Volumetric Solids Concentration Research Articles

Development and substantiation of an improved version of a main drainage facility classical scheme at a kimberlite mine developed by block caving method

Evidence demonstrates that as the production capacity of a kimberlite mine increases, there is a corresponding increase in the volumetric concentration of suspended solids in the mine water extracted from its watercollecting workings. The Udachny mine, known for its high productivity in comparison to other domestic kimberlite mines, experiences a higher concentration of suspended solids in the mine waters, leading to significant sludge settling within the primary drainage facility’s water-collecting workings. This determinal effect adversely affects the operational efficiency of pumping equipment and the reliability of LHDs. To address these issues, an enhanced version of the conventional main drainage facility scheme, specifically designed for kimberlite mine utilizing the block caving method, is proposed. This modified scheme aims to provide improved clarification of the mine water in the water-collecting workings and facilitate more efficient dewatering of the settled slurry sludges. Furthermore, a methodology has been developed to determine the time required for slurry sludge removal, the sedimentation characteristics of the solid phase, and the rheological properties of the liquid phase of the mine water.

Natural convective non-Newtonian nanofluid flow in a wavy-shaped enclosure with a heated elliptic obstacle

A numerical investigation has been carried out in a wavy-shaped enclosure with an elliptical inner cylinder to find out the effect of an inclined magnetic field and a non-Newtonian nanofluid on fluid flow and heat transfer. Here, the dynamic viscosity and thermal conductivity of the nanofluid are also taken into account. These properties change with the temperature and nanoparticle volume fraction. The vertical walls of the enclosure are modeled through complex wavy geometries and are kept at a constant cold temperature. The inner elliptical cylinder is deemed to be heated and the horizontal walls are considered adiabatic. Temperature difference between the wavy walls and the hot cylinder leads to natural convective circulation flow inside the enclosure. The dimensionless set of the governing equations and associated boundary conditions are numerically simulated using the COMSOL Multiphysics software, which is based on finite element methods. Numerical analysis has been scrutinized for varying Rayleigh number (Ra), Hartmann number (Ha), magnetic field inclination angle (γ), rotation angle of the inner cylinder (ω), power-law index (n), and nanoparticle volume fraction (ϕ). The findings demonstrate that the solid volumetric concentration of nanoparticles diminishes the fluid movement at greater values of φ. The heat transfer rate decreases for larger nanoparticle volume fractions. The flow strength increases with an increasing Rayleigh number resulting in a best possible heat transfer. A higher Hartmann number diminishes the fluid flow but converse behavior is exhibited for magnetic field inclination angle (γ). The average Nusselt number (Nuavg) values are maximum for γ = 90°. The power-law index plays a significant role on the heat transfer rate, and results show that the shear-thinning liquid augments the average Nusselt number.

NOVEL MODEL FOR ESTIMATING GAS-SOLID TWO-PHASE FLOW RATE IN A HORIZONTAL PIPE

Dilute and dense conveying systems through pipelines are a common practice in our everyday life. It is used in many industries to convey a mixture of gas and solids from one location to another through pipes. Gas-solid transport is desirable in some industries but unwanted in others. Depending on the density, size, and shape, these solid particles may result in erosion and subsequent damage to piping and other equipment. Understanding the gas-solid two-phase flow dynamics can help develop efficient and cost-effective pipe transport systems, thereby mitigating the problems associated with the gas-solid two-phase flow. Models for estimating volumetric flow rates and other gas-solid two-phase flow properties are scarce as most are very complex, expensive, and unavailable proprietary commercial software. This study, therefore, developed a simple model using the general energy balance equation and relevant mixing theories for estimating the volumetric flow rate of natural gas-solid two-phase flow in horizontal pipes. The results from the model showed that the gas-solid flow rate is a function of pipe diameter, pressure drop, pipe length, solid volumetric concentration, solid-to-gas density ratio, and solid-to-gas friction factor ratio.

