Continuous Mixing Research Articles

Achievement of the High-Capacity Retention Rate for the Li[Ni0.8Co0.15Al0.05]O2 (NCA) Cathode Containing an Aqueous Binder with CO2 Gas Treatment Using the Cavitation Effect (CTCE)

The Li[Ni0.8Co0.15Al0.05]O2 (NCA) cathode containing an aqueous binder for Li ion batteries was fabricated by the CO2 gas treatment method using the cavitation effect (CTCE) with the continuous mixing device process. The CTCE is a simple process for decreasing the pH value of the cathode slurry containing an aqueous binder from the alkaline region to neutral region. With the CTCE, the retention rate of the discharge capacity at the 50th cycle with respect to that at the 2nd cycle achieved 92%. It was confirmed that almost all of the NCA particle surfaces were uniformly covered with a Li2CO3 layer after the CTCE. The Li2CO3 layer formed on the NCA particle surfaces and prevented increasing the film resistance and charge transfer resistance because the layer suppressed the electrolyte decomposition and stabilized the surfaces. These phenomena lead to improvement of the cyclability. Moreover, a part of the Li2CO3 layer on the NCA particle surfaces contains carbon black (CB) because CB is uniformly dispersed by the mixing equipment using the cavitation effect. This result improved the electrical conductivity of the NCA powder, resulting in increased capacities for all the cycles.

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.

T-junction experiments to investigate thermal-mixing pipe flow with combined measurement techniques

In context with thermal fatigue of T-junction pipelines caused by thermal mixing of flows, experiments are carried out at the Fluid-Structure-Interaction (FSI) test facility at the University of Stuttgart with a horizontal T-junction, in which a cold water flow (20° C) in the branch pipe (DN40) and a hot water flow (max. 280° C) in the main pipe (DN80) are mixed at pressure up to 75 bar. The focus of present investigation is on the flow mixing behavior close to the T-junction with presence of a weld root model inside the pipe, which is representing a typical pipeline weld connection with internal circumferential weld root.In this work, the experimental investigation is performed with multiple measurement techniques. Temperature measurement in the mixing region and inlet flow is performed with micro-thermocouple technique. The Near-Wall LED Induced Fluorescence (NW-LED-IF) method is applied to investigate the influence of the rimmed weld root in the mixing region. Due to the operation safety, the experiments are performed with 30 bar. The experiments are conducted with different flow temperatures in the main pipe line of 150 °C, 120 °C and 90 °C. The experiments are performed with periodical and continuous mixing processes. This paper presents the results of the experiments with two different measurement techniques. Fatigue assessment for the piping materials in the mixing region is discussed according to the thermocouple measurements. The impact of the rimmed weld root on the nearby flow field is shown in the NW-LED-IF measurement. The results show mixing behavior in the T-junction can be changed with temperature difference in the inlet flow and the rimmed weld root can increase the possibility of thermal fatigue damage significantly.

Novel evaluation method for the continuous mixing process of bimodal particles

The continuous mixing process of powder is used in many industries. Careful evaluation of the degree of the mixing is essential to enhance equipment performance. However, no single evaluation method has been universally adopted for the continuous mixing process of bimodal particles due the methods' poor applicability across multiple process concepts. Presented here are two indices to evaluate mixing in the transverse and axial directions. In this study, the indices are estimated at steady state based on Variance among Bimodal Bin Counts (VBBC), which was introduced as an evaluation method of a bimodal particle mixing system in our previous study. The VBBC mixing index for a continuous mixer is introduced to evaluate the transverse mixing of particles, while an axial stability factor is introduced to evaluate the mixing in the axial direction, which is indicative of the consistency of the process. The importance of each index depends on the characteristics of the process. Therefore, several strategies are suggested for applying the methods to practical cases. In addition, a hypothetical example is presented to illustrate their application: five continuous mixers having differently angled blades are assumed because the blade angle is the most easily modifiable design factor. The bimodal particle mixing processes are simulated using the Discrete Element Method (DEM). Based on the application example, both indices are calculated and the optimal design of a screw is suggested.

