زبان منتخب کریں:
Lucas سنانے والا Rojas مینڈوزا, سینٹ کا سامان & ٹیکنالوجی, امریکہ
lrojasmendoza@steqtech.com
فرینک ہراکہ, سینٹ کا سامان & ٹیکنالوجی, امریکہ
کیلی فلینن, سینٹ کا سامان & ٹیکنالوجی, امریکہ
ابھیشیک گپتا, سینٹ کا سامان & ٹیکنالوجی, امریکہ
سینٹ کا سامان & ٹیکنالوجی LLC (سٹیٹ) has developed a novel processing system based on tribo-electrostatic belt separation that provides the mineral processing industry a means to beneficiate fine materials with an energy-efficient and entirely dry technology. In contrast to other electrostatic separation processes that are typically limited to particles >75µm in size, the STET triboelectric belt separator is suited for separation of very fine (<1µm) to moderately coarse (500µm) particles, with very high throughput. The STET tribo-electrostatic technology has been used to process and commercially separate a wide range of industrial minerals and other dry granular powders. Here, bench-scale results are presented on the beneficiation of low-grade Fe ore fines using STET belt separation process. Bench-scale testing demonstrated the capability of the STET technology to simultaneously recover Fe and reject SiO2 from itabirite ore with a D50 of 60µm and ultrafine Fe ore tailings with a D50 of 20µm. The STET technology is presented as an alternative to beneficiate Fe ore fines that could not be successfully treated via traditional flowsheet circuits due to their granulometry and mineralogy.
لوہا زمین کی تہہ میں چوتھا سب سے عام عنصر ہے [1]. لوہا سٹیل مینوفیکچرنگ کے لئے ضروری ہے اور اس لئے عالمی اقتصادی ترقی کے لئے ایک ضروری مواد ہے. [1-2]. لوہے کو گاڑیوں کی تعمیر اور مینوفیکچرنگ میں بھی بڑے پیمانے پر استعمال کیا جاتا ہے [3]. لوہے کے زیادہ تر وسائل تبدیل شدہ بینڈڈ لوہے کی تشکیل پر مشتمل ہوتے ہیں۔ (بی آئی ایف) جس میں لوہا عام طور پر آکسائڈ کی شکل میں پایا جاتا ہے۔, ہائیڈروکسیڈز اور کچھ حد تک کاربونیٹ [4-5]. A particular type of iron formations with higher carbonate contents are dolomitic itabirites which are a product of the dolomitization and metamorphism of BIF deposits [6]. The largest iron ore deposits in the world can be found in Australia, چین, کينڈا, يوکرين, India and Brazil [5].
لوہے کے اجزاء کی کیمیائی ساخت میں خاص طور پر ایف ای مواد اور متعلقہ گینگو معدنیات کے لئے کیمیائی ساخت میں واضح طور پر وسیع رینج ہے۔ [1]. زیادہ تر لوہے کے اجزاء سے وابستہ اہم لوہے کے معدنیات ہیماٹائٹ ہیں۔, گویٹہاٹی, لیمونائٹ اور میگنیٹائٹ [1,5]. لوہے کے اجزاء میں اہم آلودہ عناصر ایس آئی او 2 اور ایل 2 او 3 ہیں۔ [1,5,7]. لوہے کے اجزاء میں موجود عام سلیکا اور ایلومینا رکھنے والے معدنیات کوارٹج ہیں۔, کاؤلاناٹی, گبندا, ڈائسپور اور کورنڈم. Of these it is often observed that quartz is the mean silica bearing mineral and kaolinite and gibbsite are the two-main alumina bearing minerals [7].
لوہے کی کھدائی بنیادی طور پر کھلے گڑھے کی کان کنی کی کارروائیوں کے ذریعے انجام دی جاتی ہے, جس کے نتیجے میں اہم ٹیلنگ پیدا ہوتی ہے [2]. لوہے کی پیداوار کے نظام میں عام طور پر تین مراحل شامل ہوتے ہیں: کان کنی, پروسیسنگ اور پیلٹائزنگ کی سرگرمیاں. ان میں سے, پروسیسنگ اس بات کو یقینی بناتی ہے کہ پیلٹائزنگ مرحلے سے پہلے مناسب آئرن گریڈ اور کیمسٹری حاصل کی جاتی ہے۔. پروسیسنگ میں کرشنگ شامل ہے, درجہ بندی, ملنگ اور ارتکاز کا مقصد لوہے کے مواد کو بڑھانا ہے جبکہ گینگو معدنیات کی مقدار کو کم کرنا ہے [1-2]. لوہے اور گینگو رکھنے والی معدنیات کے حوالے سے ہر معدنی ذخائر کی اپنی منفرد خصوصیات ہوتی ہیں۔, اور لہذا اس کے لئے ایک مختلف ارتکاز تکنیک کی ضرورت ہوتی ہے [7].
