Slurry Processing Research Articles

Two-stage fast flotation of coal tailings using reflux flotation

Low pulp density and low grade slurries in the coal and minerals industries are discharged as waste to tailings dams, incurring significant losses of valuable particles. This paper investigates the rapid processing and cleaning of hydrocyclone overflow coal slurry using two laboratory scale Reflux Flotation Cells in series as a means to economically beneficiate low quality tailings streams. The Reflux Flotation Cell incorporates a novel arrangement of inclined channels to enhance bubble-liquid segregation, enabling extremely high gas rates and liquid rates per unit of vessel area. Hence, in the first stage, fast flotation is employed to rapidly recover fine coal particles using a feed flux of 11.4±0.5cm/s, up to an order of magnitude increase in the throughput rate over conventional flotation systems. First stage product was then sent to a second stage for counter-current washing using fluidisation wash water to produce a fully deslimed product, having ash percent in agreement with the minimum ash attainable using flotation as determined through tree flotation analysis. The results demonstrate the potential for two-stage Reflux Flotation to deliver high throughput at a high separation efficiency from low quality slurry, with a fivefold reduction in the required vessel footprint, thus overcoming the principal economic deterrent of having to install banks of large-scale flotation cells.

Towards high durable lithium ion batteries with waterborne LiFePO4 electrodes

The positive electrodes based on nano- and micrometric carbon coated LiFePO4 (LFP) powders are prepared via aqueous slurry processing using “normal” and “intensive” mixing procedures. The XRD, XPS, and electrochemical characterization reveal that the “intensive” mixing process improves the discharge C-rate capability of the n-LFP cathode however provokes formation of an undesirable thin surface layer enriched by Fe3+ species. The waterborne graphite anodes and LiFePO4 cathodes for the energy and power cells are being developed, upscaled and manufactured on a pilot plant. Energy LiFePO4/C pouch cells demonstrate outstanding durability maintaining 80% of initial discharge capacity (IDC) after 7450 and 2400 full cycles under 1D and 4D discharge currents, respectively. Moreover, further cycling of the energy cell working under 1C/4D protocol reveals its extra-long secondary life (70% of IDC on 9200th cycle). Power LiFePO4/C pouch cell shows long lasting cycle life retaining 80% of IDC after 3350 cycles under harsh cycling conditions (3C/8D). The reported results are being achieved despite confirmed water release from lithium iron phosphate cathodes to the electrolyte. Finally, viability of aqueous processing of the electrodes without sacrificing electrochemical performance of LiFePO4/C batteries is clearly proven.

Optimizing Energy Density of Li-Ion Batteries Using Thick Electrodes

Low-cost, high energy density lithium-ion batteries (LIBs) have been consistently pursued in consumer electronics, electrical vehicles (EVs) and stationary (grid) energy storage. Modern Li-ion cells can have an energy density of up to 550 Wh/L, compared to only 200 Wh/L in the late 1990s [1]. The gradual energy density improvement over the last 15-20 years was mostly due to the improved engineering of the electrode coatings and, to some extent, some improvement in active material development and manufacturing. The former has significantly increased the volume ratio of active materials (which provides the capacity of the battery) from ~20% at early stages to ~45% in the state-of-art LIBs [2,3]. Thickening the cathode and anode is one effective approach to further increase the active material content, enabled from reducing current collector and separator layers in the stack, which further improves the energy density and lowers the cost of LIBs. It has been estimated that significant reduction in pack cost can be realized when compared to conventional manufacturing if electrode thickness is doubled and aqueous slurry processing is utilized [4]. However, thicker electrodes lead to poor kinetics and electrolyte salt depletion and thus underutilization of active materials. The major concern of thick coatings is electrolyte salt depletion, which results in fewer lithium ions available in the liquid phase for reaction at the active material surface. Therefore, there is an optimum thickness for maximum energy and power density. To maximize energy and power density, the effect of various coating parameters on the reaction kinetics and thus battery performance must be considered during electrode design. The operation of LIBs follows porous electrode theory and electrochemical reaction thermodynamics, and the governing equations have been summarized by Newman et al. [5]. Thus, the porous electrode model is used in the present work to investigate the effect of manufacturing parameters such as electrode thickness and porosity. In the present study, the following will be discussed: (1) The effect of thickness on active material utilization, areal capacity, voltage and energy density. (2) The effect of porosity on active material utilization, areal capacity, voltage and energy density. (3) Possible solutions to further increase the energy density of thick-electrode battery. Acknowledgement This research at Oak Ridge National Laboratory (ORNL), managed by UT Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725, was sponsored by the Office of Energy Efficiency and Renewable Energy Vehicle Technologies Office (VTO) Applied Battery Research (ABR) subprogram (Program Managers: Peter Faguy and David Howell).

