Effect Of Mixing Intensity Research Articles

Effect of Mixing Intensity on Electrochemical Performance of Oxide/Sulfide Composite Electrolytes

Despite the variety of solid electrolytes available, no single solid electrolyte has been found that meets all the requirements of the successor technology of lithium-ion batteries in an optimum way. However, composite hybrid electrolytes that combine the desired properties such as high ionic conductivity or stability against lithium are promising. The addition of conductive oxide fillers to sulfide solid electrolytes has been reported to increase ionic conductivity and improve stability relative to the individual electrolytes, but the influence of the mixing process to create composite electrolytes has not been investigated. Here, we investigate Li3PS4 (LPS) and Li7La3Zr2O12 (LLZO) composite electrolytes using electrochemical impedance spectroscopy and distribution of relaxation times. The distinction between sulfide bulk and grain boundary polarization processes is possible with the methods used at temperatures below 10 °C. We propose lithium transport through the space-charge layer within the sulfide electrolyte, which increases the conductivity. With increasing mixing intensities in a high-energy ball mill, we show an overlay of the enhanced lithium-ion transport with the structural change of the sulfide matrix component, which increases the ionic conductivity of LPS from 4.1 × 10−5 S cm−1 to 1.7 × 10−4 S cm−1.

Evaluating the aeration efficiency of hydraulic flume on photo-oxidative disinfection of wastewater

Photosensitized oxidation has been considered to offer better disinfection mechanism under natural sunlight and the efficiency of its inactivation pathway depends on the concentration of dissolving oxygen, the solar irradiance, and the reactive nature of the liquid. This study aimed to evaluate the hydraulic mixer's aeration performance during photo-oxidation treatment. A hydraulic jump was created to aerate the sewage prior to its passage into a reactor, and the amount of dissolved oxygen generated was measured. The effect of mixing intensity on sunlight inactivation of faecal coliforms in a reactor was investigated for 60 min using velocity gradients of 520 s−1, 640 s−1, 720 s−1 and 960 s−1 produced under flow rates of 3 L min−1, 5 L min−1 and 7 L min−1 and 10 L min−1 respectively. The photo-oxidation kinetics of faecal coliform contained in settled and raw sewage samples were also studied under two dark control tests (static and dynamic tests) and a light test. The system achieved a 2.0–2.34 log reduction of faecal coliforms and dissolved oxygen was within the range of 1.9 mg L−1 - 3.0 mg L−1. In the dynamic control test, the inactivation rate constant of bacteria indicated a reduction of 1.11 log (92%) for settled sewage and 1.0 log (90%) for raw sewage. The coliform inactivation rate constant, due to the combined effect of turbulent mixing speed and dark inactivation rate constant, was 2.3 h−1, and the solar irradiance inactivation rate constant was 2.4 h−1. These results have demonstrated that induced aeration is an economically friendly approach to enhance wastewater treatment in developing nations with long sunshine hours.

Effect of mixing intensity on volatile fatty acids production in sludge alkaline fermentation: Insights from dissolved organic matter characteristics and functional microorganisms

Alkaline fermentation for volatile fatty acids (VFAs) production has shown potential as a viable approach to treat sewage sludge. The hydrolysis and acidogenesis of sludge are greatly influenced by mixing. However, the effects of mixing intensity on VFAs production in sludge alkaline fermentation (SAF) remain poorly understood. This study investigated the impacts of mixing intensity (30, 90 and 150 rpm continuous mixing, and 150 rpm intermittent mixing) on VFAs production, dissolved organic matter (DOM) characteristics, phospholipid fatty acid profiles and microbial population distribution in SAF. Results showed that 150 rpm continuous and intermittent mixing enhanced the hydrolysis of sludge, while 150 rpm intermittent mixing resulted in the highest VFAs production (3886 ± 266.1 mg COD/L). Analysis of fluorescent and molecular characteristics of DOM revealed that 150 rpm intermittent mixing facilitated the conversion of released DOM, especially proteins-like substances, into VFAs. The abundance of unsaturated and branched fatty acids of microbes increased under 150 rpm intermittent mixing, which could aid in DOM degradation and VFAs production. Firmicutes and Tissierella were enriched at 150 rpm intermittent mixing, which favored the maximum VFAs yield. Moreover, Firmicutes were found to be the key functional microorganisms influencing the yield of VFAs during SAF. This study provides an understanding about the mixing intensity effects on VFAs production during SAF, which could be helpful to improve the yield of VFAs.

