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AbstractThe present investigation demonstrates the effect of red mud concentration on the rheological, pipe flow, and pipe wear behavior during slurry pipeline transportation. Rheology data indicate that 40–70 wt.% red mud slurries exhibit shear thinning flow behavior in the shear rate range of 15–300 s−1. Both slurry viscosity and shear stress increase with the increase in red mud concentrations. The yield stress and startup pressure exponentially vary with red mud concentrations. The critical velocity is estimated as 1.5 m/s, above which sedimentation of red mud particles can be avoided in the pipeline. The pipe head loss and specific energy consumption increase with red mud concentration and slurry velocity; however, these parameters decrease with an increase in pipe diameter. Results suggest that the repetitive impingement of the red mud particles on the surface of mild steel specimens causes erosion wear, which intensifies at higher solid loading and velocity. The abrasivity of red mud slurries and the abrasive response of the pipe material are found as a function of red mud concentration. A favorable economic flow condition is achieved, when 60–65 wt.% of red mud slurry is transported at a velocity of 1.5 m/s in a pipe of diameter 0.3 m. [ABSTRACT FROM AUTHOR]

Zinc is an important metal useful in hydrogen production. Mining of zinc also involves zinc tailings disposal using pipeline transportation which is an energy- and water-intensive process. In this study, the multisized slurry of zinc tailings is modeled using CFD to investigate the flow field characteristics in a straight horizontal pipe fitted with swirl-inducing sections. The primary objective was to study the pressure drop by adding swirl-inducing pipe of different numbers of lobes to the conventional pipe. Nine configurations of multi-lobed swirl-inducing pipes were studied for transport characteristics of solids at three flow rates and three overall solids concentrations. Eulerian-Eulerian modeling with the RNG k-ε turbulence model is employed for simulations. The numerical model is validated for pressure drop against available experimental results, and excellent agreement is achieved. The study shows that 10-lobed swirl-inducing section fitted to the conventional pipe reduces the pressure drop by nearly 35%, offering the potential for further exploration. • Swirl-inducing motion is utilized for reducing settling of solid particle in pipeline. • The slurry is modeled as multi-sized particles considering six size classes. • Nine configurations of lobed swirl pipes for dense slurries. • The 10 lobed swirl-inducing pipe is found to reduce pressure drop by approximately 35% as compared with the conventional pipe. [ABSTRACT FROM AUTHOR]

Self-amplifying density waves in hydraulic transport pipelines is a scarcely researched topic. Density waves are in essence the result of a spatial redistributing effect and clustering of solids in hydraulic transport pipelines. Self-amplifying density waves are very undesirable for practical applications, as these waves increasing the risk of pipeline blockages. The two available experimental studies (Talmon et al., 2007; Matoušek and Krupička, 2013) report conflicting properties of the density waves, such as wave length and wave celerity. This new experimental research aims to shed light on the reported differences, by broadly varying particle size and concentration in a new dedicated experiment. The main highlight of this research is that two separate mechanisms were identified that can cause density waves, and Talmon et al. (2007) and Matoušek and Krupička (2013) in hindsight were studying the two different mechanism respectively. Both wave type mechanisms come into effect at mixture velocities close to the deposit limit velocity, and require a stationary bed layer to initiate. The first mechanism is caused by an imbalance of erosion and sedimentation of the bed layer, which is predominant for fine sand particles (∼ 242 μ m and ∼ 308 μ m in this research). The second mechanism occurs when the bed layer starts sliding, instead of being eroded, and is specific for larger sand sizes (∼ 617 μ m and ∼ 1. 08 mm in this research). These two mechanisms are clearly distinguishable, having different wave lengths, celerity, amplitudes and amplification rates. The results also show a clear relationship between the mean concentration of a density wave, the wave amplitude and wave celerity specific for each of the two mechanisms. • Two types of density waves have been unraveled during these experiments. • Peak concentration, celerity and length was found to be specific to the wave type. • The density wave peak concentration correlates with the average concentration. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper deals with the flow of solid/liquid mixtures through long-distance pipelines. Such flows can be destabilized by the formation of local plugs which may impede or even block the flow. Plugs may develop at the interface between regions of different mean concentration. The driving force for the development of such plugs is the existence of local gradients of the axial flux of solids.A mathematical model is developed which describes this mode of plug formation in slurry pipelines. Several assumptions and approximations enable us to reduce the 3D continuity equation of the solid particles to an effective 1D-equation that contains a concentration-dependent flux function. The latter equation is solved numerically.Illustrative calculations lead to the conclusion that the accumulation of material in a plug does not con- tinue without limit but instead levels off at values that are pumpable under most practical conditions, provided that a certain margin of overdesign is in place.