Structural interpretations on tensile fracture mechanism and elongational rheology of poly(vinylidene fluoride)/halloysite nanotubes nanocomposites

Halloysite nanotubes (HNTs)‐filled poly(vinylidene fluoride) (PVDF) nanocomposites were fabricated using continuous mixing extrusion with and without water injection. The HNTs dispersion state was qualitatively and quantitatively analyzed by using transmission electron microscopy and the Halpin‐Tsai equation, suggesting better HNTs dispersion in the nanocomposites fabricated with water injection. To grasp the relationship between the structure and properties, the effect of the HNTs dispersion on the tensile fracture mechanism and melt elongational rheology of the nanocomposites was investigated. It was deduced from morphological observations on the fractured surfaces that for the nanocomposites fabricated without and with water injection, cracks initially formed at the vicinity of HNTs aggregates and the thinner brittle fracture edge region, respectively. This was attributed to the important roles of the PVDF crystallization behavior and HNTs dispersion on the formation of the voids, wedges and ridges, which are the origins for forming cracks and easily formed at region with more HNTs aggregates or lower crystallinity. The nanocomposites fabricated with water injection exhibited lower elongational viscosities and 17–60% increments for the draw ratios at break than those fabricated without water injection, due to better HNTs dispersion induced by injected water. POLYM. ENG. SCI., 59:773–780, 2019. © 2018 Society of Plastics Engineers

Asymptotic Properties of the Method of Observead Means for Nonstationary Random Fields

The author considers a stochastic programming problem where the estimator is approximated by its empirical estimate based on observations of a non-homogeneous random field with continuous time and strong mixing. The strong consistency of this estimate is investigated and its asymptotic distribution is found under the constraint imposed on the unknown parameter in the form of systems of inequalities.

Liquid Distribution and Mixing in Rotating Packed Beds

In this study, two different approaches for investigating micromixing in a rotating packed bed (RPB) with a Villermaux-Dushman protocol are presented and detailed information on the operation, design, and power consumption of the RPB is given. First, a novel nozzle liquid distribution design is investigated for micromixing. A structured approach for experimental investigations is introduced, and the influence of different liquid distribution parameters on the micromixing results is presented. It is shown that the outlet velocity from the nozzles and the liquid hold-up at the inner rim of the packing play a crucial role in the mixing process. Second, micromixing in RPBs with equal flow rates is investigated. A comparison with other continuous mixing devices is conducted based on flow rates, pressure drop, and the micromixing time parameter tm. It is demonstrated that RPBs show a large potential for fast mixing at high flow rates and low pressure drop.

A Passive Mixing Microfluidic Urinary Albumin Chip for Chronic Kidney Disease Assessment.

Urinary albumin level is an important indicator of kidney damage in chronic kidney disease (CKD) but effective routine albumin detection tools are lacking. In this paper, we developed a low-cost and high accuracy microfluidic urinary albumin chip (UAL-Chip) to rapidly measure albumin in urine. The UAL-Chip offers three major features: (1) we incorporated a fluorescent reaction assay into the chip to improve the detection accuracy; (2) we constructed a passive and continuous mixing module in the chip that provides user-friendly operation and greater signal stability; (3) we applied a pressure-balancing strategy based on the immiscible oil coverage that achieves precise control of the sample-dye mixing ratio. We validated the UAL-Chip using both albumin standards and urine samples from 12 CKD patients and achieved an estimated limit of detection (LOD) of 5.2 μg/mL. The albumin levels in CKD patients' urine samples measured by UAL-Chip is consistent with the traditional well-plate measurements and clinical results. We foresee the potential of extending this passive and precise mixing platform to assess various disease biomarkers.

Optimization-Based Linear Network Coding for General Connections of Continuous Flows

For general connections, the problem of finding network codes and optimizing resources for those codes is intrinsically difficult and a little is known about its complexity. Most of the existing methods for identifying solutions rely on very restricted classes of network codes in terms of the number of flows allowed to be coded together, and are not entirely distributed. In this paper, we consider a new method for constructing linear network codes for general connections of continuous flows to minimize the total cost of the edge use based on mixing. We first formulate the minimum-cost network coding design problem. To solve the optimization problem, we propose two equivalent alternative formulations with discrete mixing and continuous mixing, respectively, and develop distributed algorithms to solve them. Our approach fairly allows general coding across flows and guarantees no greater cost than existing solutions. Numerical results illustrate the performance of our approach.

