Ultrafine Tailings Research Articles

Micro-scale mechanism of sealed water seepage and thickening from tailings bed in rake shearing thickener

Paste and Thickened Tailings (PTT) technology has the advantages of water-saving, dam safety, and environmentally friendly, which can improve tailings disposal and backfill operation. In the process of thickening preparation, the ultra-fine tailings particles are prone to form suspended water-locking flocs, which are severely detrimental to the underflow concentration improvement in the thickener. This study focuses on the deep cone thickener underflow density improvement. The high-precision CT scanning and three-dimensional reconstruction technology were used to explore the pore structure shear evolution to enhance underflow slurry dewatering behavior and reveal the thickening mechanism. Results show that when the shearing rate of the rake is two revolutions per minute (rpm), the concentration of tailings underflow rises from 59.2% wt to 68.5% wt, increases by 15.71%. The rake shearing breaks the pore structure of the flocs network, the pores quantity increases and the porosity decreases by 21.74%. After shearing, suspended particles fill the pores, the pore connectivity decreases by 26.74%, the absolute permeability decreases by 31.35%, the sealed pore water is discharged, and the bed slurry can be thickened. The study can improve the utilization rate of tailings (from classified tailings to whole tailings), make the thickening process going deep(raising high concentration slurry to paste slurry), and increase the backfill capacity (backfill underground goaf in time), so as to effectively reduce the tailing pond and goaf quantity.

An Experimental Study on Strength Characteristics and Hydration Mechanism of Cemented Ultra-Fine Tailings Backfill

In order to study the strength characteristics and hydration mechanism of the cemented ultra-fine tailings backfill (CUTB), the uniaxial compressive strength (UCS) tests of CUTB and cemented classified tailings backfill (CCTB) with cement-tailing ratio (C/T ratio) of 1:4 and 1:6 and curing ages of 3, 7, 14 and 28 days were carried out. The hydration products and morphology of the cemented paste backfill (CPB) were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the UCS of the CUTB is significant compared to the CCTB under the same conditions; the greater the C/T ratio and curing age, the greater the UCS difference value. The UCS growth curve of the CUTB is approximately S-shaped, and there is a relationship between the UCS and curing age. The ultra-fine tailings particles in the CUTB have potential activity; in the alkaline environment–generated cement hydration, active SiO2 and Al2O3 particles undergo secondary hydration reaction, resulting in no or very little Ca (OH)2 crystals generated in the CUTB, and the hydration products and morphology are also different.

Rheological Properties of Ultra-Fine Tailings Cemented Paste Backfill under Ultrasonic Wave Action

Ultra-fine tailings cemented paste backfill (UCPB) exhibits special rheological characteristics with the effect of an ultrasonic sound field. In this study, in order to explore the thickening effect of slurry under ultrasonic wave action, we examined the rheological properties with ultrasonic wave tests of UCPB and the rheological properties after ultrasonic wave tests of UCPB. We found that the rheological curve of the slurry changed; the Herschel–Bulkley (HB) model in the initial state transformed into the Bingham model under the action of ultrasound. Ultrasonic waves have a positive effect on reducing slurry viscosity and yield stress. The rheological test of the slurry with ultrasonic wave action had a positive effect on significantly reducing the apparent viscosity and initial yield stress of slurry with a 62% mass concentration. The rheological test of slurry with ultrasonic wave action and the rheological test after ultrasonic wave action both have positive effects on reducing the viscosity and yield stress of the slurry with a 64% to 68% mass concentration; the overall effect of reducing the viscosity and yield stress of UCPB is greater after ultrasonic wave action of UCPB.

Effect of fine particle content on mechanical properties of tailings under high confining pressure

The influence of dam height and fine grain content on the stability of the tailings dam is not a simple function. According to the layering rules of ultra-fine tailings in deep and large tailings ponds, four kinds of fine-grained (particle size less than 0.074 mm) tailings materials were prepared. Simulation of the physical and mechanical properties of ultra-fine tailings during the accumulation of high tailings dam was conducted. The optimal tailings mix ratio was determined through multi-physical index experiments and multi-evaluation index analysis. Multi-stage confining pressure triaxial shear failure test was conducted using TSZ-6A strain-controlled triaxial apparatus to recur the change law of mechanical properties of tailings based on large amounts of experimental data. Through high-precision laser particle size analysis and analysis of pore water pressure at full pressure, intrinsic influence factors and mechanism of physical and mechanical properties from the perspective particle fracture and pore water were analyzed. Finally, using elementary error theory, the method for evaluating Mohr strength parameter of tailings materials was modified, and the factor that caused confining pressure to change the structure of the material was taken into account.

