International Journal of Mineral Processing最新文献

In many parts of the world, important reserves of Microscopic Biogenous Sediments or Pelagic Sediments occur which primarily consist of settled siliceous or calcareous microorganisms. Such sediments typically have zones, in which an intimate association of siliceous remains of diatoms and CaCO₃ is experienced. The purity of diatomite crude ores is very important for producing the filter grade finished products by means of the conventional flux calcination procedures. Calcination of DE materials with high calcium carbonate is not economically or environmentally friendly. The prime objective of this study was to evaluate the advanced STET tribo-electrostatic separator for the beneficiation of DE having relatively high quantities of CaCO₃ to produce a suitable calciner feed for the production of filter grade finished products.

In the best operating conditions, the STET technology showed the ability to reduce the calcium carbonate content of a natural-grade DE product from 19.5% to 10.9% which is an acceptable quantity of CaCO₃ for calciner feeds. Limitations of the DE recovery process using this technology was primarily due to superficial heterogeneity of some DE particles. The validation process of the beneficiated DE confirmed that the STET technology has the potential for upgrading natural-grade DE products having relatively high quantities of CaCO₃ to produce a suitable calciner feed for the production of filter grade finished products with the exception of the brewery industry.

The present paper was aimed at developing innovative hybrid composites by using cheap filler, like red mud (RM). The study importance refers to RM recycling, a recent trend in environmental science. Besides its causticity, large amounts of RM are produced yearly, calling for recovery measurements. Herein, poly (acrylic acid)- based inorganic-organic hybrid hydrogels (PAA hydrogels) incorporating RM were synthesized.

Furthermore, the possibility of involving inorganic additives (kaolin and/or sodium silicate) together with RM was investigated. Incorporation of all three inorganic compounds (RM + Kaol + Sil) in hydrogels was also evaluated, novel hybrids being prepared. The obtained hybrids were characterized by different techniques (DR UV-VIS; DRIFT; TGA/DTG; SEM) and in terms of swelling behavior. DRIFT and DR UV-VIS confirmed the occurrence of characteristic bands of raw materials. Final properties (water uptake, thermal stability, porosity) can be controlled by modifying preparation conditions. Hydrogels yielded, by calcinations, iron- rich ceramic foams, able to promote water removal of sulfide ions from wastewaters.

The particle settling is a basic phenomenon: however, it determines the design of many unit operations and machines of mineral processing. A new test device has been developed in order to measure the terminal settling velocity of large steel balls settling in fine particulate solids - water mixtures. The developed inductive sensor does not influence the motion of the ball and it can be applied for non-transparent and non-Newtonian fine suspensions. A new hypothesis, namely a continuity theory for coarse disperse systems is introduced here. According to this theory, if the particles of a fine suspension are so small that they fit into the laminar sub-layer around a settling coarse particle, the fine suspension can be treated as a continuum. If they do not fit, hindered settling dominates between the coarse and fine particles. It was also recognised that if a particle settles at a constant speed in any media that is in an equilibrium state, therefore, the “equilibrium mean surficial shear stress (τ_e)” and the “equilibrium mean surficial shear rate” have been introduced. The equilibrium mean surficial shear stress can be calculated initially, because it is simply the force of gravity minus the buoyant force over three times the total surface of the particle. Once τ_e is known, the equivalent Newtonian absolute viscosity can be determined and the terminal settling velocity of particles falling in non-Newtonian media can be calculated by the known procedures for Newtonian fluids.

In this study, the effect of sodium chloride on the flotation of a fine coal sample was investigated. The results indicated that flotation of coal was highly dependent on changes in sodium chloride concentration. An increase in the sodium chloride concentration resulted in increases in the combustible recovery as well as concentrate ash content. The froth stability and particle size distribution in the slurries with different sodium chloride concentrations were measured. The results showed that the increase in froth stability and enlargement in particle size were both favorable for the recovery of coal particles in flotation. The underlying mechanism was investigated by examining the zeta potential of pure coal particles and pulp rheology. The pulp rheology measurements clearly indicated that changes in froth stability were attributed to changes in slurry viscosity, which ultimately enhanced the recovery of coal particles. The decrease in zeta potential was responsible for the increase in particle size in slurries due to particle coagulation, which is caused by a decrease in electrostatic repulsion among the particles.

