Сайлагыз Тел:
Санкт-җиһазлар & Технологияләр " ҖЧҖ (НТОО) tribo-electrostatic belt separator is ideally suited for beneficiating very fine (<1мкм) чамасын грубый (500мкм) mineral particles, with very high throughput. Experimental findings demonstrated the capability of the STET separator to beneficiate bauxite samples by increasing available alumina while simultaneously reducing reactive and total silica. STET technology is presented as a method to upgrade and pre-concentrate bauxite deposits for use in alumina production. Dry processing with the STET separator will result in a reduction in operating costs of refinery due to lower consumption of caustic soda, savings in energy due to lower volume of inert oxides and a reduction in volume of alumina refinery residues (ARR or red mud). Моннан тыш,, the STET technology may offer alumina refiners other benefits including increased quarry reserves, extension of red mud disposal site life, and extended operating life of existing bauxite mines by improving quarry utilization and maximizing recovery. The water-free and chemical-free by-product produced by the STET process is usable for manufacture of cement in high volumes without pre-treatment, in contrast to red mud which has limited beneficial reuse.
1.0 Introduction
Aluminum production is of central importance for the mining and metallurgy industry and fundamental for a variety of industries [1-2]. While aluminum is the most common metallic element found on earth, in total about 8% of the Earth’s crust, as an element it is reactive and therefore does not occur naturally [3]. Биредән, aluminum-rich ore needs to be refined to produce alumina and aluminum, resulting in significant generation of residues [4]. As the quality of bauxite deposits globally decline, the generation of residue increases, posing challenges to the alumina and aluminum-making industry in terms of processing costs, costs of disposal and the impact on the environment [3].
The primary starting material for aluminum refining is bauxite, the world’s main commercial source of aluminum [5]. Bauxite is an enriched aluminum hydroxide sedimentary rock, produced from the laterization and weathering of rocks rich in iron oxides, aluminum oxides, or both commonly containing quartz and clays like kaolin [3,6]. Bauxite rocks consists mostly of the aluminum minerals gibbsite (Әл(Турында)3), boehmite (γ-AlO(Турында)) and diaspore (α-AlO(Турында)) (Таблица 1), and is usually mixed with the two iron oxides goethite (Фео(Турында)) and hematite (Бу пересчете бу Fe2O3), the aluminum clay mineral kaolinite, small amounts of anatase and/or titania (TiO2), ilmenite (FeTiO3) and other impurities in minor or trace amounts [3,6,7].
The terms trihydrate and monohydrate are commonly used by industry to differentiate various types of bauxite. Bauxite that is totally or nearly all gibbsite bearing is called a trihydrate ore; if boehmite or diaspore are the dominant minerals it is referred to as monohydrate ore [3]. Mixtures of gibbsite and boehmite are common in all types of bauxites, boehmite and diaspore less common, and gibbsite and diaspore rare. Each type of bauxite ore presents its own challenges in terms of mineral processing and beneficiation for the generation of alumina [7,8].
Таблица 1. Chemical composition of Gibbsite, Boehmite and Diaspore [3].
| Химик Составы | Gibbsite AL(Турында)3 or Al2O3.3H2Турында | Boehmite ALO(Турында) or Al2Турында3.С2Турында | Diaspore ALO(Турында) or Al2Турында3.С2Турында |
|---|---|---|---|
| Әл2Турында3 wt% | 65.35 | 84.97 | 84.98 |
| (Турында) wt% | 34.65 | 15.03 | 15.02 |
Bauxite deposits are spread worldwide, mostly occurring in tropical or subtropical regions [8]. Bauxite mining of both metallurgical and non-metallurgical grade ores is analogous to the mining of other industrial minerals. Normally, the beneficiation or treatment of bauxite is limited to crushing, sieving, washing, and drying of the crude ore [3]. Flotation has been employed for the upgrading of certain low-grade bauxite ores, however it has not proven highly selective at rejecting kaolinite, a major source of reactive silica especially in trihydrate bauxites [9].
