Solid Mixing Research Articles

Experimental Investigation of Segregation for Nonspherical Particles in a Fluidized Bed Solids Mixer

A binary mixture of particles varying in size, shape, or density tends to segregate in many different flow situations. Removal of segregation is an important goal as it is often detrimental to process efficiency and product quality. The focus of the current work is to see the effect of the shape of particles on segregation in the particular case of a fluidized bed solids’ mixer. The present work describes an experimental method to study the evolution of segregation and its dependence on both the shape and size of the particles. The outcome shows a decreasing order of the axial segregation index as follows: cubic > spherical > oblate > prolate > elongated needle. An increase in the angularity of fine particles improves mixing. The particle shape plays a vital role in determining the extent of segregation. Overall, segregation can be reduced using nonspherical particles.

Pyrolysis-gas chromatography/mass spectrometry to identification of the solid waste characteristic of imported polyamide recycled plastics

An analytical method for the determination of content of PA66 in PA6/PA66 blends by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) with silica (SiO2) as dispersant was established. After the sample was frozen and crushed into powder, silica was used as a solid dispersant mix with the sample, and the mixtures was injected. At 600°C cracking temperature, the corresponding cracking chromatogram was obtained, and the characteristic of PA66 on the cracking chromatogram of PA6/PA66 blend, the cyclopentanone, was selected as the quantitative peak to calculate the mass of PA66 in the PA6/PA66 blend. The content of PA66 in the dispersion was in the range of 0.50 g/kg ∼ 100 g/kg, and the results had a good linear relationship. The detection limit of the PA66 was 0.50 g/kg (the corresponding PA66:PA6 ratio was 0.5:99.5). The PA6/PA66 samples with known mixing ratio were measured, and the recovery of the results was 95.7%∼102.1%, and the relative standard deviation(RSD) was 1.6%∼5.9% (n=3). It can accurately determine the content of PA66 in PA6/PA66 blends, and provide technical support for the attribute identification of related imported recycled plastic solid wastes. Introduction. Py-GC/MS; Recycled polyamide; Solid dispersant; Solid waste Characteristic identification

Sustainable Construction Using EPS Beads in Light Weight Blocks to form Innovative Foam Concrete as a Green Building Material

We assume to build up another sort of basic light weight concrete by supplanting the coarse total with EPS dabs. Extended Polystyrene (EPS) this is light in weight and it has been utilized as in building applications. EPS is in granular structure and it is utilized in light weight cement to make the solid lighter from 950 kg/m³ to 1350kg/m³. In this paper we did test examination on the designing properties, as compressive quality, modulus of flexibility, drying shrinkage and creep, of polystyrene total cement fluctuating in density. Factors, for instance, water/solid extent, polystyrene/solid extent, solid substance, advancement, compaction, fire, resistance. At the completion of the examination, a philosophy for arranging EPS light weight solid mixes is plot.

Co-Composting of Khat-Derived Biochar with Municipal Solid Waste: A Sustainable Practice of Waste Management

Biochar is a way to improve the performance of the composting process and the quality of compost. This study was aimed to investigate the optimum ratio of khat straw (Catha edulis) biochar and organic municipal solid waste mixtures to improve the quality of the resulting co-composts. Khat-derived biochar during pyrolysis at 350 °C was added to organic municipal solid waste mix and four co-composting treatments were prepared with the compositions (% w/w): control compost (no biochar) and 5%, 15%, and 25% co-composted biochar in three replicates. The total organic carbon, organic matter, total nitrogen, available phosphorus, and potassium values ranged as 16.76–21.45%, 30.77–40.26%, 0.97–1.68%, 0.58–0.76%, and 12.72–15.29%, respectively. The results confirmed that 5% and 15% co-composted khat biochars had significantly reduced (p < 0.05) organic matter loss and increased the contents of cation exchange capacity, pH, phosphorous, potassium, calcium, magnesium, and zinc compared to the control compost, while some heavy metals (Fe, Cu, and Mn) and EC values in co-composted biochars are lower than the control compost. Khat-derived biochar could be added to municipal organic waste mix at 5–15% (w/w) in order to get better quality of compost, which can be used as biofertilizer.

