| 1. |
- Ahmadi, R., et al.
(författare)
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Rapid determination of Bond rod-mill work index by modeling the grinding kinetics
- 2013
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Ingår i: Advanced Powder Technology. - : Elsevier BV. - 0921-8831 .- 1568-5527. ; 24:1, s. 441-445
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Tidskriftsartikel (refereegranskat)abstract
- Generally, Bond work index is a common method for selecting comminution equipment as well as estimation of grinding efficiency and calculating required power. In the current research, a simple, fast and accurate procedure is introduced to find the rod-mill work index based on the conventional Bond work index. The grinding experiments were carried out on four typical samples of iron, copper, manganese and lead–zinc ore with three test-sieves in specified time periods and aimed to shortening the procedure. Furthermore, the grinding kinetics and mass balance equations were applied to model the standard Bond rod-mill work index. For comparing the standard Bond rod-mill work index and the new modeled method, work index (Wi) and produced fine particles in a cycle (Gi) for the four samples determined. The performed paired Student’s t-test results indicated that the Standard Deviation for Gi and Wi obtained by the shortened method are respectively 0.50 and 0.58 in respect of traditional Bond method.
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| 2. |
- Bonmann, Marlene, 1988, et al.
(författare)
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Sub-millimetre wave range-Doppler radar as a diagnostic tool for gas-solids systems - solids concentration measurements
- 2023
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Ingår i: Advanced Powder Technology. - : Elsevier BV. - 0921-8831 .- 1568-5527. ; 34:1
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Tidskriftsartikel (refereegranskat)abstract
- Current non-intrusive measurement techniques for characterising the solids flow in gas-solids suspensions are limited by the low temporal or low spatial resolution of the sample volume, or in the case of optical methods, by a short range of sight. In this work, a sub-millimetre wave range-Doppler radar is developed and validated for non-intrusive sensing of solids concentrations in a gas-solids particle system with known characteristics. The radar system combines favourable features, such as the ability to see through at optical frequencies opaque materials, to measure the local solids velocity and the reflected radar power with a spatial resolution of a few cubic centimetres over distances of a few metres. In addition, the radar hardware offers flexibility in terms of installation. After signal processing, the output of the radar is range-velocity images of the solids flowing along the radar’s line-of-sight. The image frame rate can be close to real-time, allowing the solids flow dynamics to be observed. While the well-established Doppler principle is used to measure the solids velocity, this paper introduces a method to relate the received radar signal power to the solids volumetric concentrations (cv) of different particulate materials. The experimental set-up provides a steady stream of free-falling solids that consist of glass spheres, bronze spheres or natural sand grains with known particle size distributions and with particle diameters in the range of 50–300 µm. Thus, the values of cv found using the radar measurements are validated using the values of cv retrieved from closure of the mass balance derived from the measured mass flow rate of the solids stream and the solids velocity. The results show that the radar system provides reliable measurements of cv, with a mean relative error of approximately 25 % for all the tested materials, particle sizes and mass flow rates, yielding values of cv ranging from 0.2 × 10-4 m3/m3 up to 40 × 10-4 m3/m3 and solids velocities within the range of 0–4.5 m/s. This demonstrates the ability of the radar technology to diagnose the solids flow in gas-solids suspensions using a unique combination of penetration length, accuracy, and spatial and time resolution. In future work, the radar technique will be applied to study non-controlled solids flow at a larger scale, and to understand flow conditions relevant to industrial reactor applications, e.g., fluidised bed, entrained flow, and cyclone units.
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| 3. |
- Chelgani, Saeed Chehreh, et al.
(författare)
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Modeling of particle sizes for industrial HPGR products by a unique explainable AI tool- A “Conscious Lab” development
- 2021
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Ingår i: Advanced Powder Technology. - : Elsevier. - 0921-8831 .- 1568-5527. ; 32:11, s. 4141-4148
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Tidskriftsartikel (refereegranskat)abstract
- High-Pressure Grinding Rolls (HPGR), as a modified type of roll crushers, could intensively reduce the energy consumptions in the mineral processing comminution units. However, several problems counted for their operational modeling, especially in the industrial scales. Expanding a conscious laboratory (CL) as a recently developed concept based on the recorded datasets from the HPGR operational variables could be tackled those complications and fill the gap. Moreover, constructing such a CL base on explainable artificial intelligence (EAI) systems would be an innovative point for the digitalizing powder technology industries. Using a robust EAI model as a strategic approach could significantly improve system transparency and trustworthiness to convert any complicated black-box machine learning to a logical human basis system. This study introduced the SHapley Additive exPlanations (SHAP) and extreme gradient boosting (XGBoost) as the latest powerful EAI tool for the CL modeling of the particle sizes produced by an industrial HPGR (P80) in the Fakoor Sanat iron ore processing plant (Kerman, Iran). SHAP precisely assessed multivariable relationships between the monitored operational variables and correlated them with the HPGR P80. SHAP values showed relationship magnitudes among variables and ranked them based on their effectiveness on the P80 prediction. The working gap demonstrated the highest importance for the P80 prediction. XGBoost could precisely predict the P80 and showed higher accuracy than typical machine learning methods (random forest and support vector regression) for constructing the CL of HPGR. These significant outcomes would open a new window for robust consideration of the EAI models within powder technology.
