Range Of Solids Concentrations Research Articles

Analysis of friction mechanism and homogeneity of suspended load for high concentration fly ash & bottom ash mixture slurry using rheological and pipeline experimental data

The particle–fluid and particle–particle interactions governing the flow of highly concentrated power plant ash slurries containing fine-grained and coarse-grained ash particles have been investigated. The friction mechanism and suspension of coarse bottom ash fractions conveyed in a finer fly ash slurry vehicle were analyzed using the rheological and pipeline experimental data in a solid concentration range of 62.5–67.5% by weight. The degree of homogeneity and possible heterogeneously distributed solid fraction for the mixture slurry along the vertical axis of the pipe were evaluated using the well known Ismail's equation. A nearly non-settling nature of the pseudo-homogeneous mixture slurry at high solid concentration under laminar pipe flow regime has been observed. It has been determined that this sort of response is mainly due to the presence of granular Coulombic and Bagnold forces.

Morphology Development in Amorphous Polymer:Fullerene Photovoltaic Blend Films During Solution Casting

The evolution of film structure is reported during solution casting of PCDTBT:PC70BM 1:4 wt%, a polymer:fullerene blend system that finds application in an organic photovoltaic device. Using the complimentary techniques of grazing‐incidence wide‐angle X‐ray scattering and spectroscopic ellipsometry, a number of distinct processes that occur during film formation are identified. This includes the growth of fullerene molecules into nanoscale aggregates, the onset of which coincides with the solubility limit of the material in the casting solvent being reached. An apparent delay in Bragg scatter from the PCDTBT‐rich phase of the film suggests that, for the film composition studied here, the aggregation of PC70BM precedes weak self‐organisation of the conjugated polymer. This behaviour is compared with the drying dynamics of a number of different polymer:fullerene blends that each contain a high weight fraction of fullerene molecules, and a range of comparable solid concentrations are identified beyond which the precipitation of fullerene aggregates from solution occurs. These observations provide an insight into the development of structure in relatively amorphous polymer:fullerene blends for organic photovoltaic applications and potentially assists the future optimisation of this category of materials.

Thermophilic bioleaching of heavy metals from waste sludge using response surface methodology

The bioleaching process is considered to be more efficient and environmentally friendly than conventional technologies for removal of heavy metals from waste sludge. The objective of this study was to develop an optimal thermophilic bioleaching process for the treatment of waste sludge containing high concentrations of heavy metals. In this study, two operating parameters, sludge solid content and sulfur (substrate) concentration, were studied based on a central composite design (CCD) for their metal solubilization and solid degradation performances. The optimal bioleaching operation conditions were then determined using the response surface methodology (RSM). The results indicated that an increase in sludge solid content range from 0.5% to 5.0% resulted in a decrease in the pH reduction rate due to the increase in buffering capacity. The rate of acidification corresponded to sulfur concentration until sulfur itself became inhibitory. At sulfur concentration beyond approximately 2.75%, the lower acidification rate was caused by a lower bacteria growth rate. Similar trends were also observed in the variations of ORP and sulfate concentrations during this thermophilic bioleaching process. At the optimum conditions of a sludge solid content of 0.5% and sulfur concentration of 2.5%, the thermophilic bioleaching process achieved the maximum solubilization of 97%, 99%, 99% and 78% for Cu, Zn, Ni and Pb, respectively. At the same time, the maximum SS and VSS destruction efficiency were 69% and 63%, respectively.

