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By A. Shibayama

Soil contamination by organic compounds is one of the most concerned issues on polluted soil. It is well known that there are limited methods to remediate the contaminated soil on site. Especially, the in-situ method for contaminated soil is too difficult to de-contaminate the organic pollutant. In this study, the fundamental ability of soil remediation, which aimed to decrease oil concentration in, in-situ process, have been researched by using a high pressure gas generated from ?crush composition? on artificially oil contaminated soil. The n-hexadecane (n-C16H34) and other organic compounds were selected as soil oil contaminators, gravimetric analysis by soxhlet extraction and GC-MS were used as qualitative and quantitative analysing methods. For the experimental examination, the influences on the difference in the concentration of n-hexadecane (and other organics), the tamping amount, position and repetition of crush composition in soil, and scale (size) of experimental model were investigated. The n-hexadecane concentration reduced by the explosive effect of crush composition showed a reasonable decrease of about 30 wt%~60 wt% compared to the initial n-hexadecane. The removed amount of n-hexadecane and distance from explosion point of the crush composition was related in scale and model of contaminated soil.

Jan 1, 2014

The energy dispersion X-ray fluorescence (EDXRF) analysis technique is a rapid and accurate method for describing sample?s element component and percentage composition. On the base of profound research for the national and international development and research condition, the author researched the EDXRF analyze technique and the EDXRF analyzer?s principle in depth, the difficulties and the key points for research and development of EDXRF analyzer; gave a scheme for re-search of bench EDXRF analyzer; researched some algorithms used in energy spectrum analysis; developed the energy spectrum analysis software based on the Visual C++ 6.0; together with the energy spectrum analysis software, the author designed and processed the structural of the bench XRF analyzer and integrated the import X-ray tube, thermoelectrically cooled Si-PIN photodiode X-ray detector and pulse amplitude analyzer as a model machine. The result shows: The model machine can be used in multi-element analysis at the same time for different types of dry mineral samples, with fast analysis speed, accurate model and high stability.

Jan 1, 2014

By Rasool Hejazi

The feed to Chadurmalu iron ore concentrator plant is a mixture of magnetite and haematite iron ore with a Fe/FeO ratio of about 8. The feed to plant, after grinding via wet SAG mill, is pre-separated by wet low intensity magnetic separator. Magnetic product is conducted to magnetite processing circuit for producing magnetite concentrate, and nonmagnetic product is directed to haematite processing circuit. Due to surface oxidization of magnetite particles and a decrease in magnetic attraction properties, significant amount of these particles are misled to tailing which results in decreasing the efficiency of haematite processing circuit. This problem can be remedied by using magnetic drum separator with more magnetic intensity and/or gradient. In this paper, the replacement of LIMS separators with wet medium intensity magnetic separators with a field intensity of 3800 gauss on drum surface (MIMS) have been suggested and considered as the most suitable solution to prevent the loss of magnetite particles. The results of carried out investigations with replacement of drum separators in industrial scale, showed that utilizing MIMS in magnetite processing circuit resulted in increasing final concentrate weight recovery on average by 2.59%, without any adverse effect on the concentrate quality; decreasing the magnetite content in the feed to high gradient magnetic separator (HGMS) by about 3.5%; decreasing the feed to floatation part by about 7% and consequently decreasing consumption of chemical reagents; increasing Fe/FeO ratio of the feed to plant. Keywords: iron ore, medium intensity magnetic separator, haematite, Chadurmalu

Sep 1, 2012

By V. K. Chandaliya

N-Methyl-2-pyrollidone (NMP) has already been proven a good solvent for extraction of coal. It is believed that organic components of coal are likely to be dissolved with the solvolytic power of NMP. During dissolution process, original coal also gets disintegrated and thus helps in further extraction. Coal extraction highly depends on temperature, coal to solvent ratio, N-Methyl-2-pyrollidone (NMP) to Ethylenediamine (EDA) ratio and the size of coal particles. The process has been established in the laboratory. There is no reference available beyond lab scale. In present study, we are running a bench scale plant with 40 kg/batch capacity. Design of experiment was done in such a way that the optimum zone of the process gets evaluated for clean coal having low ash with high yield. Bench scale plant trial was conducted based on optimum zone developed during design of experiments (DOE). From the DOE analysis it was observed that feed size and coal to solvent ratio are important parameters for this process. Total 27 experiments (four factors with 3 level of variation) were designed through Box-Behnken model. It was observed that -0.5 mm feed size of coal, 150 °C extraction temperature, 17:1 NMP to EDA ratio, 1:9 coal to solvent ratio was optimum conditions. The results obtained at optimum conditions are 50% clean coal yield with 5% ash.