Detailed modeling and process design of an advanced continuous powder mixer

A vertical in-line continuous powder mixing device (CMT – Continuous Mixing Technology) has been modelled with the discrete element method (DEM) utilizing a calibrated cohesive contact model. The vertical design of the mixing device allows independent control of mean residence time (MRT) and shear rate. The hold-up mass and outlet flow are controlled by an exit valve, located at the bottom of the in-line mixer. A virtual design of experiments (DoE) of DEM simulations has been performed and parameters such as particle velocities, powder bed shape, residence time distribution (RTD), travel distance, and mixing quality are evaluated for the complete operating space. The RTD of the DEM model has been validated with tracer experiments. The resulting RTD has been fitted with an analytical form (generalized cascade of n continuous stirred tank reactors) and utilized to study the downstream response of the continuous mixing device to upstream fluctuations in the inlet material stream. The results indicate a high mixing quality and good filtering properties across the operating space. However, the combination of low hold-up mass and high impeller speeds leads to a reduced filtering capability and wider exit valve openings, indicating a less desirable operating point.

Evidence for Continuous Mixing of Individually Fractionated, Coeval Felsic and Mafic Magmas Forming Synextensional Plutons, the Menderes Core Complex, Western Turkey

AbstractThe Egrigoz and Koyunoba monzogranites in western Turkey contain igneous enclaves that provide important information concerning the magma-forming processes and their petrogenetic origin in ...

Influences of shear-mixing rate and fly ash on rheological behavior of cement pastes under continuous mixing

The shear rate experienced by the cement pastes inside fresh concrete depends on the placing operations and the nature of concrete, and it plays an important role in the evolution of rheological properties and stability of fresh concrete over time. In this study, the effects of continuous shear mixing and fly ash on thixotropy, apparent viscosity, and shear-thickening behavior of cement pastes were experimentally investigated. Various shear rates of 1 s−1, 15 s−1 and 30 s−1 were selected to continuously shear the cement pastes. Results showed that the action of high-rate shear mixing slowed down the evolution of thixotropy, but the efficiency of reduction was gradually limited. Under the state of continuous shear mixing, the apparent viscosity of reference paste was significantly increased and the shear-thickening intensity at higher shear rate range was decreased. However, for the cement pastes containing fly ash, only slight increase in apparent viscosity was observed and the shear-thickening intensity also exhibited a slight increase behavior. It would be an effective way to hinder the evolution of flocculation structure by exerting a continuous shear mixing at an appropriate shearing rate and adding fly ash.

Effect of continuous and daytime mixing on Nannochloropsis growth in raceway ponds

Turbulence mixing is critical for generating high microalgal biomass productivity. Mixing also represents a major operational cost in large-scale microalgal production. The integration of photovoltaic cells with microalgae cultivation systems has been shown to eliminate the requirement of conventional grid-supplied electricity in rural areas. However, through such systems, the availability of electricity and the operation of equipment would solely depend on available sunlight and limited to only daytime. In accordance, in this study, we evaluated the effect of continuous paddle wheel mixing (24 h) and daytime mixing (12 h) on the growth, productivity and photosynthesis of Nannochloropsis sp. grown in outdoor paddle wheel driven raceway ponds operated at different depths (15 and 25 cm). Specific growth rates, volumetric and aerial biomass productivities were found to be significantly higher in ponds with 24 hour mixing compared to ponds with only 12 hour mixing operated at the same depth. The depth of the cultures did not affect the growth rate and volumetric productivity of cultures in both mixing conditions. Photosynthetic performance of cultures evaluated through chlorophyll a fluorescence measurements of photosystem II trended higher in ponds with 24 hour mixing compared to ponds subjected to 12 hour mixing. Our results clearly indicate the importance of continuous mixing to achieve high biomass productivity in cultures of Nannochloropsis sp.

Acoustofluidics-based enzymatic constant determination by rapid and stable in situ mixing

Microfluidic mixings create considerable opportunities for microscale exploration of biomacromolecule function and local reaction kinetics. However, a robust and efficient way for localized mixing performance is not yet well established. In this study, we describe a simple and reliable method for rapid, stable, and controllable in situ mixing using a single-layer acoustofluidic system with a microneedle. We developed the single microstructure for region-confined mixing, which can be controlled dynamically by intentional acoustic activation. Various acoustofluidic impacts including driving frequency, microstructure design, driving voltage, and flow control on homogeneous mixing were systematically investigated. The microneedle-based device allows a fast (∼ 85 ms) mixing operation. Robust and high reusability of acoustofluidic system was experimentally demonstrated with up to 200 times of repetitive mixing and 100 min of continuous mixing. Furthermore, the proof-of-concept applications including real-time characterization of fluorescein quenching and β-glucuronidase-catalyzed hydrolysis of 4-methyl-umbelliferyl-β-d-glucuronide were successfully accomplished in the in situ mixing platform. We believe this microfluidic system could be suitable for investigation of different instantaneous chemical/biochemical events associated with various molecular interactions and reactions. Also, the acoustofluidic approach is potentially valuable to the development of mixing-based integrated microfluidic systems for applications in molecular science and life science.