Dataset for "Volumetric solid concentration as a main proxy for basal force fluctuations generated by highly concentrated sediment flows"

Dataset for "Volumetric solid concentration as a main proxy for basal force fluctuations generated by highly concentrated sediment flows"

Dataset for "Volumetric solid concentration as a main proxy for basal force fluctuations generated by highly concentrated sediment flows"

Dataset for "Volumetric solid concentration as a main proxy for basal force fluctuations generated by highly concentrated sediment flows"

Dataset for "Volumetric solid concentration as a main proxy for basal force fluctuations generated by highly concentrated sediment flows"

Dataset for "Volumetric solid concentration as a main proxy for basal force fluctuations generated by highly concentrated sediment flows"

Control factors for mobility of dense and dilute debris flows

<p indent=0mm>Debris flow is a commonly occurring geological hazard in mountainous areas. The solid-liquid coupling makes the debris flows distinct from other geophysical fluids such as debris avalanches and floods. Owing to the complexity of this solid-liquid interaction, current research of debris-flow mobility focuses mainly on dense debris flows with a volumetric solid concentration of ~0.6. However, few studies focus on the physical processes occurring in the transition from dense to dilute debris flows with volumetric solid concentrations of 0.6–0.4. The objectives of this study are to explore the effects of changes in volumetric solid concentration on pore water pressure response and debris-flow mobility and to reveal the mechanisms in the transition from dense to dilute debris flows. Taking the debris-flow volumetric solid concentration and fluid viscosity as variables, a series of well-instrumented flume experiments is conducted. The results show that the high mobility of debris flow is closely related to the state of liquefaction. In the transition from dense to dilute debris flows, the shear dilatancy (state of solid particles) shifts from positive (dilation) to negative (contraction). As a result, the increase in pore water pressure causes the debris flow to liquefy, and the mobility surges accordingly. According to the calculated and measured shear stresses, it is apparent that the shear resistance of dense (dilute) debris flows is dominated by friction between the particles (viscous drag). An employed rheological model shows that the shear resistance in dense debris flows is insufficient for describing the rheological behavior of dilute flows. Models considering the interaction between particles, including friction and collision, and the viscosity of the fluid phase are warranted in future research.

Numerical modeling of multifrequency complex dielectric permittivity dispersion of clay-rich rocks

Dielectric permittivity measurements in sedimentary rocks are dominated by mineralogy, the volumetric concentration and spatial distribution of solids and fluids, and interfacial polarization. Conventional interpretation models oversimplify these factors, leading to uncertainties in estimates of formation properties such as hydrocarbon reserves. Interpretation challenges are magnified in clay-rich rocks, such as shaly sands and organic-rich mudrocks, due to convoluted rock fabric and mineralogical composition. However, the impact of fabric features and mineralogy on broadband permittivity is not well understood. Therefore, the main objective of this work is to develop a numerical framework to quantify the impact of different minerals and corresponding spatial distribution on the multifrequency complex permittivity of clay-rich rocks. We have solved the quasielectrostatic approximation to Maxwell’s equations in the frequency domain through the finite-volume method. We also introduce a workflow to calculate the effective admittance of the clay network. Furthermore, we derive an equation to incorporate the induced polarization effect into the effective admittance of pyrite particles. Finally, we perform a sensitivity analysis of the complex permittivity of clay-rich rocks in the frequency range from 100 Hz to 1 GHz to the volumetric concentration and spatial distribution of clays, cation exchange capacity (CEC), volumetric concentration of pyrite, and the orientation of the electric field. The simulation results confirm that the presence of clay minerals affects the permittivity and conductivity of the rocks. However, clays can enhance or diminish electrical conductivity values at different frequencies depending on their intrinsic properties and spatial distribution. For instance, laminations significantly enhance permittivity in the sub-MHz frequency range, but their effect is imperceptible at 1 GHz. The CEC variation affects conductivity in the entire frequency range from 100 Hz to 1 GHz and the permittivity at sub-MHz frequencies. A volumetric concentration of pyrite of 5% can enhance permittivity and conductivity at 100 Hz by approximately 50% and 30%, respectively.

Developing and evaluation of an electrical impedance tomography system for measuring solid volumetric concentration in dredging scale

In this study, an electrical impedance tomography (EIT) system was developed for measuring of sediments flow properties in dredging pipes. Considering relatively large diameter of the dredger pipe, salinity of seawater and online commitment of the system, some trade-offs were considered. A finite element model (FEM) was established for 16 EIT sensor to study the detection sensitivity. In the first stage, the EIT system is embedded in the loop of flow with diameter of 610 mm for the laboratory experiments, then the system performance was investigated in real conditions on a Suction Hopper Dredger. The EIT system performance was evaluated at three levels of NaCl concentration (7.5, 11.59 and 13.68 gr/lit) and temperature (17, 25, 30.7 °C). The standard deviation (SD) and root mean squire error (RMSE) parameters were used to evaluate the system performance, behind some conceptual assessments. Analysis of variance (ANOVA) of measured data show that the changes in salinity and temperature of liquid phase have no significant effect on the measured concentration by the EIT-based system. The coefficient of determination was almost 0.98 to 0.99 in different levels of sediment concentration that shows a linear trend and acceptable correlation between the data obtained from the EIT-based system and the data measured by the sampling method.