OPTIMAL MIX RATIO, TOTAL SOLIDS AND ORGANIC LOADING RATES FOR ANAEROBIC DIGESTION

Biogas technology is a sustainable and valid alternative to fossil fuels. It reduces greenhouse gas (GHG) emissions and can enhance energy security. pH, temperature, retention time, particle size, volatile solid content, inoculums, mix ratios (MR), total solid (TS) and organic loading rate (OLR) are among the factors that influence biogas production. Some studies have been done to determine optimal values of these factors for various feedstocks. The aim of this work was to determine the dependency of mix ratios (MR), total solids (TS) and organic loading rate (OLR) and their corresponding optimal values during anaerobic co-digestion of cow dung (CD), pig (PM) and sheep manure (SM). Tests were done using a 0.15m3 fixed dome laboratory reactor under a constant temperature of 35±1℃, 20 days operation period and gas yield was measured using water displacement method. A mix ratio of 1:1:2 (CD: PG: SM) lead with yield rate of 1.707m3/m3day followed by 3:1:3 with 1.300, then 1:1:3 with 0.782 and lastly 1:0:0 with 0.314m3/m3day. These values were significantly different at α=0.05 (LSD=0.392). There was an increase in biogas yield as TS increases from 6 to 8% followed by a decrease from 8% to 12%. Mean gas yields for 6, 8, 10 and 12% TS were 0.782, 0.644, 0.511 and 0.301m3/m3day respectively. TS 6 and 8%, 6 and 10%, 10 and 12 % were not significantly different from at α=0.05 but for 8 and 10% and 8 and 12% were significantly different (LSD=0.212). The biogas production rate for 1, 2, 3 and 4kgVS/m3day OLR were 0.599, 0.671, 0.769 and 0.386m3/m3day respectively. Mean yields for 1 and 2, 1 and 3, 1 and 4 and 2 and 3kgVS/m3day were not significantly different at α=5% but for 3 and 4, 2 and 4kg/m3day were significantly different (LSD=0.2417). It was then concluded that 1:1:3, 3:1:3 and 1:1:2 resulted in an increase in biogas production rate of 0.468, 0.986, and 1.393 respectively compared to pure cow dung. There was a 21.43% increase in biogas yield as TS increases from 6 to 8% followed by a 61.48% decrease from 8% to 12%. Increasing loading rate from 1-3kg VS/m3 resulted in 29% increase in biogas production rate and further increase from 3 to 4 kg VS/m3 day decreases biogas production rate by 50%. Mix ratio of 1:1:2, TS 6 and 8% and OLR 2 and 3kgVS/m3day were then recommended.

Behavior of alkali activated fly ash slag paste at room temperature

Abstract This study involves to explores the mechanical strength effect of Alkali Activated Fly Ash Slag paste (AAFS) at normal room temperature and its microstructure properties. Weight mixing percentages of Fly Ash (FA) and Ground Granulated Blast-furnace Slag (GGBS) are varying as 30/70, 50/50, and 70/30. Each proportion was activated by a combination of sodium hydroxide (NaOH) of 3 M, 6 M, 9 M, and 12 M and sodium silicate solution (Na2SiO3) keeping the ratio as 1:1. Each sample gets cured at normal room temperature. The result shows the strength variation with the molar concentration of NaOH solid mix proportion, the weight percentage of Na2O/SiO2 of alkali activated (AA) paste. Maximum strength is observed in AAF30S by the combined solution of N12W i.e. 88.65 MPa; in AAF50S by N9W i.e. 71.62 MPa; in AAF70S by N6W i.e. 41.89 MPa. Maximum percentage of GGBS leads to increase of calcium percentages with a high pH value. This cause to high strength achieved in AAF30S than AAF50S and AAF70S.

On the microstructure and solidification behavior of new generation additively manufactured Al-Cu-Mg-Ag-Ti-B alloys

Abstract Laser powder bed fusion (LPBF) was used to horizontally print A205 ( Al — Cu — Mg — Ag — Ti — B ) metal powder. The samples have been cut in various directions to analyze their phases, grain morphology, size, crystallographic orientation, and distribution of elements via X-ray diffraction (XRD), electron backscatter diffraction (EBSD), and X-ray energy dispersive spectroscopy (XEDS) in a transmission electron microscope (TEM). To monitor deformation behavior and strain distribution, several uniaxial tensile tests accompanied by digital image correlation (DIC) technique were carried out. The results showed that the as-built microstructure fully contains fine equiaxed grains with no strong preferential crystallographic orientation. The XEDS elemental maps confirmed the solute trapping phenomenon taking place during the LPBF. The stress-strain curves obtained by the uniaxial tensile testing revealed a quasi-isotropic behavior in terms of building direction; moreover, the DIC strain contour maps confirmed yield-point phenomenon and Luders bands propagation during uniaxial tensile testing. Finally, a time/temperature interdependence grain growth model was successfully applied based on no diffusion in solid and partial mixing in liquid through the entire melt pool.

