopted because the dynamics of hydrate slurry are insufficiently understood. The present contribution examines a flow of gas, hydrates and water using computational fluid dynamics (CFD). The model couples the effective viscosity of gas-water slurry with the average size of hydrate agglomerates and the adhesive force that binds them. The model was validated against experimental pressure drop, demonstrating tolerable discrepancies. According to the simulations, onset of hydrate plugging is most probably related to the formation of a viscous bed at the gas-slurry interphase at hydrate concentrations slightly above 15%. A simplified theoretical approach is proposed for engineering estimates of pressure drop in the hydrate slurry pipes. [ABSTRACT FROM AUTHOR]

A theoretical model for predicting the suspension stability of slurry Taylor flow is presented. Force balance analysis is conducted on a particle that moves downward along the leading meniscus of a Taylor bubble towards the thin liquid film between the bubble and the channel wall. The concept of maximum resistance force is proposed for calculating critical values of capillary number, particle size and density, and contact angle that determine whether solid particles stay suspended in the same liquid slug or fall through the thin liquid film and travel among different liquid slugs. It was found that the deformation of bubble surface enforced by the particle motion appeared independent of the particle material that has rough surface. The maximum capillary force decreased as the capillary number increased, but increased faster than the downward drag force as the particle size increased. A particle with relatively more hydrophobic surface was more prone to fall into the liquid film. It was implied that devices of Taylor flow might be applied to achieve particle selection based on particle size, density and surface hydrophobicity. The model proves capable of accurately predicting the suspension stability of slurry Taylor flow for the design and operation of industrial chemical reaction processes. [ABSTRACT FROM AUTHOR]

Dense three-phase slurry flows are important in several industrial processes (e.g., Methanol/ DME synthesis, Fischer Tropsch synthesis). In the present work, gas–liquid–solid flow in a pseudo 3D slurry bubble column is characterized under dense flow conditions for superficial gas velocity ( U G ) of 5–30 cm s - 1 and overall solid loading ( α S ) of 0–40 vol.%. In-house developed voidage probes were used to measure local gas volume fraction fluctuations. The high frequency fluctuations (∼1–10 Hz) caused by individual bubbles or swarms of bubbles were found to increase with increase in α S and U G . The low frequency oscillations (∼< 1 Hz) corresponding to column-scale recirculating flow were found to decrease with increase in α S . Importantly, time-averaged gas volume fraction and its internal composition (i.e. gas volume fraction contained in different bubble size groups) and bubble size distribution were measured at different locations in the slurry bubble column. With an increase in α S , local gas volume fraction was found to decrease, accompanied by an increase in bubble size. Based on the distribution of bubble chord lengths, the gas volume fraction contained in different bubble size groups was measured for different α S and U G . With increase in α S , the gas volume fraction for small bubbles was found to decrease while that for large bubbles was found to increase. Under the dense flow conditions (at high U G and α S ), while small bubbles were found to accumulate near the column walls, as indicated by the wall peaking in α ‾ G profiles, large bubbles/gas slugs were found to flow predominantly through the column center. In addition to the new experimental data, the present work helps to improve the understanding of dense slurry flows that will aid the development and verification of Eulerian multiphase models. [ABSTRACT FROM AUTHOR]

[Display omitted] • CO 2 hydrate slurry stability is improved with AOT. • AOT helps reducing the viscosity of CO 2 hydrate slurry. • Effects of AOT are close to the effects of a stirred tank. • A shear-thinning behaviour of CO 2 hydrate slurries + AOT is observed. Recent studies have shown real potential for using hydrate slurries as a secondary fluid in indirect refrigeration systems. However, pipeline clogging problems can appear due to hydrate agglomeration. Additives are generally used to counteract these problems. In this study, rheological properties of CO 2 hydrate slurries in the presence of an additive Dioctyl sodium sulfosuccinate (AOT) are investigated. The capillary viscometer method is used to determine the fluid behaviour and the AOT impact on the slurry rheology. A dynamic loop is set up to collect experimental pressure drop and volume flow rate data. Based on the Rabinowitch and Mooney approach and Herschel-Bulkley model to determine the rheological properties, a shear-thinning behaviour was observed. The importance of the behaviour index choice in the procedure is discussed. Finally, the results obtained with AOT are compared with pre-existing studies. The present study highlights the AOT potential to significantly improve the CO 2 hydrate slurries properties. [ABSTRACT FROM AUTHOR]