Coupling Hierarchical Sulfur Composites with in-situ Cross-linked Binder to Build Stable High-areal-capacity Sulfur Cathodes

Lithium-sulfur battery is considered one of the most promising electrochemical system for energy storage, owing to the high theoretical energy density (2600 kWh/kg) and the natural abundance of sulfur. Their practical challenges facing commercial viability lie in the insulating feature of the end-products (S and Li2S), lithium polysulfide dissolution and shuttling between electrodes and random precipitation of Li2S from the dissolved polysulfides. This leads to rapid capacity fading over long-term cycling and relatively low sulfur utilization. This becomes even more problematic for high sulfur loading cells, since the large concentration of dissolved polysulfides can not only lead to uncontrolled precipitation of Li2S that eventually clog the cathodes, but also to increased side-reactions with lithium anodes. Great efforts have been made to address these issues with a focus on the cathode materials, but mostly thin electrodes with sulfur loadings below 2 mg/cm2.[[1]] In order to fabricate high-loading Li-S cells, recently reported approaches are to construct 3D conductive framework composed of graphene or carbon nanofibers. However, one intrinsic problem is the high porosity of the 3D architecture usually requires large volume of electrolyte, leading to high electrolyte/sulfur ratio and thus low volumetric energy density. Therefore, developing high loading electrodes using traditional slurry-based process is critical for practical applications.[[2]] Here we will present a multifaceted strategy to construct stable and high sulfur loading cathodes based on the traditional slurry processing, by coupling a hierarchical sulfur composite with in-situ cross-linked polymer. We incorporated our previously reported highly nitrided material with conductive framework. A light-weight, electrically conductive and highly porous hybrid was thus obtained. The hybrid material exhibit a micrometer sized structure, which is beneficial to fabricate crack-free thick electrodes. This is due to the enhanced connection between individual particles even with lower percentage of binder compared to nanoparticles with low tap density. The XPS survey spectrum shows the presence of a high concentration of nitrogen at 19.9 at%. Our first-principles calculations show that our hybrid has a much higher polysulfide binding energy towards than functionalized polymer or doped carbons. We will further present an integrated cathode enabled by in-situ cross-linked binder and a combination of CNTs and Super P carbon additives. The inter-particle electronic connection is greatly enhanced. Fourier transform infrared spectroscopy (FTIR) confirms the successful cross-linking. The low-magnification SEM images clearly shows that on contrary to the large cracks in the PVDF based electrodes (formed upon evaporation of the slurry solvent), the cross-linking binder based electrode surface is flat and compact, without any cracks. It is worth noting that such an integrated structure was achieved with as low as 5 wt% of binder, which greatly increases the gravimetric energy density. We demonstrate that cathodes with sulfur loading up to 15.0 mg/cm2 have been fabricated with stable cycling performance. Insights into the evolution of the impedance will also be presented.