مقناطیسی جدائی عام طور پر اعلی درجے کے لوہے کے اجزاء کے فوائد میں استعمال ہوتی ہے جہاں غالب لوہے کی معدنیات فیرو اور پیرامیگنیٹک ہیں۔ [1,5]. گیلے اور خشک کم شدت کی مقناطیسی علیحدگی (LIMS) مضبوط مقناطیسی خصوصیات جیسے میگنیٹائٹ کے ساتھ اجزاء پر عمل کرنے کے لئے تکنیک کا استعمال کیا جاتا ہے جبکہ گیلے اعلی شدت والے مقناطیسی علیحدگی کا استعمال کمزور مقناطیسی خصوصیات جیسے ہیماٹائٹ کو گینگو معدنیات سے الگ کرنے کے لئے کیا جاتا ہے۔. لوہے کے اجزاء جیسے گوئتھائٹ اور لیمونائٹ عام طور پر ٹیلنگ میں پائے جاتے ہیں اور کسی بھی تکنیک کے ذریعہ بہت اچھی طرح سے الگ نہیں ہوتے ہیں۔ [1,5]. Magnetic methods present challenges in terms of their low capacities and in terms of the requirement for the iron ore to be susceptible to magnetic fields [5].
Flotation, on the other hand, is used to reduce the content of impurities in low-grade iron ores [1-2,5]. لوہے کے اجزاء کو یا تو آئرن آکسائڈ کے براہ راست اینیونک فلوٹیشن یا سلیکا کے ریورس کیٹیونک فلوٹیشن کے ذریعہ مرکوز کیا جاسکتا ہے۔, تاہم ریورس کیٹینک فلوٹیشن لوہے کی صنعت میں استعمال ہونے والا سب سے مقبول فلوٹیشن روٹ ہے۔ [5,7]. فلوٹیشن کا استعمال ریجنٹس کی لاگت سے محدود ہے, سلیکا اور ایلومینا سے بھرپور پتلیوں کی موجودگی اور کاربونیٹ معدنیات کی موجودگی [7-8]. علاوہ, فلوٹیشن کے لئے گندے پانی کے ٹریٹمنٹ اور خشک حتمی ایپلی کیشنز کے لئے ڈاؤن اسٹریم ڈی واٹرنگ کے استعمال کی ضرورت ہوتی ہے۔ [1].
لوہے کے ارتکاز کے لئے فلوٹیشن کے استعمال میں ڈیسیلمنگ بھی شامل ہے کیونکہ جرمانے کی موجودگی میں تیرنے کے نتیجے میں کارکردگی میں کمی اور اعلی ریجنٹ لاگت ہوتی ہے۔ [5,7]. ایلومینا کو ہٹانے کے لئے ڈیسلیمنگ خاص طور پر اہم ہے کیونکہ کسی بھی سطح پر فعال ایجنٹوں کے ذریعہ گبسائٹ کو ہیماٹائٹ یا گوئٹائٹ سے الگ کرنا کافی مشکل ہے۔ [7]. زیادہ تر ایلومینا رکھنے والے معدنیات باریک سائز کی حد میں پائے جاتے ہیں۔ (<20um) ڈی سلیمنگ کے ذریعے اسے ہٹانے کی اجازت دینا. مجموعی طور پر, جرمانوں کا ایک بڑا ارتکاز (<20um) اور ایلومینا مطلوبہ کیٹیونک کلکٹر خوراک میں اضافہ کرتا ہے اور انتخاب کو ڈرامائی طور پر کم کرتا ہے۔ [5,7].
علاوہ, the presence of carbonate minerals – such as in dolomitic itabirites- can also deteriorate flotation selectivity between iron minerals and quartz as iron ores containing carbonates such as dolomite do not float very selectively. Dissolved carbonates species adsorb on the quartz surfaces harming the selectivity of flotation [8]. Flotation can be reasonably effective in upgrading low-grade iron ores, but it is strongly dependent on the ore mineralogy [1-3,5]. Flotation of iron ores containing high alumina content will be possible via desliming at the expense of the overall iron recovery [7], while flotation of iron ores containing carbonate minerals will be challenging and possibly not feasible [8].
Modern processing circuits of Fe-bearing minerals may include both flotation and magnetic concentration steps [1,5]. For instance, magnetic concentration can be used on the fines stream from the desliming stage prior to flotation and on the flotation rejects. The incorporation of low and high intensity magnetic concentrators allows for an increase in the overall iron recovery in the processing circuit by recovering a fraction of the ferro and paramagnetic iron minerals such as magnetite and hematite [1]. Goethite is typically the main component of many iron plant reject streams due to its weak magnetic properties [9]. In the absence of further downstream processing for the reject streams from magnetic concentration and flotation, the fine rejects will end up disposed in a tailings dam [2]. Tailings disposal and processing have become crucial for environmental preservation and recovery of iron valuables, بالترتیب, and therefore the processing of iron ore tailings in the mining industry has grown in importance [10].
