Parameters of hydraulic fracturing and disintegration of impervious rocks while preparing blocks for leaching

Conclusions 1. The maximum water injection pressure for hydrofracturing of Blyava ores was 12.1–12.9 MPa and for hydrodisintegration, 4.5–5.5 MPa. The calculated values of these pressures differ from the experimental ones by 20–25% and 25–36% respectively, which is satisfactory for natural-scale studies.2. The probability of hydrofracturing or hydrodisintegration of the mass depends a great deal on the distance between the packer and the borehole face. It has been demonstrated experimentally that hydrofracturing occurred at a distance of 0.1–0.6 m and only hydrodisintegration was noticed at a distance of 4–10.2 m. These data show that, all other conditions being equal, the packer (interpacker) spacing of the boreholes is of great importance for producing, in practice, some type of hydrodynamic impact on the rock mass.3. Water injection through boreholes into the ore body under conditions of hydrofracturing and hydrodisintegration showed the real possibility of establishing a hydrodynamic link between boreholes at distances of 5 m, 10 m, and greater.4. The technology and equipment developed by the Institute of Mining make it possible to prepare blocks of impervious ores for leaching by employing hydrofracturing and hydrodisintegration of rocks and creating in the block a borehole — slit — borehole system.5. As a result of suffosion of the ore, slime is released intensely from the drainage boreholes, which is typical for hydrofracturing and hydrodisintegration processes and for subsequent fluid injection under pressure. This may be used to augment the performance of the borehole — slit — borehole system.6. If conditions in the mining industry become favorable, it would be advisable to continue the operations, the essential features of which are elucidated in this paper.Translated from Fiziko-tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 5, pp. 100–105, September–October, 1996.     

Two-dimensional mathematical model of leaching dynamics for a cracked and porous ore mass

Far-East Branch, Russian Academy of Sciences, Magadan. Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 3, pp. 87–95, May–June, 1993.     

Enhanced hydrochloric acid leaching of nickel

Dissolution rates of nickel in hydrochloric acid with and without the presence of thiourea have been studied by means of rotating disc methods with solution analysis. In the absence of thiourea an apparent activation energy value of 61.1 ± 12.1 kJ. mol⁻¹ was determined. Such a high value is inconsistent with a diffusion controlled process and this was supported by the lack of dependency of the dissolution rate on rotational speed. A reaction controlled process is indicated. In 8.4 mol. dm⁻³ hydrochloric acid the thiourea concentration range producing optimum dissolution rates was 10⁻³ to 10⁻² mol. dm⁻³. At 70° C the rate of leaching was enhanced by some 105 %. Tests using radiochemical labelling of the sulphur and of the carbon separately in the thiourea molecule confirmed previous proposals, for cobalt dissolution, that hydrogen sulphide is produced as a by-product of the cathodic depolarisation reaction involving the thiourea and is adsorbed on the metal surface in the molecular state, forming activated anodic sites which enhance anodic dissolution. At the 10⁻¹ mol. dm⁻³ thiourea concentration level stimulation of the nickel dissolution process gave way to its partial inhibition with a maximum diminution at 30°C of 50 %.     

Characterisation and treatment of Australian salt cakes by aqueous leaching

Salt cakes are complex waste products derived from the melting of aluminium drosses to recover some of the metallic aluminium present. This paper reports the results of detailed characterisation studies on two different Australian salt cakes and proposes a flowsheet that could be used to render the salt cakes less toxic, reduce waste volumes for disposal, and, importantly, recover valuable products from them.Characterisation data showed that the salt cakes contained at least 12 major metals present in at least 19 identifiable phases. Typical total aluminium levels were 37% with the aluminium present in at least 13 phases. Potentially valuable components identified included aluminium metal, salt (NaCl and KCl), and residual aluminium units.Coarse aluminium metal was recovered in a high grade product by grinding and screening. Various aqueous treatments were then investigated to extract soluble salts and decompose aluminium nitrides and carbides present. Variables considered included leach feed size (−2 mm or finely ground), leach time (0–4 h), temperature (25 °C or 60 °C), and lixiviant type (water or 16% w/v NaOH). Typically more than 90% of the chlorides were extracted within 1 h. Full decomposition of nitrides present, however, was only achieved with hot alkaline leaching of finely ground salt cake. Over 40% of the residual alumina present in the leach residues was readily extracted using Bayer digestion conditions.Based on these results, and practical considerations, an integrated flowsheet for the treatment of salt cakes is proposed. This involves crushing and screening the salt cake to recover coarse aluminium metal, followed by wet grinding and screening to recover fine metallic aluminium. Screen undersize material is then leached in cold water and the pulp filtered and washed. The solution is evaporated in solar ponds to recover the dissolved salts for recycling, while the leach residues can be treated in a Bayer digestion plant to recover residual aluminium units.     