A common way to transport solids in large quantities is by using a carrier fluid to transport the solids as a concentrated solid/liquid mixture or slurry through a pipeline. Typical examples are found in dredging, mining and drilling applications. Dependent on the slurry properties and flow conditions, horizontal slurry pipe flow is either in the fixed-bed, sliding-bed or fully-suspended regime. In terms of non-dimensional numbers, the flow is fully characterized by the bulk liquid Reynolds number (R e), the Galileo number (G a , a measure for the tendency of particles to settle under gravity), the solid bulk concentration (ϕ b), the particle/fluid density ratio ( ρ p / ρ f ), the particle/pipe diameter ratio ( D p / D p i p e ), and parameters related to direct particle interactions such as the Coulomb coefficient of sliding friction (μ c). To further our fundamental understanding of the flow dynamics, we performed experiments and interface-resolved Direct Numerical Simulations (DNS) of slurry flow in a horizontal pipe. The experiments were performed in a transparent flow loop with D p i p e = 4 cm. We measured the pressure drop along the pipeline, the spatial solid concentration distribution in the cross-flow plane through Electrical Resistance Tomography (ERT), and used a high-speed camera for flow visualization. The slurry consisted of polystyrene beads in water with D p = 2 mm , ρ p / ρ f = 1. 02 , G a between 40–45 and ϕ b between 0.26–0.33. The different flow regimes were studied by varying the flow rate, with R e varying from 3272 till 13830. The simulations were performed for the same flow parameters as in the experiments. Taking the experimental uncertainty into account, the results from the DNS and the experiments are in reasonably good agreement. The results for the pressure drop agree also fairly well with popular empirical models from literature. In addition, we performed a parametric DNS study in which we solely varied R e and G a. In all flow regimes, a secondary flow of Prandtl's second kind is present, ascribed to the presence of internal flow corners and a ridge of densely packed particles at the pipe bottom during transition towards the fully-suspended regime. In the bulk of the turbulent flow above the bed, secondary flow transport of streamwise momentum dominates over turbulent diffusion in regions where the secondary flow is strong and vice versa where it is weak. The transition between flow regimes appears to be governed by the competition between the net gravity force on the particles and shear-induced particle migration from particle–particle interactions. This competition can be expressed by the Shields number, θ. For θ ≲ 0. 75 , gravity is dominant and the flow is in the fixed-bed regime. For θ ≳ 0. 75 , shear-induced migration becomes progressively more important for increasing θ. Low-concentration zones flanking the sliding bed start to form at the top corners of the bed, and gradually expand downwards along the pipe wall till the pipe bottom is reached. For θ ≳ 1. 5 , shear-induced migration is responsible for lifting the particle bed away from the wall, associated with the onset of the suspended regime. For θ ≫ 1 , gravity is of minor importance and the mean flow eventually reaches axi-symmetry with a high-concentration particle core at the pipe center and negligible secondary flow. [Display omitted] • First particle-resolved Direct Numerical Simulation of slurry pipe flow. • New insights in transition from fixed to sliding bed to suspended flow. • Lifted particle core when shear-induced migration dominates over gravity. • Intriguing axi-symmetric flow regime for high Shields number. • Presence secondary flow ascribed to flow corners and dense particle ridge. [ABSTRACT FROM AUTHOR]

We revisit the laminar-turbulent transition of a fine-grained slurry in a large pipe. The combination of long measurement times in an industrial-scale facility and ultrasound imaging allows us to observe and address anomalous trends. Under turbulent conditions, the flow is homogeneous and steady. However, under laminar conditions, two types of long-time-scale transient behaviours are captured. In the first scenario, the system has been homogenized, following which the flow rate is reduced to laminar conditions. The flow rate continues to gradually drop, while particles settle and form a stationary bed. In the second scenario, the system has been shut down for a prolonged period and the flow rate is slowly increased. The flow rate continues to rise while particles are slowly resuspended from the gradually eroding bed. Near the laminar-turbulent transition point, two types of intermittent structures are responsible for resuspension. The equilibrium phase, with steady flow rate, coincides with complete resuspension. These two long-time-scale transients correspond to the phenomena of 'slow settling' and 'self-equilibration', respectively. While the former can lead to shutdowns, the latter generates a stable system. Being aware of these phenomena is of relevance while operating slurry pipelines near the favourable operating point of the laminar-turbulent transition. [ABSTRACT FROM AUTHOR]