Effect of mixing intensity on biodegradation of phenol in a moving bed biofilm reactor: Process optimization and external mass transfer study

In this work, an effort has been made to design the process variables and to analyse the impact of mixing intensity on mass transfer diffusion in a moving bed biofilm reactor (MBBR). A lab-scale MBBR, filled with Bacillus cereus GS2 IIT (BHU) immobilized-polyethylene biocarriers, was employed to optimize the process variables, including mixing intensity (60–140 rpm), phenol concentration (50–200 mg/L), and hydraulic retention time (HRT) (4–24 h) using response surface methodology. The optimum phenol removal of 87.64 % was found at 100 rpm of mixing intensity, 200 mg/L of phenol concentration, and 24 h of HRT. The higher mixing intensity improved the substrate diffusion between the liquid phase and the surface of the biofilm. The external mass transfer coefficients were found in the range of 1.431 × 10-5-1.845 × 10-5 m/s. Moreover, the detection of catechol and 2-hydroxymuconic semialdehyde revealed that the Bacillus sp. followed the meta-cleavage pathway during the biodegradation of phenol.

Enhancing Efficiency of Anaerobic Digestion by Optimization of Mixing Regimes Using Helical Ribbon Impeller

The appropriate mixing system and approach to effective management can provide favorable conditions for the highly sensitive microbial community, which can ensure process stability and efficiency in an anaerobic digester. In this study, the effect of mixing intensity on biogas production in a lab-scale anaerobic digester has been investigated experimentally and via modeling. Considering high mixing efficiency and unique feature of producing axial flow, helical ribbon (HR) impeller is used for mixing the slurry in this experiment under various conditions. Three parallel digesters were analyzed under identical operating conditions for comparative study and high accuracy. Effects of different mixing speeds (10, 30, and 67 rpm for 5 min h−1) on biogas production rate were determined in 5-L lab-scale digesters. The results demonstrated 15–18% higher biogas production at higher mixing speed (67 rpm) as compared to 10 rpm and 30 rpm and the results proved statistically significant (p < 0.05). Biogas production at 10, 30, and 67 rpm were 45.6, 48.6, and 52.5 L, respectively. Higher VFA concentrations (7.67 g L−1) were recorded at lower mixing intensity but there was no significant difference in pH and ammonia at different speeds whereas the better mixing efficiency at higher speeds was also the main reason for increase in biogas production. Furthermore, model simulation calculations revealed the reduction of dead zones and better homogeneous mixing at higher mixing speeds. Reduction of dead zones from 18% at 10 rpm to 2% at 67 rpm was observed, which can be the major factor in significant difference in biogas production rates at various mixing intensities. Optimization of digester and impeller geometry should be a prime focus to scale-up digesters and to optimize mixing in full-scale digesters.

Food waste treatment through anaerobic co-digestion: Effects of mixing intensity on the thermohydraulic performance and methane production of a liquid recirculation digester

This paper investigates the thermohydraulic performance and methane production of a Liquid recirculation Mesophilic Digester with Submerged solid waste (LMDS) under different mixing strategies. A combination of food waste and cow dung was used as a substrate in the co-digestion experiments. After 24 days of digestion, we reported a higher specific methane yield (301.84 Nm3 CH4 tvs−1) when gentle mixing was adopted, compared to intense mixing (221.32 Nm3 CH4 tvs−1). As for the unmixed co-digestion, it produced the lowest methane yield (112.88 Nm3 CH4 tvs−1). Furthermore, the thermal study showed that the gentle mixing caused less heat loss from the LMDS (20.90 kWh) compared to the intense mixing (40.21 kWh). Moreover, CFD results showed that intense mixing caused a higher pumping energy consumption (through increasing pressure drop) without inducing a significant improvement in the mixing inside the LMDS. Additionally, the liquid flow fields, force distribution, and percolation of the submerged waste were qualitatively evaluated for the considered mixing strategies. Based on these findings, we presented several recommendations aimed at reducing thermal and hydraulic energy losses while guaranteeing optimal methane production in LMDS digesters.