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| 4. |
- Das, B, et al.
(författare)
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High performance metal nitrides, MN (M = Cr, Co) nanoparticles for non-aqueous hybrid supercapacitors
- 2015
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Ingår i: Advanced Powder Technology. - : Elsevier BV. - 0921-8831 .- 1568-5527. ; 26:3, s. 783-788
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Tidskriftsartikel (refereegranskat)abstract
- In this study, metal nitrides MN (M = Cr, Co) nanoparticles of particle size similar to 20-30 nm have been prepared under NH3 + N-2 atmosphere at relatively low temperature. The Cr-urea complex was directly converted to CrN with an intermediate formation of Cr2O3, whereas CoN was prepared from Co3O4. These compounds were characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM) techniques. The electrochemical properties were evaluated by galvanostatic cycling, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical performance of the resultant MN nanoparticles showed that they can be used as potential electrode materials for non-aqueous hybrid electrochemical supercapacitors (HESCs). The MN/AC showed high specific capacitance of 75 and 37 F g (1) for M = Cr, Co, respectively when cycled at 30 mA g (1) in non-aqueous electrolyte.
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| 5. |
- Feng, Peizhong, et al.
(författare)
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Combustion synthesis of (Mo1-xCrx)Si-2 (x=0.00-0.30) alloys in SHS mode
- 2012
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Ingår i: Advanced Powder Technology. - : Elsevier BV. - 0921-8831 .- 1568-5527. ; 23:2, s. 133-138
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Tidskriftsartikel (refereegranskat)abstract
- Combustion synthesis was adopted to successfully synthesize molybdenum-silicon-chromium (Mo-Si-Cr) alloys by the mode of self-propagating high-temperature synthesis (SHS). The experimental study of combustion synthesis of Mo-Si-Cr alloys was conducted on elemental powder compacts. Powder compacts with nominal compositions including MoSi2, (Mo0.95Cr0.05)Si-2, (Mo0.90Cr0.10)Si-2, (Mo0.85Cr0.15)Si-2, (Mo0.80Cr0.20)Si-2, (Mo0.75Cr0.25)Si-2 and (Mo0.20Cr0.30)Si-2 were employed in combustion synthesis experiments. The combustion mode, combustion temperature, flame-front propagation velocity and product structure were investigated. The results showed that Mo-Si-Cr alloys were synthesized by an unsteady state combustion mode with a spiral-trajectory reaction front. The peak combustion temperature reduced with the addition of Cr to Mo-Si system. The flame-front propagation velocity decreased with an increase in Cr content of the powder compact. The X-ray diffraction (XRD) results showed that the crystal structure of the combustion product changed from CIIb-type structure (Mo0.90Cr0.10)Si-2 to C40-type structure (Mo0.80Cr0.15)Si-2 with increase in Cr content of Mo-Cr-Si alloys. The intensities of diffraction peaks of the C40-type phase gradually increased with increase in Cr content.
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| 6. |
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| 7. |
- Javadi, Alireza, et al.