T-junction experiment with high temperature and high pressure to investigate flow rate influence on mixing characteristics

Thermal fatigue is one of the typical phenomena of fluid-structure interaction. It is a degradation mechanism to the piping materials and mostly found close to mixing tees where flow streams with temperature difference are mixed. At the University of Stuttgart, experiments have been performed at the Fluid-Structure-Interaction (FSI) test facility for investigating thermal fatigue effect close to a horizontal T-junction. The cold water flow of the branch pipe line (20 °C) and the hot water flow of the main pipe line (max. 280 °C) are mixed in a horizontally oriented 90° T-junction at pressure p = 75 bar. Particularly for simulating the rimmed weld root of a weld connection in the mixing region, a weld seam model is installed in the pipe line downstream of the T-junction.In this investigation, 48 micro-thermocouples are installed in six measurement cross-sections close to the T-junction to capture the near-wall fluid temperatures. The temperature signals are recorded with 100 Hz. The experiments are performed with different flow rates in the main pipe line respectively branch pipe line. For each flow condition, measurements are conducted with continuous and periodic cold flow injection from the branch pipe. The temperature measurement data are analyzed and discussed from the view point of their relevance to thermal fatigue. The flow mixing characteristics are discussed on the basis of different measurement positions. The results show that the inlet flow rates is a crucial factor on the mixing behavior at the T-junction. The potential of thermal fatigue in the mixing region changes with variation of the inlet flow rate. Furthermore, variation of the flow rate shows a different impact in continuous mixing processes compared to periodical mixing processes.

Refolding kinetics of cytochrome c studied with microsecond timescale continuous-flow UV–vis spectroscopy and rapid freeze-quench EPR

The study of the structure, function, folding and conformational transitions of cytochrome c is of great interest because this protein plays an important role in biological electron transport and apoptosis. The different native and non-native conformations have been studied extensively under equilibrium conditions at different pH values, however, kinetic studies are rare because they require technically challenging rapid mixing and spectroscopic monitoring techniques. Here we present the refolding kinetics of acid denatured cytochrome c using the pH jump technique from pH 2 to pH 4.7 in combination with a new ultrafast continuous flow mixing device that allows time resolved measurements to the microsecond time scale. Our results show that the initial refolding of denatured oxidized cytochrome c occurs very rapidly with a time constant τ = 10 μs, and is followed by discrete refolding steps with time constants of 56 and 208 μs. Electron paramagnetic resonance analysis of the different intermediates, obtained by microsecond freeze hyper quenching showed that the first two intermediates are predominantly high spin, and the third intermediate is the low spin species with complete His/Met coordination. The initial rapid phase is characterized by the formation of high spin species distinct from the completely unfolded state. We interpret this as the formation of a five coordinate species with His18 as the axial ligand or six coordinate with water and His18 as the axial ligands.

Enhanced nitrogen removal and energy saving in a microalgal–bacterial consortium treating real municipal wastewater

The optimization of total nitrogen removal from municipal wastewater was investigated in a laboratory-scale photo-sequencing batch reactor (PSBR) operated with a mixed microalgal-bacterial consortium spontaneously acclimatized to real wastewater. No external aeration was provided in the PSBR to reduce energy consumption: oxygen was only supplied by the microalgal photosynthesis. The enhancement of total nitrogen removal was achieved through: (1) feeding of wastewater in the dark phase to provide readily biodegradable COD when oxygen was not produced, promoting denitrification; (2) intermittent use of the mixer to favor simultaneous nitrification-denitrification inside the dense flocs and to achieve 41% energy saving with respect to continuous mixing. Efficient COD removal (86 ± 2%) was observed, obtaining average effluent concentrations of 37 mg/L and 22 mg/L of total COD and soluble COD, respectively. TKN removal was 97 ± 3%, with an average effluent concentration of 0.5 ± 0.7 mg NH4 +-N/L. Assimilation of nitrogen by heterotrophic bacteria accounted only for 20% of TKN removal, whilst the major part of TKN was nitrified. In particular, the nitrification rate was 1.9 mgN L-1 h-1 (specific rate 2.4 mgN gTSS-1 h-1), measured with dissolved oxygen near zero, when the oxygen demand was higher than the oxygen produced by photosynthesis. Total nitrogen of 6.3 ± 4.4 mgN/L was measured in the effluent after PSBR optimization.