Facile green path to interconnected nano-graphite networks to overtake graphene as conductive fillers

Carbon nanomaterials are effective conductive fillers for permanent antistatic composites due to their long-term stability in electrical conductivity under ambient temperature and humidity. Where graphene or graphene-like materials have been demonstrated to be the most promising conductive fillers. However, the preparation of graphene and further dispersion into polymer matrices to obtain interconnected conductive networks is still a big challenge for conductive composites. A facile green path (all solid states), microsphere rolling transfer method, has been adopted to introduce nano-graphite conductive fillers for polyethylene. The nano-graphites were well dispersed into polyethylene matrices to give interconnected networks with low loading. The conductivity reinforcements of nano-graphite fillers even overtake those of complicated graphene fillers. The percolation threshold of the conductive composites with nano-graphite fillers for polyethylene has been demonstrated to be as low as 0.85 wt%. The electrical conductivity of the conductive composites was measured to increase by 13 orders of magnitude with 2.05 wt% nano-graphite fillers (0.02 S/m), much higher than traditional solid mixing methods and approaching to the best effects from complicated solution mixing of graphene fillers. The nano-graphite conductive networks are easily adjusted and the method is feasible to almost all conventional solid resins and industrial production.

CFD-DEM model study of gas–solid flow in a spout fluidized bed with an umbrella-like baffle

In this paper, a new flow regime is identified by applying an umbrella-like baffle in a rectangular spout fluidized bed and studied by Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) approach. The simulations indicate the new flow regime features a multistage spouting – first spouting and second spouting. It is studied in aspects of spout robustness, mixing efficiency and formation mechanism. In the multistage spouting, the first spout and second spout always deflect but in opposite directions largely. This dynamic balance of the two spouts enables the high robustness in the multistage spouting pattern. Moreover, the efficiency of the gas–solid mixing is improved as four extra mesoscale particle circulations are formulated, reducing solids residence time in the dense region. The formation mechanism and regulation of the second spouting is also explored. It is indicated that the baffle opening angle of >60° can ensure the continuum and compressible property of particle flow.

Particle Mixing in Bubbling Fluidized Bed Reactors with Immersed Heat Exchangers and Continuous Particle Exchange

Tracer experiments were conducted in a lab-scale cold flow model of 0.4 m by 0.2 m in cross section to investigate the solid mixing behavior of bubbling fluidized beds under continuous particle exc...

Numerical optimization for blades of Intermig impeller in solid–liquid stirred tank

The multiphase flow in the solid–liquid tank stirred with a new structure of Intermig impeller was analyzed by computational fluid dynamics (CFD). The Eulerian multiphase model and standard k–ε turbulence model were adopted to simulate the fluid flow, turbulent kinetic energy distribution, mixing performance and power consumption in a stirred tank. The simulation results were also verified by the water model experiments, and good agreement was achieved. The solid–liquid mixing performances of Intermig impeller with different blade structures were compared in detail. The results show that the improved Intermig impeller not only enhances the solid mixing and suspension, but also saves more than 20% power compared with the standard one. The inner blades have relatively little influence on power and the best angle of inner blades is 45°, while the outer blades affect greatly the power consumption and the optimized value is 45°.

Interlocking screws crank out pharmaceuticals

For the first time, researchers have synthesized biologically active pharmaceutical ingredients using twin-screw extrusion—where two solid reactants mix via a pair of interlocking screws and are gr...

A Detailed One-Dimensional Hydrodynamic and Kinetic Model for Sorption Enhanced Gasification

Increased installation of renewable electricity generators requires different technologies to compensate for the associated fast and high load gradients. In this work, sorption enhanced gasification (SEG) in a dual fluidized bed gasification system is considered as a promising and flexible technology for the tailored syngas production for use in chemical manufacturing or electricity generation. To study different operational strategies, as defined by gasification temperature or fuel input, a simulation model is developed. This model considers the hydrodynamics in a bubbling fluidized bed gasifier and the kinetics of gasification reactions and CO2 capture. The CO2 capture rate is defined by the number of carbonation/calcination cycles and the make-up of fresh limestone. A parametric study of the make-up flow rate (0.2, 6.6, and 15 kg/h) reveals its strong influence on the syngas composition, especially at low gasification temperatures (600–650 °C). Our results show good agreement with the experimental data of a 200 kW pilot plant, as demonstrated by deviations of syngas composition (5–34%), lower heating value (LHV) (5–7%), and M module (23–32%). Studying the fuel feeding rate (22–40 kg/h), an operational range with a good mixing of solids in the fluidized bed is identified. The achieved results are summarized in a reactor performance diagram, which gives the syngas power depending on the gasification temperature and the fuel feeding rate.

