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Abstract
SFitaovana T & teknolojia, LLC (STET) dia nitombo ny fomba tribo ny electrostatic fehikibo ny fisarahana mampiodina izay manome fahafahana ny mineraly mampiodina mba beneficiate ireo fitaovana tsara amin' ny teknôlôjia izay tanteraka.. Mifanohitra amin' ireo electrostatic hafa izay dingan' izay tsy dia voafetra loatra ny particles mihoatra ny 75 μm amin' ny habeny, ny triboelectric fehikibo separator dia ideally hifanentana mba ho amin' ny fisarahana tsara. (<1μm) mba moderately marokoroko (300μm) particles-tena avo be throughput. Ny triboelectric fehikibo separator ny teknôlôjia dia nampiasaina mba hanasaraka ireo fitaovana ao anatin' ny vainafo combustion ny manidina lavenona, calcite/quartz, talc/magnesite, barite/quartz, ary feldspar/quartz. Ireo vokatra avy amin' ny fisarahana dia aseho amin' ny famaritana ny tribo mihoa ho an' ny bauxite mineraly.
Fampidirana
Ny tsy fisian' ny rano vaovao dia ho lasa antony nahatonga lehibe mahakasika ny feasibility ireo tetikasa harendrika manerana izao tontolo.. Araka ny Hubert Fleming, mpitarika teo aloha teo ho eo ho eo amin' ny Rano Foy, "Amin' ireo asa harendrika rehetra eto amin' ny tontolo izay efa nitsahatra na nihamora tamin' ny taona lasa., izany, saika 100% ny tranga., vokatry ny rano., na mivantana na ankolaka ". ny fomba 1 mineraly Maina dia manome vahaolana an' io olana looming io..
Ireo fomba maina toy ny electrostatic ny fisarahana dia manaisotra ny filana rano vaovao., ary manolotra ny hery anaty mba hampihena ny vola.. Elektrika ireo fomba fisarahana izay mampiasa amin' ny, na tribo-elektrika, ny mihoa dia particularity mahaliana noho ny hery anaty izay azon' izy ireo atao mba hanasaraka ireo mixtures maro izay ahitana conductive, ireo, ary vaventy-conductive particles.
Tribo elektrika-mihoa dia mitranga rehefa hafa, dissimilar particles hifandona ny tsirairay, na amin' ny toerana fahatelo, ny vokatr' izany eo amin' ny toerana dia misy fahasamihafana eo amin' ireo karazana sombiny roa. Ny famantarana sy ny halehiben' ny fahasamihafana amin' ny andraikitra dia miankina amin' ny ampahan' ny fahasamihafana eo amin' ny electron fisolokiana (na asa miasa) eo anelanelan' ireo karazana sombiny. Ny fisarahana dia azo tratrarina amin' ny alalan' ny fampiasana ety ivelany elektrika an-tsaha..
Ny teknika dia vahiny industrially amin' ny alalan' ny tsy fahafahana ho an' ny fahalavoana separators.. Ao anatin' ny separators, ny particles voalohany., then fall by gravity through a device with opposing electrodes that apply a strong electric field to deflect the trajectory of the particles according to sign and magnitude of their surface charge.2 Free-fall separators can be effective for coarse particles, but are not effective at handling particles finer than about 0.075 ny 0.1 mm.3,4 One of the most promising new developments in dry mineral separations is the tribo-electrostatic belt separator. Io teknôlôjia io dia nanolotra ny habeny particles tsara kokoa noho ny fihetsiketsehana electrostatic ny fisarahana teknôlôjia, tao anatin' ny fotoana izay vao flotation ny fahombiazana tamin' ny lasa..