The bulk of bauxite produced in the world is used as feed for manufacturing of alumina via the Bayer process, a wet-chemical caustic-leach method in which the Al_2 O_3 is dissolved out of the bauxite rock by using a caustic soda rich solution at elevated temperature and pressure [3,10,11]. Subsequently, the bulk of alumina is utilized as feed for the production of aluminum metal via the Hall-Héroult process, which involves electrolytic reduction of alumina in a bath of cryolite (Na3AlF6). It takes about 4-6 tons of dried bauxite to produce 2 t of alumina, which in turns yields 1 t of aluminum metal [3,11].
The Bayer process is initiated by mixing washed and finely ground bauxite with the leach solution. The resulting slurry containing 40-50% solids is then pressurized and heated with steam. At this step some of the alumina is dissolved and forms soluble sodium aluminate (NaAlO2), but due to the presence of reactive silica, a complex sodium aluminum silicate also precipitates which represents a loss of both alumina and soda. The resulting slurry is washed, and the residue generated (т. е., кызыл пычрак) is decanted. Sodium aluminate is then precipitated out as aluminum trihydrate (Әл(Турында)3) through a seeding process. The resulting caustic soda solution is recirculated into the leach solution. Ниһаять, the filtered and washed solid alumina trihydrate is fired or calcined to produce alumina [3,11].
Leaching temperatures may range from 105°C to 290°C and corresponding pressures range from 390 kPa to 1500 kPa. Lower temperatures ranges are used for bauxite in which nearly all the available alumina is present as gibbsite. The higher temperatures are required to digedepositsst bauxite having a large percentage of boehmite and diaspore. At temperatures of 140°C or less only gibbsite and kaolin groups are soluble in the caustic soda liquor and therefore such temperature is preferred for the processing of trihydrate alumina . At temperatures greater than 180°C alumina present as trihydrate and monohydrate are recoverable in solution and both clays and free quartz become reactive [3]. Operating conditions such as temperature, pressure and reagent dosage are influenced by the type of bauxite and therefore each alumina refinery is tailored to a specific type of bauxite ore. The loss of expensive caustic soda (NaOH) and the generation of red mud are both related to the quality of bauxite used in the refining process. Гомумән алганда,, the lower the Al_2 O_3 content of bauxite, the larger the volume of red mud that will be generated, as the non-Al_2 O_3 phases are rejected as red mud. Моннан тыш,, the higher the kaolinite or reactive silica content of bauxite, the more red mud will be generated [3,8].
High-grade bauxite contains up to 61% Al_2 O_3, and many operating bauxite deposits -typically referred as non-metallurgical grade- are well below this, occasionally as low as 30-50% Al_2 O_3. Because the desired product is a high purity
Al_2 O_3, the remaining oxides in the bauxite (Бу пересчете бу Fe2O3, Ѕіо2, TiO2, organic material) are separated from the Al_2 O_3 and rejected as alumina refinery residues (ARR) or red mud via the Bayer process. Гомумән алганда,, the lower quality the bauxite (т. е., lower Al_2 O_3 content) the more red mud that is generated per ton of alumina product. Моннан тыш,, even some Al_2 O_3 bearing minerals, notably kaolinite, produce undesirable side reactions during the refining process and lead to an increase in red mud generation, as well as a loss of expensive caustic soda chemical, a large variable cost in the bauxite refining process [3,6,8].
Red mud or ARR represents a large and on-going challenge for the aluminum industry [12-14]. Red mud contains significant residual caustic chemical leftover from the refining process, and is highly alkaline, often with a pH of 10 – 13 [15]. It is generated in large volumes worldwide – according to the USGS, estimated global alumina production was 121 million tons in 2016 [16]. This resulted in an estimated 150 million tons of red mud generated during the same period [4]. Despite ongoing research, red mud currently has few commercially viable paths to beneficial re-use. It is estimated that very little of red mud is beneficially re-used worldwide [13-14]. Урынына, the red mud is pumped from the alumina refinery into storage impoundments or landfills, where it is stored and monitored at large cost [3]. Шуңа күрә, both an economic and environmental argument can be made for improving the quality of bauxite prior to refining, in particular if such improvement can be done through low-energy physical separation techniques.