Heterogenous photocatalysis has been paid much attention in the last decades since it can utilize clean and abundant sunlight energy to drive reaction systems for cleaner productions and environmental protections. Those applications are usually conducted by multiphase reactors to make immobilized or dispersed solid photocatalyst in contact with reactants involved in gas (G) or liquid (L) single phase, otherwise in GL-multiphase medium. Such GS/LS/GLS multiphase microreactors have intrinsic advantage of high specific surface area leading to high mass transport in liquid/gas bulk or through interface. This study at first provided a set of general references on fundamentals of such reactors, and subsequently review on the state of the art researches highlighting engineering efforts to intensify the merits of multiphase photocatalytic microreactors. It was also shown that one of recent trends was to use photocatalyst slurry in millimeter/centimeter scale reactors rather than in microreactors to combine advantages of high surface area, sufficient illumination and high-throughput without clogging, even by leaving the issue of catalyst recovery aside. The intensification of photocatalytic processes in such mini-size reactors was also discussed. [ABSTRACT FROM AUTHOR]

In recent years, the concept of flow sheet simulation of fluid processes has been extended to the dynamic performance of solids handling by considering the particle size distribution as one relevant material property. Continuous centrifugation is widely used throughout the process industry and applied to separate finely dispersed particles from a liquid phase. Current process simulation tools for calculation of separation in decanter centrifuges are limited to steady-state conditions and are currently not applicable for real time simulations. This work illustrates the basic framework of a new dynamic flow sheet approach to predict the clarification process of stabilized particles in decanter centrifuges. The solids residence time distribution describes the transient behavior of a lab decanter centrifuge. This allows the simulation of the complex process behavior with small numerical effort. In the presented approach, the number of related compartments is one key parameter. It could be shown that the concept is suitable for real time simulations of decanter centrifuges. The presented numerical algorithm is capable of real time simulations and model-based process control of a lab decanter centrifuge. This is guaranteed by connecting the solids residence time distribution with the properties of the material for the sedimentation and sediment build-up. The accuracy of the new approach is shown by comparing numerical simulations with experimental results. The presented model is unsuitable to predict the sediment solids concentration of a material which forms a compressible cake. An extension of the basic framework to tubular centrifuges or filter centrifuges is also applicable by considering the solids residence time distribution of these types of machines, the properties of the processed materials and neglecting the sediment transport. [ABSTRACT FROM AUTHOR]

Secondary refrigeration and thermal energy storage are promising solutions to enhance the performance of refrigeration systems and reduce the impact of refrigerants on the environment. To improve the energy efficiency of secondary refrigeration loops, phase change material (PCM) slurries with a high energy density, such as CO 2 hydrate slurries, can be used as a secondary refrigerant. In addition, hydrate-based processes could be an innovative option to capture CO 2 from flue gas. In both applications, the rheological properties of the CO 2 hydrate slurry have to be controlled. In the present study, CO 2 hydrate slurry in the presence of Sodium Dodecyl Sulfate (SDS) was studied in a dynamic flow loop. The results show that SDS used at concentrations of 1500–2000 ppm significantly decreases agglomeration and improves the flow properties of the slurry. Moreover, SDS helps decrease the viscosity of the CO 2 -hydrate slurry at high fraction (>10 vol%) and therefore could be suitable for use in industrial applications such as secondary refrigeration, in which hydrate slurries must be easy to handle. [ABSTRACT FROM AUTHOR]