Sep 1, 2012

In this study, selective flocculating of diaspore using anion macromolecular reagent as flocculant was tested to separate diaspore from alum-silicate minerals. Firstly, the effect of pH on settling behavior of diaspore and kaolinite dispersions has been investigated. The results show that the maximum settling speed of diaspore and kaolinite appeared re-spectively at pH7 and pH3.33 which is close to the point of zero charge (PZC) of diaspore (6.8) and kaolinite(3.5). This result is in well agreement with the double electric layer theory. Secondly, the settling behavior of diaspore and kaolinite particles in different anion flocculant solution have been researched. The results indicate that flocculant solution concentration significantly affect the selectivity and the flocculating performance of anion molecular. In high concentration solution, both diaspore and kaolinite have faster settling rate compared to blank solution. How-ever, in low concentration solution, the anion macromolecular can enhance the settling rate of diaspore remarkably but has no apparent effect on the settling rate of kaolinite. This result suggests that the tested anion flocculant is a promising reagent for de-silica of diasporic bauxite. Lastly, FTIR method was employed to probe the adsorption mechanism of flocculant on diaspore and kaolinite. The results reveal that there are anion flocculant characteristic bands on the spectra of diaspore but no obvious characteristic bands of flocculant on the FTIR spectrum of kaolinite. This result is in good correspondence with settling test.

Jan 1, 2014

By U. S. Chattopadhyay

The estimated requirement of the nation by the year 2020 is approx. 80 Mt of steel and more than 0.2 million MW installed capacity of the electricity, thereby increasing the consumption of the coking and non-coking coal, which is expected to be in tune of about 75 Mt & 500 Mt respectively. One of the major deleterious factors in achieving the goal is the deteriorating quality of the feed coal used in both steel and power industries. Indian coking coals, in general, are typified by high ash, high inert (both organic and inorganic), low rank, low reactive macerals content, heterogeneous petrographic make-up, inferior coking properties and poor amenability to washing, thereby necessitating suitable washing measure. Coke-based steel industries in India require washed coking coal containing ash % varying between 17-19. The situation demands taking on immediate challenges to fill up the gap between the requirements and supply of coking coal. This paper reviews the R&D attempts in this laboratory and throws light on the key measures as long-term solution to the problem. Search for alternative source of coking coal, like LVC coal and their judicious preparation technology. The low volatile coking coal (LVCC) constitutes about 50% of the total coking coal reserves in India. These coals are characterized by high raw coal ash content (37 to 40%) and very difficult washability potential. If these coals are treated in the existing washeries, which are generally 2 or 3-product systems, the cost of clean coal is high as the byproduct sale value is low. It has been proposed to produce a new type of by product, which enjoys high demand and good coking properties.

Sep 1, 2012

By T. C. Alex

Mechanical activation of gibbsite [?-Al(OH)3] is the theme of this paper. Industrially prepared gibbsite used in the study has a mono modal size distribution with a median size, d50=110 µm. Mechanical activation of this gibbsite has been carried out in a planetary mill at ambient conditions. Mechanical activated gibbsite samples are characterised in terms of particulate characteristics, structural characteristics and reactivity. As a result, of milling, mono modal size distribution of the unmilled gibbsite changes to a broad multimodal distribution. Size reduction has been sharp in the initial stages of milling; median size reduces to ~7 µm during 15 min of milling. Thereafter no decrease in median size is observed; rather it is found to increase gradually with further increase in milling time, indicating particle aggregation. Morphological studies of milled gibbsite have shown that the platelets forming the agglomerate are separated first; the separated platelets then undergo breakage. Aggregation of particles sets in the later stages of milling as a result of increased surface area and surface energy. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies have clearly revealed the changes in gibbsite structure during milling. Analyses of XRD data show that the crystallite size of gibbsite decreases as the milling time progresses whereas its microstrain is found to increase. Accumulation of energy in the structure is the result in both cases. TEM micrographs with signs of defects leading to disordering of gibbsite structure complement the XRD results. Reactivity of milled gibbsite, decrease in its deydroxylation temperature and increase in alkali dissolution, is found to increase with mechanical activation. Increased reactivity of milled gibbsite is found to have a strong correlation with the BET specific surface area. Keywords: mechanical activation, gibbsite, alkali dissolution, thermal dehydroxylation, reactivity