Slurry pipeline transport, which is widely used in dredging, is an important method of solid material transportation. The internal structure information of flows with different shaped particles must be obtained to investigate the effects of different particle shapes on the efficiency and flow characteristics of slurry transport. To solve this problem, a numerical method which couples the computational fluid dynamics (CFD) and the discrete element method (DEM) is established in this study. Using the coupled CFD-DEM, the internal flow structure for spherical, square platens and line-shaped coarse particles is studied, and the working conditions under which clogging of non-spherical particles occurs are explored. The flow states of different shaped particles at velocities of 2, 4.1 and 8 ms−1 are qualitatively analyzed in a horizontal pipeline system within the diameter of 100 mm, and quantitative analyses of the concentration distribution in different flow regimes are performed. The study describes the particle flow characteristics under clogging conditions based on the flow regime transition and concentration distribution. Abnormal transport is analyzed using qualitative and quantitative indications. In addition, along with the particle force and robustness of transport, the conditions for stable transport are discussed.

Abstract Slurry transport has become a subject of interest in several industries, including oil and gas. The importance of slurry/solid transport in the oil and gas industry is evident in areas of cuttings transport, sand transport and, lately, hydrates. Hydrate formation, if not properly monitored and controlled, may lead to pipeline blockage. To avoid pipeline blockage and other hydrate formation risks, chemical additives are added to the system. Additives such as anti-agglomerants help improve hydrate transportability by dispersing the formed hydrates into slurries and preventing them from sticking to the pipe wall. This enables transportation of highly concentrated slurries. However, the high hydrate volume fractions (HVF) slurries may exhibit complex rheology. There is therefore a great need to correlate flow properties such as friction factor and viscosity to HVF. Hydrate slurry transport is important whether hydrates are deliberately generated for energy storage purposes or hydrates formed because of the prevailing flow conditions. However, when determining the viscosity of a fluid containing solid particles, the conventional viscometer types such as concentric cylinders and cone and plate are often not suitable. This is because either the narrow gap would not accommodate the particle size or their inability to maintain the particles suspended leading to bed formation. In this work, a high-pressure mixer-type viscometer was used to generate and characterize hydrate slurries. This work aims to generate a significant amount of hydrate slurry characterization data that may be used as basis for better rheometer designs, hydrate slurry flow properties modeling or integration of hydrate transportability into general multiphase modeling. Results showed that intermediate watercuts posed the greatest pipeline plugging risk for all the oils tested. The amount of transportable hydrates increased with oil viscosity. Generally, hydrate slurries generated exhibited shear thinning behavior that increased with increasing hydrate volume fraction. However, the overall rheology of these slurries is a complex function of the oil used, watercut, gas added to the system and hydrate solid fraction. Lowering shear rates for high HVF systems resulted in separation. Results in this work further suggest that hydrate transportation may be possible with minimum risk if anti-agglomerants are used and high enough shear is applied. On the other hand, if no anti-agglomerant is used, severe aggregation may result in flow line plugging.

The different slurry transport properties in horizontal pipeline are investigated using a steady three-dimensional hydrodynamic model based on the kinetic theory of granular flow. The flow velocity and solid concentration distributions of slurry transported by pipeline and their regularly changing trends with varying pipe diameter (D = 51.5, 54.9, 103, 263, and 495 mm), solid volume concentration (Cvf = 20%, 30%, 40%, and 50%), grain diameter (dp = 0.09, 0.125, 0.165, 0.27, and 0.44 mm) and flow velocities (v = 2, 3, 4, and 5 m/s) are studied. The simulation result shows that under heterogeneous regime, fine particles, smaller than the sum of thickness of the viscous sublayer and buffer layer are most concentrated toward the pipe bottom (maximum concentration at the relative location ymax ≈ 0.02 D) while the greatest concentration of coarser particles is away from the pipe bottom (ymax ≈ 0.1 D). The results obtained in this work provide a solid foundation for further study of the resistance mechanism and pipe wear and can be used as a reference for analyzing the mesoscopic processes of slurry transport by pipeline. [ABSTRACT FROM AUTHOR]