While proven reserves of bauxite are expected to last for many years, the quality of the reserves that can be economically accessed is declining [1,3]. For refiners, who are in the business of processing bauxite to make alumina, and eventually aluminum metal, this is a challenge with both financial and environmental implications
Dry methods such as electrostatic separation may be of interest of the bauxite industry for the pre-concentration of bauxite prior to the Bayer process. Electrostatic separation methods that utilize contact, яки Трибо-электрический, charging is particularity interesting because of their potential to separate a wide variety of mixtures containing conductive, изолируя, һәм полупроводящие частицы. Трибо-электр корылмасы туа каршындагы дискретных, разнородные частицы очраша һәм бер-беребез белән, яки өченче өслегенә, нәтиҗәдә, поверхностном аерманы заряда арасында ике типами частиц . Билгесе һәм зурлыгы разности заряд өлешчә бәйле аерма шул сродства к электрону (яки эш ) арасында типами частиц . Ул чакта бүленеш булырга мөмкин ирешелгән ярдәмендә тышкы электр кыры.
Методикасы кулланылды производствода вертикальное ирекле төшү сепараторы тибындагы . Бу ирекле падении сепараторы, частицы башта өлкәннәр алырга, 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 [18]. Free-fall separators can be effective for coarse particles but are not effective at handling particles finer than about 0.075 өчен 0.1 мм [19-20]. One of the most promising new developments in dry mineral separations is the tribo-electrostatic belt separator. Бу технология расширила диапазон күләмен частиц артык вак частицы караганда, гади электростатические технологияләр аеру, сериясендә кайда иде уңышлы узган генә флотирования .
Tribo-electrostatic separation utilizes electrical charge differences between materials produced by surface contact or triboelectric charging. Бу гадиләштерелгән режимында, when two materials are in contact, the material with a higher affinity for electros gains electrons thus changes negative, шул ук вакытта материал белән артык түбән түләү сродства к электрону уңай.
Санкт-җиһазлар & Технология (НТОО) tribo-electrostatic belt separator offers a novel beneficiation route to pre-concentrate bauxite ores. The STET dry separation process offers bauxite producers or bauxite refiners an opportunity to perform pre-Bayer-process upgrading of bauxite ore to improve the quality. This approach has many benefits, including: Reduction in operating cost of refinery due to lower consumption of caustic soda by reducing input reactive silica; savings in energy during refining due to lower volume of inert oxides (Фе2Турында3, TiO2, Non-reactive SiO2) entering with bauxite; smaller mass flow of bauxite to refinery and therefore less energy requirement to heat and pressurize; reduction in red mud generation volume (т. е., red mud to alumina ratio) by removing reactive silica and inert oxide; һәм, tighter control over input bauxite quality which reduces process upsets and allows refiners to target ideal reactive silica level to maximize impurity rejection. Improved quality control over bauxite feed to refinery also maximizes uptime and productivity. Моннан тыш,, reduction in red mud volume translates into less treatment and disposal costs and better utilization of existing landfills.
The preprocessing of bauxite ore prior to the Bayer process may offer significant advantages in terms of processing and sales of tailings. Unlike red mud, tailings from a dry electrostatic process contain no chemicals and do not represent a long-term environmental storage liability. Unlike red mud, dry by-products/tailings from a bauxite pre-processing operation can be utilized in cement manufacture as there is no requirement to remove the sodium, which is detrimental to cement manufacture. In fact – bauxite is already a common raw material for Portland cement manufacturing. Extending operating life of existing bauxite mines may also be reached by improving quarry utilization and maximizing recovery.
2.0 Эксперименталь
2.1 Материаллар
STET conducted pre-feasibility studies in over 15 different bauxite samples from different locations around the world using a bench-scale separator. Шушы, 7 different samples were
Таблица 2. Result of chemical analysis bauxite samples.
2.2 Ысуллары
Экспериментлар үткәрелгән кулланып, лаборатор Трибо-электростатический сепаратор поясы , алга таба-разделитель настольная'. Стендовые сынаулар беренче фаза өч этапта гамәлгә ашыру технологияләр (См. Таблицасын 3) шул исәптән стендовую бәя, тәҗрибә-сәнәгать сынауларын һәм сәнәгый кулланышка кертү.