Sep 1, 2012

By H. Deng

Oxidized zinc ores are the main source of zinc metal except sulfides. To have a better understanding about the performance of smithsonite and the main gangue, quartz, in flotation, the aggregation behaviors of smithsonite and quartz in water were confirmed by different techniques (sedimentation tests and optical microscopy). The experimental results show that smithsonite and quartz particles aggregate in the pH range 7.5-11. The results of zeta potential suggest that the aggregation does not correlate with the DLVO theory, when the iso-electric point of smithsonite and quartz is 8.0 and 2 respectively. When the solution pH is less than 8.0, smithsonite has an opposite charge to the quartz particles. Electrostatic adsorption makes effort on these two kinds of particles according to DLVO theory. Whereas, solution chemistry calculation shows the pH range 8-11 corresponds to hydroxide formation, suggesting that this is the species responsible for aggregation. And their concentrations are much higher in sodium hydroxide system than that in sodium carbonate system. Aggregation of smithsonite and quartz due to the flocculation action of zinc hydroxide is proposed.

Sep 1, 2012

By G. Unland

The sizing of crushers depends on the expected crushing forces. However, the crushing forces develop differently with every individual rock while it is compressed by the working surfaces of the crusher. For sizing, this compression process has to be characterized by the maximum crushing force. The maximum crushing force depends on the strength, shape and size of the rock, the amount and velocity of the imposed displacement of the working surfaces of the crusher on the rock and the conditions of the contact surfaces. From experience it is known that the strength of the material and, therefore, the crushing forces depend on the size of the specimen. This dependence is the so called size effect. The determination is based on compression tests. The force development is recorded during the compression of the specimen and for every individual test the maximum force is determined. The occurring maximum crushing forces of several rocks with the same diameter comminuted under the same conditions can be assessed by a mean value and a variance. The relationship between the mean values of the cross section related maximum crushing forces FAmax and the corresponding sizes d of the specimens can then be described by mathematical functions. They are derived from different approaches (phenomenological, statistical and statistical-physical methods). The phenomenological methods are subjective and yield functions depending on the assumptions of a person, whereas the statistical and statistical-physical methods are based on an evaluated function and the optimization of the parameters.

Jan 1, 2014

By J. Zou

With the increasing applications of the Chinese metal magnetic liners, the requirement for their technical specifications has become stricter and stricter. It is necessary to deeply analyse the metal magnetic liners in order to improve their reliability and economics. The key issue of metal magnetic liners is magnetic forces: their attractions to mill shell and protection layer. Mathematical models were developed using finite-element analysis software and systematic simulation analyses of the two most critical indexes of magnetic liners were performed to find out the most important parameters and their effect on the liner?s characteristics. The relationships between magnetic forces and installation gaps, thickness of permanent magnets and thickness of protection layer may be used to guide the design of metal magnetic liners for ball mills in order to achieve good economic indexes.