Evaluation of the residual moisture content in pilot scale vibrating screening operating with pressure reduction in the screen drying region

To study the aspects of solid-liquid separation in vibrating screening operations, experiments were carried out with a 3k experimental design, analyzing the following independent variables: g-force, angle of inclination of the screen, and volumetric concentration of solids in the feed. The influence of a reduction of the pressure on the dewatering process was also taken into account. The results obtained for the screening operation without pressure reduction indicate that the minimum residual moisture content was reached with a g-force of 3.0, screen inclination of 1.5°, and volumetric concentration of 6.0%. Additionally, the use of pressure reduction with a sieve allows for the lowest residual moisture content with a g-force of 3.0, 3.0° screen inclination, and 6.0% volumetric concentration. The major influence of pressure reduction in the residual moisture content was observed for the experiments with 2.0% of volumetric concentration, the lowest level adopted for this variable in the experimental design.

Vibration screening: A detailed study using image analysis techniques to characterize the bed behavior in solid–liquid separation

Particulate suspensions systems are present in various industrial sectors, vibrating screens being some of the most versatile pieces of equipment for the separation of these two phases. This paper presents a study of the dynamics of the mixture on the screen during solid–liquid separation using vibration screening. The independent variables studied were g-force, volumetric concentration of solids in the feed, feed flow rate and inclination of the screen. The equipment used was a vibrating screen of 175 mesh with 95 μm aperture size. The evaluated response variables were the residual moisture content of the retained solids, the screen area occupied by the liquid, the transport velocity of the retained solids and the screen area occupied by the retained solids. The solid material used was sand with a density of 2.67 g/cm3 and a Sauter mean diameter of 373 μm, and the liquid phase was composed of water containing 0.1% xanthan gum. A central composite design was applied to the experiments and the results for each response were analyzed statistically. It was possible to verify that the increase in the g-force and screen inclination variables increased the operational capacity, since the areas occupied by the liquid and the retained solids were reduced. It was also found that higher volumetric concentrations of solids in the feed favored a reduction in the moisture content of the retained solids and their transport on the screen, since larger particulate material conglomerates were formed, which had a more uniform displacement path.

Evaluation of the settling behavior of hematite in an olefin-based drilling fluid using gamma-ray attenuation technique

As oil is the main component of the world's energy matrix, it has a strong influence on the dynamics of countries' economic and monetary systems. The drilling of an oil well is performed using specific drilling fluids, so that this process is as fast and safe as possible. Each region of the well requires a drilling fluid with particular characteristics. The rheological behavior of fluids affects both the cleaning process of wells, via transportation of cuttings to the surface, and the sedimentation of cuttings and particles present in the fluid formulation during drilling fluid flow interruptions due to corrective or preventive operating stops. Thus, this study aimed (i) to evaluate the rheological behavior of the additive hematite in olefin-based drilling fluids, (ii) to indirectly monitor the volumetric concentration variation of hematite particles during sedimentation using a non-destructive method called gamma-ray attenuation technique, and (iii) to determine constitutive equations for pressure on solids. The results showed that the addition of hematite in the olefin-based drilling fluid resulted in a non-Newtonian behavior, indicated by the behavior index of the power-law rheological model below 1. This behavior was accentuated by the increase in the proportion of hematite from 7.27 to 9.28%. Regarding the variation of volumetric concentration of solids in sedimentation, the increase in solids concentration retarded the settling process. In addition, the sediment formed presented a compressible behavior; therefore, the constitutive equations for pressure on solids presented a power index.

NUMERICAL INVESTIGATIONS ON FLOW CHARACTERISTICS OF SAND-WATER SLURRY THROUGH HORIZONTAL PIPELINE USING COMPUTATIONAL FLUID DYNAMICS

The study presents the numerical computational fluid dynamics (CFD) analysis of sand-water slurry flow with different sand particle sizes viz. 90µm, 125µm, 150µm, 200µm and 270µm having specific gravity of 2.65 through a 103 mm diameter, 5.5 m long horizontal pipeline for a high flow velocity of 5.4 m/s at various solid volumetric concentrations viz. 10%, 20%, 30%, 36% and 40%. Granular version of Eulerian two-phase model with dispersed particles along with RNG –epsilon approach has been utilized. Non-uniform structured mesh with a refinement near the wall boundary has been selected for discretizing the computational flow domain while Navier-Stokes governing equations are solved in FLUENT 14.0. The effects of the size of sand particles and solid volumetric concentrations on territorial concentration distributions, particle flow velocity and pressure drops have been studied and analyzed. Generalized mathematical correlation has been developed from the simulated results for calculating the consequences of the size of solid particles and solid volumetric concentration on pressure drop analytically. The simulated outcomes of pressure drop are validated with the experimental results. These outcomes will be very helpful in the setup of an experimental model for sand/water slurry flow pipelines in many industries viz. mining, construction, power generation etc.