Сепаратор настольная өчен кулланыла скрининг өчен булуы Трибо-электростатический өлкәннәр өчен билгеләргә, әгәр дә материал булып тора, яхшы кандидат өчен электростатического баету. Төп тамгасын һәр берәмлек җиһаз түбәндә таблица формасында күрсәтелгән 3. Кулланганда җиһазлар кысаларында һәр этапта төрлечә күләме буенча, эш принцибы асылда шул ук.
Таблица 3. Өч этапта процессын кертү файдаланып, СТЕТ Трибо-электростатическая технология ленточного сепаратора
| Phase | Used for: | Electrode Length cm | Type of Process |
|---|---|---|---|
| 1- Bench Scale Evaluation | Qualitative Evaluation | 250 | Batch |
| 2- Pilot Scale Тест | Quantitative evaluation | 610 | Batch |
| 3- Commercial Scale Implementation | Commercial Production | 610 | Continuous |
Күрәсең таблицасында 3, төп аерма арасындагы сепаратором кыр һәм эксперименталь һәм сәнәгать сепараторов булып тора, ягъни озынлыгы сепаратора настольная тәшкил итә, якынча 0.4 тапкыр озынлыгы пилот һәм сәнәгать җайланмалары. Ничек нәтиҗәлелеген сепаратора бәйле длины электрода , стендовые сынаулар да булырга мөмкин материаллары сыйфатында алыштыру өчен тәҗрибә-сәнәгать сынауларын. Тәҗрибә-сәнәгать сынавы өчен кирәк булган билгеләү дәрәҗә аеру, процессы СТЕТ җитәргә мөмкин, һәм билгеләү өчен, әгәр процессы СТЕТ очратырга мөмкин продукт максатка каршындагы заданных скоростях бирү . Урынына, сепаратор настольная кулланыла куймас өчен материаллар кандидат, ул икеле күрсәтә ниндидер зур бүленеш өчен эксперименталь дәрәҗәдә. Нәтиҗәләр алынган на скамейке-масштабтагы булмаячак оптимизированной, һәм наблюдаемое бүленеш азрак, ул билгеләп үтеләчәк коммерция күләмен сепаратора СТЕТ .
Сынаулар өчен эксперименталь кую кирәк кадәр коммерция күләмендәге җәелдерү, әмма, сынаулар бүген лаборатор киңәш ителә сыйфатында беренче этабы процессын тормышка ашыру нинди дә булса материал. Моннан тыш,, очракларда булу материал чикләнгән, сепаратор уборщик benchtop булып тора файдалы инструмент скрининг өчен потенциаль уңышлы проектлар (т. е., проектлар, алар заказ бирүче һәм сыйфаты күрсәткечләренең сәнәгать мөмкин канәгать технологиясе ярдәмендә СТЕТ ).
2.2.1 STET Triboelectrostatic Belt Separator
Бу Трибо-электростатический сепаратор поясы (Дөге. 1 һәм дөге. 2), материал бирелә " тонком зазоре 0.9 – 1.5 см арасында ике параллельными плоскими электродами. Частицы triboelectrically, взимаемые межчастичного бәйләнеш. Мәсәлән, in the case of a bauxite sample which main constituents are gibssite, kaolinite and quartz mineral particles, the positively charged (gibssite) and the negatively charged (kaolinite and quartz) җәлеп итә к противоположным электродам. Аннары частицы заметенного өзлексез хәрәкәт ачык сетка пояс һәм колесниковка, шул противоположных юнәлешләре. Пояс двигает частицы янында һәр электрода бу противоположных концах сепаратора. Электр җиһазлары басуда, кирәк хәрәкәт итә гына частицы крошечную өлешен санти өчен переместить частицы сул өчен правую движущийся агымы. The counter current flow of the separating particles and continual triboelectric charging by particle collisions provides for a multi-stage separation and results in excellent purity and recovery in a single-pass unit. Югары тизлек белән хәрәкәт тасмалар таратканнар тәэмин итә, шулай ук бик югары җитештерүчәнлек, кадәр 40 тонна-сәгатенә бер сепаратор. Аша контроль төрле параметрлары процессын , the device allows for optimization of mineral grade and recovery.