Slurry pipeline transport, which is widely used in dredging, is an important method of solid material transportation. The internal structure information of flows with different shaped particles must be obtained to investigate the effects of different particle shapes on the efficiency and flow characteristics of slurry transport. To solve this problem, a numerical method which couples the computational fluid dynamics (CFD) and the discrete element method (DEM) is established in this study. Using the coupled CFD-DEM, the internal flow structure for spherical, square platens and line-shaped coarse particles is studied, and the working conditions under which clogging of non-spherical particles occurs are explored. The flow states of different shaped particles at velocities of 2, 4.1 and 8 ms−1 are qualitatively analyzed in a horizontal pipeline system within the diameter of 100 mm, and quantitative analyses of the concentration distribution in different flow regimes are performed. The study describes the particle flow characteristics under clogging conditions based on the flow regime transition and concentration distribution. Abnormal transport is analyzed using qualitative and quantitative indications. In addition, along with the particle force and robustness of transport, the conditions for stable transport are discussed. [ABSTRACT FROM AUTHOR]

The depletion of high-grade nickel sulfide ores has led to an increased interest in low-grade ultramafic ores, which are widely available but challenging to process due to their high content of phyllosilicate serpentine. The anisotropic surface charge and shape of serpentine particles lead to attractive interactions, which increase the viscosity of ore slurry and associated operational and equipment costs. To overcome this challenge, we investigate the application of an environmentally benign reagent, sodium citrate, to modify the particle-particle interactions in serpentine aqueous suspensions. Our results show that at alkaline pH (10), sodium citrate selectively adsorbs on the brucite plane of serpentine, making the entire particle overall negatively charged, which weakens the interparticle attraction and reduces the suspension's shear viscosity, yield stress, and storage modulus. We confirmed these results using colloidal probe atomic force microscopy (AFM) technique, which showed a significant weakening of attraction between silica and brucite surfaces upon the addition of citrate. This work enhances the understanding of surface interaction mechanisms of phyllosilicate serpentine particles in aqueous media with the addition of sodium citrate and provides useful implications for the application of green reagents in mineral operations involving phyllosilicate gangues. Our findings suggest that sodium citrate has great potential as an effective and sustainable reagent in the processing of abundantly available low grade ultramafic nickel ores. [Display omitted] • Depletion of high-grade nickel sulfide ores has spurred interest in processing challenging low-grade ultramafic ores rich in phyllosilicate serpentine. • Sodium citrate modifies particle-particle interactions by selectively adsorbing onto the brucite plane of serpentine. • Sodium Citrate adsorption results in weakening interparticle attractions and reduces suspension viscosity, yield stress, and storage modulus. [ABSTRACT FROM AUTHOR]

Slurry transport has become a subject of interest in several industries, including oil and gas. The importance of slurry/solid transport in the oil and gas industry is evident in areas of cuttings transport, sand transport and, lately, hydrates. Hydrate formation, if not properly monitored and controlled, may lead to pipeline blockage. To avoid pipeline blockage and other hydrate formation risks, chemical additives are added to the system. Additives such as anti-agglomerants help improve hydrate transportability by dispersing the formed hydrates into slurries and preventing them from sticking to the pipe wall. This enables transportation of highly concentrated slurries. However, the high hydrate volume fractions (HVF) slurries may exhibit complex rheology. There is therefore a great need to correlate flow properties such as friction factor and viscosity to HVF. Hydrate slurry transport is important whether hydrates are deliberately generated for energy storage purposes or hydrates formed because of the prevailing flow conditions. However, when determining the viscosity of a fluid containing solid particles, the conventional viscometer types such as concentric cylinders and cone and plate are often not suitable. This is because either the narrow gap would not accommodate the particle size or their inability to maintain the particles suspended leading to bed formation. In this work, a high-pressure mixer-type viscometer was used to generate and characterize hydrate slurries. This work aims to generate a significant amount of hydrate slurry characterization data that may be used as basis for better rheometer designs, hydrate slurry flow properties modeling or integration of hydrate transportability into general multiphase modeling. Results showed that intermediate watercuts posed the greatest pipeline plugging risk for all the oils tested. The amount of transportable hydrates increased with oil viscosity. Generally, hydrate slurries generated exhibited shear thinning behavior that increased with increasing hydrate volume fraction. However, the overall rheology of these slurries is a complex function of the oil used, watercut, gas added to the system and hydrate solid fraction. Lowering shear rates for high HVF systems resulted in separation. Results in this work further suggest that hydrate transportation may be possible with minimum risk if anti-agglomerants are used and high enough shear is applied. On the other hand, if no anti-agglomerant is used, severe aggregation may result in flow line plugging. [ABSTRACT FROM AUTHOR]

