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By V Radmehr

Ammonia and Amonium salts have been recognized as effective leaching agents in hydrometallurgical processes due to low toxicity and cost, easy recovery and high selective recovery of metals. New research findings of considerable advantages of leaching by these agents and elimination of problems associated with acid leaching has resulted in a new approach in the world to this method. The investigations in this field indicate more frequent use of this method for extracting copper from ore and concentrate relative to other basic metals. In this paper, we have attempted to describe the basis and different ammonia leaching methods and present the major research activities in this field for copper. We have also presented the latest findings and related novel processes. Comparative assessment of advantages and disadvantages of this method relative to acid leaching method, kinetic study of copper ammonia leaching and evaluation of Eh-pH diagrams in a system containing water and ammonia are other parts of our study. Finally, by describing the studies on copper extraction from the resulting pregnant solutions, the applicable extraction agents have been reviewed.

Sep 1, 2012

By R. S. Wang, S. Z. Zhou, L. Wan, K. W. Zeng, Z. J. Sun, W. G. Wu, Z. B. Qian, X. R. Zhang, Z. K. Hu, Y. Yu

"In view of the present situation that the traditional environment friendly depressants for galena aren’t very effective in the separation of mixed concentrate including copper sulfide and lead sulfide, this research describes a new environment friendly depressant PD-1 and investigates its effects and mechanism in the separation of chalcopyrite and galena. This study is carried out through flotation tests, analysis of infrared spectra and absorption measurements. It is shown that when O-isopropyl-N-ethyl thionocarbamate (Z200) is used as collector, chalcopyrite and galena can be separated in the presence of PD-1 under appropriate conditions. Therefore, it can be concluded that PD-1 has an excellent depression ability and great selectivity for galena. Meanwhile, analysis of infrared spectra demonstrates that PD-1 can strongly absorb on the galena surface by chemical interaction with Pb2+, while it hardly absorbs on the chalcopyrite surface. In addition, the results of absorption measurements reveal that competitive adsorption occurs on the galena surface between PD-1 and Z200, PD-1 can block the absorption of Z200 on the galena surface. However, PD-1 has a little effect on the absorption of Z200 on the chalcopyrite surface under above conditions. What’s more, the hydrophilic groups of PD-1 molecules can make galena effectively depressed. The results of mechanism analysis are in accordance with those of flotation tests.INTRODUCTION In the processing of copper-lead sulfide ores, the process, copper increase and lead reduction (Zhang et al., 2017) after reagents removal of rough concentrate produced by mixed flotation of chalcopyrite and galena, is usually adopted. However, as a result of tight symbiosis and the similar flotability of chalcopyrite and galena, the separation is difficult (Hu and Feng, 2006). There are 3 kinds of depressants for galena in the separation of chalcopyrite and galena concentrate,including dichromate, sulfite and combined depressants of organic or inorganic reagents (Wei, 2012). As dichromate would cause serious environmental pollution, it is gradually banned to be used in industry (Xu et al., 2017; Lin et al., 2017). what’s more, due to the need of acidic slurry, using sulfite is not conductive to the maintenance of equipment and stable production(Wang, 1999). As for the combined depressants, they also have disadvantages of complex pharmaceutical system and no ideal separation effect (Wei and Sun, 2008). Therefore, the development of new safe and effective depressants for galena is a research focus for researchers in the minerals processing (Chen, 2000). In this paper, a new type of organic depressant PD-1 is applied to the copper-lead separation process of ""copper increase and lead reduction"" using Z200 as the collector. In addition, the performances and mechanism of its depression to galena are studied emphatically."

Jan 1, 2018

The ball level and pulp load play a key role in the operation of industrial scale ball mills. These two operating variables have a significant influence on the performance of the ball mill and any attempts to optimize these devices require manipulating either one or both of these variables. There are several models that can be employed to perform simulations to optimize the performance of industrial ball mills. However, most of these models require ball load and pulp load measurements as inputs to calibrate the model. The changes suggested by the simulator also provide operating regimes that involve moving either the ball level or pulp load and sometimes both of these variables. A ball mill model coded in JKSimMet was used in conjunction with the Sensomag to optimize the secondary ball mill at Waterval concentrator in South Africa. The results show that the perfect mixing ball mill model can be used in conjunction with the Sensomag to optimize the performance of the secondary ball mill.