Clearly, the processing of tailings from traditional iron beneficiation circuits and the processing of dolomitic itabirite is challenging via traditional desliming-flotation-magnetic concentration flowsheets due to their mineralogy and granulometry, and therefore alternative beneficiation technologies such as tribo-electrostatic separation which is less restrictive in terms of the ore mineralogy and that allows for the processing of fines may be of interest.
Tribo-electrostatic علیحدگی سطح رابطے یا triboالیکٹرک چارج کی طرف سے تیار مواد کے درمیان بجلی کا چارج فرق استعمال کرتا ہے. سادہ طریقوں سے, جب دو مواد رابطے میں ہیں, the material with a higher affinity for electron gains electrons thus charges negative, جبکہ کم برقی تعلق کے ساتھ مواد مثبت چارج کرتے ہیں. In principle, low-grade iron ore fines and dolomitic itabirites that are not processable by means of conventional flotation and/or magnetic separation could be upgraded by exploiting the differential charging property of their minerals [11].
Here we present STET tribo-electrostatic belt separation as a possible beneficiation route to concentrate ultrafine iron ore tailings and to beneficiate dolomitic itabirite mineral. The STET process provides the mineral processing industry with a unique water-free capability to process dry feed. The environmentally friendly process can eliminate the need for wet processing, downstream waste water treatment and required drying of final material. اضافی طور پہ, STET عمل معدنی کا تھوڑا پری علاج کی ضرورت ہوتی ہے اور اعلی صلاحیت پر چلاتا ہے-اپ کرنے کے لئے 40 فی گھنٹہ ٹن. توانائی کی کھپت سے کم ہے 2 کالوواٹ مواد کے فی ٹن گھنٹے عملدرآمد.
مواد
Two fine low-grade iron ores were used in this series of tests. The first ore consisted of an ultrafine Fe ore tailings sample with a D50 of 20 µm and the second sample of an itabirite iron ore sample with a D50 of 60 µm. Both samples present challenges during their beneficiation and cannot be efficiently processed through traditional desliming-flotation-magnetic concentration circuits due to their granulometry and mineralogy. Both samples were obtained from mining operations in Brazil.
The first sample was obtained from an existing desliming-flotation-magnetic concentration circuit. The sample was collected from a tailings dam, then dried, homogenized and packed. The second sample is from an itabirite iron formation in Brazil. The sample was crushed and sorted by size and the fine fraction obtained from the classification stage later underwent several stages of desliming until a D98 of 150 µm was achieved. The sample was then dried, homogenized and packed.
Particle size distributions (PSD) were determined using a laser diffraction particle size analyzer, a Malvern’s Mastersizer 3000 مشرقی. Both samples were also characterized by Loss-on-ignition(لؤي), XRF and XRD. The loss on ignition (لؤي) was determined by placing 4 grams of sample in a 1000 ºC furnace for 60 minutes and reporting the LOI on an as received basis. The chemical composition analysis was completed using a wavelength dispersive X-ray Fluorescence (WD-XRF) instrument and the main crystalline phases were investigated by XRD technique.
The chemical composition and LOI for the tailings sample (Tailings), and for the itabirite iron formation sample (Itabirite), is shown in Table 1 and particle size distributions for both samples are shown in Fig 1. For the tailings sample the main Fe recoverable phases are goethite and hematite, and the main gangue mineral is quartz (Fig 4). For the itabirite sample the main Fe recoverable phases are hematite, and the main gangue minerals are quartz and dolomite (Fig 4).
جدول 1. Result of chemical analysis for major elements in tailings and Itabirite samples.
| Sample | Grade (wt) | |||||||
|---|---|---|---|---|---|---|---|---|
| فے | SiO2 | Al2O3 | MnO | MgO | سی اے او | LOI** | Others | |
| Tailings | 30.3 | 47.4 | 4.3 | 1.0 | * | * | 3.4 | 13.4 |
| Itabirite | 47.6 | 23.0 | 0.7 | 0.2 | 1.5 | 2.2 | 4.0 | 21.0 |
Particle Size Distributions
طریقے
A series of experiments were designed to investigate the effect of different parameters on iron movement in both iron samples using STET proprietary tribo-electrostatic belt separator technology. ایک بنچ-پیمانے پر tribo-electrostatic بیلٹ جداکار کا استعمال کرتے ہوئے تجربات کئے گئے ۔, "بانچٹوپ جداکار ' کے طور پر آخرت کا حوالہ دیا گیا. بینچ کے پیمانے پر ٹیسٹنگ تین مرحلے ٹیکنالوجی عمل درآمد کے عمل کا پہلا مرحلہ ہے (دیکھیں ٹیبل 2) بینچ کے پیمانے پر تشخیص سمیت, پائلٹ پیمانے پر ٹیسٹنگ اور تجارتی پیمانے پر عملدرآمد. بانچٹوپ جداکار tribo-electrostatic چارج کے ثبوت کے لئے اسکریننگ کے لئے استعمال کیا جاتا ہے اور اس بات کا تعین کرنے کے لئے کہ ایک مواد electrostatic بانیفاکیاشن کے لئے ایک اچھا امیدوار ہے. سامان کے ہر ٹکڑے کے درمیان اہم اختلافات کی میز میں پیش کر رہے ہیں 2. جبکہ ہر مرحلے کے اندر استعمال ہونے والے سامان سائز میں مختلف ہوتی ہیں, آپریشن کے اصول بنیادی طور پر ایک ہی ہے.