CFD-DEM study of the effects of solid properties and aeration conditions on heat transfer in fluidized bed

The solid properties are of significant influence on the thermal performance of the fluidized bed. In order to provide valuable information for the application of this equipment, a numerical study is carried to clarify the effects of solid properties on the heat transfer characteristics in a lab-scale fluidized bed by means of the CFD-DEM method. Specially, two aeration conditions, i.e. the same superficial velocity and the same fluidization number, are considered. The results show that the violent convective mechanism at bed bottom plays a significant role in the heating of the bed material. The entrainment of rising bubbles and hence solid mixing are the key factors to get better temperature uniformity of the bed during the heating process. With the decrease of particle density and size, the internal circulation of solid phase is strengthened under the same superficial velocity, while slightly weakened under the same fluidization number. Obvious resemblance can be captured between solid mixing and temperature uniformity, and the enhanced solid mixing usually leads to homogeneous temperature distribution of the bed. It can be found that the heating rate decreases with increasing solid density regardless of aeration setup. In addition, it is positively related to particle diameter under the same fluidization number, while keep unchanged under the same superficial velocity. Furthermore, enhanced solid mixing and better temperature uniformity can be captured with increasing solid heat capacity, which confirms that gas temperature shows considerable effect on gas-solid flow.

Particle-Scale Simulation of Solid Mixing Characteristics of Binary Particles in a Bubbling Fluidized Bed

The behavior of solid mixing dynamic is of profound significance to the heat transfer and reaction efficiencies in energy engineering. In the current study, the solid mixing characteristics of binary particles in the bubbling fluidized bed are further revealed at particle-scale. Specifically, the influences of gas superficial velocity, Sauter mean diameter (SMD) in the system and the range distribution of particle sizes on the performance of mixing index are quantitatively explored using a computational fluid dynamics-discrete element method (CFD-DEM) coupling model. The competition between solid segregation and the mixing of binary particles is deeply analyzed. There is a critical superficial velocity that maximizes the mixing index of the binary mixture in the bubbling fluidized bed. Solid mixing performs more aggressive when below the critical velocity, otherwise solid segregation overtakes mixing when above this critical velocity. Moreover, superficial velocity is a major factor affecting the mixing efficiency in the binary bubbling fluidized bed. Additionally, the mixing behavior is enhanced with the decrease of SMD while it is deteriorated in the binary system with a wide range of particle size distribution. Therefore, it is highly recommended to perform a binary particle system with smaller SMD and closer particle size distribution for the purpose of enhancing the mixing behavior. The significant understanding of mixing characteristics is expected to provide valuable references for the design, operation, and scale-up of binary bubbling fluidized bed.

Field experimental investigation on filling the soda residue soil with liquid soda residue and liquid fly ash

In order to reuse waste soda residue, the feasibility of utilizing liquid soda residue and liquid fly ash to prepare soda residue soil was investigated. The mechanical properties of the soda residue soil were studied and analyzed through laboratory tests and field tests. The raw materials preparation process and liquid-liquid mixing method in the field were determined, and the optimal mixing proportion of the soda residue soil was investigated by compaction test and micro penetration test. And the filling quality of the liquid-liquid mixing and solid-liquid soda residue soil was measured by micro penetration test, light dynamic penetration test, and variable energy dynamic penetration test. The test results showed that the optimal mass ratio of soda residue to fly ash is 7:3. The optimal water content and maximum dry density of the soda residue soil with the optimal mix ratio are 63.5% and 0.88 g/cm3, respectively. After 5 months of natural drying, the soda residue soil filled by liquid soda residue and liquid fly ash has higher strength and better uniformity of hardness. The water content of the soda residue soil is between 160% to 180%, and drainage consolidation is the effective method to reduce the water content and improve the strength of the soda residue soil. Compared with the method of preparing the soda residue soil by solid mixing, the method used in this experiment is simple, efficient and feasible.