Investigation on stability and rheological properties of nanofluid of ZnO nanoparticles dispersed in poly(ethylene glycol)

The nanoparticles of ZnO have been dispersed in base fluid of poly(ethylene glycol), PEG. Stability of this nanofluid has been verified with UV–vis spectroscopy. Dynamic light scattering was used to obtain particle size of investigated nanofluid. Rheological behavior of this nanofluid has been investigated over a range of volumetric solid concentrations (ϕ1=0.41–4.71%) and shear rates (γ=0.01–1000s−1) at 298.15K. The nanoparticle suspensions generally exhibited a pseudoplastic flow behavior, indicating an existence of particle aggregations in the liquid medium. Bingham plastic and Herschel–Bulkley models were used to evaluate the shear stress–shear rate dependency. The colloid yield stresses were determined from these models. The suspension structure was estimated from the values of fractal dimension which obtained from colloid yield stress and concentration dependency. Carreau–Yasuda model was used to evaluate the shear rate dependency of viscosity at each concentration. The new method was also proposed for correlating the viscosity values of ZnO–PEG nanofluid including concentration and shear rate dependency on the basis of Carreau–Yasuda model, Eyring absolute rate theory, NRTL, mNRF and Krieger–Dougherty models.

The impact of achieving a higher aggregate density on polymer-bridging flocculation

The polymer-bridging flocculation processes that take place in hydrometallurgical thickening are very much affected by the solid concentration at the point of flocculant dosing, with the optimum concentrations maximising settling flux often well below that of the thickener feed. This is a consequence of the open, low density aggregate structures formed by flocculation. Achieving adequate solids dilution in full-scale applications can be problematic, and a flocculant that can produce a denser aggregate and thereby reduce the extent of solids dilution required may offer practical advantages. There is evidence that Rheomax® DR 1050 (BASF) has such potential, although detailed quantification of this has not been previously published.The kinetics of flocculation of fine calcite slurries in turbulent pipe flow by Rheomax DR 1050 was contrasted against a conventional acrylamide/acrylate copolymer over a range of solid concentrations and dosages. Focused beam reflectance measurement (FBRM) was used to provide in-line monitoring of aggregate size as a function of reaction time, with batch sampling also producing corresponding settling rates. These reaction profiles confirmed distinct responses to solid concentration for the two flocculants; the conventional flocculant was superior in the range 20–40kgm−3, while the optimum for Rheomax DR 1050 was near 60kgm−3. Fitting of a population balance model to this kinetic data indicated that this behaviour primarily reflected a higher fractal dimension from flocculation with Rheomax DR 1050. The experimental results and model predictions are used to explore the practical scenarios under which Rheomax DR 1050 would be expected to perform best, showing that even at high solids, the benefit may only be realised in applications requiring higher dosages and mass throughputs. The practical limitations of the experimental approach used here to measure flocculation kinetics are also discussed.

Characterisation of dewaterability from equilibrium and transient centrifugation test data

A knowledge of the properties that quantify the rate and extent of particulate suspension dewatering through sedimentation and consolidation is critical to the prediction of dewatering performance for industrial processes such as gravity settling, centrifugation and filtration. The strength of a network of particles in compression is quantified as a compressive yield stress or modulus, Py(ϕ). The rate of dewatering is inversely related to the hindered settling function, R(ϕ), which is a measure of hydrodynamic resistance. Dewaterability characterisation over a broad range of solids concentrations is a challenging task requiring tests including batch settling and pressure filtration. Unfortunately, for many systems, these tests are prohibitively slow and an alternative such as centrifugation is useful in accelerating the characterisation. This paper validates algorithms for the characterisation of dewaterability from centrifugal sedimentation data obtained in a laboratory centrifuge with interface height detection and provides guidelines for obtaining accurate results over a broad range of solids concentrations.Typical dewaterability data for a flocculated industrial mineral slurry and a biological sludge are used as inputs for the numerical prediction of centrifugal sedimentation behaviour. Equilibrium centrifugation at a range of rotation speeds has been simulated and Py(ϕ) data determined using a method described by Buscall and White (1987). The result is shown to be accurate to within 10% of the expected values. Transient centrifugation data has been simulated and R(ϕ) determination using a new algorithm is shown to be accurate over a broad range of solids concentrations extending beyond the gel point, provided a new data rejection criterion is utilised. In addition, errors at low concentration in R(ϕ) data, caused by dilution, are described. It is shown that currently available analysis techniques are unlikely to quantify these errors.