Дөге. 1. Схемасы трибоэлектрический сепаратор поясы
Төзелеш исә сепаратора булып, чагыштырмача гади генә кебек. Поясы һәм бәйле роликлар булып автоспорт движущимися өлешләре. Электроды писчебумажными торалар һәм берсе шактый нык материал. Пояс изготовлен берсе-пластик. Озынлыгы электрода сепаратора тәшкил итә, приблизительно 6 метрдан (20 футов.) ә киңлеге 1.25 метрдан (4 футов.) өчен тулы күләмен коммерция бүлекләре. Кереме энергиясе азрак 2 киловатт-сәгатенә бер тонна обработанного материал белән зур өлеше энергиясе, потребляемой ике моторами управляя поясы.
Дөге. 2. Нәрсә аеру зонасы
Процесс тулысынча коры, таләп итми, өстәмә материаллар да җитештерә суларны яки атмосферага . For mineral separations the separator provides a technology to reduce water usage, киңәйтергә запасы тормыш һәм/яки торгызу һәм кабат үткәрелгән эшкәртү хвостов.
Компактность системасын тәэмин итә гибкость " конструкцияләр урнаштыру . 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 1997. Технология нәтиҗәле бу бүлекчәсе частиц углерод нче неполного яну күмер, нче стекловидные алюмосиликатные минераль частицы " пепел. Технология мөһим роль уйный, тәэмин итү, эшкәртү, минераль золы уноса буларак алыштыру цемент җитештерүдә бетон.
Шулай 1995, өчен 20 million tonnes of product fly ash have been processed by the STET separators installed in the USA. Индустриаль тарих оча сепарации золы китерелгән Табл. 4.
In minerals processing, the triboelectric belt separator technology has been used to separate a wide range of materials including calcite/quartz, тальк/магнезитовые, һәм барит/кварц.
Дөге. 3. Commercial tribo-electrostatic belt separator
Таблица 4. Сәнәгый куллану Трибо-электростатической сепарации пояс өчен пепла.
| Утилита / электростанция | Урнашуы | Башы коммерция операцияләре | Детальләрен урнаштыру |
|---|---|---|---|
| Герцог Энергиясе – Станция Роксборо | Төньяк Каролина, АКШ | 1997 | 2 Сепараторы |
| Тален Энергиясе- Брэндон Буенда | Мэриленд, АКШ | 1999 | 2 Сепараторы |
| Шотландские Хакимияте- Станциясе Longannet | Шотландия Бөекбритания | 2002 | 1 Сепаратор |
| Электрический Джексонвилл-Иске. Johns River Power Park | Флорид АКШ | 2003 | 2 Сепараторы |
| South Mississippi Electric Power -R.D. Морроу | Миссисипи, АКШ | 2005 | 1 Сепаратор |
| Яңа Хакимият Белән Belledune Брансуик | Нью-Брансуик Канада | 2005 | 1 Сепаратор |
| Компания RWE гсостояние-Дидкот вокзалы | Англия Бөекбритания | 2005 | 1 Сепаратор |
| Talen Energy-Brunner Island Station | Пенсильвания, АКШ | 2006 | 2 Сепараторы |
| Тампа Электрический-Зур Станциясе Согнуть | Флорид АКШ | 2008 | 3 Сепараторы |
| Компания RWE гсостояние-отель aberthaw вокзалы | Уэльс Бөекбритания | 2008 | 1 Сепаратор |
| ЭДФ Энерджи-Көнбатыш станциясе Бертон | Англия Бөекбритания | 2008 | 1 Сепаратор |
| Тагын да күбрәк ләззәт (Lafarge Cement /Ciech Janikosoda JV) | Польша | 2010 | 1 Сепаратор |
| Корея Егәрлек Көньяк-Көнчыгыш - Yeongheung | Көньяк Корея | 2014 | 1 Сепаратор |
| PGNiG Termika-Sierkirki | Польша | 2018 | 1 Сепаратор |
| Taiheiyo Cement Company-Chichibu | Япония | 2018 | 1 Сепаратор |
| Armstrong Fly Ash- Eagle Cement | Филиппин | 2019 | 1 Сепаратор |
| Корея Егәрлек Көньяк-Көнчыгыш - Samcheonpo | Көньяк Корея | 2019 | 1 Сепаратор |
2.2.2 Стендовое сынау
Standard process trials were performed around the specific goal to increase Al_2 O_3 concentration and to reduce the concentration of gangue minerals. Сынаулар үткәрелгән бу сепараторе настольная астында замес шартлары, with testing performed in duplicate to simulate steady state, and ensure that any possible carryover effect from the previous condition was not considered. Алдында елдан-сынау, a small feed sub-sample was collected (урыннар сыйфатында "азык"). Шул урнаштыру барлык операцияләр переменные, материал бирелә шул сепаратор столу ярдәмендә электр вибрационного питателя үзәге аша сепаратора өстәл . Үрнәкләре җыелган иде ахырында һәр эксперимент һәм авырлыкка продукция 1 (урыннарны ничек "Е1") һәм соңгы продукт 2 (урыннарны ничек "Е2") билгеләнде нигезендә коммерческом подсчитывая маштаб. For bauxite samples, ‘E2’ corresponds to the bauxite-rich product. Өчен һәр подвыборок (т. е., Ашатырга, Е1 һәм Е2) ЛОИ, main oxides composition by XRF, reactive silica and available alumina was determined. XRD characterization was performed on selected sub-samples.