Jan 1, 2014

By S. Groudev

Acid drainage waters generated in the uranium deposit Curilo, Bulgaria, were treated by means of a pilot-scale passive system consisting of a permeable reactive multibarrier and a constructed wetland connected in a series. The multibarrier had a total volume of 23 m3 and consisted of an alkalizing limestone drain and an anoxic section for microbial dissimilatory sulphate reduction, bio-sorption and additional chemical neutralization. The waters had a pH in the range of about 2.5 ~ 4.0 and contained radionuclides (uranium, radium), heavy metals (copper, zinc, cadmium, lead, nickel, cobalt, iron, manganese), arsenic and sulphates in concentrations usually much higher than the relevant permissible levels for waters intended for use in agriculture and/or industry. The water flow rate through the multibarrier varied in the range of about 1 ~ 17 m3/24 h, reflecting water residence times of about 300 ~ 18 hours. An efficient removal of pollutants was achieved by the multibarrier during different climatic seasons, even during cold winter days at external air and water temperatures close to 0oC. The multibarrier effluents were enriched in dissolved organic compounds and in some cases still contained manganese and iron in concentrations higher than the relevant permissible levels. These pollutants were removed in the constructed wetland as a result of the activity of different heterotrophic microorganisms, including some bacteria able to oxidize the bivalent manganese and iron ions to Mn4+ and Fe3+, respectively.

Jan 1, 2014

By Sharma K. K.

India is the third largest producer with accounting to fifth largest reserves base of coal in the world. Indian coal has high ash content (15-45%) and low calorific value. The basic processes being used in India at different places for coal washing adopts old techniques. Much of the valuable part is being lost during washing processes. With enhancement of the available techniques and use of new processes like flotation process indicates better recovery of carbon values during washing stage. The same will increase the reserve base, improve economy of operation and alleviate environment related problems. In the above backdrop this paper portrays the case study of an existing coal processing plant in India. The case study includes the modifications being incorporated in the existing process to enhance the product value. The existing practices and the future trend of process technology that could be adopted to meet the requirements in this country are also discussed. Keywords: washing, dense media cyclone, magnetite media, flotation

Sep 1, 2012

By S. J. Ma

To look into the ionic release laws of the sulphide tailings in some copper mine, the effects of the soaking period, temperature, oscillating speed, and pH of the solution on the heavy metals ionic re-lease were investigated through static soaking leaching experiments. The results show that Cu2+, Zn2+, Pb2+, Cr3+ are of different leaching behaviors with soaking period. The ionic concentration in soaking solution for four ions has a great gap. Zn2+ is more easily released out of sulfide tailings than Cu2+, Pb2+, Cr3+ , and the ion release concentrations are not proportion to their contents in the tailings. The time for each ion to reach its maximum concentration are different. The minimum concentration do not occur at the first day. Each ion concentration shows different fluctuation characteristic during soaking process. Solution pH, oscillating speed, and temperature affect the releases of Cu2+, Zn2+, Pb2+, Cr3+ out of the tailings to different extent. The effect of pH value on ion re-lease for the four ions ranks as Zn2+>Cu2+>Pb2+>Cr3+, the oscillating speed ranks as Pb2+>Zn2+>Cu2+>Cr3+, and the temperature ranks as Cr3+>Pb2+>Zn2+>Cu2+.

Jan 1, 2014

By G. W. Zhang

Ultra-fine Stirred Mill is a kind of high energy efficient equipment for ultra-fine grinding, and has been the mainstream equipment in the submicron powder and slurry industry. This paper mainly describes flow-field numerical simulation of the three popular ultra-fine grinding mills: (respective-ly as) Disc Stirred Mill, Pin Stirred Mill and Spiral Stirred Mill, by means of the software Computational Fluid Dynamics (CFD). In the flow-field numerical simulation, the velocity gradient, shear rate dispersion of the flow-field, the viscosity dissipation rate were analyzed with CFD. It is discovered that Pin Stirred Mill has the highest velocity gradient in circular directions and the most homogeneous distribution of shear rate among the three. Flow-field numerical simulation provides a new way (and means to) for the parameter optimization design and project enlargement of Ultra-fine Stirred Mill. The experiments were also carried out, the results are consistent with the results of the simulation analysis. For example, in GCC grinding experiments under the same conditions, the specific energy consumption of Pin Stirred Mill with 3600L in volume is 15%~17% less, and its processing capability is 13%~15% better than Disc Stirred Mill. Now with its optimized structure and excellent performances, more than ten sets Pin Stirred Mill with 3600L in volume have been used in industrial production in Shandong, Guangdong and Hunan province.