جدول 2. STET tribo-electrostatic بیلٹ جداکار ٹیکنالوجی کا استعمال کرتے ہوئے تین مرحلے عمل درآمد عمل
| مرحلہ | کے لئے استعمال: | الیکٹروڈ Dimensions (W x L) سم | Type of Process/ |
|---|---|---|---|
| Bench Scale Evaluation | Qualitative Evaluation | 5*250 | بیچ |
| پائلٹ پیمانے ٹیسٹنگ | Quantitative Evaluation | 15*610 | بیچ |
| Commercial Scale Implementation | Commercial Production | 107 *610 | مسلسل |
STET Operation Principle
The operation principle of the separator relies on tribo-electrostatic charging. Tribo-electrostatic بیلٹ جداکار میں (اعداد و شمار 2 اور 3), material is fed into the narrow gap 0.9 – 1.5 دو متوازی مسطح مخطط الیکٹروڈ کے درمیان سینٹی میٹر. ذرات کو انٹرذرہ رابطہ کی طرف سے چارج ٹرابویلیکٹراکالل جاتا ہے. The positively charged mineral(s) and the negatively charged mineral(s) مخالف الیکٹروڈ کو اپنی طرف متوجہ کر رہے ہیں. Inside the separator particles are swept up by a continuous moving open-mesh belt and conveyed in opposite directions. The belt is made of plastic material and moves the particles adjacent to each electrode toward opposite ends of the separator. The counter current flow of the separating particles and continual triboelectric charging by particle-particle collisions provides for a multistage separation and results in excellent purity and recovery in a single-pass unit. ٹرائیبوالیکٹرک بیلٹ سیپریٹر ٹیکنالوجی کا استعمال مختلف قسم کے مواد کو الگ کرنے کے لئے کیا گیا ہے جس میں شیشے کی الومینیوسیلیکیٹس/کاربن کے مرکب بھی شامل ہیں (مکھی ایش), کیلسائٹ/کوارٹز, پاؤڈر/ماگنیساٹی, اور باریا کوارٹج.
مجموعی طور پر, the separator design is relatively simple with the belt and associated rollers as the only moving parts. الیکٹروڈ اسٹیشنری ہیں اور مناسب طریقے سے پائیدار مواد پر مشتمل ہے. جداکار کی لمبائی تقریبا ہے 6 میٹر (20 فٹ.) اور چوڑائی 1.25 میٹر (4 فٹ.) مکمل سائز کے تجارتی یونٹس کے لئے. The high belt speed enables very high throughputs, کرنے کے لئے 40 tons per hour for full size commercial units. بجلی کی کھپت سے کم ہے 2 kilowatt-hours per ton of material processed with most of the power consumed by two motors driving the belt.
Triboelectric بیلٹ جداکار کی سکہیمٹاک
علیحدگی منطقہ کی تفصیل
جیسا کہ میز میں دیکھا جا سکتا ہے 2, بانچٹوپ جداکار اور پائلٹ اسکیل اور تجارتی اسکیل separators کے درمیان اہم فرق یہ ہے کہ بانچٹوپ جداکار کی لمبائی تقریبا ہے 0.4 بار پائلٹ-پیمانے اور تجارتی پیمانے پر یونٹس کی لمبائی. جیسا کہ جداکار کی کارکردگی الیکٹروڈ لمبائی کی ایک تقریب ہے, بینچ کے پیمانے پر جانچ پائلٹ-پیمانے کی جانچ کے لئے ایک متبادل کے طور پر استعمال نہیں کیا جا سکتا. پائلٹ پیمانے کی جانچ کی علیحدگی کی حد کا تعین کرنے کے لئے ضروری ہے کہ STET کے عمل کو حاصل کر سکتے ہیں, اور اس بات کا تعین کرنے کے لئے کہ STET کے عمل کو دیا فیڈ کی شرح کے تحت مصنوعات کے اہداف کو پورا کر سکتے ہیں. بجائے, بانچٹوپ جداکار امیدواروں کے مواد کو مسترد کرنے کے لئے استعمال کیا جاتا ہے جو پائلٹ اسکیل سطح پر کسی بھی اہم علیحدگی کا مظاہرہ کرنے کا امکان نہیں ہے. بینچ کے پیمانے پر حاصل کردہ نتائج غیر مرضی کے ہو جائے گا, اور علیحدگی کا مشاہدہ اس سے کم ہے جس میں ایک تجارتی سائز STET جداکار پر مشاہدہ کیا جائے گا.