Improving the accuracy of the slurry flow predictions in different operating flow regimes remains a major focus for multiphase flow research, and it is especially targeted at industrial applications such as oil and gas. In this paper we develop a robust integrated method consisting of an artificial neural network (ANN) and support vector regression (SVR) to estimate the critical velocity, the slurry flow regime change, and ultimately, the frictional pressure drop for a solid–liquid slurry flow in a horizontal pipe, covering wide ranges of flow and geometrical parameters. Three distinct datasets were used to develop machine learning models with totals of 100, 325, and 125 data points for critical velocity, and frictional pressure drops for heterogeneous and bed-load regimes respectively. For each dataset, 80% of the data were used for training and the rest 20% for evaluating the out of sample performance. The K-fold technique was used for cross-validation. The prediction results of the developed integrated method showed that it significantly outperforms the widely used existing correlations and models in the literature. Additionally, the proposed integrated method with the average absolute relative error (AARE) of 0.084 outperformed the model developed without regime classification with the AARE of 0.155. The proposed integrated model not only offers reliable predictions over a wide range of operating conditions and different flow regimes for the first time, but also introduces a general framework of how to utilize prior physical knowledge to achieve more reliable performances from machine learning methods.

In slurry transport of settling slurries in Newtonian fluids, it is often stated that one should apply a line speed above a critical velocity, because blow this critical velocity there is the danger of plugging the line. There are many definitions and names for this critical velocity. It is referred to as the velocity where a bed starts sliding or the velocity above which there is no stationary bed or sliding bed. Others use the velocity where the hydraulic gradient is at a minimum, because of the minimum energy consumption. Most models from literature are one term one equation models, based on the idea that the critical velocity can be explained that way.

Slurry transport in horizontal and vertical pipelines is one of the major means of transport of sands and gravels in the dredging industry. There exist 4 main flow regimes, the fixed or stationary bed regime, the sliding bed regime, the heterogeneous flow regime and the homogeneous flow regime. Of course the transitions between the regimes are not very sharp, depending on parameters like the particle size distribution. The focus in this paper is on the homogeneous regime. Often the so called equivalent liquid model (ELM) is applied, however many researchers found hydraulic gradients smaller than predicted with the ELM, but larger that the hydraulic gradient of liquid. Talmon (2011, 2013) derived a fundamental equation (method) proving that the hydraulic gradient can be smaller than predicted by the ELM, based on the assumption of a particle free viscous sub-layer. He used a 2D velocity distribution without a concentration distribution.

Centrifugal pump has been used for the transport of the multiphases particularly slurry (solid–liquid mixture) in the petroleum and chemical industry. The present article describes the experimental analysis of a centrifugal pump delivering non-Newtonian fluids and reports the pump’s performance characteristics under different flow conditions. The mixture is prepared by mixing right quantities of bentonite powder, water, and Na2CO3to give the desired fluids having different viscosities. It was observed that the head and the efficiency of the pump decrease with the increase in fluid viscosity at the rated speed. The pump performance depends on the bentonite concentration in water, which changes rheological property of the fluid. To avoid experimental difficulties and to find correlations among the parameters, a polynomial regression (PR) model was fit to predict the head and efficiency. The PR models predict head and efficiency with relative percentage error of 3.137% and 5.096%, respectively. [ABSTRACT FROM PUBLISHER]

Prediction of horizontal pressure drop in dilute phase pneumatic conveying or slurry transport is among the fundamental issues of designing these systems. In this work a thorough literature survey demonstrates that there is no consensus on an integrative solution for conveying pressure drop, therefore a large data base of conveying systems' operating points at dilute phase is established and analyzed. It includes measurements taken at our 52 mm bore laboratory pneumatic conveying line, as well as thousands of data points collected from the literature. Two modelling approaches are attempted – the first is frictional representation based on dimensional analysis, which presents linear dependency between the pressure drop and the superficial fluid velocity normalized by the minimum pressure velocity of the transport curve. It had also been found that the pressure drop increase rate has a strong dependency on the Archimedes number. The second approach is an energy balance between the power of the drag force applied to the particles and the additional power required to drive the fluid due to particle presence. Unlike the common expressions, a modification to the drag coefficient is suggested, which takes into account pipe turbulence and particle acceleration. The two presented models do not require pilot plant calibration, and an applicability of one of them to slurry transport is demonstrated. Some future research routes are offered. [ABSTRACT FROM AUTHOR]

