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The mineralogy and liberation characteristics of the comminuted Penouta leucogranite host of the Sn-Ta ore were determined. Grinding developed by a combination of high-pressure grinding rolls (HPGR) followed by a ball mill (BM) was compared with a single ball mill process. The mineral characteristics of the grinding products were analyzed using a Tescan Integrated Mineralogical Analyzer (TIMA-X) and X-ray powder diffraction (XRD). The ore contains 103 ppm of Ta and is mainly composed of quartz, albite, microcline, muscovite, and kaolinite. Nb, Ta-rich minerals are columbite-(Mn) and tantalite-(Mn), as well as minor microlite and wodginite. The liberation in the product is high in the size fraction of less than 250 m (51–52 wt % for columbite-group minerals (CGM) and 74–80 wt % for cassiterite) and reduced in larger particles (8.8–17 wt % for CGM and
28–37 wt % for cassiterite). The recovery in the ¿250 m fraction was high, while in the larger fraction it is limited, remaining up to 80 ppm in some tailings. The combined use of HPGR and a BM reduces the particle size distribution of the product and, thus, increases the liberation of the ores. Smaller fractions can be treated directly using gravity methods; however, particles of a size greater than +250 m should be ground more., Peer Reviewed

In this paper, the modeling of the liberation of scheelite is presented. A pattern of concentration experiments was performed to investigate the scheelite liberation and distribution density calculation procedure. In this work, one sample from a Mittersill tungsten ore was studied.
This work describes a method for determining the downstream milling energy requirements for rod mill products based on a Bond mill test performance. The grade distribution of particles at a given size fraction was calculated using a predictive liberation model. The concentration behavior of these particles in size fractions was evaluated using batch concentrate tests. The recovery of particles in
size/grade classes, image analysis using mineral liberation analysis (MLA), and function calculations were implemented for the modeling of the liberation. By describing the size, grade, and recovery data of particles in size/grade classes, a technique for the measurement of distribution functions was developed that relates beta distribution, a model for the function based on the incomplete beta function, and a solution to produce liberation modeling. It was shown that the predicted results agreed well with the observed results. With a procedure for measuring the liberation, it was possible to carry out the first experimental measurement of the beta distribution. This liberation/concentrate model has wide potential applications for metallurgy and plant design, where the liberation modeling is to be determined with the distribution density solution to the predictive mineral liberation function equation, which includes the liberation of ore samples and their liberation characteristics., Peer Reviewed

The data base is related to the High Pressure Grinding Rolls (HPGR) modelling. This data was generated in a HPGR manufacturer pilot plant in Freiberg, Germany, and represents the particle size distribution measurement of the feed and the product of the milling reactor, and the calculation of some material features, as the moisture or the density. This data is necessary for the correct modelization of the comminution in a HPGR, and it can be used for different mathematical models., A model for High Pressure Grinding Rolls (HPGR) was developed in this work based on the widely used Population Balance Model (PBM). This approach uses a variety of different functions one of which is the breakage distribution function. The methodology to determine the function parameters is presented and using these values, the model was compared with real processed materials from an HPGR pilot plant, with tungsten ore as the test material. The results of the model parameter determination, and the product of the comminution in the HPGR, showed the dependency of material breakage on the material characteristics, and on the operative and process conditions. The model presented is reasonably robust, showing less error than the 3.0 Root Mean Square Error when compared with a heterogeneous feed particle size distribution material. The operational gap was also studied, and its dependency on the feed particle size, porosity, moisture, and specific pressing force was proven.

Peer Reviewed

Peer Reviewed

A model for High Pressure Grinding Rolls (HPGR) was developed in this work based on thewidely used Population Balance Model (PBM). This approach uses a variety of different func-tions one of which is the breakage distribution function. The methodology to determine thefunction parameters is presented and using these values, the model was compared with realprocessed materials from an HPGR pilot plant, with tungsten ore as the test material. Theresults of the model parameter determination, and the product of the comminution in theHPGR, showed the dependency of material breakage on the material characteristics, and onthe operative and process conditions. The model presented is reasonably robust, showingless error than the 3.0 Root Mean Square Error when compared with a heterogeneous feedparticle size distribution material. The operational gap was also studied, and its dependencyon the feed particle size, porosity, moisture, and specific pressing force was proven., Peer Reviewed