پائلٹ پلانٹ پر ٹیسٹنگ تجارتی پیمانے پر تعیناتی سے پہلے ضروری ہے, تاہم, بینچ کے پیمانے پر ٹیسٹنگ کسی بھی مواد کے لئے عمل درآمد کے عمل کے پہلے مرحلے کے طور پر حوصلہ افزائی کی جاتی ہے. مزید برآں, ان صورتوں میں جن میں مواد کی دستیابی محدود ہے, بانچٹوپ جداکار ممکنہ کامیاب منصوبوں کی اسکریننگ کے لئے ایک مفید آلہ فراہم کرتا ہے (یعنی., منصوبوں جس میں کسٹمر اور صنعت کے معیار کے اہداف STET ٹیکنالوجی کا استعمال کرتے ہوئے ملاقات کی جا سکتی ہیں).
بینچ کے پیمانے پر ٹیسٹنگ
Standard process trials were performed around the specific goal to increase Fe concentration and to reduce the concentration of gangue minerals. Different variables were explored to maximize iron movement and to determine the direction of movement of different minerals. The direction of movement observed during benchtop testing is indicative of the direction of movement at the pilot plant and commercial scale.
The variables investigated included relative humidity (RH), temperature, electrode polarity, belt speed and applied voltage. ان میں سے, RH and temperature alone can have a large effect on differential tribo-charging and therefore on separation results. لہذا, optimum RH and temperature conditions were determined before investigating the effect of the remaining variables. Two polarity levels were explored: میں) top electrode polarity positive and ii) top electrode polarity negative. For the STET separator, under a given polarity arrangement and under optimum RH and temperature conditions, belt speed is the primary control handle for optimizing product grade and mass recovery. Testing on the bench separator helps shed light on the effect of certain operational variables on tribo-electrostatic charging for a given mineral sample, and therefore obtained results and trends may be used, to certain degree, to narrow down the number of variables and experiments to be performed at the pilot plant scale. جدول 3 lists the range of separation conditions used as part of phase 1 evaluation process for the tailings and itabirite samples.
جدول 3 lists the range of separation conditions
| Parameter | Units | Range of Values | |
|---|---|---|---|
| Tailings | Itabirite | ||
| Top Electrode Polarity | - | Positive- Negative | Positive- Negative |
| Electrode Voltage | -kV/+kV | 4-5 | 4-5 |
| Feed Relative Humidity (RH) | % | 1-30.7 | 2-39.6 |
| Feed Temperature | °F (°C) | 71-90 (21.7-32.2) | 70-87 (21.1-30.6) |
| Belt Speed | Fps (م/ایس) | 10-45 (3.0-13.7) | 10-45 (3.0-13.7) |
| Electrode Gap | Inches (ملی میٹر) | 0.400 (10.2 ملی میٹر) | 0.400 (10.2 ملی میٹر) |
بیچ کے حالات کے تحت بانچٹوپ جداکار پر ٹیسٹ کئے گئے ۔, with feed samples of 1.5 lbs. per test. A flush run using 1 lb. of material was introduced in between tests to ensure that any possible carryover effect from the previous condition was not considered. Before testing was started material was homogenized and sample bags containing both run and flush material were prepared. At the beginning of each experiment the temperature and relative humidity (RH) was measured using a Vaisala HM41 hand-held Humidity and Temperature probe. The range of temperature and RH across all experiments was 70-90 °F (21.1-32.2 (°C) اور 1-39.6%, بالترتیب. To test a lower RH and/or higher temperature, feed and flush samples were kept in a drying oven at 100 °C for times between 30-60 minutes. اس کے برعکس, higher RH values were attained by adding small amounts of waters to the material, followed by homogenization. After RH and temperature was measured on each feed sample, the next step was to set electrode polarity, belt speed and voltage to the desired level. Gap values were kept constant at 0.4 انچ (10.2 ملی میٹر) during the testing campaigns for the tailings and itabirite samples.
ہر ٹیسٹ سے پہلے, a small feed sub-sample containing approximately 20g was collected (' فیڈ ' کے طور پر نامزد). تمام آپریشن متغیرات کو قائم کرنے پر, مواد بانچٹوپ جداکار کے مرکز کے ذریعے ایک برقی وٹریٹری فیڈر کا استعمال کرتے ہوئے بانچٹوپ جداکار میں کھلایا گیا تھا. نمونے ہر تجربہ کے اختتام پر جمع کیے گئے تھے اور مصنوعات کے اختتام کے وزن 1 (' E1 ' کے طور پر نامزد) اور مصنوعات کا اختتام 2 (' E2 ' کے طور پر نامزد) ایک قانونی تجارت کی گنتی پیمانے کا استعمال کرتے ہوئے مقرر کیا گیا. Following each test, small sub-samples containing approximately 20 g of E1 and E2 were also collected. Mass yields to E1 and E2 are described by:
جہاںYE1 اور YE2 are the mass yields to E1 and E2, بالترتیب; and are the sample weights collected to the separator products E1 and E2, بالترتیب. For both samples, Fe concentration was increased to product E2.