The Adsorption Selectivity of Short and Long Per- and Polyfluoroalkyl Substances (PFASs) from Surface Water Using Powder-Activated Carbon

Nine per- and polyfluoroalkyl substances (PFASs), including six perfluoroalkyl carboxylic acids (PFCAs) and three perfluoroalkyl sulfonic acids (PFSAs), were tested to find their adsorption selectivity from surface water and the feasibility of the powder activated carbon (PAC) process between the perchlorination and coagulation processes by operating parameters such as mixing intensity, dosage, contact time, initial pH, and concentration of perchlorination. The removal efficiency of four types of PAC revealed that the coal-based activated carbon was clearly advanced for all of the PFASs, and the thermal regenerated PAC did not exhibit a significant reduction in adsorption capacity. The longer carbon chain or the higher molecular weight (MW) obtained a higher adsorption capacity and the MW exhibited a more proportional relationship with the removal efficiency than the carbon chain number, regardless of the PFCA and PFSA species. Approximately 80% and 90% equilibria were accomplished within 60 and 120 min for the long chain carbon PFAS, respectively, while for the short chain PFAS, 240 min was required to reach 85% equilibrium. The effect of mixing intensity (rpm) was not considered for the removal of the PFAS, although it was relatively influenced in the short PFAS species. Due to the surface charge of the PAC and the properties of protonation of the PFASs, the acid condition increased the PFASs’ adsorption capacity. The prechlorination decreased the removal efficiency, and the reduction rate was more significantly influenced for the short chain PFAS than for the long chain PFAS.

Describing Mining Tailing Flocculation in Seawater by Population Balance Models: Effect of Mixing Intensity

A population balance model (PBM) is used to describe flocculation of particle tailings in seawater at pH 8 for a range of mixing intensities. The size of the aggregates is represented by the mean chord length, determined by the focused beam reflectance measurement (FBRM) technique. The PBM follows the dynamics of aggregation and breakage processes underlying flocculation and provides a good approximation to the temporal evolution of aggregate size. The structure of the aggregates during flocculation is described by a constant or time-dependent fractal dimension. The results revealed that the compensations between the aggregation and breakage rates lead to a correct representation of the flocculation kinetics of the tailings of particles in seawater and, in addition, that the representation of the flocculation kinetics in optimal conditions is equally good with a constant or variable fractal dimension. The aggregation and breakage functions and their corresponding parameters are sensitive to the choice of the fractal dimension of the aggregates, whether constant or time dependent, however, under optimal conditions, a constant fractal dimension is sufficient. The model is robust and predictive with a few parameters and can be used to find the optimal flocculation conditions at different mixing intensities, and the optimal flocculation time can be used for a cost-effective evaluation of the quality of the flocculant used.

Effect of Mixing Intensity on Bio-Hydrogen Yield Through Photo-Fermentation by Photosynthetic Bacteria HAU-M1

Effect of Mixing Intensity on Bio-Hydrogen Yield Through Photo-Fermentation by Photosynthetic Bacteria HAU-M1

Reactive Crystallization of Paracetamol in a Continuous Oscillatory Baffled Reactor

In this article, we report, for the first time, a reactive seeded cooling crystallization of paracetamol successfully performed in a continuous oscillatory baffled reactor (COBR). The synthesis of acetaminophen took place in the first part of the COBR and generated the solvent for crystallization via a specific ratio of starting materials. Seeded cooling crystallization was immediately commenced after the completion of the reaction in the second part of the COBR. We investigated the seeding strategy of three seed masses (10, 15, and 20 w/w%) at a fixed size in this work, enabling smooth and encrustation-free runs. We also estimated agglomeration by comparing the ideal to actual normalized product/seed sizes, which was confirmed by SEM images. The effect of mixing intensity on crystal properties was reported. Samples at two ports a known distance apart along the COBR enabled the study of steady states of the paracetamol concentration and crystal mean size in both temporal and spatial domains as well as the...