An improved approach is presented to model the product particle size distribution resulting from grinding in high-pressure roll crusher with the aim to be used in standard high-pressure grinding rolls (HPGR). This approach uses different breakage distribution function parameter values for a single particle compression condition and a bed compression condition. Two materials were used for the experiments; altered Ta-bearing granite and a calc-silicate tungsten ore. A set of experiments was performed with constant operative conditions, while varying a selected condition to study the influence of the equipment set-up on the model. The material was comminuted using a previously determined specific pressing force, varying the feed particle size, roll speed and the static gap. A fourth group of experiments were performed varying the specific pressing force. Experimental results show the high performance of the comminution in a high-pressure environment. The static gap was the key in order to control the product particle size. A mathematical approach to predict the product particle size distribution is presented and it showed a good fit when compared to experimental data. This is the case when a narrow particle size fraction feed is used, but the fit became remarkably good with a multi-size feed distribution. However, when varying the specific pressing force in the case of the calc-silicate material, the results were not completely accurate. The hypothesis of simultaneous single particle compression and bed compression for different size ranges and with different parameters of the distribution function was probed and reinforced by various simulations that exchanged bed compression parameters over the single particle compression distribution function, and vice versa., Peer Reviewed

Tantalum is a strategic metal with multiple applications in the new technologies. Tantalum deposits are scarce in EU. Thus, more efficient extracting processes are necessary to contribute to major European independency on these critical raw materials. Tantalum occurs mainly in pegmatites and leucogranite deposits and its placers. Europe does not produce tantalum; however, several deposits are susceptible of being exploited if technologies of processing are improved. This work is part of the Optimore Project which aims to develop modelling and control technologies, using advanced sensing and advanced industrial control by using artificial intelligence techniques, for the more efficient and flexible tantalum and tungsten processing from crushing to separation process. In this paper, a preliminary study of characterization of tantalum ores from leucogranite and alluvial deposits is presented to be used as a base for design the milling experiments to optimize the tantalum recovering during the processing. In the ore deposits tantalum appears in solid solution with niobium in complex oxides, which forms low grade aggregates which need to be processed by means of a separation process. Tantalum ores characterised here belong to alluvial placers of pegmatitic origin located in the Bolivian Amazon Craton and to leocogranites of Penuota, in Spain. Ta bearing minerals of the Bolivian placers are mainly from the columbite group minerals. In Penouta microlite is abundant and often it has a zoning characterised by a Nb-rich core followed by a Ta-rich rim of several cm in thickness., Peer Reviewed

The modelling of high pressure grinding rolls is described by the population balance model, a mass balance which includes several functions that are related to the mineral characteristics,
material kinetics and operative conditions of the device. The breakage distribution function is one of these functions and refers to the way in which the daughter particles are generated by the process of comminution. The piston-die press is presented as a methodology to determine the breakage distribution function of two different materials, from the mechanical response point of view: altered granite and a cal-silicate material. The aim is to determine the relation between the
operative conditions and the mineral characteristics in order to explain and predict the breakage function parameters. The materials were characterised using XRD and single compression strength tests. The altered granite is a brittle material, which generates more fines under single compression conditions compared to bed compression conditions, mainly due to the mineral composition and the
response of the material to the breakage action. The cal-silicate material shows a normal trend in its breakage behaviour. As is expected, the mineralogical characterisation is a useful tool to predict the values of the parameters of the breakage distribution function., Peer Reviewed