Physicochemical and Rheological Behavior of African Star Apple Chrysophyllum Albidium) Juice as Affected by Concentration and Temperature Variation

The viscosity, shear stress and shear rate of African star apple juice (Chrysophyllum albidium) at different concentrations of 8 % to 32% total solid concentration and temperature range of 20°C to 70°C were obtained in order to determine the effect of changes in concentration and temperature on the rheological properties of the juice. Also, the physico-chemical analyses of the sample were carried out. Plot of shear stress against shear rate showed that at all concentrations, African star apple juice behaved as a non-Newtonian fluid at temperature below 60°C. At 70°C, however, lower concentration (8% and 12%) behaves non-Newtonian while higher concentrations behave Newtonian. Increase temperature decreases the viscosity of the juice. The knowledge of rheological properties of African star apple juice is essential for the design and optimization of energy process and heat transfer.

The Czochralski growth and structural investigations of Ba(MoO4)x(WO4)1−x solid solution single crystals

Ba(MoO4)x(WO4)1−x (x=0; 0.05; 0.1; 0.25; 0.5; 0.7; 0.95; 1) single crystals were grown by the Czochralski technique for the first time. A complete mutual solubility of the entire solid solution concentration range with tetragonal scheelite structure at room temperature was established by XRD analysis and Raman spectroscopy of as-grown crystals. By comparison of the differential-thermal analysis data and the high temperature Raman spectra, the existence of a cubic α-modification of the solid solutions is identified at x>0.5 in the temperature region above 1200°С. The double-mode behavior of the ν1(Ag) band in the vibration spectrum, weak broadening and high peak cross section of the ν1(Ag) vibration modes make these single crystals a promising material for dual-line SRS-conversion with a Raman shift of 889 and 925cm−1.

Thermophysical Properties of Papaya Puree

The effects of soluble solids content and temperature on thermal properties of papaya puree were studied. Density and specific heat were measured using a pycnometer and differential scanning calorimeter, respectively, while thermal conductivity was measured using a line heat source probe. Thermal diffusivity was then calculated from the experimental results of the specific heat, thermal conductivity, and density. Thermal properties of papaya puree were experimentally determined within a soluble solids content range of 10 to 25 °Brix and temperature between 40 and 80°C. The density, specific heat, thermal conductivity, and thermal diffusivity of papaya puree were found to be in the ranges of 1014.6 to 1098.9 kg/m3, 3.652 to 4.092 kJ/kg °C, 0.452 to 0.685 W/m °C, and 1.127 × 10−7 to 1.650 × 10−7 m2/s, respectively. Moreover, the empirical models for each property as a function of soluble solids content and temperature were obtained.

Comportamiento de flujo y caracterización fisicoquímica de pulpas de durazno

Rheological and physicochemical analyses were conducted on nine varieties of peach pulps from Mendoza (Argentina) at a range of soluble solids concentration (12.5 to 28°Brix) and temperatures (30 to 50°C).The rheology of the pulps followed the power law model for all conditions, behaving as pseudoplastic fluids. Rheological: consistency coefficient and flow behavior index, using a rotational type viscometer and physicochemical parameters (methods proposed by AOAC): soluble solids, pH, water content, insoluble solids, acidity and pectin content (refractometric method) were determined in this study. Cluster analysis established two groups (1: Halford, Andross, Astengo, Bowen, Sim’s Cling; 2: Fortuna, Loadel and Palora; Sullivan Cling variety could not be assigned to any group) with significant differences.