[Display omitted] • Flow characteristics for CO 2 + TBAB or TBPB hydrate slurries with PVA were measured. • Flow characteristics and particle shapes assessed the aggregability of slurry. • The aggregability of TBPB hydrate slurry was higher than that of TBAB. • An appropriate degree of polymerization and concentration of PVA was found. • PVA had an anti-agglomeration effect on the slurries formed under CO 2 bubbling. The rheological properties of tetra- n -butylammonium bromide (TBAB) and tetra- n -butylphosphonium bromide (TBPB) semi-clathrate hydrate (SCH) slurries with polyvinyl alcohol (PVA) were measured using a viscometer to evaluate the anti-agglomeration effect of PVA. The TBAB and TBPB hydrate slurries exhibited a stronger dilatant trend with yield stress and more aggregates with increasing solid fraction. Only TBPB had plate-like crystals, and the frictional force between particles and aggregability in TBPB hydrate slurries were higher than those in TBAB hydrate slurries. The appropriate degree of polymerization (DP) of PVA was 1000, and the appropriate PVA (DP of 1000) concentrations were 0.53 wt% for TBAB hydrate and 1.8 wt% for TBPB hydrate among the SCH solid fractions examined. CO 2 bubbling weakens the anti-agglomeration effect of PVA by promoting particle aggregation and enhancing the interactions between plate-like particles. However, adding PVA changed the rheological properties of slurries to a Bingham fluid even under CO 2 bubbling conditions. [ABSTRACT FROM AUTHOR]

• Electrical Resistance Tomography (ERT) sensor vessel was used as a rheometer cup. • Solids settling velocity was measured in the gap between the rheometer cup and bob. • Solids settling velocity decreases as solids concentration and shear rate increase. • Correlation for settling velocity under sheared conditions developed using ERT data. Studying solids settling under sheared conditions is important for designing and operating slurry transportation pipelines. Electrical resistance tomography (ERT) is used for the first time to determine solids settling velocity under sheared conditions in a rheometer. The settling velocity of glass particles descending in 90 vol% glycerol solution located in the annular space between the ERT rheometer cup and bob was evaluated from conductivity data tracking particles' downward movement. The shear rate was varied from 5 to 125 s−1 by changing the bob rotational speed. Solids concentration ranged from 5 to 25 vol%. Settling velocity decreased with increasing solids concentration, slurry viscosity and shear rate. An empirical settling velocity correlation was developed using a modified Richardson-Zaki model incorporating the effects of solids concentration, slurry viscosity and shear rate. This correlation could be adopted as the basis for determining solids settling velocity for slurry transport in laminar flow in a pipeline. [ABSTRACT FROM AUTHOR]

• A new bubble breakup model considering the effect of solid particles. • A phenomenological modification of the bubble coalescence probability to include the impact of solid particles. • An integrated population balance and hydrodynamic model to simulate the hydrodynamics of slurry bubble columns. Bubble size distribution (BSD) is a crucial parameter in the design and scale-up of slurry bubble columns (SBCs) as it affects the hydrodynamics, heat and mass transfers, and, consequently, the column overall performance. It is necessary to understand the impacts of various parameters on the bubble size to adequately predict the BSD. The population balance model is widely adopted to estimate the BSD by considering the bubble coalescence and breakup rates. Many bubble coalescence and breakup models have been proposed in literature to predict the BSD. However, the available models have been developed for two-phase (gas–liquid) systems. They are, hence, less appropriate for three phase (gas–liquid-solids) systems, as the presence of particles in these systems has considerable impacts on their hydrodynamics. Novel bubble breakup and coalescence models are developed in the present study to predict the effects of solids concentration and particle size on the bubble breakup and coalescence rates. The results showed that the presence of solids can increase both bubble coalescence and breakup rates, while the effect is more pronounced on the coalescence rate. In addition, an increase in the particle size increases the bubble breakup rate and decreases the bubble coalescence rate. An integrated population balance and hydrodynamic model was also developed to estimate the BSD and gas holdup in a slurry bubble column. The developed models in this study were successfully validated by experimental hydrodynamic data from literature and those obtained in our pilot-scale slurry bubble column. A set of parametric studies were accomplished to investigate the effects of solid particles on the bubble breakup, bubble coalescence, and BSD in two common industrial applications of SBCs. [ABSTRACT FROM AUTHOR]