A low-error calibration function for an electrostatic gas-solid flow meter obtained via machine learning techniques with experimental data

In this paper, modeling and machine learning with experimental data and a novel calibration function for a gas-solid flow sensor fusion are presented. Sensor fusion is the use of software that intelligently combines data from multiple sensors in order to improve overall system performance. This technique can be applied to measurement of mass flow rate of solids in a pipeline with non-intrusive electrostatic techniques. Data fusion from multiple heterogeneous/homogenous sensors can overcome the limitations of an individual sensor and measured variable. It is shown that the output voltage of a ring-shaped electrode is predominantly a function of solids mass flow rate and velocity for a flow of bulk solids in a pipeline, when particle size, properties and ambient conditions remain constant. By incorporating solids flow velocity in a proposed mathematical model (obtained via machine learning), meter output voltage could be predicted with superior accuracy, for wide range of different flow parameters from numerous experiments with a pneumatic conveying system. Transposing the model yields a new calibration function which, when deployed in signal processing software, enables accurate mass flow measurement with velocity compensation. The described method also de-necessitates determination of air solids ratio or solids volumetric concentration, thereby enabling simplification of the overall measurement system whilst yielding higher accuracy than calibration methods from previous studies. Accurate flow measurement facilitates enhanced monitoring and controllability of blast furnaces, power stations, chemical reactors, process plants etc. where there are bulk solids flows in pipelines. Optimization of such highly materially consumptive and energy intensive processes can yield significant reductions in waste and emissions (CO2, NOx) and increased efficiencies in global production of energy and materials.

Gas dispersion and solid suspension in a three-phase stirred tank with triple impellers

The hydrodynamics is still not fully understood in the three-phase stirred tank equipped with multi-impeller due to the intensive interaction between phases. In this work, the solid critical suspension speed ( N JSG ), relative power demand (RPD) and overall gas holdup ( ε G ) were measured in an air–water–glass beads stirred tank equipped with multi-impeller, which consists of a parabolic blade disk turbine below two down-pumping hydrofoils. Results show that either the N JSG or the specific power consumption increases when increasing the volumetric solid concentration or superficial gas velocity. RPD changes less than 10% when solid volumetric concentration ranges from 0 to 15%. ε G decreases with the increase of solid concentration, and increases with the increase of both superficial gas velocity and the total specific power consumption. The quantitative correlations of N JSG , RPD and ε G were regressed as the function of superficial gas velocity, specific power consumption, Froude number and gas flow number, in order to provide the reference in the design of such three-phase stirred tank with similar multi-impellers. • Just-suspension speed, RPD and gas holdup with triple impeller were measured. • Superficial gas velocity significantly affects the suspension speed. • Overall gas holdup is evidently affected by the solid.

Quantification of Poinsettia Root Growth by Image Scans or X-ray Computed Tomography Scans in Three Propagation Substrates at Varied Moisture Levels

ABSTRACTThe objective was to refine protocols to quantify rooting of plant cuttings and the water/air microenvironment of substrates using x-ray computed tomography (CT). Poinsettia (Euphorbia pulcherrima) cuttings were propagated in three substrates (peat, rockwool, and phenolic foam) at varied moisture levels. In Experiment 1, adventitious rooting occurred in cuttings grown in rockwool or foam from 12% to 86% volumetric water content (VWC) and 12% to 80% volumetric air content (VAC). The highest root growth occurred in rockwool at 59% VWC and 33% VAC. There was an advantage to quantifying root growth by CT in rockwool and foam, in contrast to peat, because of clear differences in material density between root and substrate during image processing. In Experiment 2, root growth was quantified in peat by two-dimensional image scans under similar growth chamber environments, with rapid root growth from 52% to 63% VWC and 16% to 26% VAC. In Experiment 3, CT was used to quantify the substrate microenvironment at 0.5 cm slices to further describe the environment at the base of the plant cutting. Rapid rooting occurred in microenvironments above 56% VWC and 14% VAC, whereas the low 3% VAC in foam at high moisture may limit root growth.Abbreviations: volumetric water content (VWC), volumetric air content (VAC), volumetric solid content (VSC)