Using a previous mechanical characterization of two types of material, several lab-test work have been done. The data shows the particle size distribution of these tests, all the inputs and the model simulation presented in the related paper to this data base. The new mathematical approach use the operative conditions and the feed particle size distribution to obtain a product, which is compared with the lab-test results, An improved approach is presented to model the product particle size distribution resulting
from grinding in high-pressure roll crusher with the aim to be used in standard high-pressure grinding
rolls (HPGR). This approach uses different breakage distribution function parameter values for a
single particle compression condition and a bed compression condition. Two materials were used
for the experiments; altered Ta-bearing granite and a calc-silicate tungsten ore. A set of experiments
was performed with constant operative conditions, while varying a selected condition to study the
influence of the equipment set-up on the model. The material was comminuted using a previously
determined specific pressing force, varying the feed particle size, roll speed and the static gap.
A fourth group of experiments were performed varying the specific pressing force. Experimental
results show the high performance of the comminution in a high-pressure environment. The static
gap was the key in order to control the product particle size. A mathematical approach to predict
the product particle size distribution is presented and it showed a good fit when compared to
experimental data. This is the case when a narrow particle size fraction feed is used, but the fit
became remarkably good with a multi-size feed distribution. However, when varying the specific
pressing force in the case of the calc-silicate material, the results were not completely accurate.
The hypothesis of simultaneous single particle compression and bed compression for different size
ranges and with different parameters of the distribution function was probed and reinforced by
various simulations that exchanged bed compression parameters over the single particle compression
distribution function, and vice versa.

Peer Reviewed

Peer Reviewed

Another title in MEI Conference: Energy consumption applied to high pressure grinding rolls modelling with population balance models. http://www.min-eng.com/comminution16/paps.html, High pressure grinding rolls are a good alternative for comminution. This device presents low operative cost and high energy performance. Modelling of 16 mono-size assays have been carried out using grinding rolls with controlled operative pressure and tangential velocity. Back-calculation of the different parameters of the model have been developed with MATLAB software. The fitting of the simulated curve is in a good agreement with the experimental data in a wide range of tests. The present model describes correctly the physical behaviour of the particles within the high pressure grinding roll. The error is low except for experiments with small feed particle size. This situation could be explained because for fine particle sizes the bed compression phenomenon is predominant. The particle size distribution has been monitored in the input and output for each assay. The validation experiments show that the model is consistent. The selection function describes adequately the breakage probability of the particles inside the high pressure grinding rolls. Then, the present model is a good alternative for simulating a high pressure grinding roll process., Peer Reviewed

De data base shows the results of a new methodology to determine the breakage distribution function parameters to be used in High pressure grinding rolls modelling. The piston die test tries to simulate a high pressure enviroment, thus the resulted particle size distribution can be normalized to describe a breakage mechanism. Furthermore, one example of how to obtain the breakage function parameters is presented., The modelling of high pressure grinding rolls is described by the population balance
model, a mass balance which includes several functions that are related to the mineral characteristics,
material kinetics and operative conditions of the device. The breakage distribution function is
one of these functions and refers to the way in which the daughter particles are generated by the
process of comminution. The piston-die press is presented as a methodology to determine the
breakage distribution function of two different materials, from the mechanical response point of
view: altered granite and a cal-silicate material. The aim is to determine the relation between the
operative conditions and the mineral characteristics in order to explain and predict the breakage
function parameters. The materials were characterised using XRD and single compression strength
tests. The altered granite is a brittle material, which generates more fines under single compression
conditions compared to bed compression conditions, mainly due to the mineral composition and the
response of the material to the breakage action. The cal-silicate material shows a normal trend in its
breakage behaviour. As is expected, the mineralogical characterisation is a useful tool to predict the
values of the parameters of the breakage distribution function.