Tribo-Electrostatic Belt Separation
Ao amin' ny tribo-electrostatic fehikibo separator (Figure 1 ary ny Sary 2), Ny fitaovana dia namahana ny banga manify. 0.9 - 1.5 santionany eo anelanelan' ny araky roa planar electrodes. Ny particles dia triboelectrically ny interparticle.. Ohatra, Raha ny momba ny fisian'ny laso-drivotra., Fifangaroan'ny entona karbona sy ireo singa mineraly., Ny karbôna voampanga tsara sy ny mineraly voampanga dia voasarika amin'ny herinaratra mifanohitra amin'izany.. Avy eo ny particles dia voafafa amin' ny alalan' ny mesh ny fehikibo sy ny fomba mifanohitra amin' izany.. Ny fehikibo dia mifanila ny mifanila ny electrode tsirairay mankany amin' ny faran' ny separator. Ny sahan' ny elektrika dia mila mamindra fotsiny ihany ny particles ny ampahany kely centimeter mba handrosoana ny ampahany iray avy any amin' ny toerana iray izay mandeha any amin' ny toerana tokony hatao.. The counter current flow of the separating particles and continual triboelectric charging by carbon-mineral collisions provides for a multi-stage separation and results in excellent purity and recovery in a single-pass unit. Ny hafainganam-pandeha firotsaky avo koa dia manome fahafahana avo throughputs, hatramin'ny 40 tonnes isaky ny adiny iray separator. Amin' ny alalan' ny fifehezana dingana samihafa andinindininy, Toy ny fanafainganana ny voamaina., Teboka famahanana, Ny tahan'ny herinaratra sy ny tahan'ny famahanana., Ilay fitaovana dia mamokatra lakozia kely karbôna eo amin'ny votoatin'ny karbôna. 2 % ± 0.5% Avy amin'ny lavenona mantsaka eo amin'ny karbôna. 4% tapitra 30%.
Ny separator dia tsotra.. Ny fehikibo sy ny rollers no hany ampahany mandeha.. Ny electrodes dia hiantsona ary misy fitaovana durable tsara.. Ny fehikibo dia vita amin'ny fitaovana plastika.. Ny separator electrode dia eo amin' ny 6 metatra (20 ft.) ary ny sakany 1.25 metatra (4 ft.) ho an' ireo vondrona hitadiavam-bola feno.. Ny hery fanekena dia latsaky ny 2 kilowatt ny ora tonne ny fitaovana io amin' ny ankamaroan' ny hery izay azon' ny motors roa mitondra ny fehikibo.
Maina tanteraka ny dingana., tsy mitaky fitaovana fanampiny ary tsy mamoa rano na emissions ny rivotra.. Raha ny momba ny karbôna avy amin'ny fisarahana lamaody., Ireo fitaovana sitrana dia ahitàna lafaoro mihena ao anatin'ny votoaty karbôna ka hatramin'ny ambaratonga mety ampiasaina ho toy ny firaisana tsikombakomba amin'ny simenitra., ary ampahany avo amin'ny karbôna izay azo may ao amin'ny orinasa mpamokatra herinaratra.. Ny fampiasana ireo renirano roa ireo dia manome 100% Vahaolana amin'ny fisondrotam-bidy amin'ny fanariana lamba.. For mineral separations, processing bauxite for example, the separator provides a technology to reduce water usage, manolotra fiainana sy/na sitrana ary reprocess tailings.
The tribo-electrostatic belt separator is relatively compact. Milina natao hizotra 40 tonnes per hour is approximately 9.1 metatra (30 ft.) ela, 1.7 metatra (5.5 ft.) midadasoka sy midadasoka 3.2 metatra (10.5 ft.) avo. Ny fifandanjana ilaina amin'ny zavamaniry dia ny rafitra fampitana fitaovana maina sy avy amin'ny mpampisaraka.. Ny compactness ny rafitra dia mamela fanovanovana amin' ny fikasan' installation..