An innovative technology named solid-state metalized reduction–magnetic separation (SSMRMS) was developed to produce ferronickel concentrates from magnesium-rich nickel oxide ores. A pilot-scale plant with a daily processing capacity of 500 kg of dry ores was assembled and tested. SSMRMS involves four steps: feed preparation, solid-state metalized reduction, quenching and ball milling, and magnetic separation. After 40 days of continuous tests, the operational stability of the proposed technology was good, and accretion did not form in a rotary kiln. Results revealed that (i) an appropriate positive pressure in the kiln terminal was beneficial to metallization; (ii) the overall recoveries of nickel and iron could reach 91.3% and 73.8%, respectively, whereas the nickel and iron grades of the produced ferronickel concentrate could be 7.4% and 69.6%, respectively; (iii) residual nickel to tailings was 0.16%; and (iv) the return ratio of dusts was approximately 8%. Notably, nickel could be released and sufficiently metalized at an appropriate temperature once the structures of the Ni-bearing silicates were destroyed in the presence of fluorite. The metalized nickel aggregated with the metalized iron surrounding the margins of the minerals. Therefore, fluorite could promote the generation and growth of ferronickel alloy particles, thereby increasing the recoveries of nickel and iron. Preliminary calculation showed that the electricity consumption of the solid-state metalized process was 52.5 kWh/t-ore. Hence, SSMRMS is a competitive strategy for the processing of magnesium-rich nickel oxide ores.

The carbothermic reduction behavior of original ilmenite and pre-oxidized ilmenite concentrates were investigated by a non-isothermal method using a thermogravimetry facility. The reaction degree was calculated using the tail gas composition and the Starink method to analyze the activation energy of the reduction. The results demonstrated that trends of different reaction degree curves are similar under the same conditions. The average activation energy of the pre-oxidized ilmenite concentrate was less than that of the original form by approximately 25%, and the starting reduction temperature was lower by 67 K than that of the original ilmenite concentrate. However, the reduction time of the pre-oxidized ilmenite concentrate was longer than that of the original ilmenite concentrate for the same reaction degree; therefore, a slow reduction rate for the oxidization sample was observed. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersion spectroscopy (EDS) were used to characterize the phase and micro-morphology of the two raw materials and compare the reduction products.

The main purpose of this study is to investigate the effect of reaction temperature and NH₄HCO₃ on the overall performance of a pH swing mineral carbonation. The overall performance of the pH swing process is investigated in terms of carbonation efficiency and product purity. Initially, 2 M H₂SO₄ is used for red gypsum dissolution at 70 °C. Then in the second stage, NH₄OH is added for increasing the solution pH and removing the impurities from solutions. Finally, CO₃^2– is introduced to calcium rich solution in the form of pure CO₂ and NH₄HCO₃. The experimental results show that using NH₄HCO₃ improves carbonation efficiency and product purity. Carbonation efficiency attains a maximum value at 75 °C and then decreases gradually with increasing temperature up to 300 °C, with both CO₂ and NH₄HCO₃. In this research, CaCO₃ with the maximum purity of 99.05% is produced successfully when NH₄HCO₃ is used as a CO₃^2– source.

This paper presents a method evaluating in numerical value the magnitude of vibration component contained in the rotor angular velocity of a hammer crusher and a new structure to remove them. In the hammer crusher, while rotating by the rotor, hammers are swinging around their pivots simultaneously. This swinging gives effect on the motion of the rotor, making vibration component contained in the rotor angular velocity. By simulating the rotating process of the hammer crusher, the rotor angular velocity and motor power are obtained, and by using the digital filtering technique, a method is developed to evaluate its magnitude in root mean square value by extracting vibration component contained in this simulation result. With this evaluating method is evaluated the simulation result on the motion process of various structures to find out a new structure model of very little value of vibration components in angular velocity and motor power.

Continuing industrial development results in ever greater consumption of products and materials. These include electrical and electronic equipment (EEE) such as mobile phones and, consequently, lithium ion batteries (LIBs). Therefore, an efficient and environmentally friendly recycling technology is vital for the recovery of valuable materials from spent LIBs. This work describes an alternative process for the recovery of these materials, using mechanical processing and electrostatic separation. Firstly, the batteries are dismantled and their components are characterized. This is followed by comminution, drying (to remove the organic electrolyte), separation according to particle size, and electrostatic separation of the conductive and nonconductive parts of the LIBs. Parameters evaluated in the electrostatic separation were the electrode voltage, roll rotation speed, distance of the electrostatic electrode, and the inclination angle of the deflector. The results showed recovery of a conductive fraction containing 98.98% of metals and a nonconductive fraction containing 99.6% of polymers, demonstrating that electrostatic separation is a promising and efficient method for the recovery of high purity materials from spent LIBs.