Peer Reviewed

The Penouta Sn-Ta deposit, in the northwest of Spain, is a greisenized granitic cupola where Ta minerals occur mainly as disseminations in a leucogranite body intruded in Precambrian–Lower Cambrian gneisses and mica-schists. This leucogranite is a medium- to fine-grained inequigranular rock consisting mainly of quartz, albite, K-feldspar and muscovite. Accessory minerals are mainly of spessartine, zircon, cassiterite, Nb-Ta oxides, monazite, xenotime, native bismuth and pyrite. The alteration processes were mainly albitization, muscovitization and kaolinitization.
This leucogranite is peraluminous and P-poor, with 0.03–0.07 wt.% P2O5, 900–1500 ppm Rb, 30–65 ppm Cs, 120–533 ppm Li, 80–140 ppm Ta, 51–81 ppm Nb and up to 569 ppm of Sn. Mineralogical characterization of Nb-Ta oxide minerals was determined by X-ray diffraction, scanning electron microscopy, electron microprobe analysis and mineral liberation analysis. Mn-rich members of the columbite-group minerals (CGM) are the most common Ta-bearing phases, but microlite, wodginite, tapiolite and Ta-rich cassiterite occur also. CGM crystals are commonly zoned concentrically, with a Nb-rich core surrounded by a Ta-rich rim, with a sharp boundary between them. Convoluted zoning occurs also. Dissolution textures resulting from the corrosion of columbite and tantalite rims, in particular, are common. TheMn/(Mn + Fe) ratio varies between 0.33 and 0.97 and the Ta/(Ta + Nb) ratio between 0.07 and 0.93. Wodginite and microlite formed as late replacements of CGM and occur associated with tantalite and cassiterite. Subhedral to anhedral cassiterite crystals, usually up to 200 µmacross, occur in two generations: the earlier one is Nb,Ta-poor whereas in the later generation, the Ta content can reach >9 wt.%of Ta2O5 and 1.7 wt.%of Nb. The presence of a fluid phase in the apical zone of the granite, probably related to the separation of a fluid/vapour of the melt, could explain the sponge-like textures, the Ta enrichment associated with these textures, the occurrence of Taenriched mineral phases (microlite and wodginite) and their common interstitial character., Peer Reviewed

This work is part of the OPTIMORE project funded by the European Union Horizon 2020 Research and Innovation Programme under grant agreement No 642201.

This study has been partially funded by the Spanish Ministry of Economy and Competitiveness, under project MOLIMON DPI2011-26535, the European Union's Horizon 2020 research and innovationprogramme, under grant agreement OPTIMORE 642201, and by FICYTco-financed with FEDER funds under the Res earch Proj ect FC-15-GRUPIN14-004.

The modelling of high pressure grinding rolls is described by the population balance model, a mass balance which includes several functions that are related to the mineral characteristics, material kinetics and operative conditions of the device. The breakage distribution function is one of these functions and refers to the way in which the daughter particles are generated by the process of comminution. The piston-die press is presented as a methodology to determine the breakage distribution function of two different materials, from the mechanical response point of view: altered granite and a cal-silicate material. The aim is to determine the relation between the operative conditions and the mineral characteristics in order to explain and predict the breakage function parameters. The materials were characterised using XRD and single compression strength tests. The altered granite is a brittle material, which generates more fines under single compression conditions compared to bed compression conditions, mainly due to the mineral composition and the response of the material to the breakage action. The cal-silicate material shows a normal trend in its breakage behaviour. As is expected, the mineralogical characterisation is a useful tool to predict the values of the parameters of the breakage distribution function.

The mineralogy and liberation characteristics of the comminuted Penouta leucogranite host of the Sn-Ta ore were determined. Grinding developed by a combination of high-pressure grinding rolls (HPGR) followed by a ball mill (BM) was compared with a single ball mill process. The mineral characteristics of the grinding products were analyzed using a Tescan Integrated Mineralogical Analyzer (TIMA-X) and X-ray powder diffraction (XRD). The ore contains 103 ppm of Ta and is mainly composed of quartz, albite, microcline, muscovite, and kaolinite. Nb, Ta-rich minerals are columbite-(Mn) and tantalite-(Mn), as well as minor microlite and wodginite. The liberation in the product is high in the size fraction of less than 250 m (51-52 wt % for columbite-group minerals (CGM) and 74-80 wt % for cassiterite) and reduced in larger particles (8.8-17 wt % for CGM and 28-37 wt % for cassiterite). The recovery in the 􀀀250 m fraction was high, while in the larger fraction it is limited, remaining up to 80 ppm in some tailings. The combined use of HPGR and a BM reduces the particle size distribution of the product and, thus, increases the liberation of the ores. Smaller fractions can be treated directly using gravity methods; however, particles of a size greater than +250 m should be ground more.