Sep 1, 2012

By Yang Zhao, Tao Xiu-xiang, Chen Song-jiang

"China is rich in low-rank coals that account for 45.68% of existing coal reserves in China. The clean and efficient utilization of low rank coals is of great significance for ensuring the effective energy supply and promoting economic development and environmental protection. In order to solve the difficult problem in flotation of low rank coal, it has become the focus of research in the related field that oily bubbles instead of air bubbles are taken as a carrier in flotation to improve the attachment efficiency and recovery of low rank coal. In this paper, low rank coal slime collected from Shendong mining area was used as the experimental material, and it focused on the characteristics of oily-bubble flotation process of low rank coal. Additionally, difference in conventional flotation and oily-bubble flotation was discussed. The induction time between air bubbles, oily-bubbles and fine low rank coal particles was measured. The results indicated that the induction time between oily-bubbles and coal particles was obviously lower than that of air bubbles. By comparing the foam height of air and oily bubbles, it was found that the amount of oily bubbles is less than air bubbles, causing relative low flotation rate of oily-bubble flotation at initial stage. Besides, the maximum foam height and half-life of air bubbles and oily-bubbles were measured respectively. The results showed that the stability of oily-bubbles was higher than that of air bubbles, which is benefit for the enrichment of concentrates. The clean coal water recovery of oily-bubble flotation is lower than that of air bubble flotation, which indicated oily-bubble flotation is lower in water entrainment. INTRODUCTION China is the largest energy consumer in the world, accounting for 23% of global energy consumption in 2016 and 27% of global energy consumption growth. Whereas coal is taken as the major primary energy source and its share of China’s primary energy consumption is 62% in 2016, in which the low rank coals, such as lignite, long-flame coal, weakly caking coal, and non-caking coal, accounted for about 50% of total coal production capacity (China’s energy market in 2016, BP). Moreover, the exploitation and utilization of low rank coals and other coals that are difficult to float have been an important strategy for China’s sustainable development of the coal industry (Liu et al., 2014). However, the combustion of low-quality coals leads to a serious environmental pollution. In addition, the deterioration in geological conditions of coal resources, and the increasing improvement in the mechanization for mining significantly caused the increased amount of fine coal."

Jan 1, 2018

By Swati Mohanty

Spiral concentrator, which works on the principle of gravity separation, is widely used in the mineral industries for separation of solid particles based on the size and density. In the present study, CFD simulation of the flow profile on a laboratory scale spiral concentrator of height 2.29 m, pitch 0.435 m and width 0.17m was carried out. A single computational domain covering the entire spiral was considered. Volume-of-Fluid algorithm was used to track the interface and predict the flow profile. In the present study the Donor-Acceptor method was used for the calculation of volume fraction in the cell. Simulation results show that the velocity increases as the water flows down due to the convective force and gravitational force, but the viscous force acting in the opposite direction retards the flow. Thus the maximum velocity is attained at turn three at which the viscous force overpowers the other forces and further down the velocity decreases. Measured water depths along the radius of the spiral at various heights were compared with simulated depths, which were in good agreement. The simulated liquid phase velocity profile was used to carry out preliminary studies on the flow profile of solid particles of size 500 micron and densities 2600kg/m3 and 5100kg/m3, based on the Lagrangian model taking into consideration fluid-particle interaction.

Sep 1, 2012

By Mario Gerards, Marco Steinberg, Jan Huben

"Wet high intensity magnetic separation or WHIMS is a widely used technical process for the recovery of magnetic susceptible iron ore particles, mostly for fine and ultrafine grain sizes. The JONES® WHIMS - Wet High Intensity Magnetic Separator, has been used for many years and in countries all around the world. This paper outlines the physical principles utilized for the separation inside the unit, as well as some of the recent changes and developments on the design. It will also give an outlook on the theoretical potential of different alternative yoke materials. The aim of this paper is to analyse the suitability of different yoke materials to improve the equipment. This will be done comparing the magnetic and mechanical parameters and analysing availability and price to find the best compromise regarding cost and benefit. As far as the different kinds of materials are concerned, a special material has been identified as suitable during the comparison exercise. After running the economical calculations, especially with respect to the reduction of the total power consumption of the equipment, a tremendous reduction of the total power consumption has been determined. In addition, to the theoretical exercises and due to the promising results of the same, the Pilot Unit P 40 of the JONES® WHIMS has been manufactured with the special material in order to get practical results as well. Finally, this paper outlines the theoretical and practical results focused on the power consumption. The results are showing that the total power consumption can be reduced tremendously. Hence, the way for a new generation of JONES® WHIMS - environmentally friendly - has been paved."