A progress of slurry transport is described in this report. In around 1980, slurry transport was extensively studied. Papers on pressure losses of slurry flows, transition velocity, measurement of in-situ concentration, snow/ice-water slurry flows were published by several researchers. Recently, the study on slurry transport is not so active, but solid-liquid flows can be seen in many fields. It is anticipated that studies on solid-liquid flows in the fields of disaster site restoration and next-generation resources and energy development will be progressed. [ABSTRACT FROM AUTHOR]

Many models for slurry transport exist. Usually the models describe one of the 5 main flow regimes: fixed or stationary bed transport; sliding bed transport; heterogeneous transport; homogeneous transport and sliding flow transport. The transition between these flow regimes is seldom described, as well as the difference between spatial and delivered concentration and the behavior of graded sands or gravels. A framework is described connecting the different flow regimes. Additional models for; the limit deposit velocity, the holdup function, the bed height, the concentration distribution and graded sands and gravels, complete the framework. The framework is based on constant spatial volumetric concentration curves for uniform sands and gravels. The models for the flow regimes and the limit deposit velocity are based on energy considerations. By means of a holdup function, the constant spatial volumetric concentration curves can be transformed into constant delivered volumetric concentration curves. Curves for graded sands and gravels can be constructed by splitting the particle size distribution (PSD) into fractions and use the superposition principle on the resulting curves of each fraction. The framework is validated with many experiments from literature. [ABSTRACT FROM AUTHOR]

Models for modeling slurry flow present difficulties on long lines with large pipe diameters and with broad graded sands or gravels. In order to get more insight into the slurry flow process, the Delft Head Loss & Limit Deposit Velocity Framework has been developed that integrates the 5 main flow regimes of slurry transport: fixed or stationary bed transport, sliding bed transport, heterogeneous transport, homogeneous transport and sliding flow transport. Additional models for; the limit deposit velocity, the holdup function, the bed height, the concentration distribution and graded sands and gravels, complement the Framework. The Framework is based on constant spatial volumetric concentration curves for uniform sands and gravels. The models for the flow regimes and the limit deposit velocity are based on energy considerations. At line speeds near the transition of the heterogeneous and homogeneous flow regimes however, there is no sharp transition between the two flow regimes for medium sized particles. The limits of medium sized particles depend on the solid and liquid properties and on the pipe diameter. It is often observed that the hydraulic gradient lies in between the Equivalent Liquid Model (ELM) and the pure liquid Darcy Weisbach model at higher line speeds, resulting in the conclusion that at higher line speeds the pure liquid hydraulic gradient is approached. Based on energy considerations however, it is shown that the heterogeneous hydraulic gradient collapses due to turbulent near wall lift neutralizing the particle submerged weight and collisions with the pipe wall, while at higher line speeds the turbulent eddies integrate particles, resulting in a hydraulic gradient approaching a reduced ELM (RELM). For medium sized particles in large diameter pipes there is a gap between the moment the heterogeneous hydraulic gradient collapses and the homogeneous hydraulic gradient builds up, resulting in a hydraulic gradient approaching the RELM hydraulic gradient. The model for this transition is described and derived and experimental evidence is given. [ABSTRACT FROM AUTHOR]

Although sophisticated 2 and 3 layer models exist for slurry flow (here the flow of sand/gravel water mixtures), the main Dutch and Belgium dredging companies still use modified Durand and Condolios (1952) and Fuhrboter (1961) models, while the main companies in the USA use a modified Wilson et al. (1992) model for heterogeneous transport. These older models use one term for the excess pressure losses, the pressure losses resulting from the solids, with an empirical character. A new model has been developed based on energy considerations. The model consists of two terms for the excess pressure losses, one for the potential energy losses and one for the kinetic energy losses. This gives more flexibility matching experimental results. Although the model is derived fundamentally, the slip velocity of the particles is still an unknown in the model. An equation for this slip velocity is derived, based on physical parameters. The resulting model is validated with numerous experimental data from the literature and from the Delft Dredging Laboratory and matches very well. The advantage of this model is, that it requires the parameters known to the dredging industry and is thus easy to use. [ABSTRACT FROM AUTHOR]