In this paper, the modeling of the liberation of scheelite is presented. A pattern of concentration experiments was performed to investigate the scheelite liberation and distribution density calculation procedure. In this work, one sample from a Mittersill tungsten ore was studied. This work describes a method for determining the downstream milling energy requirements for rod mill products based on a Bond mill test performance. The grade distribution of particles at a given size fraction was calculated using a predictive liberation model. The concentration behavior of these particles in size fractions was evaluated using batch concentrate tests. The recovery of particles in size/grade classes, image analysis using mineral liberation analysis (MLA), and function calculations were implemented for the modeling of the liberation. By describing the size, grade, and recovery data of particles in size/grade classes, a technique for the measurement of distribution functions was developed that relates beta distribution, a model for the function based on the incomplete beta function, and a solution to produce liberation modeling. It was shown that the predicted results agreed well with the observed results. With a procedure for measuring the liberation, it was possible to carry out the first experimental measurement of the beta distribution. This liberation/concentrate model has wide potential applications for metallurgy and plant design, where the liberation modeling is to be determined with the distribution density solution to the predictive mineral liberation function equation, which includes the liberation of ore samples and their liberation characteristics.

The Penouta Sn-Ta deposit, in the northwest of Spain, is a greisenized granitic cupola where Ta minerals occur mainly as disseminations in a leucogranite body intruded in Precambrian-Lower Cambrian gneises and mica-schists. This leucogranite is a medium- to fine-grained inequigranular rock consisting mainly of quartz, albite, K-feldspar and muscovite. Accessory minerals are mainly of spessartine, zircon, cassiterite, Nb-Ta oxides, monazite, xenotime, native bismuth and pyrite. The alteration processes were mainly albitization, muscovitization and kaolinitization. This leucogranite is peraluminous and P-poor, with 0.03-0.07 wt.% P2O5, 900-1500 ppm Rb, 30-65 ppm Cs, 120-533 ppm Li, 80-140 ppm Ta, 51-81 ppm Nb and up to 569 ppm of Sn. Mineralogical characterization of Nb-Ta oxide minerals was determined by X-ray diffraction, scanning electron microscopy, electron microprobe analysis and mineral liberation analysis. Mn-rich members of the columbite-group minerals (CGM) are the most common Ta-bearing phases, but microlite, wodginite, tapiolite and Ta-rich cassiterite occur also. CGM crystals are commonly zoned concentrically, with a Nb-rich core surrounded by a Ta-rich rim, with a sharp boundary between them. Convoluted zoning occurs also. Dissolution textures resulting from the corrosion of columbite and tantalite rims, in particular, are common. TheMn/(Mn + Fe) ratio varies between 0.33 and 0.97 and the Ta/(Ta + Nb) ratio between 0.07 and 0.93. Wodginite and microlite formed as late replacements of CGM and occur associated with tantalite and cassiterite. Subhedral to anhedral cassiterite crystals, usually up to 200 μmacross, occur in two generations: the earlier one is Nb,Ta-poor whereas in the later generation, the Ta content can reach >9 wt.%of Ta2O5 and 1.7 wt.%of Nb. The presence of a fluid phase in the apical zone of the granite, probably related to the separation of a fluid/vapour of the melt, could explain the sponge-like textures, the Ta enrichment associated with these textures, the occurrence of Taenriched mineral phases (microlite and wodginite) and their common interstitial character.

The strategic importance of tantalum and its scarcity in Europe makes its recovery from low grade deposits and tailings interesting. In Penouta, the contents of Ta and Sn in old tailings from an Sn mine are of economic interest. Due to the relatively low grade of Ta of around 100 ppm, a detailed study of the mineralogy and liberation conditions is necessary. In this study, the mineralogy and the liberation characteristics of Sn and Ta ores of the Penouta tailings were investigated and compared with the current leucogranite outcropping ores. The characterization was conducted through X-ray diffraction, scanning electron microscopy, and electron microprobe. In addition, automated mineralogy techniques were used to determine the mineral associations and liberation characteristics of ore minerals. The grade of the leucogranite outcropping was found to be about 80 ppm for Ta and 400 ppm for Sn, and in the tailings used for the liberation study, the concentrations of Ta and Sn were about 100 ppm Ta and 500 ppm Sn, respectively. In both, the leucogranite outcropping and tailings, the major minerals found were quartz, albite, K-feldspar, and white mica. Ore minerals identified were columbite-group minerals (CGM), microlite, and cassiterite. The majority of CGM examined were associated with cassiterite, quartz, and muscovite particle compositions and cassiterite was mainly associated with CGM, quartz, and muscovite. The liberation size was 180 µm for CGM.