Jan 1, 2014

By X. L. Wang

Hydrothermal method was applied in the preparation of calcium sulfate whiskers in airtight re-actor using gypsum as primary materials. The optimum conditions of preparation are as follows: pH value 9.8~10.1, concentration 5%, material size 18.1µm, which were determined by the analysis of the diameter of CaSO4 whiskers through SEM. On these conditions a product of ultrafine CaSO4 whiskers with diameter of 0.19µm and aspect ratio of 98 is obtained. Ultrafine CaSO4 whiskers with different concentrations, modified by titanate NDZ-401, were added into polypropylene as intensifier and composites of Ultrafine CaSO4 whiskers/ polypropylene were prepared by melting-extruding method. Mechanical performance of the composites was tested and surface morphology of the composites was observed by SEM. The results indicated that impact notched izod of the composites was enhanced by 49.5% compared with pure polypropylene when 10.0% Ultrafine CaSO4 whiskers were added into polypropylene and toughening effect was very remarkable. Dispersion behaviour and interface phenomenon of Ultrafine CaSO4 whiskers in polypropylene matrix were investigated by SEM. The results indicated that Dispersion performance of Ultrafine CaSO4 whiskers modified by titanate NDZ-401 in polypropylene matrix is good, which improved mechanical performance of composites to some extent.

Jan 1, 2014

Under the AMIRA P9 project the three-product cyclone-an off-shoot of the conventional hydro-cyclone-that produces three distinct products has been developed. The three-product cyclone shows great promise as a classifier in mineral processing. Industrial and pilot plant trials performed to assess its performance in the classification of the UG2 platinum ore, indicate that the presence of an extra overflow product stream that captures the mid-sized particles, provides improved classification efficiency. To assess the split on component density, samples from the feed and product streams were screened and assays by size for chromite (? = 4.8) and silica (? = 2.65) were obtained. Results from tests performed using this type of hydrocyclone in a number of applications indicates that it can be applied successfully in circuit configurations where the conventional hydrocyc-lone is not suitable. Utilising the three-product cyclone to classify the UG2 platinum ore resulted in an intermediate overflow product stream containing the mid-sized low density silicates and relatively fine high density chromite particles while the finer overflow contained mostly fine silicates and chromite particles. The coarse chromite and silicates reported to the underflow. Due to the increased number of products, the method of using efficiency curves was extended to cater for the increased number of products in the three-product cyclone. Although significant differences in the classification performance of the three-product cyclone were noticed with variations in machine variables a consistent method of assessing the performance was applied. The efficiency curve was adopted and applied and separate efficiency curve properties were obtained for each product stream. The methodology was applied to the component data, and efficiency curve proper-ties for each key component were obtained and compared. This paper discusses the application of the efficiency curve to cyclones producing more than two products and extending the methodology to the different components in the feed.

Jan 1, 2014

By J. C. van Dyk

In a previous study by Van Dyk, et al., (2006) and Van Dyk et al. (2006), a FactSage model was developed to understand the chemistry and interpret mineral matter transformation during a fixed bed counter-current gasification process. It was concluded that the FactSage model developed, compared with HT-XRD experimental results and that the FactSage thermodynamic modeling sup-plies insight into specific mineral reactions and slag formation. The specific value for Sasol in using FactSage, in combination with HT-XRD is that it can be used to analyze equilibrium conditions for reactions occurring between inorganic and organic materials together, as well as to provide insight into mineral transformation and slag formation. The purpose of the present study was to improve the current FactSage modeling approach, by combining specific zones in the gasification process. This can improve and speed-up the interpretation of mineral matter transformations and flow properties of reacted mineral matter in coal and assist in identifying and quantifying slag formation in the gasifier operation at temperatures not reflected by normal AFT analyses. The updated and improved FactSage model compared favorably with the original model as well as with HT-XRD results and thus will be able to supply results in a faster and more convenient manner. In the new FactSage model, supported by HT-XRD experimental findings, it is indicated that feldspar formation (including anorthite) correlated with slag formation at temperatures around 1000°C and no slag formation in the base case coal was observed in the drying and devolitilization zone, as was to be expected. Feldspar is one is the mineral species which has the lowest AFT causing the most slag-liquid formation and forms probably as a product between the SiO2, Al2O3 and Ca-containing species. In the gasification zone it was clear that slag-liquid formed at a temperature of 1000°C, with a decrease in the feldspar content. Mullite formation was also observed in the base case sample in the temperature range 1000°C and 1100°C. The decrease in the amount of SiO2 at 1100°C is related to the formation of mullite, but also that the slag-liquid phase also contains an amount of SiO2 in the molten form.