Trends and Constraints of Grain Slurry Food Processing in Kaduna State, Nigeria

, 2016Purpose: Grain slurry diet are described as food obtained from ground grain paste. They serve as highly nutritious food for both adults and infants in Nigeria because of their immense nutritive and economical value. However, the production of these grain slurry diets is confronted with challenges that have hampered their commercialization. This study examines the trends and constraints of grain slurry food processing in Kaduna State. Methods: A survey was conducted using a structured questionnaire to elicit information from 192 selected processors, including both men and women. The survey was structured in line with the study objectives. The information was collated and synopsized into frequency distribution. Results: These findings revealed that 80% of the respondents processed between 1.0 tons and 13.0 tons of grain slurry per month. More than 90% of the processors processed grain slurry into koko, kunu, agidi, and pito. Accordingly, 80% of the interviewed processors indicated that sieving is one of the major constraints. Furthermore, inadequate modern machinery required to perform this operation makes it highly discouraging. One of the major challenges faced by the grain slurry producers in Nigeria is the lack of processing machinery for most operations (39.1%), followed by the tedious processing nature (27.1%), high labor cost (18.1%), and lack of market (9.4%). The traditional method of grain slurry processing was more popular than using modern equipment, except milling (96.5%), which is the only mechanized unit operation in grain slurry processing. Conclusion: Grain slurry processing and marketing were found to be profitable. However, these limitations could extremely reduce the level of grain slurry production, processing, and economic returns, thereby affecting the general wellbeing of the processors. The study also raised concerns about the safety and hygiene associated with traditionally processed grain slurry diets in the investigated areas.Keywords: Constraints, Equipment, Grain slurry, Processing, Sieving

Recycling liquid effluents in a ceramic industry

In this work is presented a study on the recycling of liquid effluents in a ceramic installation for sanitary industry. The effluents were characterized by X-ray diffraction and inductively coupled plasma to evaluate their compositions. It was also assessed the daily production rate. Several glaze–slurry mixtures were prepared and characterized according to procedures and equipment of the company's quality laboratory. The results show that for most of the properties, the tested mixtures exhibited acceptable performance. However, the pyroplasticity parameter is highly influenced by the glaze content and imposes the separation of glaze and slurry liquid effluents. In addition, it is necessary to invest on a storage plant, including tanks with constant stirring and a new pipeline structure to implement the reincorporation method on the slurry processing.

Effect of polishing parameters on abrasive free chemical mechanical planarization of semi-polar (112¯2) aluminum nitride surface

An abrasive free chemical mechanical planarization (AFCMP) of semi-polar (112¯2) AlN surface has been demonstrated. The effect of slurry pH, polishing pressure, and platen velocity on the material removal rate (MRR) and surface quality (RMS roughness) have been studied. The effect of polishing pressure on the AFCMP of the (112¯2) AlN surface has been compared with that of the (112¯2) AlGaN surface. The maximum MRR has been found to be ~562 nm/h for the semi-polar (112¯2) AlN surface, under the experimental conditions of 38 kPa pressure, 90 rpm platen velocity, 30 rpm carrier velocity, slurry pH 3 and 0.4 M oxidizer concentration. The best root mean square (RMS) surface roughness of ∼1.2 nm and ∼0.7 nm, over a large scanning area of 0.70 × 0.96 mm2, has been achieved on AFCMP processed semi-polar (112¯2) AlN and (AlGaN) surfaces using optimized slurry chemistry and processing parameters.

Attaining near-theoretical densification in nanograined pyrochlore La2Zr2O7 (LZ) ceramic at 1150 °C by spark plasma sintering

Phase-pure Lanthanum zirconate nanopowders (La2Zr2O7, LZ) were synthesized by co-precipitation method and subjected to densification studies. No additive/sintering aid was used, neither was any slurry processing performed to improve the quality of the powders. LZ ceramic with near-theoretical density (>98%) was obtained at 1150°C by spark plasma sintering; the lowest sintering temperature reported till date. The LZ ceramic comprised of small equiaxed grains (~300nm) and recorded a significant improvement in hardness (~14GPa) and scratch resistance measured by nanoindentation. The study clarifies that all previous reports involving poor sinterability of LZ system was related to inferior quality precursors.