Thermo-catalytic reforming of co-form® rejects (waste cleansing wipes)

Co-form® products are typically used for personal hygiene care (cleansing wipes), household cleaning (pads and mops) and absorbent applications. Co-form® is a thermo-bonded multilayer nonwoven composite and Kimberly-Clark patented its process in 2008. Co-form® rejects are composed of 30% plastic polypropylene and 70% wood pulp fibre. It is difficult to recycle and to-date no research articles explore pyrolytic valorisation for its energy recovery. This paper investigated pyrolytic valorisation of co-form® rejects into energy vectors. Pelletised co-form® rejects obtained from a secondary fibre paper mill were processed using a laboratory scale 2 kg/h Thermo-Catalytic Reforming (TCR®) reactor. The TCR® process combines intermediate pyrolysis, using an auger reactor to heat the material under moderate temperatures (350–450 °C) and moderate solid residence times (minutes) in the complete absence of Oxygen, with post catalytic reforming in a fixed bed reactor at 700 °C. Pelletised co-form® rejects were successfully converted into 12 wt% bio-oil, 9 wt% aqueous phase liquid, 8 wt% char and 71 wt% syngas products. The bio-oil higher heating value was found to be 39.36 MJ/kg, comparable to biodiesel. Naphthalene was found to be the most abundant aromatic compound within the oil, with a relative abundance of 15.22% measured by GC–MS. Oleic acid methyl ester (15.86%) was the most abundant long chain hydrocarbon detected. The higher heating value of produced gas was 11.02 MJ Nm3 and char 30.79 MJ/kg. TCR® conversion of co-form® rejects proved to be a feasible route for the valorisation of this waste stream into sustainable energy vectors. In previous works, gasification processes could not successfully convert organic waste streams with a high plastic content, without implications attributed to agglomeration and melting of plastics. The TCR® process overcome these issues with no evidence of agglomeration or melting of plastics present within the reactor. The success was believed to be through applying moderate heating rates (°C/min) and temperatures (max 700 °C), as well as the mechanical effect of continuous mixing of material within the reactor via the internal auger screw. Overall, TCR® is a promising future route for the valorisation of co-form® rejects to produce energy vectors.

Mixing effects on the kinetics and the dynamics of two-phase enzymatic hydrolysis of hemicellulose for biofuel production

This work uses a coupled experimental and modeling approach to explore the effects of macro- and micro-mixing on the kinetics and the dynamics of two-phase enzymatic hydrolysis of hemicellulose. Reactor mixing does not alter the non-competitive nature of product inhibition in hemicellulose hydrolysis by endoxylanase, but produces stronger inhibition that reduces the soluble sugar yield by 8–14.5%, as the mixing speed increases from 0 to 200 rpm. The kinetic constants (Km, Vmax, Kx) assume mass-transfer disguised values at 0–200 rpm. An optimal mixing strategy, comprising of 55–70 min of initial rapid convective macromixing followed by diffusive micromixing (without any macromixing) for the rest of the hydrolysis, increases xylose and reducing sugar yields by 6.3–8% and 13–20%, respectively, over continuous mixing at 200 rpm, for 1–5 mg/ml substrate loading at an optimum enzyme to substrate ratio of 1:20, with an energy saving of 94–96% over 24 h.

Production of Micro- and Nanoscale Lignin from Wheat Straw Using Different Precipitation Setups.

Micro- and nanosize lignin has recently gained interest due to its improved properties compared to standard lignin available today. As the second most abundant biopolymer after cellulose, lignin is readily available but used for rather low-value applications. Applications for lignin in micro- to nanoscale however, ranging from improvement of mechanical properties of polymer nanocomposites, have bactericidal and antioxidant properties and impregnations to hollow lignin drug carriers for hydrophobic and hydrophilic substances. This research represents a whole biorefinery process chain and compares different precipitation setups to produce submicron lignin particles from lignin containing an organosolv pretreatment extract from wheat straw. A batch precipitation in a stirred vessel was compared with continuous mixing of extract and antisolvent in a T-fitting and mixing in a T-fitting followed by a static mixer. The precipitation in the combination of T-fitting and static mixer with improved precipitation parameters yields the smallest particle size of around 100 nm. Furthermore, drying of particles did not influence the particle sizes negatively by showing decreased particle diameters after the separation process.