Triple-doped Ceria–Carbonate (Ce0.82La0.06Sm0.06Gd0.06O2-δ – (Li–Na)2CO3) nanocomposite solid electrolyte materials for LT–SOFC applications

The Ce0.82La0.06Sm0.06Gd0.06O2-δ triple-doped ceria (LSG) and triple-doped ceria–carbonate nanocomposites (Ce0.82La0.06Sm0.06Gd0.06O2-δ – (Li–Na)2CO3) (LSG–LN) were prepared through sol-gel auto-combustion technique and followed by solid state mixing methods. The characterization of prepared triple-doped ceria (LSG) and triple-doped ceria–carbonate nanocomposites (LSG–LN) (such as LSG, 85LSG–15LN, 75LSG–25LN, and 65LSG–35LN, respectively) was carried out by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy, impedance spectroscopy (IS), and the thermal expansion analyses. Sample formation, phase identification, surface morphologies and presence of elements in the prepared materials were analyzed with the help of XRD, SEM and EDS studies. The presence of oxygen vacancies and further structural analysis were investigated by the micro Raman spectroscopy. Total-ionic-conductivity and activation energies in the temperature range from 250 to 600 °C were evaluated from the IS measurements. Thermal expansion analysis revealed the moderate values of coefficients of expansion in all the samples. Triple-doping with carbonate phase resulted in highest total-ion-conductivities i.e., 4.2 × 10−1 S/cm and 4 × 10−1 S/cm for 65LSG–35LN and 75LSG–25LN, respectively. Total-ion-conductivities of the triple-doped ceria–carbonate nanocomposite materials were found to be high when compared to the triple-doped ceria (i.e., 3.8 × 10−2 S/cm). Therefore, it is concluded that these triple-doped ceria–carbonate nanocomposite materials will be useful as a promising electrolyte in low temperature solid oxide fuel cell (LT–SOFC) applications.

A machine learning framework for computationally expensive transient models

Transient simulations of dynamic systems, using physics-based scientific computing tools, are practically limited by availability of computational resources and power. While the promise of machine learning has been explored in a variety of scientific disciplines, its application in creation of a framework for computationally expensive transient models has not been fully explored. Here, we present an ensemble approach where one such computationally expensive tool, discrete element method, is combined with time-series forecasting via auto regressive integrated moving average and machine learning methods to simulate a complex pharmaceutical problem: development of an agitation protocol in an agitated filter dryer to ensure uniform solid bed mixing. This ensemble approach leads to a significant reduction in the computational burden, while retaining model accuracy and performance, practically rendering simulations possible. The developed machine-learning model shows good predictability and agreement with the literature, demonstrating its tremendous potential in scientific computing.

A novel experimental method for determining lateral mixing of solids in fluidized beds – Quantification of the splash-zone contribution

An experimental method to investigate the lateral mixing of bulk solids in bubbling fluidized beds is presented. The method utilizes finite volume analysis of the measured temperature field over the bed surface, from which the solids dispersion coefficient is determined. The temperature field is measured with a thermographic camera, which in this work is applied to a fluid-dynamically down-scaled fluidized bed that resembles the conditions relevant for hot large-scale operation. The method is applied to investigate the effect of key parameters for the solids mixing process; fluidization velocity, particle size and pressure drop over the air distributor plate. The results showed up-scaled dispersion coefficients in the order of 10−3 m2/s for the conditions investigated. The lateral mixing of solids decreased with increasing particle size and increased with increases in the fluidization velocity and pressure drop over the air distributor. The method was also used to quantify the contribution of the splash zone to the total lateral solids mixing. When lateral solids mixing in the splash zone was blocked with a vertical baffle the lateral solids dispersion was reduced by some 90%.

Quantification of Solid Mixing in Bubbling Fluidized Beds via Two-Fluid Model Simulations

The influence of particle density and fluidization velocity on the mixing behavior of Geldart B particles was investigated in bubbling fluidized beds for various operating conditions using a two-fluid model approach. The simulation results proved that the predicted solid flow pattern for a wide range of Geldart B particles differs from particles of Geldart B/D classification at identical fluidization numbers. Quantitative analysis of the predicted solid velocity variances revealed that the solid axial dispersion rate is higher than the lateral one. In detail, a Peclet number of 1.54 and 3.92 was predicted for axial and lateral mixings, respectively. Also, the solid dispersion and diffusion coefficients were linearly correlated with the excess gas velocity for a range of particle properties. Finally, the characteristic global particle mixing times were computed. Thereby, the characteristic mixing time can be correlated with the particle Froude number, expanded bed height, and solid dispersion coefficient with high accuracy.