Feed Solids Concentration Research Articles

The Effect of Feed Solids Concentration and Inlet Temperature on the Flavor of Spray Dried Whey Protein Concentrate

Previous research has demonstrated that unit operations in whey protein manufacture promote off-flavor production in whey protein. The objective of this study was to determine the effects of feed solids concentration in liquid retentate and spray drier inlet temperature on the flavor of dried whey protein concentrate (WPC). Cheddar cheese whey was manufactured, fat-separated, pasteurized, bleached (250 ppm hydrogen peroxide), and ultrafiltered (UF) to obtain WPC80 retentate (25% solids, wt/wt). The liquid retentate was then diluted with deionized water to the following solids concentrations: 25%, 18%, and 10%. Each of the treatments was then spray dried at the following temperatures: 180 °C, 200 °C, and 220 °C. The experiment was replicated 3 times. Flavor of the WPC80 was evaluated by sensory and instrumental analyses. Particle size and surface free fat were also analyzed. Both main effects (solids concentration and inlet temperature) and interactions were investigated. WPC80 spray dried at 10% feed solids concentration had increased surface free fat, increased intensities of overall aroma, cabbage and cardboard flavors and increased concentrations of pentanal, hexanal, heptanal, decanal, (E)2-decenal, DMTS, DMDS, and 2,4-decadienal (P < 0.05) compared to WPC80 spray dried at 25% feed solids. Product spray dried at lower inlet temperature also had increased surface free fat and increased intensity of cardboard flavor and increased concentrations of pentanal, (Z)4-heptenal, nonanal, decanal, 2,4-nonadienal, 2,4-decadienal, and 2- and 3-methyl butanal (P < 0.05) compared to product spray dried at higher inlet temperature. Particle size was higher for powders from increased feed solids concentration and increased inlet temperature (P < 0.05). An increase in feed solids concentration in the liquid retentate and inlet temperature within the parameters evaluated decreased off-flavor intensity in the resulting WPC80.

Computational Study of the Multiphase Flow and Performance of Hydrocyclones: Effects of Cyclone Size and Spigot Diameter

This paper presents a numerical study of multiphase flow in hydrocyclones with different configurations of cyclone size and spigot diameter. This is done by a recently developed mixture multiphase flow model. In the model, the strong swirling flow of the cyclone is modeled using the Reynolds stress model. The interface between liquid and air core and the particle flow are both modeled using the so-called mixture model. The solid properties are described by the kinetic theory. The applicability of the proposed model has been verified by the good agreement between the measured and predicted results in a previous study. It is here used to study the effects of cyclone size and spigot diameter when feed solids concentration is up to 30% (by volume), which is well beyond the range reported before. The flow features predicted are examined in terms of the flow field, pressure drop, and amount of water split to underflow, separation efficiency and underflow discharge type. The simulation results show that the mult...

The theoretical partition curve of the hydrocyclone

In many cases, the hydrocyclone partition curve exhibits a non-monotonic course in the fine particle range. The so-called fish-hook effect indicates an increased separation of the fine fraction, which is of practical interest and has a positive effect on solid/liquid separation. However, for classification purposes, the separation is less distinct. In this contribution an equation of a partition curve containing a fish-hook is derived considering the laws of disturbed settling in dense, polydisperse suspensions. The following effects are considered: the entrainment of fine particles in the boundary layer of the coarse settling particles, the hindered settling due to the increased effective density and viscosity of the fluid, and the counter flow of the displaced fluid caused by the settling particles. The calculations indicate that the fish-hook effect is primarily caused by fine particle entrainment, which is influenced by the feed solid content and the feed particle size distribution. An approximated analytical solution for the partition curve is presented for aRosin–Rammler–Sperling–Bennet (RRSB)-distributed feed. Experiments using 25-mm hydrocyclone confirm the calculations.

Treatment of a Nickel-Copper Sulphide Concentrate Using Bioleaching

This paper describes bioleach test work performed in continuously operated bench-scale reactor systems on a nickel-copper containing sulphide concentrate at 45 and 70°C, respectively. Optimisation of the process focused on determining the effects of process parameters such as residence time, grind size and feed solids concentration on the leach kinetics, metal extractions and performance of both the moderate thermophile and thermophile cultures. The results showed that nickel recoveries in excess of 96% could be achieved using a moderate grind size and leach temperatures, whereas ultrafine grinding and higher operating temperatures were required to achieve Cu extractions in excess of 93%.