Zwietering's Equation for the Suspension of Porous Particles and the Use of Curved Blade Impellers

The minimum speed for just-suspension,Njs, of porous palm shell-activated carbon (PSAC) particles has been determined in a 15 cm diameter cylindrical tank using a 6-curved blade (6CB) impeller, compared to a 6-blade downpumping mixed-flow (6MFD) impeller and a Rushton turbine (6DT). The particles size ranged from 0.75–1.00 mm, 1.00–1.40 mm, and 1.40–2.36 mm with concentrations between 0 and 5% by weight. The 6CB being a radial impeller performed similarly to 6DT in terms of speed and power requirement at just-suspension, and particles distribution on the base. The 6MFD, with power requirement 100% to 200% less than the radial impellers, was the most efficient for suspending the particles, as usually reported for the range of solid concentrations used here. Specific power per unit mass for all three impellers showed reduction towards minima as the concentration of particles increased. The geometric factor,S, values agreed reasonably with published data, when the particle density was adjusted taking into account water filling the pores of the submerged activated carbon. This result means that Zwietering’s equation can be used to predict suspension for porous particles with adjustment to the particle density.Svalues for curved-blade impellers are presented for the first time.

Dispersion and rheology of surfactant-mediated silver nanoparticle suspensions

Polycrystalline silver (Ag) nanoparticles were dispersed in solvent mixtures consisting of 2-butoxyethyl acetate (BCA) and diethylene glycol monoethyl ether acetate (CA) in a BCA:CA weight ratio of 5:1. Three commercially available polymeric surfactants were used, and the gravitational sedimentation, agglomerate-size distribution, isothermal adsorption, and rheological behavior of the nanoparticle suspensions were examined. One of the surfactants (hereafter termed 9250) was found effective in stabilizing the Ag nanoparticle suspensions. Both the adsorption isotherm and the Fourier transform infrared spectroscopy revealed the preferential adsorption of the 9250 surfactant molecules on the nanoparticle surface, forming a Langmuir-type monolayer adsorption in the given solvents so that a steric stabilization was rendered. An optimal surfactant concentration of 5wt.% (in terms of the solids weight) was determined experimentally. In addition, the Ag suspensions with a broad range of solids concentration (ϕ=1–16vol.%) showed a shear-thinning flow character over a shear-rate range from 1 to 4000s−1, revealing that an attractive interparticle interaction was operative. Relative viscosity (ηr) of the nanoparticle suspensions deviated from the linearity when ϕ was greater than ∼10 vol.%; at which, the attractive potential began to dominate the interparticle interactions. This ηr–ϕ dependence was compared with various existing models and the (viscosity) predictive capability of the models was discussed.

Extended Triple Layer Modeling of Arsenate and Phosphate Adsorption on a Goethite-based Granular Porous Adsorbent

The extended triple layer model (ETLM), which is consistent with spectroscopic and theoretical molecular evidence, is first systematically tested for its capability to model adsorption of arsenate and phosphate, a strong competitor, on a common goethite-based granular porous adsorptive media (Bayoxide E33 (E33)) in water treatment systems under a wide range of solution conditions. Deprotonated bidentate-binuclear, protonated bidentate-binuclear, and deprotonated monodentate complexes are chosen as surface species for both arsenate and phosphate. The estimated values of the ETLM parameters of arsenate for the adsorbent are close to those for pure goethite minerals previously determined by others. The ETLM predictions for arsenate and phosphate adsorption basically agree with experimental results over a wide range of pH, surface coverage, and solid concentrations. High background electrolyte concentration (i.e., I = 0.1 M), however, was found to strongly impact arsenate and phosphate adsorption on E33 probably because of the porous structure of the adsorbent, which cannot be observed for pure goethite minerals and could not be completely modeled by the ETLM. Prediction of phosphate adsorption isotherms at higher pH were relatively poor, and this may suggest searching for alternative surface species for phosphate. Since adsorption equilibrium constants of major coexisting ions encountered in water treatment systems for goethite minerals have been estimated by others, the application of ETLM theory to this common goethite-based adsorptive media will enable us to understand how those coexisting ions macroscopically and thermodynamically interact with arsenate and phosphate in the environment of adsorptive water treatment system in a way consistent with molecular and spectroscopic evidence.