(författare)
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Formation of hydrogen peroxide by galena and its influence on flotation
- 2014
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Ingår i: Advanced Powder Technology. - : Elsevier BV. - 0921-8831 .- 1568-5527. ; 25:2, s. 832-839
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Tidskriftsartikel (refereegranskat)abstract
- Formation of hydrogen peroxide (H2O2), an oxidizing agent stronger than oxygen, during the grinding of galena (PbS) was examined. It was observed that galena generated H2O2 in pulp liquid during wet grinding and also when the freshly ground solids were placed in water immediately after dry grinding. The generation of H2O2 during either wet or dry grinding was thought to be due to a reaction between galena and water, when the mineral surface is catalytically active, to produce OH• free radicals by breaking down the water molecule. It was also shown that galena could generate H2O2 in the presence or absence of dissolved oxygen in water. The concentration of H2O2 formed increased with decreasing pH. The effects of using mixtures of pyrite or chalcopyrite with galena were also investigated. In pyrite-galena mixture, the formation of H2O2 increased with an increase in the proportion of pyrite. This was also the case with an increase in the fraction of chalcopyrite in chalcopyrite-galena mixtures. The oxidation or dissolution of one specific mineral rather than the other in a mixture can be explained better by considering the extent of H2O2 formation rather than galvanic interactions. It appears that H2O2 plays a greater role in the oxidation of sulphides or in aiding the extensively reported galvanic interactions. This study highlights the necessity of further study of electrochemical and/or galvanic interaction mechanisms between pyrite and galena or chalcopyrite and galena in terms of their flotation behaviour.
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| 8. |
- Kim, Se-Hoon, et al.
(författare)
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Nanophase oxalate precursors of thermoelectric CoSb3 by controlled coprecipitation predicted by thermodynamic modeling
- 2016
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Ingår i: Advanced Powder Technology. - : Elsevier. - 0921-8831 .- 1568-5527. ; 27:2, s. 773-778
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Tidskriftsartikel (refereegranskat)abstract
- The precursors for the formation of thermoelectric skutterudite CoSb3 nanoparticles are predicted by thermodynamic modeling of the complex chemical species. Based on the results, equimolar mixture of CoC2O4 center dot 2H(2)O and Sb(C2O4) OH are successively co-precipitated under controlled conditions of pH = 2.7 and concentration of reactants. The as synthesized powder was decomposed at 350 degrees C to remove the organic molecules and further reduced to CoSb3 phase by heating at 530 degrees C under hydrogen flow. The obtained powder was consolidated by spark plasma sintering (SPS). CoSb3 prepared by controlled chemical co-precipitation has p-type behavior with a positive sign of the Seebeck coefficient. TE transport properties were measured, which revealed that the Seebeck coefficient increased 2.5 times with increasing the temperature and it is lower than the ball milled CoSb3. Thermal conductivity of sintered CoSb3 at 773 K starts from 0.06 W/cm K at room temperature and decreases to 0.04 W/cm K at 700 K, which is lower than the bulk counterpart. The ZT of coprecipitated CoSb3 and SPS consolidated at 773 K shows 2 times higher than the ball milled one. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.
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| 9. |
- Leduc, Sylvain, et al.
(författare)
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Particle-tracking option in Fluent validated by simulation of a low-pressure impactor
- 2006
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Ingår i: Advanced Powder Technology. - : Elsevier BV. - 0921-8831 .- 1568-5527. ; 17:1, s. 99-111
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Tidskriftsartikel (refereegranskat)abstract
- To decrease the emission of particles from a domestic wood-log boiler, particle traps based on intertial separation could be used. These could be designed and optimized with simulation tools, i.e. computational fluid dynamics (CFD) modeling. To find out whether the particle-tracking option in a commercial CFD code is reliable, a low-pressure impactor has been studied and each stage of the impactor simulated. By comparing experiments, it has been possible to determine the accuracy of the particle-tracking option for the CFD code. It has been shown that the particle-tracking procedure in the CFD software Fluent V6.0 offers good accuracy at velocities below 12 m/s with Reynolds numbers between 790 and 2150. Acceptable accuracy was shown for velocities of 20-170 m/s at Reynolds numbers between 960 and 2980. Considering actual flow velocities in a wood-log boiler and many other similar applications, the particle-tracking procedure should be accurate enough, at least for flows with a Reynolds number lower than 3000. Thus, it is recommended to use the software Fluent for simulations to find ways to reduce the particle emissions by use of mechanical traps. Three-dimensional simulations with either the Reynolds Stress Model (RSM) turbulence model, for accuracy, or the Renormalization Group (RNG) k-ε model, to save calculation time, should be used together with the stochastic particle tracking.
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| 10. |
- Pourkarimi, Z., et al.