Spray drying of the mixtures of mono-, di-, and oligosaccharides

Abstract Optimal conditions of spray drying of a fructooligosaccharide-rich mixture prepared by enzymatic conversion of sucrose were investigated. It was found that efficient drying of the mixture containing about 40 % of monosaccharides and sucrose required addition of a compound with a high glass transition temperature. The addition of maltodextrin helped to achieve satisfactory solids yield and moisture. Optimized process parameters were the feed flow rate and solids concentration, drying air flow rate and inlet temperature.

Towards spray drying of high solids dairy liquid: Effects of feed solid content on particle structure and functionality

A micro-fluidic-jet spray dryer was used to fabricate spray freeze dried (SFD) and spray dried (SD) uniform microparticles with feed solid content >30wt% of reconstituted skim milk. The effects of feed solid content on the particle size, morphology, surface composition, wettability and solubility were investigated. The surface composition of SFD and SD sample was characterized via an X-ray photoelectron spectroscopy. Fat and protein was found to be over-represented on the SD particle surface, while lactose significantly declined. Such ingredient segregation was quantitatively shown to occur during atomization and continue within the drying process, i.e. atomization-induced ingredient segregation (AIIS) and drying-induced ingredient segregation (DIIS). The wettability and solubility of the spray dried samples were quantified using scaled-down GEA Niro Methods in relation to the feed solid contents.

Towards direct potable reuse with forward osmosis: Technical assessment of long-term process performance at the pilot scale

In this study we evaluated the performance of forward osmosis (FO) at the pilot scale to achieve simultaneous seawater desalination and wastewater reclamation. The investigation was performed with a commercial spiral wound FO membrane element for approximately 1300h of continuous operation, processing 900,000L of wastewater effluent and producing 10,000L of purified water through a hybrid FO-RO process. Water and solute fluxes were monitored during the study. Reversible and irreversible membrane fouling was observed; however, water flux was maintained at a relatively constant rate of 5.7±0.2Lm−2h−1 with MBR permeate feed and seawater draw solution. Subsequent increase of total suspended solids (TSS) concentration in the FO feed (secondary treated effluent with 5 to 16mgL−1 TSS) resulted in incremental flux decline; however, the membrane typically achieved stable water flux after the initial exposure to foulants. Additional analysis focused on bi-directional transport of inorganic species and a detailed evaluation of dissolved organic matter permeation through the membranes in the hybrid process. Evaluation of sample fluorescence revealed that the FO membrane and the hybrid process provide a strong barrier to protein-like fluorophores associated with wastewater effluent. Results also demonstrated the robust nature of dual barrier membrane systems to achieve greater than 99.9% removal of orthophosphate and dissolved organic carbon and more than 96% rejection of nitrate. Upon completion of the study a comprehensive membrane autopsy was performed on the FO and RO membranes. Organic fouling on the FO membrane was observed to have low adhesion to the membrane surface, but did result in some modification to membrane active layer properties.

A mechanistic model for ultrafiltration membrane fouling by latex

A mathematical model was developed to predict the amount of fouling based on analyses of particle attachments. Fouling could be primarily attributed to the attachments among foulant entities (coagulation attachment) and between foulants and membrane surfaces (depositional attachment). The model was combined with the Hermia model to further develop models for transmembrane pressure prediction. Simulation results indicate that depositional attachment is primarily responsible for reversible and irreversible membrane fouling.The model was validated using experimental data of ultrafiltration of a latex paint solution under a constant feed flow rate and cross-flow mode with a polycarbonate membrane. Feed solid concentration, feed flow rate, permeate flow rate and membrane properties influenced the latex retention and the transmembrane pressure. It was found that increase in the feed concentration and the permeate flow rate resulted in increasing fouling probabilities, latex retention and transmembrane pressure. On the other hand, increasing the feed flow rate led to an opposite effect. Transmembrane pressure estimated from the mathematical models agreed with the transmembrane pressure experimentally measured within 5–8% error. Overall, this study established a mechanistic model useful in understanding and predicting UF membrane fouling with the use of experimentally determined attachment probabilities.