Novel strategies towards the realization of larger lithium sulfur/silicon pouch cells

We report the fabrication of functional lithium sulfur full cells in button and pouch cell formats with the help of a prelithiation approach utilizing stabilized lithium metal powders (SLMP). A silicon electrode was prepared from silicon nanoparticles, carbon black and aqueous lithiated polyacrylic acid as a binder. The anode capacity was restricted to 900mAhg−1 based on the mass of composite. In a half cell configuration it may be cycled reversibly for at least 60 cycles at a specific current of 100mAg−1​ until the capacity starts to fade significantly. Coulombic efficiencies are well above 99%. However, the system possesses significant irreversible capacity of around 22%. For this reason a spray coating approach was used to coat the surface with SLMP. With this strategy the irreversible capacity could be compensated effectively. On the cathode side carbon/sulfur composites have been prepared by melt impregnation of activated charcoal. The composite was processed into electrodes with a polyethylene oxide/anisol binder solution. The composition ratio in wt% for the cathode was composite/carbon black/binder 80/10/10. At a specific current of 200mAg−1, the final electrode showed reversible capacities of 500mAhg−1 based on composite for at least 100 cycles with coulombic efficiencies above 90%. To add cycleable lithium into the cell, a slurry processing approach for the cathode was developed. SLMP was simply added to the cathode slurry. Resulting coatings have been stable under glove box conditions and could be further processed to full cells with the prelithiated anode as counter electrode. At first, button cell configurations were investigated. The cells showed higher initial discharge capacities of 400–500mAhg−1 based on the amount of cathode composite. Cells are relatively stable for 50 cycles. Larger single layer pouches with effective electrode areas of 24cm2 and an initial discharge capacity of 45 mAh at 200mAg−1 could successfully be assembled in a next step. The cells show almost the same performance as the smaller button cells.

Calcium-phosphate slurry processing: A novel chemical treatment technique to activate osteogenesis on titanium

Calcium-phosphate slurry processing: A novel chemical treatment technique to activate osteogenesis on titanium

Phase Segregation during Processing of Semi-Solid Slurry by Rheocasting Method SEED

The paper describes specific phenomena of semi-solid casting process, especially rheo-casting method SEED, which uses mechanical swirling for reaching proper structure in semi-solid state. The eutectic segregation during processing of semi-solid slurry can cause specific casting defects. Heat treated alloy AlSi7Mg0.3 was applied for producing castings. For observing structure, metallographic observation by light and SEM microscopy was used as well as spectral analysis.

Energy production from anaerobic co-digestion processing of cow slurry, olive pomace and apple pulp

This paper deals with anaerobic co-digestion of cow slurry, apple pulp and olive pomace mixture and results obtained shown that the production of methane by co-digestion of cow slurry, olive pomace and apple pulp is not only possible but also economically and energetically attractive. Tests were performed with a pilot scale anaerobic digester, 128 l in volume, operating under batch and fed-batch condition. The biogas production, methane yield and quality, plus other operating parameters were evaluated under four feeding regimes, to simulate a real situation. Stable biogas production was obtained of about 400 l/kg Volatile Solids at a Hydraulic Retention Time of 40 days in a mixture containing 85% cow slurry, 10% olive pomace and 5% apple pulp (% by volume). The percentage of methane inside the biogas was around 52% and the maximum COD removal was 63%.

Improved hydration resistance of magnesia by EDTA and ammonium phosphate as additives

Abstract The control of magnesia (MgO) hydration ratio is a key factor in refractory slurry processing. The volumetric expansion that follows this reaction can result in MgO product cracks as MgO greatly tends to react with water. Thus, the antihydration of MgO is a key concern in refractory suspension processing. The performances of ammonium phosphate (AP) and ethylene diamine tetraacetic acid (EDTA) as antihydration additives were evaluated by using hydration tests, and ionic conductivity, pH, and particle distribution of MgO powders in water and ethanol were used to provide information related to the MgO powder in different liquids. The results showed that the antihydration additives AP and EDTA can inhibit MgO hydration to some extent; however, AP was more effective in preventing volume expansion.