Electrochemical interactions of industrially important platinum-containing minerals

Pt–Te₂ and Pt–Bi–Te are two important platinum-carrying minerals typically found in altered platinum reserves. Mineralogical studies indicate the Pt–Pd–Bi–Te class to react poorly on the flotation stimuli and indications are that these minerals are slow floaters. This paper investigates the fundamental interactions of potassium ethyl xanthate with these minerals by employing electrochemically controlled contact angle measurements, FT-IR spectroscopy and voltammetry. The electrochemical investigations revealed that Pt–Te₂ is more noble than Pt–Bi–Te at potentials lower than 300 mV (SHE) in sodium tetraborate buffer solution and the reduction peak observed during the return sweep of Pt–Bi–Te is mainly associated with the reduction of bismuth oxidation products. Both the minerals show increased anodic currents when polarised at 0.3 V (SHE) in a 0.05 M Na₂B₄O₇ solution containing 1 × 10⁻³ M potassium ethyl xanthate. According to the results of the rest potential measurements, formation of dixanthogen should be thermodynamically favourable and the very high rest potentials are attributed to the catalytic effect of platinum on the oxygen reduction reaction. The formation of dixanthogen on both the minerals was confirmed by ex situ FT-IR spectroscopy. Contact angle measurements revealed the surface of Pt–Bi–Te to be hydrophobic in nature whereas small contact angles were realized on Pt–Te₂. Surface roughness of the mineral could be responsible for these small contact angles.     

Agglomeration for heap leaching: Equipment design, agglomerate quality control, and impact on the heap leach process

In preparation for demonstration heaps, the optimum conditions for agglomeration were determined through testwork. Producing a narrow size distribution of agglomerates in which few agglomerates were smaller than a rice grain, controlling the moisture content to 8–10%, and adding 0.3 kg/t of a commercial polymeric binder were the most important conditions for creating a porous packed bed, as determined from column tests.In a continuous operation, these conditions could be controlled effectively via the ore and solution feed rates to achieve a residence time of 2 min. This ensured that very large, poorly-shaped agglomerates formed before 1.5 min were fragmented into mid-size, well-shaped agglomerates, as well as allowed consolidation of small agglomerates into mid-size ones. Although the residence time of 2 min may not be the optimum for other ores, this study proved that the residence time was the same in a batch or continuous operation regardless of ore type or size distribution.Under the same conditions of agglomeration, the demonstration heaps did not validate the results of the column tests. The heaps were more compact because of the absence of structural support otherwise present in columns through the wall effect. These results highlight the value of demonstration heaps in the scale-up process.     

Treatment of Mine Water by a Microbial Mat: Bench-scale Experiments

Abstract.   We investigated the treatment of acid mine drainage (AMD) by a blue-green algae-microbial consortium and substrate (containing powdered goat manure, wood chips, and soil) in 1 m³ bench scale biological treatment test cells. The microbial mat resulted from the interaction of bacteria and filamentous blue-green algae (predominantly Oscillatoria spp). The experiments were carried out for different water column heights, and were evaluated for 24, 48, 72, 96, and 168 hours of retention. Within 24 hours of retention, the pH increased from 2.93 to 6.78 as net alkalinity went from -125 mg/L to 197 mg/L as CaCO₃. Turbidity decreased by 33–54%, sulphate decreased by 23–29%, and hardness decreased by 19 to 26%. We also observed that: 95% of the Fe, 79–97% of the Cu, 84–86% of the Zn, 88% of the Pb, 59–83% of the Co, 22–62% of the Ni, and 28–45% of the Mn were removed. A blue-green algae/microbial mat consortium may be a cost–effective treatment technique for removing metals from AMD.     

Study of ways of reducing energy consumption in a ventilation system

Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 6, pp. 88–98, November–December, 1996.     

Failure of underground workings in rock of block structure under the action of dynamic forces. I. Experimental data on the failure mechanics of real rock under the action of powerful explosions

Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 4, pp. 51–61, July–August, 1994.     

Division of supporting-pressure zones

Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 4, pp. 3–11, July–August, 1995.     

Breeze circulation in open-pit mines

Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 3, pp. 69–73, May–June, 1995.     

Automatic design and planning system for the open-pit mining of coal deposits

Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 2, pp. 101–107, March–April, 1994.     

Methods of solving problems and designing equipment for mine ventilation

Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 2, pp. 117–127, March–April, 1994.     

Mechanics of the effect of water-gas pulsations on fissured-porous rocks subjected to hydraulic hole mining

Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 6, pp. 70–83, November–December, 1995.     

Contours of equal-strength rock cavity in coordinate planes

Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 1, pp. 59–66, January–February, 1994.     

Study of caving features for underground workings in a rock mass of block structure with dynamic action. Part III. Analysis of the stability of an individual rock block in the roof of a working

Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 6, pp. 3–11, November–December, 1994.     

Uniform shear crushing of rock at quarries

Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 2, pp. 67–69, March–April, 1994.     

Support of a vertical-shaft collar under complex geocryological conditions

Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 6, pp. 64–72, November–December, 1994.     

Vibrational discharge of friable materials

Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 2, pp. 93–96, March–April, 1994.     

Selection of parameters for a pneumatic impact mechanism with valve air distribution

Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 2, pp. 56–62, March–April, 1995.