3.0 Нәтиҗәләре буенча фикер алышу
3.1. Үрнәкләре Минералогия
Results of the quantitative XRD analyses for feed samples are included in Table 5. The majority of the samples were primarily composed of gibbsite and varying amounts of goethite, hematite, каолинит, and quartz. Ilmenite and anatase were also evident in minor amounts in the majority of the samples.
There was a change in the mineral composition for S6 and S7 as these feed samples were primarily composed of diaspore with minor amounts of calcite, hematite, гетит, boehmite, каолинит, гиббсит, кварцевые, anatase, and rutile being detected. An amorphous phase was also detected in S1 and S4 and ranged from approximately 1 өчен 2 percent. This was probably due to either the presence of a smectite mineral, or non-crystalline material. Since this material could not be directly measured, results for these samples should be considered approximate.
3.2 Лабораторными экспериментами
A series of test runs were performed on each mineral sample aimed at maximizing Al2O3 and decreasing SiO_2 content. Species concentrating to the bauxite-rich product will be indicative of positive charging behavior. Results are shown in Table 6
Таблица 5. XRD analysis of feed samples.
Таблица 6. Summary Results.
Testing with the STET benchtop separator demonstrated significant movement of Al2O3 for all samples. Separation of Al2O3 was observed for S1-5 which were mainly gibbsite, and also for S6-7 which were mainly diaspore. Моннан тыш,, башка мөһим элементлары бу Fe2O3, SiO2 һәм TiO2 күрсәттеләр значительного хәрәкәте күпчелек очракта. For all samples, хәрәкәт югалту каршындагы прокаливании (ЛОИ) аннан соң хәрәкәт АL2О3. In terms of reactive silica and available alumina, for S1-5 which are nearly all gibbsite (aluminum trihydrate) values should be considered at 145°C while for S6-7 for which the dominant mineral is diaspore (aluminum monohydrate) values should be assessed at 235°C. For all samples testing with the STET benchtop separator demonstrated a substantial increase in available alumina and a significant reduction in reactive silica to product for both trihydrate and monohydrate bauxite samples. Movement of major mineral species was also observed and is graphically shown below in Figure 4.
In terms of mineralogy, STET benchtop separator demonstrated concentration of the alumina bearing species gibbsite and diaspore to the bauxite-rich product while simultaneously rejecting other gangue species. Саннар 5 һәм 6 show selectivity of mineral phases to the bauxite-rich product for trihydrate and monohydrate samples, димәк. Selectivity was calculated as the difference between the mass deportment to product for each mineral species and the overall mass recovery to product. A positive selectivity is indicative of mineral concentration to the bauxite-rich product, and of an overall positive charging behavior. Киресенчә, a negative selectivity value is indicative of concentration to the bauxite-lean coproduct, and of an overall negative charging behavior.