Effects of mixing intensity on colony size and growth ofMicrocystis aeruginosa

Mixing is an integral environmental factor that affects lake ecosystems. For the cyanobacteriumMicrocystis, colony size is important with respects to migration velocity, how cells respond to grazing pressure, light attenuation, nutrient uptake and growth. To understand how mixing shapes colony size and the growth ofMicrocystis, we measured the effects of different current velocities (0, 0.16, 0.32, 0.64, and 1.28 m s−1) onM. aeruginosain Lake Taihu. After 24 h of continuous mixing, the mean colony sizes ofM. aeruginosain the controls, 0.16, 0.32, 0.64, and 1.28 m s−1groups were 23.6, 50.1, 92.9, 67.8, and 37.3 μm, respectively. Colony sizes ofM. aeruginosain all treatment groups were significantly larger than those in controls. As well, the concentration of soluble extracellular polysaccharide and bound extracellular polysaccharides ofM. aeruginosain all treatment groups were significantly higher than those in controls. Except for the highest level of mixing (1.28 m s−1), the growth rate ofM. aeruginosawas significantly higher than that in controls. This study suggested that mixing intensity over short time periods can significantly influence colony size and the growth ofM. aeruginosa.

Effect of mixing intensity on flocculation kinetics of polystyrene latex particles with high-charge density polyelectrolyte at various ionic strengths

Effect of mixing intensity on the flocculation kinetics of polystyrene latex (PSL) particles with a high-charge density polyelectrolyte was analyzed using a small stirred vessel equipped with a four-paddle impeller and four baffles. The intensity of mixing was estimated by the effective shear rate evaluated in terms of collision frequency between the colloidal particles. This estimation was performed by measuring the salt-induced rapid coagulation of PSL particles as a function of the rate of impeller rotation. Acrylamide-(dimethylamino)ethyl methacrylate methyl chloride with nominal molecular weight of 4.9×106 g mol−1 was used as a flocculant. An enhancement factor, determined by the ratio of the rate of flocculation with a polyelectrolyte in the initial stage to that of salt-induced rapid coagulation, was used as the evaluation index. It was found that the enhancement factor goes through a maximum with an increase in mixing intensity, thus implying the presence of an optimal mixing intensity for flocculation. Further, considerable fluctuation was observed for a low mixing intensity and the degree of fluctuation slightly increased as the ionic strength increased.

Effect of mixing intensity on hydrolysis and acidification of sewage sludge in two-stage anaerobic digestion: Characteristics of dissolved organic matter and the key microorganisms

Mixing should be optimized in anaerobic digestion (AD) systems to achieve excellent biomaterials production in the sewage sludge (SS) management in wastewater treatment plant. AD depends on the coordinated activity of hydrolysis, acidification and methanogenesis. However, the effect of mixing intensity on characteristics of hydrolysis and acidification in AD of SS is still poorly understood. This study focused on the mixing intensity (30, 60, 90 and 120 rpm) effect on the characteristics of dissolved organic matter (DOM) and the key microorganisms in the hydrolysis and acidification of SS. Results showed that enhanced hydrolysis and acidification efficiency was obtained at mixing of 90 and 120 rpm (p < 0.05), while the maximum acetic acid (388 ± 21 mg/L) was produced at 90 rpm. Mixing at 90 rpm enhanced the release of protein and polysaccharide as well as humic acid. Further analyses of DOM molecular features revealed that 90 rpm led to the highest molecular diversity and easily biodegradable molecules (lipid and proteins/amino sugars), which contributed to the maximum hydrolysis and acidification efficiency. Firmicutes and Actinobacteria significantly increased with mixing intensity (p<0.05), and Chloroflexi and Fusobacteria were enriched at mixing of 90 rpm, which favored the hydrolysis of SS. The enrichment of Clostridium XI and Clostridium sensu stricto contributed to the acidification of DOM at 90 and 120 rpm. The results of this study can advance our knowledge about mixing intensity effects on the AD systems of SS. This research also showed how increasing mixing intensity to a relatively high speed can enhance the hydrolysis and acidification efficiency of SS.