Jan 1, 2014

Optimising flotation designs and innovations is a complex process involving many parameters, one of which is ensuring sufficient testwork is carried out at plant level before these innovations are launched in the marketplace. This paper will describe how modern design tools are utilized, what are testwork phases at various plants and how results and observations have helped to validate and optimise flotation design innovations. Scale-up of equipment has long been the prevalent trend, but how long can it continue? Are there other means for pushing the boundaries of present technology? Some present challenges and future directions are given in the light of theoretical criteria for scale-up and how it has been applied in practice. Very large flotation cells of 300 m3 size have been installed in New Zealand, and relevant results from the metallurgical and mechanical aspects are presented and discussed. Utilization of the cell volume is also important. New innovations in the hydrodynamic domain are presented and discussed. Means to enhance flotation of coarse and fine particles are shown with results from plant testwork. Accurate control of large flotation cells is vital to optimize yields and grades. Froth image analysis and intelligent level control are presented ? again - with relevant plant results.

Jan 1, 2014

By Luis G. Bergh

Today, large size mechanical flotation cells of 100 to 300 m3 are used in rougher operation in different flotation industrial plants, in Chile and worldwide. However, in spite of the advances in fundamental research and the notable growing in equipment size, with more complete instrumentation systems, there are still a lack of reliable data for industrial flotation modeling and simulation to advance in better control systems design. In this work, a model of a rougher flotation circuit, based on operating variables and parameters fitted from industrial data, obtained in some previous work, is used to develop a set of logic rules in order to aid operating decisions. The simulator was first used to sensitize the effect of changing the froth depth profile on target variables, and then to find out the best profile to reject common disturbances coming into the plant. The flotation circuit simulator was redesigned to incorporate an expert system following the proposed control algorithm. Several tests were performed to evaluate the control responses to different correlated series of input variables, such as feed grade, tonnage, particle size distribution, and solid percentage. Control alternatives are discussed based on the circuit simulator. Keywords: modeling, industrial data, flotation control, mineral processing.

Sep 1, 2012

By Arun Appadurai

Pneumatic transport systems play a vital role in conveying discrete particles over a sizable distance with minimal energy consumption. However if such a system is not designed keeping particle physics in mind, it leads to intractable problems which could possibly assume dangerous proportions, including but not limited to expensive redesign of the entire system. This paper describes a novel method, which harnesses the powerful technique of Computational Fluid Dynamics (CFD) to investigate a problem occurring in rotary kilns using coal as a major fuel source. In some of the sites, a unique phenomenon of abnormally high CO emission was observed and owing to the highly random nature of occurrence, it was difficult to scientifically investigate the problem and its cause. Most of the published solutions for the high CO problem tend to concentrate on the incomplete combustion aspect of the kiln and resolve the situation by increasing the air supply thereby improving the stoichiometric ratio of combustion. This paper offers an alternate correlation that relates high CO emissions to the phenomenon of coal delivery fluctuations caused by the sub-standard operation of the coal transport system. A CFD model for the coal delivery pipe is validated by utilizing the actual process data sourced from the measurements taken from a functioning plant. The results of the model are used to derive correlative conditions that point to the unstable operating conditions of the coal delivery pipe prevalent in the industry. The conclusions are summarized into a series of recommendations for optimized design of coal delivery systems which are implemented in a pilot plant. The results irrevocably prove a statistically significant reduction in CO emissions without resorting to increased air supply and power consumption. Keywords:CFD, Pneumatic Conveying, Saltation Velocity, Particle Flow

Sep 1, 2012