Flocculation Settling Characteristics of Ultra-Fine Iron Tailings with Rich Gypsum

Because of the uniqueness of geological mineralization, tailings obtained from Chenchao Iron Mine have low SiO2 content of only 27.80%. Content of Al2O3 and MgO is 13.31% and CaSO4 is 22.09%. The fineness modulus of the ores is large enough for convenient mineral separation, thus resulting in 16.03% −5 μm particles and 27.76% −10 μm particles in the tailings, respectively. The average particle size is only 69.36 μm; it belongs to the category of very fine tailings. The natural sedimentation of tailings is extremely slow due to the comprehensive effects of their physical and chemical properties. Hence, sedimentation tests using four types of flocculating agents are conducted to accelerate the sedimentation of the tailings of Chenchao Iron Mine. Compared with natural sedimentation, the flocculating sedimentation is considerably quicker. Among the four flocculants, the sedimentation of sample using the special BASF flocculant is the fastest. When the tailings of 1 ton add this flocculant of 20 g, the maximum settling concentration reaches 60.98% after 40 min and its special gravity is 1.577 g/cm3, thus it fulfills future requirements of filling technologies. As the largest iron mine in the mid-southern region of China, Chenchao Iron Mine must turn to filling mining. This study can provide technological support for goaf management and environment-friendly treatment of solid waste in the Yangtze River basin, which plays important roles in ecological protection.

Experimental study on the utilization of steel slag for cemented ultra-fine tailings backfill

To improve the properties of cemented ultra-fine tailings backfill (CUTB), the authors intend to outline the framework of the effect of steel slag (SS) on the properties of CUTB. Therefore, flowability, unconfined compressive strength (UCS), hydration products, and pore structure were used to investigate the properties of CUTB samples. The results showed that the incorporation of SS increased the flow spread by increasing the water film thickness (WFT). Unconfined compressive strength (UCS) was observed to be enhanced when the content of SS did not exceed 20 wt%. Hydration phase evolution tested by X-ray diffraction, thermogravimetry, and thermodynamic modeling indicated the additional formation of hydrotalcite-like phases (Ht). This contributed to a denser microstructure. Besides, lower total porosity and critical pore diameter (dcr) obtained by mercury intrusion porosimeter tests were observed in samples with SS addition, which could favor the strength development. On the other hand, toxicity characteristic leaching procedure (TCLP) results indicated that the CUTB exhibited good environmental performance.

Analysis of the Sedimentation Characteristics of Ultrafine Tailings Based on an Orthogonal Experiment

Due to continuous improvements in the beneficiation process, the size of tailings has decreased. In many mines, more than 50% of the total tailings are finer than 74 μm. Ultrafine tailings exhibit a slow settling velocity and uneven settling, which pose new challenges to the safety and stability of tailings dams. In this paper, ultrafine iron tailings from the Makeng Iron Mine in Longyan City, Fujian Province, were used as the research object. A four-factor, three-level orthogonal test method was used to study the sedimentation characteristics of ultrafine tailings with four common curing agent materials, including polyacrylamide, polyaluminum chloride, polyaluminum sulfate, and polyferric sulfate. The results show that when the pulp concentration is 30%, the polyacrylamide is cationic and the molecular weight is 10 million, the optimal content of the flocculant is 3‰, the optimum dose of the polyaluminum chloride with a content of 28 is 0.1‰, the optimum dose of polyaluminum sulfate is 1‰, and the optimum dose of polymeric ferric sulfate is 1‰. When the flocculant is mixed according to the proportion of 2‰ polyacrylamide, 0.05‰ polyaluminum chloride, 1‰ polyaluminum sulfate, and 1.0‰ polyferric sulfate, the sedimentation speed of the ultrafine tailings is fast, and the supernatant liquid is clear. The results of multivariate nonlinear regression analysis of the sedimentation curve show that the primary and secondary factors affecting sedimentation are polyacrylamide > polyaluminum sulfate > polyaluminum chloride > polyferric sulfate. When the optimal ratio is applied, the cohesion (c) of ultrafine tailings increases from 27 kPa to 68.75 kPa and the internal friction angle (φ) increases from 25.53° to 27.53°, which shows that the shear strength improves and the stability of the tailings dam increases. The economic analysis of the composite flocculant with the optimal ratio shows that the flocculant with the optimal proportion has an obvious economic advantage over polyacrylamide alone.