In situ study of mass loss, shrinkage and stress development during drying of cast colloidal films

During constrained drying of binder-assisted colloidal coatings on rigid substrates, drying stress-induced defects such as cracks and warpage can often be observed due to the lateral confinement of the film by the substrate. The purpose of the current work is to understand the origin of these drying defects and to develop strategies for their avoidance by the adjustment of slurry composition or processing parameters. In this paper, the time-dependent drying behavior of colloidal ceramic coatings was studied in situ by observation of mass loss, drying shrinkage and drying stress by different methods, such as transparent substrate deflection and beam deflection methods. The stress development and the critical moment, at which cracks form, were investigated in films of different compositions with respect to solvent, particle size, binder and plasticizer. The origins of the measured differences in drying shrinkage, crack formation as well as residual stresses after drying were discussed.

Influence of Polishing Parameters on Abrasive Free Chemical Mechanical Planarization (AFCMP) of Non-Polar (11-20) and Semi-Polar (11-22) GaN Surfaces

In this study, an Abrasive free Chemical Mechanical Planarization (AFCMP) of non-polar (11-20) and semi-polar (11-22) GaN surfaces has been demonstrated. Effect of processing parameters, such as types and concentration of oxidizers, polishing pressure, platen velocity, and pH of the slurries, on the material removal rate (MRR) and surface quality (roughness) have been studied in details. The maximum MRR has been found to be 1.14 μm/hr and 1.85 μm/hr for non-polar (11-20) and semi-polar (11-22) GaN surfaces respectively, under optimized condition of 38 kPa polishing pressure, 90 rpm (100 for non polar surface) platen velocity, 30 rpm carrier velocity, slurry pH 2 and 0.4 M Oxidizer concentration. Root mean square (RMS) surface roughness of ∼1.9 nm and ∼0.8 nm, over large scanning area of 0.70 × 0.96 mm2, has been achieved on AFCMP processed non-polar (11-20) and semi-polar (11-22) GaN surfaces, respectively, using optimized slurry chemistry and processing parameters.

Microstructure Evolution in Lithium-Ion Battery Electrode Processing

The electrode microstructure and composition play an important role in determining the performance of the lithium ion battery (LIB). To this end, the processing of the multi-phase slurry consisting of active nanoparticles, conductive additives, binder and solvent determines the electrochemical properties and performance of the electrode. Mixing components in the slurry homogenously is one essential requirement to process the high quality electrode. Additionally, it is necessary to make these components cooperate very well with each other.1-4 Fundamentally, slurry properties and drying methods mainly determine the microstructure and the performance of the cathode composite. Viscosity of the slurry is an important property, which is determined by the concentration and the solid loading of each component, the interaction force among nanoparticles in the slurry, and the properties of active material nanoparticles that include the size of the nanoparticle, size distribution and the surface area.5 One common mechanism of the drying process is solvent evaporation from the surface of the substrate. The evaporation induced assembly is a popular scheme to make nanoparticles form desirable microstructures, and this assembly is controlled by interactions among nanoparticles and solvents, evaporation rates, mobility of nanoparticles and the morphology of nanoparticles.In our present work, a morphology-detailed mesoscale model has been developed to gain fundamental understating of the influence of active particle morphology, size, volume fraction, solvent evaporation rated, and multi-phase (active particle, conductive additive, binder and solvent) interaction. Our results demonstrate that smaller isometric active particles tend to form favorable aggregation with conductive additive particles. Two regimes, namely spontaneous aggregation and evaporation induced

Mining: Bowl dehydrator design for coal slurry processing

To improve the dewatering of coal slurry, Zheng Gangfeng and his colleagues at Anhui University of Science and Technology in China have developed and built a new design of bowl dehydrator with a spiral screen. Here, they discuss its operating principles and salient features, and present test results that demonstrate its potential for industrial-scale application.