The effect of mixing intensity on the performance and microbial dynamics of a single vertical reactor integrating acidogenic and methanogenic phases in lignocellulosic biomass digestion

The ready formation of scum in vertical reactors has been a bottleneck in the digestion of lignocellulosic materials for biogas production. This study describes a single vertical reactor that integrates the acidogenic and methanogenic phases of this process. The effects of two types of maize stover feedstock (fresh and silage) and two mixing intensities (20 and 70rpm) on methane yield were orthogonally determined. Fresh maize stover yielded approximately 14% more methane than silage maize stover. Mixing at 20rpm contributed to methane yield, while mixing at 70rpm blurred the phase boundary, resulting in accumulation of volatile fatty acids and loss of methanogens. The upper and lower phases clearly constituted a two-phase fermentation system. Clostridiales occupied the acidogenic phase, while the predominant bacteria in the methanogenic phase were Bacteroidetes, Chloroflexi, and Synergistetes. The absolute predominance of Methanosaetaceae clearly demonstrated that aceticlastic methanogenesis was the main route of methane production.

Effect of Mixing Intensity on Foaming Behavior of LLDPE/HDPE Blends in Thermal Induced Batch Process

ABSTRACTLinear low density polyethylene (LLDPE) and high density polyethylene (HDPE) (with different shear thinning behaviors) were melt blended at two different compositions (10 and 25 wt%. of HDPE) and three different rotational speeds. Batch foaming process was performed over a wide range of temperatures. Bulk density measurement, cell structure evaluation, differential scanning calorimetry (DSC), and oscillatory rheology tests were performed. Results indicated the deterioration of foamability for those blended at the highest selected speed of 120 rpm. The blends mixed at a speed of 60 rpm, exhibited a slightly lower expansion ratio compared with those of mixed at a speed of 10 rpm with the same trend over the foaming temperature. For blends with 25 wt%. HDPE, proper cellular structures were obtained through a broader range of foaming temperature.

Mixing characteristics of different tracers in extrusion of polystyrene and polypropylene

To characterize the actual flow behavior of polymer, polystyrene (PS) and polypropylene (PP) macromolecular tracers were synthesized by copolymerization and graft routes. The two tracers were then used to obtain the residence time distribution (RTD) functions of PS and PP in a twin-screw extruder. The effect of temperature on RTD is discussed using different tracers. The mixing characteristics of different tracers in the extrusion of PS and PP were compared by measuring the overall and partial RTDs. The dependence of the overall and partial RTDs on the tracer types was investigated. The effects of mixing intensity, miscibility, and melting difference on the measured distribution were also discussed. POLYM. ENG. SCI., 54:310–316, 2014. © 2013 Society of Plastics Engineers

응집을 이용한 인의 제거에 급속혼화강도 및 응집제 주입량이 미치는 영향

본 연구는 교반강도 및 응집제 주입량의 변화에 따라 플럭의 성장특성이 인의 제거에 미치는 영향을 파악하고자 수행되었다. 본 연구에서는 Al/P 몰비를 1.0, 1.5와 2.0으로 급속혼화강도 G값을 100, 300과 500 <TEX>$s^{-1}$</TEX>로 변화시켜 수행하였다. 응집시 발생되는 응집지수(floc size index, FSI)와 크기가 다른 여과지를 이용하여 인의 제거율을 측정하여 성장 특성을 파악하였다. 연구결과 교반강도가 높을수록 용존인의 제거효율이 증가하였으며 Al/P 몰비가 낮을수록 교반강도의 영향이 컸다. T-P의 제거율은 Al/P 몰비 1.0 이하에서는 급속혼화 교반강도가 높을수록 높았으나 Al/P 몰비 1.0 이상에서는 G값 300 <TEX>$s^{-1}$</TEX>에서 가장 높은 제거 효율을 나타내었다. Al/P 비 1.0 이하에서는 G값 500 <TEX>$s^{-1}$</TEX>에서 가장 큰 FSI값을 나타내었으며, Al/P 몰비 1.0 이상에서는 G값 300 <TEX>$s^{-1}$</TEX>에서 가장 큰 FSI값을 나타내었다. 실제하수처리장 유출수를 대상으로 응집에 의한 인 제거에 Al/P 몰비와 급속혼화 강도의 영향은 인공조제수의 결과와 유사하였다. In this study, the effects of mixing intensity and coagulant dosages on the characteristics of floc growth for phosphorus removal were investigated. The experiments were conducted under Al/P molar ratio of 1.0, 1.5 and 2.0; rapid mixing intensity with G value of 100, 300, and 500 <TEX>$s^{-1}$</TEX>. The characteristics of floc growth were measured by flocculation index (FSI) and the removal efficiencies of phosphorus by using different size filters. The removal efficiencies of soluble phosphorus increased as Al/P molar ratio and rapid mixing intensity increased. However, the highest removal efficiencies of T-P were observed at G value of 300 <TEX>$s^{-1}$</TEX>. When Al/P molar ratio was lower than 1.0, the value of FSI at G value of 500 <TEX>$s^{-1}$</TEX> was the largest. However, when Al/P ratio was larger than 1.0, the value of FSI at G value 300 <TEX>$s^{-1}$</TEX> was the largest. Effects of mixing intensity and Al/P molar ratio on coagulation for phosphorus removal of synthetic and real wastewater effluent were observed to be similar.