The Isamill is a horizontal stirred media mill used for fine and ultrafine grinding of slurry transported rock particles. The charge motion is analysed using two different approaches, (1) a fluid only model, and (2) a 1-way coupled DEM + SPH model. The flow pattern when the classifier is closed is regular with a pair of oppositely oriented vortices between each pair of grinding discs. A strong radial outflow from the middle of the classifier is generated by the high centrifugal force which creates a pair of toroidal vortices at the discharge end of the mill. The classifier, when open, acts as a pump drawing slurry axially along the mill. It enters the classifier through the holes in its end plate and is then forced radially outward by rotational acceleration of the classifier cage. The enhanced outflow significantly strengthens the large toroidal vortices on the outside of the classifier. This produces a strong retrograde annular flow along the mill shell that penetrates a significant distance back into the grinding chamber. The effect of the classifier is significant and strongly influences the flow over much of the mill and controls slurry (feed and product) transport and discharge. The predictions of the different models are qualitatively similar but with important differences including the fluid only model predicting higher flow speeds because it cannot capture the strong slip between the media and the grinding discs. The strength of the axial transport is strongly dependent on the slurry viscosity. A critical viscosity can be identified above which there is insufficient axial transport to enable mill operation. [ABSTRACT FROM AUTHOR]

[Display omitted] • DEM and DEM-CFD are widely used to study powder transport in single- and multi-phase systems. • Recent research interests as well as emerging applications of DEM are summarized. • Coarse grained DEM, GPU technique and periodic boundary conditions enable large-scale simulations. Powder transport systems are ubiquitous in various industries, where they can encounter single powder flow, two-phase flow with solids carried by gas or liquid, and gas–solid–liquid three-phase flow. System geometry, operating conditions, and particle properties have significant impacts on the flow behavior, making it difficult to achieve good transportation of granular materials. Compared to experimental trials and theoretical studies, the numerical approach provides unparalleled advantages over the investigation and prediction of detailed flow behavior, of which the discrete element method (DEM) can precisely capture complex particle-scale information and attract a plethora of research interests. This is the first study to review recent progress in the DEM and coupled DEM with computational fluid dynamics for extensive powder transport systems, including single-particle, gas–solid/solid–liquid, and gas–solid–liquid flows. Some important aspects (i.e., powder electrification during pneumatic conveying, pipe bend erosion, non-spherical particle transport) that have not been well summarized previously are given special attention, as is the application in some new-rising fields (ocean mining, hydraulic fracturing, and gas/oil production). Studies involving important large-scale computation methods, such as the coarse grained DEM, graphical processing unit-based technique, and periodic boundary condition, are also introduced to provide insight for industrial application. This review study conducts a comprehensive survey of the DEM studies in powder transport systems. [ABSTRACT FROM AUTHOR]

Slurry transport in horizontal and vertical pipelines is one of the major means of transport of sands and gravels in the dredging industry. There exist 4 main flow regimes, the fixed or stationary bed regime, the sliding bed regime, the heterogeneous flow regime and the homogeneous flow regime. Of course the transitions between the regimes are not very sharp, depending on parameters like the particle size distribution. The focus in this paper is on the homogeneous regime. Often the so called equivalent liquid model (ELM) is applied, however many researchers found hydraulic gradients smaller than predicted with the ELM, but larger that the hydraulic gradient of liquid. Talmon (2011, 2013) derived a fundamental equation (method) proving that the hydraulic gradient can be smaller than predicted by the ELM, based on the assumption of a particle free viscous sub-layer. He used a 2D velocity distribution without a concentration distribution. In this paper 5 methods are described (and derived) to determine the hydraulic gradient in homogeneous flow, of which the last method is based on pipe flow with a concentration distribution. It appears that the use of von Driest (Schlichting, 1968) damping, if present, dominates the results, however applying a concentration distribution may neutralise this. The final equation contains both the damping and a concentration distribution giving the possibility to calibrate the constant in the equation with experimental data. The final equation is flexible and gives a good match with experimental results in vertical and horizontal pipelines for a value of ACv = 1.3. Data of horizontal experiments Dp = 0.05-0.30 m, d = 0.04 mm, vertical experiments Dp = 0.026 m, d = 0.125, 0.345, 0.560, and 0.750 mm. [ABSTRACT FROM AUTHOR]