Investigation of a novel 3-fluid nozzle spray drying technology for the engineering of multifunctional layered microparticles

Objective: To examine the potential of a novel 3-fluid nozzle spray drying technology to formulate differentiated layered microparticles (MPs) of diclofenac sodium (DFS)/ethyl cellulose (EC).Methods: DFS/EC MPs were formulated using the inner and/or outer nozzles of a novel 3-fluid nozzle and compared with MPs formed using conventional (2-fluid) spray drying. MPs were characterised for particle size and for morphology by TEM and SEM. Distribution of DFS and EC of MPs was analysed by FT-IR and DSC. A two-factor, three-level (32) factorial design was applied to investigate the effect and interaction of total feed solid content (TSC) and feed flow rate (FFR) on MP size, D50% and D90%, bulk density and MP yield.Results: Interestingly, TEM demonstrated that MPs formed by 3-fluid nozzle spray drying showed a heterogeneous internal morphology consisting of a core and coat, characteristic of a microcapsule. In comparison, MPs from conventional spray drying showed a homogeneous internal morphology, characteristics of a matrix system. This differential distribution of DFS/EC was supported by FT-IR and DSC. Results of multiple linear regression analysis showed a linear relationship for the effect of TSC and FFR on all responses except for D50% where a quadratric model was valid. The effect of TSC/FFR on MP size and yield was similar to conventional spray drying.Conclusion: The novel 3-fluid nozzle spray drying offers a new method of designing layered microparticles or microcapsules which can have wide applications from drug stabilisation to controlled drug delivery and targeting.

A method for pomegranate seed application in food industries: Seed oil encapsulation

During the industrial processing of pomegranate, large volumes of industrial wastes (seeds, peels, leaves) are produced, which have a wide range of nutritional values. In this work, a new method for pomegranate seed application in food industries was developed based on the extraction of seed oil and its subsequent encapsulation by spray drying. Skimmed milk powder was used as encapsulating agent. Ratio of core to wall material, feed solids concentration, inlet air temperature, and drying air flow rate were the factors investigated with respect to encapsulation efficiency using a central composite design. The resulting microcapsules were evaluated in terms of moisture content, particle size, bulk density, and hygroscopicity. The optimum operating conditions were found to be: ratio of core to wall material, 1/9; feed solids concentration, 30% (w/w); inlet air temperature, 187°C; drying air flow rate, 22.80m3/h. Under these conditions, the maximum encapsulation efficiency was about 95.6%.

A compressional rheology model of fluctuating feed concentration during filtration of compressible suspensions

Abstract Filtration is a common process used to perform solid–liquid separation. This work addresses a previously overlooked yet significant aspect of filtration when the feed solids concentration varies on the same timescale of the filtration process. This affects the filtration rate and therefore the throughput of the filter. Existing one-dimensional models of fixed-cavity and flexible-membrane plate-and-frame filtration based on compressible suspension theory, in which the cake concentration as a function of thickness and time is given by a hyperbolic second-order diffusion equation, are expanded here using a filtrate volume dependent feed concentration. The key material properties are the compressive strength and the solids diffusivity. Two limiting approximations for the suspension flow behaviour above the filter cake are considered; perfect mixing and plug flow. Three case studies are presented exploring different aspects of fluctuating feed. Modelling results indicate that fluctuations in feed concentration can have a large effect on solids throughput as a function of final cake solids concentration. A key result is that, when processing a fixed volume of suspension, dilute feed followed by concentrated feed leads to faster overall filtration than the reverse case. The two limiting approximations of suspension flow behaviour show no significant difference under the examined conditions since the filtration kinetics are dominated by the rate of fluid flow through the cake, not the suspension.

Numerical study of liquid–gas–solid flow in classifying hydrocyclones: Effect of feed solids concentration

This work presents a numerical study of liquid–gas–solid flow in classifying hydrocyclones (CHs). In the numerical model, the turbulent flow of a liquid–gas–solid mixture is modelled using the Reynolds stress model. The interface between the liquid and air core, and the particle flow are both modelled using the mixture multiphase model under different conditions. The flow features are examined in terms of flow field, pressure drop, amount of water split to underflow, and separation efficiency. The approach is first verified by comparing the measured and calculated results. Then, it is used to investigate the effects of feed solids concentration and its fluctuation. The results show that when feed solids concentration is increased, the separation efficiency decreases while the cut size increases; the inlet pressure initially decreases to a minimum and then increases, and the amount of water split to underflow firstly increases to a maximum and then decreases. It is also shown that the air core, solid mass flowrates on the underflow and overflow, and inlet pressure drop fluctuate corresponding to feed solids fluctuation. However, the fluctuation only affects the average CH separation efficiency slightly.

Air-core modelling for hydrocyclones operating with solids

The air core is one of the most important internal structures in the flow field of hydrocyclones. One difficulty in predicting the flow split in cyclones is the inability to specify the form and location of the air-core surface. In the usual cyclone models the interface that bounds the air-core is described by a fixed cylindrical surface, which greatly simplifies the problem. Most of the available air core models suit only hydrocyclones operating with water or very dilute slurries. An attempt has been made in this study to develop a semi-empirical model, capable of predicting the air core diameter correctly for hydrocyclones under different operating conditions. The model considers the effect of axial length, underflow and overflow dimensions, feed solids concentration and other significant operating conditions on predict air core size. The predictions are compared with data sets available in the literature. It was observed that the air core diameter reduces with increase in the feed solids concentration and with decrease in height from the roof of the cyclone towards the apex zone.