Probing Active Particle Assembly in Lithium-Ion Battery Electrode Processing

Lithium-ion batteries (LIB) are currently considered as the primary choice for electric drive vehicles. The electrode microstructure and composition play an important role in determining the performance of the LIB. To this end, the processing of the multi-phase slurry consisting of active nanoparticles, conductive additives, binder and solvent determines the electrochemical properties and performance of the electrode. Morphology and the size of the active nanoparticles affect the LIB performance due to large active surface area, short diffusion length and fast kinetics. On the contrary, the aggregation of the active nanoparticles might have a detrimental effect. Therefore, fundamental understanding of the aggregation behavior of the active particles in the slurry is of paramount importance.In this regard, the evaporation dynamics of the slurry is a key factor which determines the microstructural heterogeneity of the electrode. The morphology of the aggregated particles is governed by a variety of physicochemical factors such as interaction between nanoparticles, diffusion rate of the nanoparticles and evaporation rate of the solvent. In this work, we present a mesoscale modeling approach in order to investigate the influence of evaporation on active particle assembly in LIB electrode processing. Our mesoscale model is based on a coarse-grain formalism combining lattice gas and kinetic Monte Carlo methodologies. We will present a comprehensive study of the active particle aggregation behavior and resultant influence due to the (1) evaporation rate of the solvent, (2) active particle and binder interaction, and (3) active particle morphology. Figure 1 shows representative aggregation characteristics of different active particle morphology. Reference J. Li, B. L. Armstrong, J. Kiggans, C. Daniel and D. L. Wood, Langmuir, 28, 3783-3790 (2012).J. Li, C. Daniel and D. L. Wood, Journal of Power Sources, 196, 2452-2460 (2011).H. Zheng, R. Yang, G. Liu, X. Song and V. S. Battaglia, Journal of Physical Chemestry C, 116, 4875-4882 (2012).E. Rabani, D. R. Reichman, P. L. Geissler and L.ha E. Brus, Nature, 426, 271-274 (2003).

Effect of Polishing Parameters on Chemical Mechanical Planarization of C-Plane (0001) Gallium Nitride Surface Using SiO2 and Al2O3 Abrasives

In this study, Chemical Mechanical Planarization (CMP) of (0001) GaN surface, using two different slurries containing colloidal silica and alumina as abrasive nanoparticles, has been reported. Effect of processing parameters, such as concentration of the oxidizer, downward pressure, head rpm, base rpm, pH of the slurries, and type and concentration of abrasive particles, on the material removal rate (MRR) and surface quality (roughness) have been studied in details. The maximum MRR has been found to be ∼39 nm/hr and ∼85 nm/hr for slurries containing SiO2 and Al2O3 abrasives, respectively, under 38 kPa pressure, 90 rpm base speed (100 rpm for Al2O3 containing slurry), 30 rpm carrier speed, slurry pH 1 (2 for Al2O3 containing slurry), 0.3 M Oxidizer concentration, and 3.75 wt% abrasive particle concentration. RMS surface roughness of 1.3 Å and 0.7 Å, over scanning area of 10 μm × 10 μm and 5 μm × 5 μm, respectively, has been achieved on polished Ga-faced GaN surface for SiO2 containing slurry using optimized slurry chemistry and processing parameters.

ASSESSMENT OF COAL SLURRY DEPOSITS ENERGETIC POTENTIAL AND POSSIBLE UTILIZATION PATHS

Coal-slurries and post-flotation mud have the highest carbon content among other mine waste produced during coal mining and preparation. Therefore, coal slurries deposited in impoundments can be regarded as potential fuel. In the article methods of energetic potential assessments of raw and beneficiated coal slurry deposits were discussed. Results of such assessment for 21 impoundments were presented and the loss of energetic potential due to the imperfection of beneficiation method was discussed. The lowest losses were observed for beneficiation by froth flotation where the loss of energetic potential was on average 15%. The highest loss was observed for beneficiation in centrifugal separators where on average it was 68%. Possible paths of utilization of such slurries in Polish national fuel balance were studied using the SWOT analysis. The results of the SWOT analysis indicate that the internal factors, i.e. the ones related to the coal slurry processing technology have much lower impact on the possibility of using coal slurry deposits in the national fuel balance. Instead, according to the experts, external factors have much greater impact.