ذیلی نمونے کے ہر سیٹ کے لئے (یعنی., کھانا کھلانا, E1 اور E2) LOI and main oxides composition by XRF was determined. فے2 اے3 contents were determined from the values. For the tailings sample LOI will directly relate to the content of goethite in the sample as the functional hydroxyl groups in goethite will oxidize into ایچ2 اےg [10]. برعکس, for the itabirite sample LOI will directly relate to the contain of carbonates in the sample, as calcium and magnesium carbonates will decompose into their main oxides resulting in the release of کمپنی2g and sub sequential sample loss weight. XRF beads were prepared by mixing 0.6 grams of mineral sample with 5.4 grams of lithium tetraborate, which was selected due to the chemical composition of both tailings and itabirite samples. XRF analysis were normalized for LOI.
آخر, Fe recovery مشرقیفے to product (E2) اور SiO2 rejection QSi were calculated. مشرقیفے is the percentage of Fe recovered in the concentrate to that of the original feed sample and Qsio2 is the percentage of removed from the original feed sample. مشرقیفے اور Qsi are described by:
جہاں سیمیں,(feed,E1,E2) is the normalized concentration percentage for the sub-sample’s i component (eg., فے, sio2)
نمونے معدنیات
The XRD pattern showing major mineral phases for the tailings and itabirite samples are shown in Fig 4. For the tailings sample the main Fe recoverable phases are goethite, hematite and magnetite, and the main gangue mineral is quartz (Fig 4). For the itabirite sample the main Fe recoverable phases are hematite and magnetite and the main gangue minerals are quartz and dolomite. Magnetite appears in trace concentrations in both samples. Pure hematite, گویٹہاٹی, and magnetite contain 69.94%, 62.85%, 72.36% فے, بالترتیب.
D patterns. A – Tailings sample, B – Itabirite sample
بینچ کے پیمانے پر تجربات
A series of test runs were performed on each mineral sample aimed at maximizing Fe and decreasing SiO2 content. Species concentrating to E1 will be indicative of a negative charging behavior while species concentration to E2 to a positive charging behavior. Higher belt speeds were favorable to the processing of the tailings sample; تاہم, the effect of this variable alone was found to be less significant for the itabirite sample.
Average results for the tailings and itabirite samples are presented in Fig 5, which were calculated from 6 اور 4 experiments, بالترتیب. Fig 5 presents average mass yield and chemistry for feed and products E1 and E2. اضافی طور پہ, each plot presents the improvement or decrease in concentration (E2- کھانا کھلانا) for each sample component e.g., فے, SiO2 Positive values are associated to an increase in concentration to E2, while negative values are associated to a decrease in concentration to E2.
Fig.5. Average mass yields and chemistry for Feed, E1 and E2 products. Error bars represent 95% confidence intervals.
For the tailings sample Fe content was increased from 29.89% کرنا 53.75%, on average, at a mass yield YE2 – or global mass recovery – of 23.30%. This corresponds to Fe recovery ( and silica rejection (QE2 ) values of 44.17% اور 95.44%, بالترتیب. The LOI content was increased from 3.66% کرنا 5.62% which indicates that the increase in Fe content is related to an increase in goethite content (Fig 5).
For the itabirite sample Fe content was increased from 47.68% کرنا 57.62%, on average, at a mass yield YE2 -of 65.0%. This corresponds to Fe recovery مشرقیفے( and silica rejection (Qsio2) values of 82.95% اور 86.53%, بالترتیب. The LOI, MgO and CaO contents were increased from 4.06% کرنا 5.72%, 1.46 کرنا 1.87% and from 2.21 کرنا 3.16%, بالترتیب, which indicates that dolomite is moving in the same direction as Fe-bearing minerals (Fig 5).
For both samples,AL2 اے3 , MnO and P seem to be charging in the same direction as Fe-bearing minerals (Fig 5). While it is desired to decrease the concentration of these three species, the combined concentration of SiO2, AL2 , اے3 , YE2 MnO and P is decreasing for both samples, and therefore the total effect achieved using the benchtop separator is an enhancement in the product Fe grade and a decrease in the contaminants concentration.
مجموعی طور پر, benchtop testing demonstrated evidence of effective charging and separation of iron and silica particles. The promising laboratory scale results suggest that pilot scale tests including first and second passes should be performed.
بحث
The experimental data suggests that the STET separator resulted in an important increase in Fe content while simultaneously reducing SiO2 content.
Having demonstrated that triboelectrostatic separation can result in a significant increase in Fe content, a discussion on the significance of the results, on the maximum achievable Fe contents and on the feed requirements of the technology is needed.