Characterization of changes in viscosity and insoluble solids content during enzymatic saccharification of pretreated corn stover slurries

Viscosity trends in pretreated corn stover slurries undergoing enzymatic saccharification were characterized for a range of initial insoluble solids concentrations from 10% to 25% and correlated with total glucose released and changes in insoluble solids concentration throughout a 7 day period. Viscosity trends are defined in two phases, which coincide with two rate zones observed in the release of sugar during enzymatic hydrolysis. Viscosity rapidly decreased as initial solids concentration decreased in the first phase, and appears to reach a steady value for the lower solids concentrations in the second phase. The first phase is defined as approximately the first 8 h of the reaction based on the rates of glucose release, viscosity changes, and insoluble solids changes. A method for premixing the slurry samples in the viscometer cup prior to viscosity measurements is introduced. The method takes into consideration the need to maintain a uniform solids suspension while ensuring steady-state flow inside the viscometer cup. The slurries exhibit pseudoplastic behavior and are well described by the power law model for non-Newtonian fluids throughout the course of the reaction. Small changes in percent solids concentration lead to order of magnitude differences in viscosity.

Dissolution of minerals during hydrolysis of fish waste solids

Biological degradation of fish waste solids in the anaerobic zones of settling basins can reduce water quality and increase the environmental impact of aquaculture farms. The objectives of this study were to measure the rate of hydrolysis of waste solids from a salmon smolt hatchery and to investigate the concomitant dissolution of phosphorus and nitrogen. Hydrolysis followed first order kinetics with a reaction time constant of about 2 days. The rate of production of volatile fatty acids (VFA) appeared to be limited by the rate of conversion of solids into soluble organic material. The total ammonia–nitrogen concentration increased linearly with VFA concentration. As the pH dropped due to the generation of VFA, the concentrations of dissolved phosphorus and calcium increased, especially once the pH dropped below 6.5. Solids content had little effect on dissolved phosphorus concentration within the range of solids concentrations tested (0.5 wt.%–9.02 wt.%). The effect of pH on the dissolved phosphorus and calcium concentrations is well described by an equilibrium model based on the solubility of dicalcium phosphate dihydrate.

Rheology and colloidal structure of silver nanoparticles dispersed in diethylene glycol

Rheological behavior of agglomerated silver nanoparticles (~ 40 nm) suspended in diethylene glycol over a wide range of volumetric solids concentrations ( ϕ = 0.11–4.38%) was studied. The nanoparticle suspensions generally exhibited a yield pseudoplastic behavior. Bingham plastic, Herschel–Bulkley and Casson models were used to evaluate the shear stress-shear rate dependency. Analyzing the effect of silver concentrations on the yield stress and viscosity of the suspensions followed an exponential form, revealing an increase in the degree of interparticle interactions with increasing solid concentrations. Fractal dimension ( D f ) was estimated from the suspension yield stress and ϕ dependence, and was determined as D f = 1.51–1.62 for the flocculated nanoparticle suspensions. This suggested that the suspension structure was probably dominated by the diffusion-limited cluster–cluster aggregation (DLCA) due mostly to the strong attractions involved in the interparticle potentials. Maximum solids concentration of the suspensions was determined to be ϕ m = 11%.