The effect of ferrous ions on hydraulic conductivity in fine tailings

The clogging of drainage facilities, which reduces the permeability coefficient, raises the phreatic line, and increases the possibility of seepage damage, seriously impacts the safety of tailings dams. The core cause of clogging is the oxidation of active minerals or ions and the formation of gelatinous materials. These materials, the most typical of which are active iron minerals (such as pyrite or ferrous ions), are adsorbed in the percolation passage to block the flow of liquid. This paper aims to study the effect of ferrous ions on the hydraulic conductivity of fine tailings. First, we introduce a new apparatus based on the column experiment to examine the permeation characteristics of fine tailings. Second, a systematic experimental study was conducted to obtain the effect of ferrous ion content, nonwoven geotextile layer number, and specimen height (reflecting the length of the seepage path) on the tailings permeability ratio using this apparatus. Third, scanning electron microscopy (SEM) was performed on selected geotextile samples that underwent filtration to assess the clogging mechanism. The results show that the ferrous ions were oxidized to form the low solubility iron(III) oxide-hydroxide (Fe(OH)3), which was deposited or adsorbed in the percolation channel and caused chemical clogging. Meanwhile, in the case of more geotextile layers or slower seepage rates, the blockage of the fine tailings formed faster in the penetration experiment. According to the results of the SEM, there were glue coverings on the fiber surface, and ultrafine tailings particles (−10 μm) were adsorbed, adhered and deposited on it and formed a chemical-physical clogging.

South African Coal Tailings Bioflotation for Desulphurization Using <i>Mycobacterium phlei</i>

The large cost of the flotation reagents used in the first-of a two-stage desulphurization flotation process, developed for the treatment of South African waste coal ultrafine tailings, has motivated the investigation of Mycobacterium phlei as an alternative coal bioflotation reagent. Attachment experiments were used to confirm that the microbe attaches to South African coal selectively over pyrite or gangue material present in the coal. Subsequent small scale batch floats using M. phlei successfully showed that the bioflotation process can upgrade and desulphurize the coal tailings feed, and delivered approximately the same concentrate yields as the optimised chemical flotation conditions (37 – 39%). However, a projected financial feasibility analysis that assessed the incorporation of the M. phlei into the two-stage flotation process found that the bioflotation process was not profitable due to the very large flow rate of cells required (2×1016 cells/ton coal) and the associated additional equipment and growth media component costs.

Backfilling behavior of a mixed aggregate based on construction waste and ultrafine tailings

To study the possibility of utilizing mixed construction waste and ultrafine tailings (CW&UT) as a backfilling aggregate that can be placed underground in a mine, physicochemical evaluation, proportioning strength tests, and pumpability experiments were conducted. It was revealed that mixed CW&UT can be used as a backfilling aggregate due to the complementarities of their physicochemical properties. In addition, as the results of the proportioning strength tests show, the compressive strength of a cemented CW&UT backfilling specimen cured for 28 days, with a mass fraction of 72–74%, a cement-sand ratio of 1:12, and a CW proportion of 30%, is higher than 1.0 MPa, which meets the safety requirements and economic consideration of backfilling technology in many underground metal mines, and can also be enhanced with an increase in the cement-sand ratio. The results of the pumpability experiments show that cemented backfilling slurry based on CW&UT can be transported to the stope underground with a common filling pump, with a 16.6 MPa maximum pressure, with the condition that the time of emergency shut-down is less than approximately 20 min. All in all, the research to utilize mixed CW&UT as a backfilling aggregate can not only provide a way to dispose of CW&UT but also will bring large economic benefits and can provide constructive guidance for environmental protection.