To start, it is important to discuss the apparent charging behavior of mineral species in both samples. For the tailings sample the main components were Fe oxides and quartz and experimental results demonstrated that Fe oxides concentrated to E2 while quartz concentrated to E1. سادہ طریقوں سے, it could be said that Fe oxide particles acquired a positive charge and that quartz particles acquired a negative charge. This behavior is consistent with the triboelectrostatic nature of both minerals as shown by Ferguson (2010) [12]. جدول 4 shows the apparent triboelectric series for selected minerals based on inductive separation, and it shows that quartz is located at the bottom of the charging series while goethite, magnetite and hematite are located higher up in the series. Minerals at the top of the series will tend to charge positive, while minerals at the bottom will tend to acquire a negative charge.
On the other hand, for the itabirite sample the main components were hematite, quartz and dolomite and experimental results indicated that Fe oxides and dolomite concentrated to E2 while quartz concentrated to E1. This indicates that hematite particles and dolomite acquired a positive charge while quartz particles acquired a negative charge. جیسا کہ میز میں دیکھا جا سکتا ہے 4, carbonates are located at the top of the tribo-electrostatic series, which indicates that carbonate particles tend to acquire a positive charge, and in consequence to be concentrated to E2. Both dolomite and hematite were concentrated in the same direction, indicating that the overall effect for hematite particles in the presence of quartz and dolomite was to acquire a positive charge.
The direction of movement of the mineralogical species in each sample is of paramount interest, as it will determine the maximum achievable Fe grade that can be obtained by means of a single pass using the tribo-electrostatic belt separator technology.
For the tailings and itabirite samples the maximum achievable Fe content will be determined by three factors: میں) The amount of Fe in Fe-bearing minerals; ii) the minimum quartz (SiO2 ) content that can be achieved and; iii) The number of contaminants moving in the same direction as Fe-bearing minerals. For the tailings sample the main contaminants moving in the same direction of Fe-bearing minerals are القاعدہ2 اے3 MnO bearing minerals, while for the itabirite sample the main contaminants are سی اے او MgO القاعدہ2 اے3 bearing minerals.
| Mineral Name | Charge acquired (apparent) |
|---|---|
| Apatite | +++++++ |
| Carbonates | ++++ |
| Monazite | ++++ |
| Titanomagnetite | . |
| Ilmenite | . |
| Rutile | . |
| Leucoxene | . |
| Magnetite/hematite | . |
| Spinels | . |
| Garnet | . |
| Staurolite | - |
| Altered ilmenite | - |
| Goethite | - |
| Zircon | -- |
| Epidote | -- |
| Tremolite | -- |
| Hydrous silicates | -- |
| Aluminosilicates | -- |
| Tourmaline | -- |
| Actinolite | -- |
| Pyroxene | --- |
| Titanite | ---- |
| فیلڈسپر | ---- |
| Quartz | ------- |
جدول 4. Apparent triboelectric series for selected minerals based on inductive separation. Modified from D.N Ferguson (2010) [12].
For the tailings sample, the Fe content was measured at 29.89%. XRD data indicates that the predominant phase is goethite, followed by hematite, and therefore the maximum achievable Fe content if a clean separation was possible would be between 62.85% اور 69.94% (which are the Fe contents of pure goethite and hematite, بالترتیب). Now, a clean separation is not possible as القاعدہ2, اے3 MnO and P-bearing minerals are moving in the same direction as the Fe-bearing minerals, and therefore any increase in Fe content will also result in an increase of these contaminants. Then, to increase the Fe content, the amount of quartz to E2 will need to be significantly decreased to the point it offsets the movement of , MnO and P to product (E2). As shown in Table 4, quartz has a strong tendency to acquire a negative charge, and therefore in the absence of other minerals having an apparent negative charging behavior it will be possible to considerably decrease its content to product (E2) by means of a first pass using the triboelectrostatic belt separator technology.
For instance, if we assume that all the Fe content in the tailings sample is associated to goethite (Fe(اوہ)), and that the only gangue oxides are SiO2, القاعدہ2اے3 اور MnO, then Fe content to product would be given by:
فے(%)=(100-SiO2 – (القاعدہ2 اے3 + MnO*0.6285
جہاں, 0.6285 is the percentage of Fe in pure goethite. Eq.4 depicts the competing mechanism that takes place to concentrate Fe as AL2اے3 + MnO increases while SiO2 decreases.
For the itabirite sample the Fe content was measured at 47.68%. XRD data indicates that the predominant phase is hematite and therefore the maximum achievable Fe content if a clean separation was possible would be close to 69.94% (which is the Fe content of pure hematite). As it was discussed for the tailings sample a clean separation won’t be possible as CaO, MgO, القاعدہ2 اے3 bearing minerals are moving in the same direction as hematite, and therefore to increase Fe content SiO2 content must be reduced. Assuming that the entirety of the Fe content in this sample is associated to hematite (فے2اے3) and that the only oxides contained in gangue minerals are SiO2, سی اے او, MgO, القاعدہ2اے3 اور MnO; then Fe content in the product would be given by:
فے(%)=(100-SiO2-CaO+MgO+القاعدہ2اے3+MnO+لؤي*0.6994
جہاں, 0.6994 is the percentage of Fe in pure hematite. It must be noticed that Eq.5 includes LOI, while Eq.4 does not. For the itabirite sample, the LOI is associated to the presence of carbonates while for the tailings sample it is associated to Fe-bearing minerals.