Modeling of viscosity for power plant ash slurry at higher concentrations: Effect of solids volume fraction, particle size and hydrodynamic interactions

The rheological behaviour of five fly ash samples (having different d 50) collected from a thermal power plant has been investigated over a range of volumetric solids concentration ( ϕ = 0.32–0.4945) in shear rate range of 10–200 s − 1 . The slurry was highly pseudo-plastic whose behavior can be described by a non-Newtonian power law model in the range of solids concentration studied. The maximum solids fraction ( ϕ m ) at which the slurry viscosity approaches infinity, was determined for the fly ash samples using the relationship between inverse of relative viscosity (i.e. 1 μ r ) and volume fraction of solids ϕ. A model incorporating maximum solids fraction ( ϕ m ), power law index ( n), median particle size ( d 50), co-efficient of uniformity ( C U), shear rate ( γ̇) has been developed to predict the viscosity. The model predictions and the experimental data matched quite well for all five samples and it is expected to be quite helpful in evaluating the hydraulic parameters for design of commercial high concentration fly ash slurry pipelines. The most important variables such as volume fraction of solids, particle size, and size distribution, and their effect on the hydrodynamic forces in a non-Newtonian laminar flow regime are discussed.

Polyacrylamide-treated kaolin: A fabric study

Abstract Particle interactions, and in turn fabric, determine the behavior of clay mineral particle systems. Polymers with deliberately chosen characteristics, such as molecular mass and ionic type, can be utilized to manipulate clay fabric. The purpose of this study is to understand fabric development in a clay–polymer system, specifically kaolin–polyacrylamide systems over a wide range of solids content. Methodologies include sedimentation tests (low solids content), viscosity measurements (moderate solids content), and liquid limit measurements (high solids content), and are conducted to determine variation in fabric for kaolin–polyacrylamide systems at various concentrations, molecular mass and ionic types of polyacrylamide. Fabric development is verified using scanning electron microscopy (SEM). Results show that the polymer charge type impacts the resulting fabric formation only at polymer concentrations above a threshold concentration. Floc/aggregate size and density tend to increase with increasing polyacrylamide concentration, while high molecular-mass polyacrylamides tend to induce the formation of open flocculated structure. The most likely particle association in the presence of nonionic polyacrylamides is face-to-face association due to polymer bridging. A relationship is found between polymer characteristics, solids contents, and micro-scale particle arrangement. This study is relevant to the emerging field of engineered soil fabrics.

Predicting Viscosity of Limestone–Water Slurry

The rheological behavior of limestone–water slurry samples was investigated for different volume concentrations, particle size distribution and slurry temperature. Experiments were conducted over a range of volumetric solids concentration (Q= 0.20 - 0.46) in shear rate range of 1-300 s-1. The slurry showed Newtonian behavior up to a volumetric solids concentration of 37.8 vol. %, beyond which the slurry was highly pseudoplastic in nature and fitted excellently to a non-Newtonian Power law model. The relative viscosity (Nr) of the mixture slurry, defined as the suspension viscosity over the viscosity of the suspending medium was found to be increasing exponentially when Q exceeds 0.404. By adopting an experimental approach, the rheological data indicated that Q might reach 0.462. Using the ( 1-Nr-1/2 ) -Q relationship proposed by Liu, the theoretical maximum solids fraction (Qm) was evaluated as Qm= 0.504 for the given slurry samples and was then used to predict the relative viscosity (Nr) by some existing models. Five empirical models namely; Liu, Dabak et al., Krieger-Dougherty, Mooney and Chong et al. were considered for the purpose. Liu’s model better predicted the relative viscosity and thus would be helpful in evaluating the hydraulic parameters accurately for design of limestone slurry pipelines operating at high concentrations.

New Calibration Methods for Accurate Electrical Capacitance Tomography Measurements in Particulate-Fluid Systems

Three different calibration techniques have been developed to greatly improve the accuracy of the solid holdup distributions obtained from electrical capacitance tomography (ECT) measurements. First, liquid mixtures are used to calibrate the ECT system. Second, the relative permittivity of solid particles is obtained by immersing the solids in different fluids: the solid relative permittivity corresponds to the point where the fluid relative permittivity matches the relative permittivity of the liquid−solid mixture. Third, the best relationship between solid holdup and electrical permittivity, over the required range of solid concentrations, is determined, for each particulate system, by suspending the particles in a viscous liquid honey.