A practice of ultra-fine tailings disposal as filling material in a gold mine

A practice of cemented backfill technology with ultra-fine tailings in a gold mine was comprehensively presented, and a series of tests were conducted in accordance with the peculiar properties of ultra-fine tailings and the mining technology conditions. The test results show that, the tailings from Shuiyindong Gold Mine have a great grinding fineness, with the average particle diameter 22.03 μm, in which the ultra-fine particles with the diameter below 20 μm occupying 66.13%. The analysis results of chemical components of tailings indicate that the content of SiO2 is relatively low, i.e., 33.08%, but the total content of CaO, MgO and Al2O3 is relatively high i.e., 36.5%. After the settlement of 4–6 h, the tailing slurry with the initial concentration of 40% has the maximum settling concentration of 54.692%, and the corresponding maximum settling unit weight is 1.497 g/cm3. During the field application, the ultra-fine tailings and PC32.5 cement were mixed with the cement-tailings ratios of 1:3–1:8, and the slurry concentration of 50 wt% was prepared. Using the slurry pump, the prepared cemented backfill slurries flowed into the goaf, and then the strength of the cemented backfill body met the mining technique requirements in Shuiyindong Gold Mine, where the ore body has a smooth occurrence, with the average thickness of approximately 2 m and the inclination angle ranging from 5 to 10°.

Fly-ash-based magnetic coagulant for rapid sedimentation of electronegative slimes and ultrafine tailings

To accelerate the flocculation and sedimentation of the electronegative slimes and ultrafine tailings in Sijiaying, a fly-ash-based magnetic coagulant (FMC) was prepared by leaching fly ash in acid mine drainage. Univariate experiments, Plackett–Burman design, steepest-ascent method, and Box–Behnken design were employed to obtain the optimum levels of the factors for the maximum settled height (SH). In addition, the action mechanism of FMC was analyzed and the application effects in Sijiaying were evaluated. The results show that the neutralization and magnetic separation are the main action mechanism of FMC. Significant economic and environmental benefits will be brought by FMC through reducing the flocculant costs greatly, recycling the overflow water for beneficiation directly, and reusing the fly ash and acid mine drainage environmentally.

Dynamic experiments on flocculation and sedimentation of argillized ultrafine tailings using fly-ash-based magnetic coagulant

In order to accelerate the sedimentation of super-large-scale argillized ultrafine tailings with bad features such as low settling velocity, muddy overflow water, and large flocculant dosage, a fly-ash-based magnetic coagulant (FAMC) was used in a dynamic experimental device. To obtain the best possible combination of the impact factors (magnetic intensity, FAMC dosage, flocculant dosage, and feed speed) for minimum overflow turbidity, a response surface methodology test coupled with a four-factor five-level central composite design was conducted. The synergy mechanism of FAMC and flocculant was analyzed based on the potential measurement and scanning electron microscopy. The results show that the flocculant dosage, overflow turbidity, and solid content can be reduced by 50%, 90%, and 80%, while the handling capacity per unit and efficiency of backfill and dry stacking can be promoted by 20%, 17%, and 13%, respectively, with a magnetic intensity of 0.3 T, FAMC dosage of 200 mL/t, flocculant dosage of 30 g/t, and feed speed of 0.6 t/(m2(h). Therefore, synergy of FAMC and flocculant has obvious efficiency in saving energy and protecting the environment by allowing 70×106 t/a of argillized ultrafine tailings slurry to be disposed safely and efficiently with a cost saving of more than 53×106 Yuan/a, which gives it great promise for use in domestic and foreign mines.

Assessment and Mechanism Investigation of Selective Flocculation Process for Ultrafine Chromite Particle

During beneficiation of low-grade chromite ore, huge amounts of ultrafine tailings are generated and contain substantial metal values which need to be recovered. Selective flocculation technique is one of the processes for beneficiation of ultrafine particles. Here an attempt was made to establish selective flocculation process by using two types of synthetic mixtures. In addition to this, selective flocculation was also attempted on natural tailings. It was found that it is possible to enrich the chromite value using the selective flocculation process. The selectivity of the wheat starch to the chromite mineral was also investigated using image analysis, FTIR analysis, and zeta potential analysis.