• Bubble slurry photoreactor is modeled and simulated. • Hydrodynamic, kinetic and radiation models have been used. • A new design for bubble slurry photoreactor including spargers is proposed. • Parametric study and detailed evaluation of model results and system behavior was performed. • A reliable model validated with minimal error was proposed. One of the attractive but still challenging ways of CO 2 utilization is photocatalytic conversion of CO 2 into fuels. Since reactor design plays an important role in both the efficiency and quality of the product, moving towards modeling and simulation of the photoreactor is vital. Thus, in this work modeling and simulation of photoreactor has been conducted using appropriate hydrodynamic and kinetic modules. The obtained model has been thoroughly validated by the experimental data which can further be utilized to scale-up the photoreduction process. The important parameters in the reactor design including the number of spargers, inlet gas flux, average bubble diameter, and light intensity have been studied. The methanol concentration after 150 s of the reaction under irradiation with light intensity of 120 W/m2 where 12 spargers delivered carbon dioxide gas into the reactor has been reported and the results have been validated accordingly. [ABSTRACT FROM AUTHOR]

The formation and agglomeration of hydrates have been a major hazard to the operating safety of deep-sea oil/gas transportation pipeline. Although many studies have been conducted to investigate the hydrates formation and particle behaviors during the transportation, studies on the gas–slurry flow properties and effects of hydrates on multiphase flow patterns are still almost blank. In this work, a series of experiments were conducted in a high pressure flow loop, using the materials of a pseudo single-liquid-phase (saturated water/oil emulsion) and a gas–liquid multiphase, respectively. It was found that hydrates agglomeration was more violent and the flow property was worse in the gas–liquid multiphase system. When hydrates formed in the gas–liquid multiphase system, the liquid flow rate would decrease in all experimental conditions while the gas flow rate showed three different changing types: decreasing, increasing or keeping constant. These changes of the flow rate would further induce a transition of the gas–liquid multiphase flow pattern in the loop. Based on the experimental data, two flow pattern maps were made. One involved the effects of hydrates while the other did not. Through the comparison between the two flow pattern maps, it is confirmed that the influence of hydrates on the flow pattern is significant. The differences between the two flow pattern maps were also analyzed using a flow pattern transition model to provide an insight into the mechanism of how hydrates affect the multiphase flow pattern. [ABSTRACT FROM AUTHOR]

Semiclatrate hydrate crystals of tetra- n -butyl ammonium bromide (TBAB) form at atmospheric pressure and at positive temperature. In suspension with water, they can be used as a heat transport medium or for gas separation. In terms of thermal energy storage and secondary refrigeration applications, TBAB hydrate slurries may be characterized by their flow properties under specific thermophysical conditions. The study presented here investigated one of these important properties, i.e. the crystal content, also called the solid fraction, that is usually estimated using the TBAB:H 2 O phase diagram. Our investigations revealed that Time-Domain Nuclear Magnetic Resonance (TD-NMR) relaxometry was remarkably sensitive to the solid content of TBAB:H 2 O hydrate slurries. Non-invasive and non-destructive measurements performed in real time demonstrated the power of NMR relaxometry to identify and quantify TBAB hydrates. Most importantly, NMR both measured and quantified type A and B hydrates, which no other technique can achieve without destroying the crystals or can only perform theoretically on the basis of a phase diagram, and thus without considering the possible conversion of type A to type B hydrates. [ABSTRACT FROM AUTHOR]