Shall we upgrade one-dimensional secondary settler models used in WWTP simulators? – An assessment of model structure uncertainty and its propagation

In WWTP models, the accurate assessment of solids inventory in bioreactors equipped with solid-liquid separators, mostly described using one-dimensional (1-D) secondary settling tank (SST) models, is the most fundamental requirement of any calibration procedure. Scientific knowledge on characterising particulate organics in wastewater and on bacteria growth is well-established, whereas 1-D SST models and their impact on biomass concentration predictions are still poorly understood. A rigorous assessment of two 1-DSST models is thus presented: one based on hyperbolic (the widely used Takács-model) and one based on parabolic (the more recently presented Plósz-model) partial differential equations. The former model, using numerical approximation to yield realistic behaviour, is currently the most widely used by wastewater treatment process modellers. The latter is a convection-dispersion model that is solved in a numerically sound way. First, the explicit dispersion in the convection-dispersion model and the numerical dispersion for both SST models are calculated. Second, simulation results of effluent suspended solids concentration (XTSS,Eff), sludge recirculation stream (XTSS,RAS) and sludge blanket height (SBH) are used to demonstrate the distinct behaviour of the models. A thorough scenario analysis is carried out using SST feed flow rate, solids concentration, and overflow rate as degrees of freedom, spanning a broad loading spectrum. A comparison between the measurements and the simulation results demonstrates a considerably improved 1-D model realism using the convection-dispersion model in terms of SBH, XTSS,RAS and XTSS,Eff. Third, to assess the propagation of uncertainty derived from settler model structure to the biokinetic model, the impact of the SST model as sub-model in a plant-wide model on the general model performance is evaluated. A long-term simulation of a bulking event is conducted that spans temperature evolution throughout a summer/winter sequence. The model prediction in terms of nitrogen removal, solids inventory in the bioreactors and solids retention time as a function of the solids settling behaviour is investigated. It is found that the settler behaviour, simulated by the hyperbolic model, can introduce significant errors into the approximation of the solids retention time and thus solids inventory of the system. We demonstrate that these impacts can potentially cause deterioration of the predictive power of the biokinetic model, evidenced by an evaluation of the system's nitrogen removal efficiency. The convection-dispersion model exhibits superior behaviour, and the use of this type of model thus is highly recommended, especially bearing in mind future challenges, e.g., the explicit representation of uncertainty in WWTP models.

Bioleaching strategies for the treatment of nickel–copper sulphide concentrates

Different process options for the bioleaching of nickel–copper containing sulphide concentrates were evaluated. Tests in continuously operated reactor systems showed >98% nickel extractions over a range of temperatures, whereas for copper occurring as chalcopyrite, extractions of >95% could only be achieved at 70 °C. During further optimisation of the process the effects of process parameters such as grind size, residence time, redox potential and feed solids concentration on the leach kinetics, metal extractions and performance of both moderate thermophile and thermophile cultures were addressed. Redox control in the first-stage reactor of thermophilic systems resulted in considerably faster copper leach rates and extractions of up to 95% could be achieved at increased feed concentrations and coarser grind sizes. High redox levels in the secondary reactors ensured >98% nickel recoveries. These operating conditions and control strategies have the potential to increase the rates of nickel and copper extractions to the extent that leaching times could be considerably reduced.

Influence of spray-drying operating conditions on Rhamnus purshiana (Cáscara sagrada) extract powder physical properties

The aim of this work was to study Rhamnus purshiana (Cáscara sagrada) extract spray-drying in order to obtain powders with good rheological properties for direct compression (DC) and stability attributes. The experiments were carried out in a Büchi B-290 Mini Spray Dryer using colloidal silicon dioxide as carrier agent. A 2 5 − 1 fractional factorial statistical design was used to find adequate spray-drying operating conditions to produce Cáscara sagrada powders with good flow, good compactability properties, high process yield, low moisture content, low hygroscopicity, and caking tendency. Morphology, size, structural and thermal properties of the particles were also evaluated. The operating variables studied were air inlet temperature, atomization air flow rate, pump feed rate, aspiration capacity, and feed solids concentration. The 2 5 − 1 factorial experimental design used was a good strategy to establish spray-drying operating conditions to produce Cáscara sagrada extract powders with good properties for direct compression and high process yields. Colloidal silicon dioxide was an effective drying adjuvant. Its use in relatively high concentrations together with low atomization air flow rates improved powder flowability, increased the product's glass transition temperature, and decreased its moisture content and hygroscopicity.