The tribo-electrostatic belt separation technology is robust and industrially proven, and was first applied industrially to the processing of coal combustion fly ash in 1995. Ny teknôlôjia dia mahomby amin' ny fanasarahana karbônina particles avy amin' ny combustion tsy feno vainafo, avy amin' ny glassy aluminosilicate mineraly particles ao amin' ny manidina lavenona. Ny teknôlôjia dia fitaovana tamin' ny alalan' ny recycle ny mineraly-karena lavenona ho toy ny ranomandry fanoloana amin' ny famokarana varafasy.. Hatramin' ny 1995, tapitra 20,000,000 tonnes of fly ash has been processed by the 19 tribo-electrostatic belt separators installed in the USA, Kanada, Angletera, Polonina, and South Korea. The industrial history of fly ash separation is listed in table 1.
table 1. Lafy ny fampiharana ny tribo-electrostatic fehikibo ho an' ny manidina lavenona
| Utility / toby misy herinaratra | Toerana | Fanombohan' ny asa hitadiavam-bola. | Antsipiriany momba ny toeram-piasana |
|---|---|---|---|
| Duke hery – Roxboro toby | Avaratra Carolina Etazonia | 1997 | 2 Separators |
| Talen hery- Brandon Amoron-Dalana | Maryland ETAZONIA | 1999 | 2 Separators |
| Ecossais Hery- Longannet ny Toby | Ecosse UK | 2002 | 1 Separator |
| Jacksonville Elektrika-St. Ny Reniranon' i John dia Herinaratra | Floride Etazonia | 2003 | 2 Separators |
| South Mississippi Elektrika Herinaratra-R.D. Ampitso | Mississippi ETAZONIA | 2005 | 1 Separator |
| Hery Brunswick vaovao Belledune | Nouvelle Brunswick Kanada | 2005 | 1 Separator |
| RWE npower-Didcot ny Toby | Angletera UK | 2005 | 1 Separator |
| Toby Talen-Brunner ny Nosy | Pennsylvanie ETAZONIA | 2006 | 2 Separators |
| Tampa Elektrika ny Toby Lehibe | Floride Etazonia | 2008 | 3 Separators two-pass scavenging |
| RWE npower-Aberthaw ny Toby | Pays de galles UK | 2008 | 1 Separator |
| Toby EDF-Burton Andrefana | Angletera UK | 2008 | 1 Separator |
| ZGP (Lafarge Simenitra/Ciech Janikosoda JV) | Polonina | 2010 | 1 Separator |
| Corée Hery Atsinanana- Yeongheung | Korea Atsimo | 2014 | 1 Separator |
| PGNiG Termika-Sierkirki | Polonina | 2018 | 1 Separator |
| Taiheiyo Valisoa-Chichibu | Japana | 2018 | 1 Separator |
| Armstrong Manidina Lavenona- Eagle Cement | Filipina | Scheduled 2019 | 1 Separator |
| Corée Hery Atsinanana- Samcheonpo | Korea Atsimo | Scheduled 2019 | 1 Separator |
Tribo-Electrostatic Separation of Bauxite Minerals
ST Fitaovana & teknolojia (STET) performed bench scale dry tribo-electrostatic separation testing on multiple samples of bauxite minerals. The samples are listed below in table 2.
table 2. Properties of bauxite samples tested by STET
| Description | Desired Product & Goals | |
|---|---|---|
| Santionany 1 | ROM Bauxite | Al2O3 recovery Reduce SiO2, Fe2O3, TiO2 |
| Santionany 2 | PLK (Partially Lateritized Khondalite) | Al2O3 recovery Reduce SiO2, Fe2O3, TiO2 |
| Santionany 3 | Red Mud | Fe2O3 recovery Reduce SiO2, Al2O3, TiO2 |
| Santionany 4 | ROM Bauxite Slimes | Al2O3 recovery Reduce SiO2, Fe2O3, TiO2 |
Chemical composition for all feed and separated product samples was measured by X-Ray Fluorescence (XRF) using a WD-XRF system. The results of the chemical analysis for the feed samples are shown below in table 3.