New approaches and materials for inexpensive carbon capture are important areas of research. Herein, we report a new material (i.e., zeolitic imidazolate framework-67 (ZIF-67)/glycol-2-methylimidazole (mIm) slurry) that can be used to capture CO 2 similar to a liquid absorbent, and ZIF-67 was synthesized on a pilot scale. This flowable slurry was formed by suspending ZIF-67 in a glycol–mIm solution. The results from the gas-–slurry equilibrium experiments indicate that this method provides a more efficient approach for the low cost capture of CO 2 compared to conventional technologies. The selectivities for CO 2 /H 2 , CO 2 /N 2 , and CO 2 /CH 4 were 1409, 723, and 222, respectively. The apparent solubility of CO 2 in the slurry was 1.3 mol L −1 , and the sorption enthalpy was only −33 kJ mol −1 at 1 bar and 303.2 K. To simulate an actual separation process for carbon capture using the ZIF-67/glycol–mIm slurry, a series of column breakthrough tests were performed in a stainless steel bubbling column to investigate the influence of temperature, ZIF-67 mass fraction in the slurry, feed gas flow rate, and composition. The slurry was completely regenerated via helium purging and heating at 323–343 K. The CO 2 capture ability of the regenerated slurry was the same as that of the fresh slurry, even after 10 adsorption/desorption cycles. [ABSTRACT FROM AUTHOR]

• Arabinose was successfully oxidized to arabinonic acid in a slurry reactor. • Dispersed gold nanoparticles were used as catalyst. • Oxygen solubility in the reaction solution was measured. • Extensive kinetic study of the oxidation process was conducted, revealing the effect of oxygen pressure and pH. • A kinetic model was developed and used to describe the experimental data. Sugar acids obtained by oxidation of sugars are very valuable molecules which are used as chelating agents, binders as well as ingredients in pharmaceuticals. Arabinonic acid was prepared by oxidation of arabinose on gold nanoparticles deposited on an aluminium oxide carrier. A systematic reaction kinetic study was conducted to reveal the influence of oxygen partial pressure and pH on reaction rate and product selectivity. Experiments were carried out in a laboratory-scale semi-batch reactor which was operated at 70 °C and oxygen partial pressures 0.125–1.0 atm. The pH of the aqueous sugar solution was 6–8. Oxygen was continuously flowing through the semibatch slurry reactor and the pH was kept constant by adding NaOH during the experiments. The oxygen solubility in the reaction mixture was determined in separate experiments. A reaction mechanism was proposed for the formation of arabinonic acid (main product) and arabinolactone (intermediate by-product). The surface reaction of competitively adsorbed arabinose and oxygen was assumed to be rate determining for the arabinose consumption. For the formation of arabinonic acid from arabinolactone, the rate determining step was presumed to be the reaction between arabinolactone and sodium hydroxide. The reactor was described with the perfect backmixing model and the component mass balances were solved numerically during the estimation of kinetic parameters by nonlinear regression analysis. The kinetic model gives new insights in the reaction mechanism and described the experimental data very well. The model has potential for application in the oxidation of other monomeric sugars, too. [ABSTRACT FROM AUTHOR]

Modeling of hydrodynamics, mass/heat transfer and chemical reactions with bubbly flow in a pilot slurry internal airlift loop reactor (IALR) for the process of direct coal liquefaction (DCL) under the conditions of elevated pressure and high temperature is performed with a steady two-fluid model. A modified numerical method for multiphase flow and the developed boundary conditions to promote the convergence of steady solutions are also proposed. The results show that the predicted average gas voidage, average liquid velocity and temperature at two locations in the riser agree reasonably well with experimental data. The snapshots of temperature and concentrations of the reactants in respective phases and the product in slurry are all well captured. The models and numerical procedure developed in this work can be used as an effective tool for design and scale-up of IALRs for the DCL process. [ABSTRACT FROM AUTHOR]

Multiphase CFD simulations have shown how to design reactors using Fischer–Tropsch chemistry. The new design uses large catalyst particles to eliminate large bubbles, has no cooling tube bundles and produces up to 50,000 bbl/day of Diesel fuel in a 7 m diameter, 12 m high reactor at a pressure of 3 MPa and a temperature of 530 K. [ABSTRACT FROM AUTHOR]