(författare)
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Proving the existence of nanobubbles produced by hydrodynamic cavitation and their significant effects in powder flotation
- 2021
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Ingår i: Advanced Powder Technology. - : Elsevier. - 0921-8831 .- 1568-5527. ; 32:5, s. 1810-1818
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Tidskriftsartikel (refereegranskat)abstract
- Selective attachment of nanobubles (NBs) generated in different conditions on the surface of valuable minerals during flotation separation was a challenge that needs to be addressed. This investigation filled this gap and proved the existence of NBs on the target mineral's surface and their selective effectiveness through the process. The bubble size analysis results showed that the mean diameter of bubbles was between 60 and 70 nm; thus, they could be correctly called “nanobubbles”. Flotation test results showed a significant increase in the flotation recovery (by 37%) and grade (more than 1%) of fine phosphate ore sample (d80: 37 µm) using NBs that generated in the presence of collector. Interestingly, surface analyses of flotation products showed that the amounts of flotation collector adsorbed onto the surface of floated particles was decreased in the presence of NBs compared with their absence. The change in the particle surface (zeta) potential in the presence of NBs also provides additional evidence of NBs “adsorbed” (i.e., the surface NBs) onto the particle surface. These results indicated that NBs produced by hydrodynamic cavitation could adsorb onto the target mineral particles. This adsorption could change their surface properties, improve their hydrophobicity and surface potentials, and enhanced the bubble-particle attachment in flotation.
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| 11. |
- Sand, Anders, et al.
(författare)
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Modelling and simulation of stamp-charged coke making by 2-D discrete element method
- 2013
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Ingår i: Advanced Powder Technology. - : Elsevier BV. - 0921-8831 .- 1568-5527. ; 24:6, s. 1039-1047
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Tidskriftsartikel (refereegranskat)abstract
- Coking of coal blends using high-volatile coals with poor caking properties can be achieved by densifying the coal prior to carbonisation. In stamp-charged coke making, the coal charge is compacted to one large cake before entering the coke oven. A coal cake density of approximately 80% of the coal solid density is needed to produce a high-quality coke. Also, sufficient mechanical strength is required when transferring the cake from the stamping machine to the oven. To gain insight into the densification process and cake structure a 2-dimensional computational model based on the discrete element method (DEM) was set up.The model was validated against force and displacement patterns from laboratory stamping tests. Stamper movement in response to cake properties could be reproduced. The approach also enables tracking of cake porosity, particle rearrangement, stress and strain rates, etc. This offers additional possibilities for studying the densification process and understanding mechanical strength development.
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| 12. |
- Semsari Parapari, Parisa, et al.
(författare)
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Breakage process of mineral processing comminution machines – An approach to liberation
- 2020
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Ingår i: Advanced Powder Technology. - : Elsevier. - 0921-8831 .- 1568-5527. ; 31:9, s. 3669-3685
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Tidskriftsartikel (refereegranskat)abstract
- Mineral liberation and size reduction are the most critical steps before mineral separation. Several investigations showed that mineral liberation degree could be affected by ore texture and/or loading mechanisms. However, varied definitions have been used for the breakage fundamentals as the leading cause of mineral liberation. This review identifies the breakage fundamentals and analyzes them in terms of process and ore breakage behavior. It is highlighted that the breakage fundamentals are essential for optimizing of comminution environments and designing the comminution machines. Three main areas of breakage processes in regard to fundamentals of breakage are classified and addressed as “Loading mechanism”, “Breakage mechanism”, and “Breakage mode”. Despite the fact that many advances have been made in the design of the comminution machines; still, the combined effect of breakage fundamentals and ore properties such as ore texture in a quantitative manner is not fully understood. In this regard, this study identifies and discusses the material and process factors influencing the breakage phenomenon. This potentially paves the way for improving the comminution environment concerning a particular ore type.
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| 13. |
- Shoaib, Muhammad, et al.
(författare)
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High-velocity compaction simulation of a two-dimensional assembly of spherical particles using the discrete element method
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Ingår i: Advanced Powder Technology. - 0921-8831 .- 1568-5527.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- High-velocity compaction of a two-dimensional assembly of spherical particles is numerically studied using discrete element simulation. Three particular cases are investigated including closely packed hexagonal assembly, loosely packed random assembly and a non-homogenous assembly of different size and material particles. Primary interest is concerned with linking the particles deformation with the elasto-plastic shock wave. Simulation results yield information on particles deformation during shock propagation and change in overall particles compaction with the velocity of the hammer. The force exerted by particles on the container walls and rearrangement of the loosely packed particles during dynamic loading are also investigated. The effects of presence of friction and adhesion on both overall particles deformation and compaction process are also simulated.
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| 14. |
- Shoaib, Muhammad, et al.