Nanobubble generation and its applications in froth flotation (part IV): mechanical cells and specially designed column flotation of coal

Coal is the world's most abundant fossil fuel. Coal froth flotation is a widely used cleaning process to separate coal from mineral impurities. Flotation of coarse coal particles, ultrafine coal particles and oxidized coal particles is well known to be difficult and complex. In this paper, the nanobubbles' effects on the flotation of the varying particle size, particle density and floatability coal samples were evaluated using a bank of pilot scale flotation cells, a laboratory scale and a pilot scale specially designed flotation column. The parameters evaluated during this study include the flow rate ratio between the nanobubble generator and the conventional size bubble generator, the superficial air velocity, collector dosage, frother concentration, flotation feed rate, feed solids concentration, feed particle size, and the superficial wash water flow rate, etc. The results show that the use of nanobubbles in a bank of mechanical cells flotation and column flotation increased the flotation recovery by 8%∼27% at a given product grade. Nanobubbles increased the flotation rate constants of 600∼355, 355∼180, 180∼75, and 75∼0 microns size coal particles by 98.0%, 98.4%, 50.0% and 41.6%, respectively. The separation selectivity index was increased by up to 34%, depending on the flotation feed characteristics and the flotation conditions.

DEWATERING THE SLUDGE GENERATED FROM WATER TREATMENT PLANTS WITH TWO HYDROCYLONES IN SERIES

A large quantity of sludge is generated each year from the water treatment plants in Egypt. Some plants dispose the generated sludge into the Nile river, the others which far from the Nile river banks dispose the sludge in the nearest site beside the plant. The pumped sludge contains at least 96 % water, which causes certain environmental problems and health hazards in the future. The future trend of sludge management, are to convert the produced sludge into useful materials. One of the industrial centrifugal separators is the hydrocyclone. It has been used widely in industry for dewatering suspensions, such as liquid clarification, slurry thickening (or both simultaneously), and solid washing. The present work focused on the use of one stage or two stage hydrocyclone as dewatering tool for thickening, the sludge generated from water treatment plant of New Assiut City (Assiut, Egypt). The effect of feed concentration on dewatering performance of the hydrocyclone was studied using two identical hydrocyclones each of 50 mm diameter. The obtained results show that, using one stage hydrocylone is not effective in thickening the sludge. To improve overall recoveries of thicker sludge and clearer overflow simultaneously, two stages hydrocyclone connected in series are used. The overall recovery of the whole system is better than the recovery of any of the individual cyclones used within 20—24 % when diluted feed solid concentration less than 2 % was used. It is hoped that this work will lead to an improvement in the utilization of the hydrocyclones in dewatering the sludge generated from fresh water treatment plants.

Study of gas holdup and pressure characteristics in a column flotation cell using coal

Present work has been carried out to observe the effect of process variables (gas flow rate, feed flow rate, solid concentration and frother concentration) on gas holdup and pressure characteristics in flotation column using coal. Gas holdup has been estimated using phase separation method while piezometers have been used to obtain column’s axial pressure profile. It was observed that gas holdup in collection zone was affected by both air as well as feed flow rates. Up to 6% change in gas holdup may occur when the feed flow rate changes from 1–2 cm/s. It was also observed that addition of coal decreased the gas holdup while addition of methyl isobutyl carbinol (MIBC) had opposite effect. Almost linear variation in columns axial pressure characteristics has been observed with gas flow rate. An empirical relationship between gas holdup in the flotation column with column’s axial pressure difference was developed.

Flow conditions in the air core of the hydrocyclone

The geometry and movement of the air core are sensitive indicators of the operational state of hydrocyclones. Therefore, an increased knowledge of the air core behaviour is desirable. Measurements of the air-core diameter in transparent hydrocyclones operated with a suspension of glass spheres are presented. The experiments indicate the dependencies between feed-solids content, air-core diameter, and spray angle of the underflow. Additionally, the air flow inside the air core in a transparent 50 mm water cyclone was experimentally investigated. Visualization techniques show the whirling motion of the air-core flow that is driven by the rotating liquid boundary of the air core. The radial distribution of the tangential air velocity was determined. The mean axial air velocity was shown to be dependent on the pressure drop and the hydrocyclone geometry. At the overflow discharge the air core is dispersed, and forms an aero suspension. Thus, the paper presents new aspects of the complex multi-phase flow in the hydrocyclone considering the gaseous phase.