A model describing a shear-thinning slurry flow in a flat channel is developed. A diffusive flux modeling approach, which allows calculating particle migration to the channel center, is employed. The model developed accounts also for a fluid leak-off through permeable channel walls. Most of the calculation examples are presented for power-law slurry rheology and a few for Herschel–Bulkley slurries. An evolution of the cross-sectional solids concentration distribution along the channel is analyzed in dependence on slurry system parameters. The computations also revealed a significant effect of particle migration to the channel center on the pressure gradient. The results obtained demonstrate that the particle migration may be important for modeling particle transport in narrow flat channels and, therefore, this phenomenon must be taken into account in the modeling of technological processes, such as proppant transport in hydraulic fracturing. [ABSTRACT FROM AUTHOR]

• Performed lattice-Boltzmann computational fluid dynamics simulations of retained hydrogen gas release from Bingham plastic slurries. • Performed sensitivity analyses to evaluate the impact of yield stress, impeller speed, and bubble size on the release of retained gas from a Bingham plastic slurry. • Compared lattice-Boltzmann computational fluid dynamics simulations of retained hydrogen gas release from Bingham plastic slurries with experimental data. Physics-based models for predicting the off-gassing characteristics of agitated slurries are presented. This approach decomposes the system into two separate but coupled slurry and headspace models. The physics driving bubble transport through the slurry and gas mixing within the headspace are discussed. An analytical expression for predicting the time evolution of the headspace concentration using first principles theory is also presented. Predictions from the numerical models, as well as expectations from the analytical solution, both agree with measured off gassing data for two different experimental operating conditions. After benchmarking the numerical model predictions against experimental data, the model was used to make predictions for gas release from a full-scale vessel and to perform sensitivity analyses to examine the sensitivity of gas release to parameters such as yield stress, consistency index, slurry density, bubble size, bubble concentration, and impeller speed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Torque monitoring during emulsification of OL into fresh GP allows to have one-line viscosity. • Torque evolution allows to predict if OL will be successfully incorporated in GP or not. • Quaternary ammonium salts such as CTAB are well adapted to adjust the viscosity of fresh GEOIL. • Capillary forces between OL and MK were shown using Zêta potential measurements and Washburn tests. Geopolymers (GP) have recently emerged as suitable binders for the conditioning of radioactive organic liquids (OL). The condition for suitably incorporating high amounts of OL into GP is assessed in this research. A series of OL has been selected, comprising alkanes (dodecane and 2 paraffinic mineral oils), an industrial gear oil and tributylphosphate (TBP), in order to cover a wide range of viscosities (0.0018–2.33 Pa.s). The incorporation of viscous OL (>0.2 Pa.s) into fresh GP results in a regular torque increase, indicating a suitable process with the dispersion of the OL in the form of fine micrometric droplets. When the torque remains stable, for OL of low viscosity (<0.2 Pa.s) like TBP/Dodecane mixtures, the incorporation is not possible, or only partial in the form of large droplets quickly coalescing and leading to an organic supernatant above the hardened GP. For low viscosity OL, surfactants are required. The use of quaternary ammoniums (QAs) like cetyltrimethylammonium bromide (CTAB) has been studied. Torque monitoring shows that the OL is incorporated similarly in the GP slurry, whether the surfactant is introduced at the beginning, through the course or at the end of the mixing process. The torque evolution also provides the optimum surfactant concentration, by evidencing that beyond a certain concentration, the medium hardens too quickly, preventing the incorporation of OL. Finally, torque monitoring highlights that QAs with shorter alkyl chains, such as hexamethyltrimethylammonium, are able to replace CTAB with the same efficiency. Therefore, the powerful action of CTAB on the incorporation of alkanes into GP is attributed to its positive charge rather than to its surfactant effect. [ABSTRACT FROM AUTHOR]