table 3. Chemical properties of bauxite samples tested by STET
| Al2O3 wt.% | Fe2O3 wt.% | SiO2 wt.% | SiO2 wt.% | LOI wt.% | |
|---|---|---|---|---|---|
| Santionany 1 | 43.7 | 25.9 | 3.9 | 2.3 | 23.6 |
| Santionany 2 | 34.9 | 19.4 | 28.5 | 2.1 | 14.7 |
| Santionany 3 | 19.0 | 52.1 | 6.7 | 4.9 | 11.1 |
| Santionany 4 | 34.6 | 23.2 | 18.0 | 4.4 | 18.8 |
Particle size was measured by laser particle size measurement using dry pneumatic dispersion. The results for the feed samples are shown below in table 4.
table 4. Particle size of bauxite samples tested by STET
| D10 micron | D50 micron | D90 micron | D90 micron |
|
|---|---|---|---|---|
| Santionany 1 | 2 | 19 | 73 | 118 |
| Santionany 2 | 2 | 45 | 575 | 898 |
| Santionany 3 | 1 | 27 | 212 | 325 |
| Santionany 4 | 1 | 7 | 59 | 93 |
Samples were separated using the STET benchtop separator. Ny separator benchtop dia ampiasaina mba tilikambo ny porofon' ny tribo-electrostatic mihoa ary hamantarana raha toa ka mpangataka tsara ny fitaovana iray mba hahazoana tombontsoa electrostatic.. The primary difference between the benchtop separator and pilot-scale and commercial-scale separators is that the length of the benchtop separator is approximately 0.4 fotoana ny halavan' ny drefy-fiaramanidina sy ny hitadiavam-bola-drefy.. Rehefa separator ny efficiency dia asan' ny halavan' ny electrode., Ny fisedrana drefy dia tsy azo ampiasaina ho toy ny fitsapana drefy.. Ny fitsapana drefy ny mpanamory dia ilaina mba hamaritana ny halehiben' ny fisarahana izay azon' ny dingan' ny STET., ary mba hamantarana raha toa ka afaka mihaona amin' ireo vokatra lasibatra eo ambanin' ny famahanana ny tahan' ny dingan' ny STET.. Fa kosa, ny separator benchtop dia ampiasaina mba hanapaka ireo fitaovana azo avy amin' ny mpangataka izay koa mba hanehoana ny fisarahana manan-danja eo amin' ny lafiny drefy.. Ireo vokatra azo avy amin' ny drefy-drefy dia tsy optimized, ary ny fisarahana dia latsaky ny hitadiavam-bola habe STET separator.
Testing with the STET benchtop separator demonstrated significant movement of Al2O3 with the majority of the samples tested. In three of the four samples tested by STET, substantial movement of Al2O3 was observed. Ankoatry ny, ireo singa lehibe hafa ao amin' ny Fe2O3, Ny SiO2 sy TiO2 dia naneho ny fanaovana asa lehibe tamin' ny tranga tena manan-danja.. In Sample 1, Santionany 3 and Sample 4, ny fihetsiky ny fahaverezan' ny firehetana (LOI) nanaraka ny fihetsiky ny Al2O3. The movement of the major elements is shown below in Figure 5.
The STET separator is a physical separation process and selectively separates mineral phases based on tribocharging, a surface phenomenon. The degree to which minerals are susceptible to tribocharging is in some cases able to be predicted via consultation of a triboelectric series, but in the case of complex mineral ores, often in practice must be determined empirically. A summary of the tribocharging properties for the samples tested is shown below in table 5.
table 5. Summary of tribocharging behaviour for major elements. POS = charged positive, NEG = charged negative.