Reactive melt blending of PS‐POSS hybrid nanocomposites

AbstractHybrid nanocomposites of polystyrene (PS) and methacryl phenyl polyhedral oligomeric silsesquioxane (POSS) were synthesized by reactive melt blending in the mixing chamber of a torque rheometer using dicumyl peroxide (DCP) as a free radical initiator and styrene monomer as a chain transfer agent. The effects of mixing intensity and composition on the molecular structure and morphology of the PS‐POSS hybrid nanocomposites were investigated. The degree of POSS hybridization (αPOSS) was found to increase with the POSS content, DCP/POSS ratio, and rotor speed. For the PS‐POSS materials processed in the absence of styrene monomer, an increase in the αPOSS led to a reduction in the molecular weight by PS chain scission, as a consequence of the free radical initiation. On the other hand, the use of styrene monomer as a chain transfer agent reduces the steric hindrance in the hybridization reaction between POSS and PS, enhancing the degree of POSS hybridization and avoiding PS degradation. The PS‐POSS morphology consists of nanoscale POSS clusters and particles and microscale crystalline POSS aggregates. PS‐POSS with higher αPOSS values and lower amounts of nonbound POSS showed improved POSS dispersion, characterized by smaller interfacial thickness (t) and greater Porod inhomogeneity lengths (lp). The processing‐molecular structure–morphology correlations analyzed in this study allow the POSS dispersion level in the PS‐POSS materials to be tuned by controlling the reactive melt blending through the choice of the processing conditions. These insights are very useful for the development of PS‐POSS materials with optimized performance. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

CFD Simulation on Solid Suspension with Continuous Operation

The aim of this work is to investigate the solid concentration distribution in a DTB crystallizer under continuous operation. The effects of mixing intensity and product removal location on solid concentration distribution in the crystallizer were studied by CFD simulation with multiphase model for different sizes of particles. The results showed that the particle distribution in a crystallizer was dependent on the size of the particles and the mixing intensity. However, the product removal location did not significantly affect particle size distribution in the crystallizer under the studied conditions.

Effect of mixing on spontaneous struvite precipitation from semiconductor wastewater

The objective of this study was to investigate on the effect of mixing intensity ( G) and mixing duration ( t d) on struvite precipitation in the chemical mechanical polishing (CMP) wastewater generated from the semiconductor manufacturing process. Batch-scale experiments revealed that struvite crystallization was affected by both G and t d. The mixing effect was to enhance the mass transfer of solute to the crystals in the process, resulting in the improvement of struvite crystallization and growth. By forming struvite, removal efficiencies of N and P increased logarithmic with the multiple values of G and t d, i.e., Gt d. Insufficient mixing energy with the Gt d value less than 10 5 caused an increase in the formation potential of unexpected precipitate unlike to pure struvite, causing a decrease in removal efficiencies of N and P in the process. At the Gt d value over 10 6, struvite precipitation was not restricted by fluoride, of which high level inherently contained in the CMP wastewater. The study results can be taken into consideration in the design and operation of the struvite precipitation process for both nutrient (N and P) removal and recovery.