The experimental volumetric liquid-phase mass transfer coefficients k L a measured in a slurry bubble column (0.095m in ID) operated with several three-phase systems (air–ligroin–polyvinylchloride (PVC), air–ligroin–polyethylene (PE) and air–water–activated carbon) were predicted successfully based on a correction of Higbie's (1935) penetration theory. A correction factor (which is a single function of the Eötvös number) developed earlier (Nedeltchev et al., 2007) in gas–liquid bubble columns was found applicable to slurry bubble columns. It varied from 0.22 to 1.91 in the above-mentioned three-phase systems. As the bubble size becomes bigger, the correction factor increases and vice versa. The two major changes in the algorithm (applied to slurry bubble columns) are associated with the calculation of the Sauter-mean bubble diameter (Lemoine et al., 2008) and the gas–liquid interfacial area. In the case of a slurry bubble column, both the slurry density and effective viscosity were used in the model correlations. It was found that the model yielded good results not only in the homogeneous regime but also in the heterogeneous regime (up to gas velocities of 0.08m/s). It worked also well at relatively high solids concentrations (up to 15%). When the bubble Reynolds number is higher than 700 and when the superficial gas velocity is beyond 0.04m/s, then the penetration theory based on the new definition of the contact time can be applied straightforwardly (without any correction factor). The developed model is applicable to ellipsoidal bubbles and it demonstrates the important effect of the geometrical characteristics (length and height) of these bubbles on the mass transfer coefficients. [ABSTRACT FROM AUTHOR]

Abstract: The flow characteristics and rheological properties of natural gas hydrate slurry, with initial water cuts ranging from 5 to 30vol%, were investigated in a flow loop. The experimental results indicate that the hydrate slurry can be considered a pseudoplastic fluid and presents more obvious shear-thinning behaviour with the increase in the hydrate volume fraction. The study on the fluid morphology demonstrated that the original structure of the water-in-oil emulsion is destroyed by the formation of gas hydrate, and the hydrate slurry is ultimately transported as a solid dispersion system. An empirical Herschel–Bulkley-type equation that considers the hydrate volume fraction was developed to improve the description of the rheological properties of the hydrate slurry. The apparent viscosities of the hydrate slurry calculated by the new equation were in accordance with the experimental data. Shutting-down/restarting tests using three shutting-down times (2h, 4h, and 8h) were performed. The experimental results indicate that the hydrate slurry can be easily and safely restarted from the static state after a long shutting-down period and exhibits obvious thixotropic behaviour with increasing shutting-down time. [Copyright &y& Elsevier]

[Display omitted] • Trialkylmethylammonium molybdate ILs with multiple long-chain alkyl groups were designed. • The molybdate ILs were synthesized from readily available reagents under mild condition. • The molybdate ILs were applied as oil-soluble precursors for slurry-phase hydrocracking. • The sulfidation behavior and hydrocracking performance of molybdate ILs were examined. • [N 6661 ] 2 MoO 4 shows even better performance than a commercial precursor (MoIV-isooctoate). Slurry-phase hydrocracking is an effective technology for the conversion of heavy oils to clean and light fuels. Herein, trialkylmethylammonium molybdate ionic liquids (ILs) with multiple long-chain alkyl groups were designed, and applied as the oil-soluble precursors of dispersed metal catalysts for slurry-phase hydrocracking. The molybdate ILs were synthesized through a two- or three-step route from readily available reagents under mild conditions. The chemical structure and sulfidation behavior of molybdate ILs were characterized first. The performance of molybdate ILs for hydrogenation was then evaluated with phenanthrene as the model compound. The dispersed MoS 2 catalysts in-situ produced in the model system were isolated and characterized to explain the different performance of oil-soluble precursors. The performance of molybdate ILs for slurry-phase hydrocracking of heavy oils was finally investigated. To figure out the favored routes for the conversion of heavy oils, the reaction rate constants were also calculated based on an established kinetical model. [ABSTRACT FROM AUTHOR]