Research on Special Cement for the Concrete with Ultra-Fine Iron Tailings

This essay is the subject of national eleventh five support schemes: The analysis of key technology on emission reduction and comprehension utilization of solid waste from large iron ore mine (Number:2008BAB32B14).For the concrete with ultra-fine iron tailings the research on the new special cement has been successfully prepared by means of using a low dosage of crystal-core-element named CCE for short (which has an excellent capability to accelerate the hydration speed and develop the strength of the cement)and high percentage of blast furnace slag and other several industrial residue. Compared to the ordinary Portland cement grade 42.5, the new cement has several outstanding virtues such as lower use level of cement clinker, higher level usage of industrial residue and lower cost. According to the cement standard GB175-2007, strength of special cement sample NO.3 is same as the ordinary Portland cement grade 42.5 with the standard sand. When with ultra-fine iron tailings, the new special cement has higher strength after 28days than the OPC. That shows the special cement has an excellent long-term performance of concretion. The manufacturing cost of the new special cement sample NO.3 is decreased by 20.76% than the ordinary Portland cement grade 42.5, that will bring a great environment and economic effect.

Iron ore slimes flotation

This investigation addressed the processing of ultrafine tailings (slimes) from an iron ore concentrator via reverse cationic flotation to produce pellet feed fines, despite the traditional view that ultrafine particles do not float. Following size analyses, chemical and mineralogical characterisation, desliming and flotation tests were performed aiming at verifying the flotation behaviour of the slimes. Different dosages of collector and depressant were used. The promising results of the laboratory scale tests led to carrying out pilot scale tests with the currently produced slimes, and the slimes that will be generated in the future, after the commissioning of the mining company’s expansion project. It was observed that a reverse cationic column flotation process, using high depressant dosage, was selective, yielding high grade concentrates with low impurity content at high levels of iron recovery, approximately 60% mass recovery and 80% metallic recovery in the flotation stage. Excellent valuable product grade (less than 1% silica) and reject product grade (approximately 12% iron) were achieved, resulting in high selectivity levels. The overall mass recovery reached 20%.

Aproveitamento econômico das lamas de ferro

A mineração iniciou suas atividades lavrando depósitos de alto teor, sem preocupação em maximizar seu aproveitamento. Ainda hoje, milhões de toneladas de minerais úteis são descartados anualmente para as barragens de rejeitos. Nesse trabalho, foram realizados testes de deslamagem e flotação com lamas de minério de ferro, primeiramente em escala de bancada. Várias dosagens de coletor e depressor foram utilizadas. Os resultados promissores dos testes em escala de bancada levaram a testes em escala-piloto. Foi constatado que, com o processo de flotação catiônica reversa em colunas, utilizando-se dosagem mais elevada de depressor, consegue-se recuperação mássica da ordem de 60% e 80% de recuperação metálica, 9 a 12 % de Fe no rejeito, 0,55 % a 0,90 % de SiO2 no concentrado (SiO2+Al2O3 < 2,00 %), além de alta seletividade no processo. A utilização da flotação de ultrafinos é uma alternativa econômica para o aumento das recuperações nos empreendimentos mineiros. A flotação de ultrafinos também pode ser avaliada para a redução ou tratamento de efluentes descartados no meio ambiente.

Optimization of multigravity separation for recovery of ultrafine coal

Enhanced gravity separation appears to be one of the most promising methods for processing all types of <200-µm coal feeds and tailings. Systems based on this technology are reviewed, and the results of investigations based on C900 Multi-Gravity Separator tests conducted to assess the treatment of <200-µm, extremely difficult-to-wash coal settling pond tailings are presented. Multi-Gravity Separator processing tests of ultra-fine tailings with a high clay particle size content (22.6% <10 µm and 60.1% <40 µm) and a 69.56% ash content show that this material can be effectively treated after desliming (<10 µm) of clay-size particles to produce a coal with a 20.6% ash at a separator combustible material recovery of 69.3%. Desliming is shown to be critical in reducing coal ash content and combustible material recovery. Similar improvements are anticipated in the recovery and separation processes for other enhanced gravity separation systems from the desliming of feeds. Although not a conventional form of treating Multi-Gravity Separator data, the existence of well-defined polynomial relationships based on the product of drum shake amplitude and shake frequency relative to product coal recovery, product ash content and yields at varying wash water flows is demonstrated. Low-amplitude and intermediate- to high-frequency bed agitation are shown to produce optimum ash reduction results.