| Al2O3 | Fe2O3 | SiO2 | TiO2 | LOI | |
|---|---|---|---|---|---|
| Santionany 1 | POS | NEG | NEG | NEG | POS |
| Santionany 2 | NEG | POS | NEG | N/A | N/A |
| Santionany 3 | POS | NEG | N/A | NEG | POS |
| Santionany 4 | POS | N/A | NEG | NEG | POS |
Dry processing with the STET separator offers opportunities to generate value for bauxite and aluminium producers. The utilization of lower grade bauxite deposits may allow for lower mining costs by reducing stripping ratios and by reduced generation of tailings. Ankoatry ny, the pre-processing of bauxite ores by dry triboelectrostatic separation may result in improved economics of aluminium refining by supplying higher grades of bauxite to the refining process, or by reducing volumes of red mud generated. Ankoatry ny, higher aluminium content in red mud may allow for reprocessing. A summary of ideal characteristics for metallurgical grade bauxite is presented, as well as a summary of the benefit of the STET separator, below in table 6.
table 6. Summary of ideal characteristics for metallurgical grade bauxite.5
| Ideal Grade Characteristic | Impact if Inadequate | Observed with STET Separation |
|---|---|---|
| Low “reactive silica” (>1.5% - <3.0%) (kaolinite) | Increases caustic usage, a critical operating cost factor. | Reduction in total silica |
| High extractable alumina | Increases capital and operating costs for mining, processing and mud disposal. | Increase in alumina |
| Low organic carbon | Increases operating costs by reducing plant efficiency. | |
| Low boehmite (<3%) | Precludes low-temperature processing that can increase capital and operating costs. | |
| Low goethite (tolerable in a high-temperature plant or with high hematite) | Slows clarification, lowers product quality and increases alumina loss via mud circuit. | Reduction in total iron |
| Low moisture (can create nuisance dust if too low) | Increases capital costs (larger evaporation facility), fuel consumption, shipping costs. | |
| Iron content (ideally >5%-<15%) | Low iron can lower product quality. High iron dilutes alumina content of bauxite. | Reduction in total iron |
| Low quartz | Increases maintenance costs (pipe wear). Increases caustic usage in high-temperature plants. | Reduction in total silica |
| Low impurities and trace elements | Can lower process efficiency (sulfur, chlorine, calcium) and metal quality (gallium, zinc, vanadium, phosphorus). | |
| Soft and friable | Increases mining and grinding costs. | |
| Dissolves readily | Increases capital (larger digestion equipment) and operating costs. | |
| Low titania | Can increase caustic usage in high-temperature plants. | Reduction in titania |
| Low carbonates | Can require special processing. |
Famaranana
Tribo-electrostatic separation was demonstrated as an effective method for generating a high-grade bauxite ore for use in alumina production. Testing with the STET benchtop separator demonstrated significant movement of Al2O3 with the majority of the samples tested. In three of the four samples tested by STET, substantial movement of Al2O3 was observed. Ankoatry ny, ireo singa lehibe hafa ao amin' ny Fe2O3, SiO2 and TiO2 demonstrated significant separation in most cases. Dry processing with the STET separator offers opportunities to generate value for bauxite and aluminium producers.
References
1. Jamba, P & Dion-Ortega, A (2013) Avo sy Maina, CIM Magazine, Vol. 8, tsy misy. 4, p. 48-51.
2. Manouchehri, H, Hanumantha Roa, K, & Fors Mountain, K (2000), Avereno jerena ny fomba fisarahan'ny herinaratra, Fizarana 1: fototra lafiny, mineraly & Metallurgical Processing, Vol. 17, tsy misy. 1 pp 23–36.
3. Manouchehri, H, Hanumantha Roa, K, & Fors Mountain, K (2000), Avereno jerena ny fomba fisarahan'ny herinaratra, Fizarana 2: Fiheverana azo ampiharina, mineraly & Metallurgical Processing, Vol. 17, tsy misy. 1 pp 139–166.
4. Ralston O. (1961) Electrostatic Separation of Mixed Granular Solids, Elsevier Publishing Company, out of print.
5. Kogel, Jessica Elzea; Trivedi, Nikhil C; Barker, James M; Krukowski, Stanley T.; Industrial Minerals and Rocks: Commodities, Markets, and Uses 7th Edition, (2006), Page 237.