Evidently, for both tailings and itabirite samples it is possible to significantly increase the Fe content by reducing the content of SiO2; تاہم, as shown in Eq.4 and Eq.5, the maximum achievable Fe content will be limited by the direction of movement and the concentration of oxides associated to gangue minerals.
In principle, the concentration of Fe in both samples could be further increased by means of a second pass on the STET separator in which سی اے او,MgO القاعدہ2 اے3 اور MnObearing minerals could be separated from Fe-bearing minerals. Such separation would be possible if most of quartz in the sample was removed during a first pass. In the absence of quartz, some of the remaining gangue minerals should in theory charge in the opposite direction of goethite, hematite and magnetite, which would result in increased Fe content. For instance, for the itabirite sample and based in the location of dolomite and hematite in the triboelectrostatic series (دیکھیں ٹیبل 4), dolomite/hematite separation should be possible as dolomite has a strong tendency to charge positive in relation to hematite.
Having discussed on the maximum achievable Fe contents a discussion on the feed requirements for the technology is needed. The STET tribo-electrostatic belt separator requires the feed material to be dry and finely ground. Very small amounts of moisture can have a large effect on differential tribo-charging and therefore the feed moisture should be decreased to <0.5 wt .%. اضافی طور پہ, the feed material should be ground sufficiently fine to liberate gangue materials and should be at least 100% passing mesh 30 (600 um). At least for the tailings sample, the material would have to be dewatered followed by a thermal drying stage, while for the itabirite sample grinding coupled with, or follow by, thermal drying would be necessary prior to beneficiation with the STET separator.
The tailings sample was obtained from an existing desliming-flotation-magnetic concentration circuit and collected directly from a tailings dam. Typical paste moistures from tailings should be around 20-30% and therefore the tailings would need to be dried by means of liquid-solid separation (dewatering) followed by thermal drying and deagglomeration. The use of mechanical dewatering prior to drying is encouraged as mechanical methods have relative low energy consumption per unit of liquid removed in comparison to thermal methods. About 9.05 Btu are required per pound of water eliminated by means of filtration while thermal drying, on the other hand, requires around 1800 Btu per pound of water evaporated [13]. The costs associated with the processing of iron tailings will ultimately depend on the minimum achievable moisture during dewatering and on the energetic costs associated with drying.
The itabirite sample was obtained directly from an itabirite iron formation and therefore to process this sample the material would need to undergo crushing and milling followed by thermal drying and deagglomeration. One possible option is the use of hot air swept roller mills, in which dual grinding and drying could be achieved in a single step. The costs associated with the processing of itabirite ore will depend on the feed moisture, feed granulometry and on the energetic costs associated to milling and drying.
For both samples deagglomeration is necessary after the material have been dried to ensure particles are liberated from one another. Deagglomeration can be performed in conjunction to the thermal drying stage, allowing for efficient heat transfer and energy savings.
The bench-scale results presented here demonstrates strong evidence of charging and separation of Fe-bearing minerals from quartz using triboelectrostatic belt separation.
For the tailings sample Fe content was increased from 29.89% کرنا 53.75%, on average, at a mass yield of 23.30%, which corresponds to Fe recovery and silica rejection values of 44.17% اور 95.44%, بالترتیب. For the itabirite sample Fe content was increased from 47.68 % کرنا 57.62%, on average, at a mass yield of 65.0%, which corresponds to Fe recovery and silica rejection values of 82.95% اور 86.53%, بالترتیب. These results were completed on a separator that is smaller and less efficient than the STET commercial separator.
Experimental findings indicate that for both tailings and itabirite samples the maximum achievable Fe content will depend on the minimum achievable quartz content. اضافی طور پہ, achieving higher Fe grades may be possible by means of a second pass on the STET belt separator.
اس مطالعے کے نتائج سے پتہ چلتا ہے کہ ایس ٹی ای ٹی ٹریبو-الیکٹراسٹک بیلٹ جداکار کے ذریعہ کم درجے کے لوہے کے لوہے کے فائن کو اپ گریڈ کیا جاسکتا ہے۔. Further work at the pilot plant scale is recommended to determine the iron concentrate grade and recovery that can be achieved. Based on experience, پائلٹ اسکیل پروسیسنگ میں مصنوعات کی بازیابی اور / یا گریڈ میں نمایاں بہتری آئے گی, ان لوہے کے تجربات کے دوران استعمال ہونے والے بینچ اسکیل ٹیسٹ ڈیوائس کے مقابلے میں. The STET tribo-electrostatic separation process may offer significant advantages over conventional processing methods for iron ore fines.