(författare)
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Simulating the dynamic loading of non-homogenous spherical particles using discrete element method
- 2011
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Ingår i: Advanced Powder Technology. - 0921-8831 .- 1568-5527.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Dynamic loading of a chain of non-homogenous spherical particles is presented by using the discrete element method. The dynamic response of particles is modeled by using elastic and plastic loading, elastic unloading and adhesion at contacts. Of particular interest is to study the transmission and reflection of elasto-plastic shock wave through a chain having; particles of different sizes and materials, voids between the particles and particles with/without adhesion between them. Simulation results yield information on shock propagation, particles velocity and their deformation during dynamic compaction. Particles deformation during normal and reflected shocks, particle velocity fluctuations due to voids between particles and affects of adhesion on particles separation during unloading stage are also simulated.
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| 15. |
- Tohry, Arash, et al.
(författare)
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Enhanced Washburn Method (EWM) : A comparative study for the contact angle measurement of powders
- 2020
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Ingår i: Advanced Powder Technology. - : Elsevier. - 0921-8831 .- 1568-5527. ; 31:12, s. 4665-4671
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Tidskriftsartikel (refereegranskat)abstract
- Washburn Method (WM) as a typical contact angle measurement (θ) method can be used for assessment of powder wettability (especially representative particle size range for flotation separation). However, as an indirect method, WM has several limitations. This investigation is going to introduce an Enhanced Washburn Method (EWM), which fills the gap of those WM obstacles, and can be applied for the meaningful indirect θ measurement of powders. For such a purpose, the wettability of quartz powders (d80: 62 μm) was measured in the absence and in the presence of the cationic surfactant Flotigam®EDA at pH 10. EWM by using pre-conditioning of hydrophobized particles via unblock capillaries measured the θ of powders in different conditions. Statistical evaluations indicated that EWM could quite accurately measure θ of the hydrophobized powders, where there is a significant coefficient of determination (R2 above 0.96) between EWM outcomes and other examined direct θ measurement methods (the captive bubble and sessile drop methods).
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| 16. |
- Tohry, A., et al.
(författare)
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Power-draw prediction by random forest based on operating parameters for an industrial ball mill
- 2020
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Ingår i: Advanced Powder Technology. - : Elsevier. - 0921-8831 .- 1568-5527. ; 31:3, s. 967-972
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Tidskriftsartikel (refereegranskat)abstract
- Estimation of mill power-draw can play a critical role in economics, operation and control standpoints of the entire mineral processing plants since the cost of milling is the single biggest expense within the process. Thus, several empirical power-draw prediction models have been generated based on a combination of laboratory, pilot and full-scale measurements of different milling conditions. However, they cannot be used in industrial plants, where in full-scale operations, only not few numbers of input parameters used in those models are measured. Moreover, empirical models do not assess the relationship between input features. This investigation is going to introduce random forest (RF), as a predictive model, beside of its associated variable importance measures system, as a sensible means for variable selection, to overcome drawbacks of empirical models. Although RF as a powerful modeling tool has been used in several problem solving systems, it has not comprehensively considered in the powder technology areas. In this investigation, an industrial ball mill database from Chadormalu iron ore processing plant were used to develop a RF model and explore relationships between power-draw and other monitored operating parameters. Modeling results indicated that RF can highly improve the prediction accuracy of power-draw as compared to the regression as a typical method (R2: 0.98 vs. 0.60, respectively) and rank operational milling parameters based on their importance.
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| 17. |
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| 18. |
- Yanmin, Wang, et al.
(författare)
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Wet centrifugal classification of calcite fines : Effect of feed size
- 2001
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Ingår i: Advanced Powder Technology. - : Elsevier BV. - 0921-8831 .- 1568-5527. ; 12:3, s. 393-412
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Tidskriftsartikel (refereegranskat)abstract
- The wet classification of various fine calcite materials ( less than or equal 8, less than or equal 12 and less than or equal 45 μm) by a disk-stack nozzle centrifuge is presented and the results are discussed with respect to feed size. It has been found that the influences of disk-geometry, G-force and feed rate on the classification performance are not related to feed size. However, the selection of a split suitable for an efficient separation depends on the particle size distribution of the feed material. Feed size has an impact on the residence time of particle separation. The results showed that an optimum efficiency can be achieved when a calcite material with a particle size below 12 μm is treated. An excessive amount of fine or coarse calcite particles in the feed affects the efficiency of the classification in the centrifuge. It is also indicated that an effective classification of calcite fines requires a moderate G-force and high flow rates through a disk section bound by stud spacers in the centrifuge.
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