For all trihydrate low-temperature samples (т. е., S1, S2 and S4) kaolinite exhibited a negative charging behavior and concentrated to the bauxite-lean co-product while gibbsite concentrated to the bauxite-rich product (Дөге. 5). For all monohydrate high-temperature samples (т. е., S6 and S7) both reactive silica bearing minerals, kaolinite and quartz, exhibited a negative charging behavior. For the latter, diaspore and boehmite reported to the bauxite-rich product and exhibited a positive charging behavior (Дөге. 6).
Дөге. 5. Selectivity of mineral phases to product.
Дөге. 6. Selectivity of mineral phases to product.
Measurements of available alumina and reactive silica demonstrate substantial movement. For low temperature bauxites (S1-S5), the amount of reactive silica present per unit of available alumina was reduced from 10-50% on a relative basis (Дөге. 7). A similar reduction was observed in the high temperature bauxites (S6-S7) as can be seen in Figure 7.
The bauxite to alumina ratio was calculated as the inverse of the available alumina. The bauxite to alumina ratio was decreased by between 8 – 26% in relative terms for all samples tested (Дөге. 8). This is meaningful as it represents an equivalent reduction in mass flow of bauxite that needs to be fed to the Bayer process.
Дөге. 7. Reactive SiO2 per unit of Available Al2O3
Дөге. 8. Bauxite to Alumina ratio.
3.3 Фикер алышу
The experimental data demonstrates that the STET separator increased available Al2O3 while simultaneously reducing SiO_2 content. Дөге. 9 presents a conceptual diagram of the expected benefits associated to the reduction of reactive silica and the increase of available alumina prior to the Bayer Process. The authors calculate that the financial benefit to an alumina refiner would be in the range of $15-30 USD per ton of alumina product. This reflects avoided cost from caustic soda lost to de-silicaton product (DSP), energy savings from reducing the input of bauxite to the refinery, reduction in red mud generation and a small revenue stream generated from selling the low-grade bauxite by-product to cement producers. Дөге. 9 outlines the expected benefits of implementing STET triboelectrostatic technology as a mean to pre-concentrate bauxite ore prior the Bayer process.
Installation of the STET separation process for bauxite pre-processing could be performed either at the alumina refinery or the bauxite mine itself. Әмма, the STET process requires dry grinding of the bauxite ores prior to separation, to liberate the gangue, therefore the logistics of grinding and processing the bauxite at the refinery may be more straightforward.
As one option – the dry bauxite would be ground using well-established dry grinding technology, for example a vertical roller mill or impact mill. The finely ground bauxite would be separated by the STET process, with the high-alumina bauxite product sent to the alumina refinery. The installation of dry grinding would allow for the elimination of wet grinding traditionally used during the Bayer process. It is assumed that the operating cost of dry grinding would be roughly comparable to the operating cost of wet grinding, especially considering the wet grinding performed today is performed on a highly alkaline mixture, leading to considerable maintenance costs.
The dry low-grade bauxite co-product (tailings) from the separation process would be sold to cement manufacture as an alumina source. Bauxite is commonly added to cement manufacture, and the dry co-product, unlike red mud, does not contain sodium which would prevent its use in cement manufacture. This provides the refinery with a method of valorizing material that would otherwise exit the refining process as red mud, and would require long term storage, representing a cost.
An operating cost calculation performed by the authors estimates a project benefit of $27 USD per ton of alumina, with the major impacts achieved through reduction in caustic soda, reduction in red mud, valorization of the co-product and fuel savings due to lower volume of bauxite to the refinery. Therefore an 800,000 ton per year refinery could expect a financial benefit of $21 M USD per year (Дөге. 10). This analysis does not consider potential savings from reducing import or logistics costs of bauxite, which may further enhance the project return.
Дөге. 10. Benefits of Reactive Silica Reduction and Available Alumina increase.
4.0 Нәтиҗәләр
In summary, dry processing with the STET separator offers opportunities to generate value for bauxite producers and refiners. The pre-processing of bauxite prior to refining will reduce chemical costs, lower the volume of red mud generated and minimize process upsets. STET technology could allow bauxite processors to turn non-metallurgical grade into metallurgical grade bauxite – which could reduce need for imported bauxite and/or extend exiting quarry resource life. STET process could also be implemented to generate higher quality non-metallurgical grade and metallurgical grade bauxite, and cement grade bauxite by-products prior to the Bayer process.
