International Journal of Mineral Processing最新文献

Mineral concentrators can be designed to support several modes of operation, which can be optimized for different geometallurgical units. Nonetheless, alternative modes often require additional equipment and processing capacity, hence an associated capital expenditure. Moreover, the concentrator designs are often based on preliminary geological data, and are therefore subject to uncertainty. The current paper describes how stochastic mine planning algorithms may be extended to quantify the net present value (NPV) of alternative operational modes in mineral processing plants, under geological uncertainty. In particular, the Variable Neighbourhood Descent method of Lamghari et al. (2014) was originally developed for open-pit mine planning, and has now been adapted to evaluate concentrator operational modes. Sample computations are presented.

The solvent extraction of iron and titanium from coal fly ash leach solution was investigated by the use of Design of Experiments. The effect of the factors: hydrogen ion concentration, Primene JMT concentration, aqueous to organic volume phase ratio and temperature on iron and titanium extraction were evaluated. A two level factorial design implemented by statistical software Design Expert® 6, determined the significant factors and any associated interactive effects amongst these factors.

Hydrogen ion concentration and the interaction between the aqueous to organic volume phase ratio with Primene JMT concentration had a significant effect on the extraction of iron while temperature did not. Hydrogen ion concentration and temperature did not have a significant effect on the extraction of titanium, while the interaction between Primene JMT concentration and the aqueous to organic volume phase ratio had a significant effect.

The maximum iron extraction achieved in the implemented design was 33.8% while 99% of titanium could be extracted from the coal fly ash leach solution. Extraction improvement tests showed that at a hydrogen ion concentration of 0.28 M, 88% iron and 99% titanium extraction from coal-fly ash leach solution could be achieved.

The adsorption mechanism of octanohydroxamic acid (OHA) on monazite was studied using kinetic, isotherm, and thermodynamic adsorption tests as well as FTIR, titration, and micro-flotation experiments. The adsorption mechanism was described as a chemisorption/surface precipitation process. At low OHA concentrations, adsorption occurred by chemisorption as a result of the reaction between surface active sites and OHA molecules. With an increase in concentration and interaction time, surface precipitation occurred. For chemisorption, adsorption was an exothermic and entropy driven process and maximum adsorption was achieved at pH 9.0 due to more active sites. In an acidic environment, such as pH 3.0, adsorption was achieved via chemisorption and hydrophobic bonding. However, a strong basic and higher temperature environment contributes to surface precipitation of basic rare earth hydroxamate. FTIR tests showed the movement of CH₂ band position from 2924 cm^− 1 to 2920 cm^− 1 with increases in pH values from 3.0 to 6.0, 9.0, and 11.0, which corresponds to the status of chemisorbed and surface precipitated OHA, respectively.

Thermomagnetic analysis was conducted on phase transformations performed for synthetic and natural hematite by reduction involving various carbohydrates (starch, glucose, fructose, sucrose, and ascorbic acid). Thermomagnetic measurements were carried out using a laboratory facility that allows the automatic registration of a sample's magnetization as the temperature changes (the rate of sample heating/cooling was 65 °/min). The results were then analyzed. The reduction reaction of synthetic hematite for all carbohydrates starts at a temperature of ~ 350 °C, while the reduction of natural hematite for all carbohydrates starts at a temperature of ~ 365 °C. The magnetite formed by the reaction has a Curie temperature of 565 °C. Both magnetite and hematite are present in all transformed samples. Saturation magnetization increases to ~ 50 Am²/kg for the samples obtained from synthetic hematite and ~ 25 Am²/kg for the sample obtained from natural hematite. The difference in the value of saturation magnetization is attributed to a lower magnetite content for the sample obtained from natural hematite. Synthetic hematite transforms more effective, suggesting the synthetic sample is characterized by a larger surface area compared to natural hematite.

A critical parameter in the design of pastefill distribution systems is the shear yield stress of the backfill. Yield stress is used in the hydraulic modelling to estimate the friction losses in the system and is generally assumed to be constant throughout the piping system. However, many sites report a change in slump during transport – sometimes up to 50 mm. As slump is used as an indicator of yield stress, it can be hypothesized that that material rheology is changing during transport potentially due to changes in particle shape and size or pastefill temperature. By sampling pastefill at the surface and at the discharge point underground, in two Canadian mines, this study shows that the yield stress and temperature of pastefill does not remain constant through the distribution system. The size and shape of the backfill particles are analyzed and no remarkable changes are found. The effect of temperature on the yield stress is investigated through laboratory testing using slump tests and a rotational viscometer and indicate that temperature is a significant factor in the yield stress change.