Power consumption and gas–liquid mass transfer in a hot-sparged three-phase stirred reactor

The volumetric mass transfer coefficient (kLa) is one of the most important parameters for design and scale-up of gas–liquid–solid three-phase mechanically stirred tank reactors. In this work, the effects of agitation speed, superficial gas velocity, temperature, and volumetric solid concentration (CV) on the power consumption and kLa were discussed and quantitatively analyzed. In an air-water-glass beads system, the gassed power number (NPG) and kLa increase remarkably with the temperature. At ambient temperature, kLa decreases significantly with increasing CV with a power law exponent of 3.10, but this decreasing effect becomes weaker at higher temperatures. In this hot-sparged three-phase system, the addition of solids slows down the increasing tendency of NPG with the temperature, but enhances the increasing tendency of kLa. The increase in temperature weakens the decreasing effect of CV on kLa. Compared with the effect of temperature on NPG and kLa, the effect of CV is nearly negligible. As a practical guide to industrial applications, it is more effective to enhance the gas–liquid mass transfer by increasing the temperature or power consumption than by changing CV or increasing superficial gas velocity. The empirical correlations of power consumption and kLa obtained in this work can provide helpful guidance for the industrial design and operation of hot-sparged three-phase stirred tank reactors.

Modelling solids friction for fluidized dense-phase pneumatic conveying

Fluidized dense-phase pneumatic conveying of powders has a number of benefits in various industries such as coal-fired thermal power plants, chemical, cement, pharmaceutical, petrochemical plants, etc. However, reliable designing of fluidized dense phase pneumatic conveying system is significantly difficult due to the complex and turbulent nature of the flow. In the present work, power station fly ash was conveyed through different pipeline configurations. Governing equations were developed for the fluidized dense-phase flow in the pneumatic conveying system and were solved using Runge-Kutta-Fehlberg method (RKF45). The results revealed that the particle velocity and actual gas velocity and the ratio of the two velocities increase along the direction of flow, while an opposite trend was observed for the solids volumetric concentration. A particle velocity model has been developed using solid loading ratio and dimensionless velocity terms. This particle velocity model, when employed in the existing two-layer model format for solids friction factor, has provided improved scale-up predictions (under diameter and length scale-up conditions) compared to the original two-layer model.

Strength development and microstructural characteristics of soft dredged clay stabilized with basic oxygen furnace steel slag

This paper presents the results of the strength development and macrostructure properties of soft dredged clay stabilized with basic oxygen furnace steel (BOS) slag, using the vane shear test, the unconfined compression test, and scanning electron microscope. The results indicate that the flowability exhibited a strong correlation with the undrained shear strength. A dormant period was observed, during which the BOS-treated clay strength did not increase during the 0.5–2 h curing times. Moreover, the strength development can be classified into three zones according to the strength increment rate in the log-log scale graph: 1) inactive zone (0.5–5 h), 2) active zone (5 h to 3 d), and 3) moderate zone (3–90 d). Empirical equations for each zone were proposed based on the volumetric solid content, initial water content, strength at 1 h of curing, and strength increment coefficients. Finally, the reticulation structure of the amorphous C-S-H gel and platy AFm phases on all samples were observed, with intergrowths of rod-like ettringite within the flat clay structure and flocculated clay-cement cluster, and the cementitious compounds became more evident with an increase in the BOS content and curing time.

Stability of oil well olefin drilling fluids: solid–liquid sedimentation and rheological characterization

Oil wells drilling processes are a crucial step in petroleum exploration and drilling fluids are an important player in this operation. Both solid–liquid sedimentation stability and appropriate rheological characteristics are significant and desirable aspects for drilling fluid. In this context, this study aimed at analyzing the stability of olefin drilling fluids, differentiated by calcium carbonate additive, related to solid–fluid interaction sedimentation and rheological behavior. Rheology, gravitational, and batch sedimentation experimental tests were performed as both time and function position. A low viscosity viscometer was used for the rheological characterization, and gamma-ray attenuation, a nondestructive technique, was applied to quantify the local volumetric solids concentration in sedimentary regions. The results showed a shear-thinning behavior and thixotropic effects in these fluids and the influence of calcium carbonate in the sedimentation profile. The thickened suspension showed higher values of apparent viscosity and lower sedimentation rates than the non-thickened system. Thus, the formulation of drilling fluids affected the solid–liquid separation process and the rheological behavior of suspensions; and, for that sense, it should be appropriated for drilling exploration.