The STET process requires little pre-treatment of the mineral and operates at high capacity – up to 40 tones per hour. Energy consumption is less than 2 kilowatt-hours per ton of material processed. Моннан тыш,, the STET process is a fully commercialized technology in minerals processing, and therefore does not require the development of new technology.
Сылтамалар
1. Bergsdal, Håvard, Anders H. Strømman, and Edgar G. Hertwich (2004), “The aluminium industry-environment, technology and production”.
2. Дас, Subodh K., and Weimin Yin (2007), “The worldwide aluminum economy: The current state of the industry” JOM 59.11, ПП. 57-63.
3. Vincent G. Холм & Errol D. Sehnke (2006), “Bauxite”, in Industrial Minerals & Rocks: Товарлар, Базарлар, and Uses, Society for Mining, Metallurgy and Exploration Inc., Englewood, Хезмәттәшлек, ПП. 227-261.
4. Evans, Ken (2016), “The history, challenges, and new developments in the management and use of bauxite residue”, Journal of Sustainable Metallurgy 2.4, ПП. 316-331
5. Gendron, Robin S., Mats Ingulstad, and Espen Storli (2013), “Aluminum ore: the political economy of the global bauxite industry”, UBC Press.
6. Hose, С. Р. (2016), “Bauxite mineralogy”, Essential Readings in Light Metals, Springer, Cham, ПП. 21-29.
7. Authier-Martin, Monique, һ. б. (2001),”The mineralogy of bauxite for producing smelter-grade alumina”, JOM 53.12, ПП. 36-40.
8. Холм, " . Г., and R. Дж. Robson (2016), “The classification of bauxites from the Bayer plant standpoint”, Essential Readings in Light Metals, Springer, Cham, ПП. 30-36.
9. Songqing, Gu (2016). “Chinese Bauxite and Its Influences on Alumina Production in China”, Essential Readings in Light Metals, Springer, Cham, ПП. 43-47.
10. Habashi, Fathi (2016) “A Hundred Years of the Bayer Process for Alumina Production” Essential Readings in Light Metals, Springer, Cham, ПП. 85-93.
11. Adamson, Ә. N., Е. Дж. Bloore, and A. Р. Carr (2016) “Basic principles of Bayer process design”, Essential Readings in Light Metals, Springer, Cham, ПП. 100-117.
12. Anich, Ivan, һ. б. (2016), “The Alumina Technology Roadmap”, Essential Readings in Light Metals. Springer, Cham, ПП. 94-99.
13. Liu, Wanchao, һ. б. (2014), “Environmental assessment, management and utilization of red mud in China”, Journal of Cleaner Production 84, ПП. 606-610.
14. Evans, Ken (2016), “The history, challenges, and new developments in the management and use of bauxite residue”, Journal of Sustainable Metallurgy 2.4, ПП. 316-331.
15. Liu, Йонг, Chuxia Lin, and Yonggui Wu (2007), “Characterization of red mud derived from a combined Bayer Process and bauxite calcination method”, Journal of Hazardous materials 146.1-2, ПП. 255-261.
16. АКШ. Geological Survey (USGS) (2018), “Bauxite and Alumina”, in Bauxite and Alumina Statistics and information.
17. Paramguru, Р. К., П. Белән. Рат, and V. Н. Misra (2004), “Trends in red mud utilization–a review”, Mineral Processing & Extractive Metall. Rev. 2, ПП. 1-29.
18. Manouchehri, С, Ханумантха Роа, К, & Forssberg, К (2000), “Review of Electrical Separation Methods, Бер өлеше 1: Фундаменталь аспектлары, Файдалы казылмалар & Metallurgical Processing”, күләме. 17, юк,. 1, ПП 23-36.
19. Manouchehri, С, Ханумантха Роа, К, & Forssberg, К (2000), “Review of Electrical Separation Methods, Бер өлеше 2: Практик Соображения, Файдалы казылмалар & Metallurgical Processing”, күләме. 17, юк,. 1, ПП 139-166.
20. Ролстон Турында. (1961), Электростатическое бүленеш катнаш сыпучих продуктлары, Нәшрият "Эльзевир", чыккан матбугат.