In this study, response surface methodology (RSM) and artificial neural network (ANN) were used to develop an approach to analyze the behavior of different process variables such as pulp density, oil dosage, agglomeration time, and particle size, which affects the coal oil agglomeration process using Linseed oil as a bridging liquid. The investigation was done using Box-Behnken design (BBD) of response surface methodology, the same design of experimental data was used in training with the artificial neural network, and the results obtained from the two methodologies were compared. The ANN model predicted responses with better accuracy with coefficient of determination (R²) 0.97 and 0.95 for % ash rejection and % organic matter recovery respectively in comparison to RSM-BBD R² of 0.97 and 0.92 for % ash rejection and % organic matter recovery respectively. The optimal condition established for the high % ash rejection and % organic matter recovery were pulp density (3.002%), oil dosage (15%), agglomeration time (15 min), particle size (0.168 mm) with predicted % ash rejection and % organic matter recovery as 68.00% and 95.24% respectively, with the desirability of 96.90%. The proposed optimal conditions were examined in the laboratory and the % ash rejection and % organic matter recovery achieved as 64.60% and 93.93 respectively.

A new oxalic acid (H₂C₂O₄) and hydrogen peroxide (H₂O₂) based extraction process was developed to recover valuable metals - in particular Ga and Ge - from the zinc refinery residues. H₂C₂O₄ and H₂O₂ leaching studies indicated that the selective leaching of metals in the residues, that primarily contain Zn, Cu, Fe, SiO₂, Ga and Ge, can be achieved. Under the optimal leaching conditions ([H₂C₂O₄] = 110 g/L, [H₂O₂] = 0.12 mol/L, L/S ratio = 8, T = 40 °C and t = 30 min), 99.32% of the Ga, 98.86% of the Ge and 30.25% of the Fe were leached out, whereas the leaching of Zn, Cu and Si only reached 0.30%, 0.82% and 0.43%, respectively. Concerning leachate purification, 98.31% of the iron could be removed in the form of FeC₂O₄·2H₂O with minor losses of Ga and Ge (1.08% and 0.68%) using an ultrasound-assisted iron powder replacement method under optimal conditions. The Ga (99.36%) and Ge (99.89%) were subsequently extracted by tri(octyl-decyl)amine (N235). After extraction, the loaded organic phase was stripped of Ga (98.91%) and Ge (99.21%) into separate solutions using sequential treatments of 2 mol/L H₂SO₄ and 4 mol/L NaOH respectively. Based on these results, a process flow sheet of efficient separation and recovery of Ga and Ge is presented.

Enrichment and migration regularity of coal particles in compound force field provided by Falcon concentrator were studied. Influence of centrifugal force and fluidization water pressure on the distribution rates and ash contents of materials that enriched in overflow, top separation area and bottom separation area were tested respectively. Radial velocity of fluidization water, having an important influence on the sedimentation of particles, was calculated and results show that radial velocity of fluidization water in top groove is greater than that in bottom groove, which contributed to the selectivity and recovery of combustible. Besides, density composition of products in different enrichment areas was studied. Results show that in the upward migration process, particles with high density are gradually captured. Therefore, the material density is gradually reduced from bottom to top separation area. Meanwhile, mismatch phenomena occurred as the existence of heavy particles in overflow, and light particles in the grooves. Based on the morphology analysis, it is can be deduced that particles mismatch is the results of the increase of drag coefficient since the irregular shape.

Utilization of N-carboxymethyl chitosan (N-CMCh) to limit the detrimental effect of serpentine on the flotation of pyrite is presented in this work. Flotation results show that the presence of hydrophilic serpentine slimes results in lower recoveries of the valuable pyrite. Utilization of N-carboxymethyl chitosan can limit the detrimental effect of serpentine on the flotation of pyrite. Zeta potential measurements illustrate that N-CMCh is with negative charge and the electrostatic interaction between serpentine and N-CMCh is occurred at pH 8.5, then the serpentine zeta potential will be changed from positive to negative, the electro-steric attraction converts into electro-steric repulsion between pyrite and serpentine and the pyrite recovery is improved.

Taixi oxidized coal surface has many hydrophilic functional groups as well as many cracks and holes. The effect of prewetting time on the flotation behavior of Taixi oxidized coal had been observed in our previous studies, and it was surmised that the oxidized coal surface was easier wrapped by water shell because the hydrophilic functional groups could be bonded with water through hydrogen bond and the cracks and holes could also be filled up with water when the coal was prewetted in the flotation cell. However, the mechanism of how the prewetting/immersion process can affect the flotation performance of Taixi oxidized coal is still poorly understood and should be investigated clearly. This paper was to conduct the fundamental studies on the effect of prewetting/immersion time in the attachment time between air bubble and Taixi oxidized coal. It was found that the attachment time increased quickly with the increase of prewetting/immersion time. The micro-bubbles are produced on the oxidized coal surface when the coal particles are immersed in the water. The micro-bubbles may be primarily from the air entrapped in the cracks and holes on the oxidized coal surface. As the prewetting/immersion time increased, the micro-bubbles would dissolve and get away from coal surface, and then the cracks and holes would be fully filled up with the water. Finally, the oxidized coal surface would be wrapped by a thick hydration shell which could prevent the oxidized coal surface from being attached by the bubbles, and hence the bubble-coal attachment time increases with the increase of prewetting/immersion time.