Jan 1, 2014

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 Lang Shiping

The criteria for designing a crushing chamber are presented and a program for designing the shape of the chamber is proposed. During the chamber shape design, major design parameters are analyzed first, optimized parameters are determined next and the basic shape of chamber is figured out finally. In the basic chamber design program, the influence of abrasion of basic chamber shape and material characteristic are not accounted for usually. Here, based on the minimum abrasion of chamber shape and uniform particle size theory, the equation for chamber surface curve and the transcending function were formulated and a low-abrasion chamber was designed. Since the chamber shape designed based on experience and experiments is not necessarily the best, optimal design of the crushing chamber shape was carried out. Cubic spline function was used to represent the chamber shape curve and a mathematical model was formulated. The optimal shape solution was obtained using a complex method. Finally, the optimal chamber shape was determined by matching the moving cone stroke S, moving cone speed N and the moving cone bottom angle Thus, superior technical performance of the cone chamber was achieved.

Sep 1, 2012

By Andrey V. Tarasov

"An environmentally clean and virtually waste-less technology for treatment of domestic and industrial solid waste (HGIW) including other toxic chloride-containing materials has been developed and proven on a full scale by the Gintsvetmet Institute in cooperation with some other Russian organizations.The essence of the process is that the HGIW are decomposing in the liquid base in air-bed slag melted layer under the temperature of 1350-1400°C.HGIW is considered as fuel heat-producing energy of 1500-1800 kCal/kg with 51,7%.Processing of municipal and industrial solid waste in molten slag is carried out autogenously without additional fuel, the blowing is enriched by oxygen up to 50-70%.The complex makes it possible to treat the furnace charge without preliminary drying and sorting with big differences in chemical and morphological composition due to the versatile firing chamber.The proposed process resolves the acute and globally significant problem of dioxin formation.The purpose of the proposed technology is to ensure such destruction of the structural lattice that would guarantee irreversible transformation of the resultant substances to prevent formation of dioxins. It was established the required preconditions to achieve this purpose."

Jan 1, 2003

By G. S. Zeng

The mechanism of cobalt removal from zinc sulfate solution with zinc dust is still not understood well. The experiments in this paper were carried out by zinc dust from zinc sulfate solution with high cobalt to study the mechanism of cobalt removal. Residues after the cementation process from zinc sulfate solution were analyzed by SEM and Electron probe micro-analysis (EPMA) to investigate the morphology of products. Different temperature will cause different structure of particles. With the increasement of temperature, cobalt removal can be improved considerably. The mechanism of cobalt removal by zinc dust is thought as follows: firstly, the cobalt ion forms Co-Zn alloy with zinc particles, and the reaction reaches equilibrium quickly; secondly, the Co-Zn alloy continues reacting to Co with Co2+, which is the control procedure of the whole reaction.

Jan 1, 2014

By Carlos Gualdron, Elizabeth Gomez, Rafael Bolivar

The productivity index of the Coopracarcegua Ltda., a mid-size coal mining company of Norte de Santander, Colombia, was related absenteeism using accident, productivity and profit data four years. The analysis was based on type, severity and frequency of accidents, number of absentee days; price per metric ton, and other relevant parameters. The enterprise is formed by 5 different mines of thermic coal, each one with different exploitation technologies and different productivity. Each mine was analysed separately and the loss of profit due to absenteeism was calculate for each one. The study showed that the foregone earnings due to absenteeism in terms of the whole productivity of the enterprise was about of 6.6% of the total profit average the 4 years, with calculated values of 14.7%, 3.5%, 8.4% and 4% per year in the evaluated period. The study identified that the most important cause of absenteeism was "General Disease". The foregone earnings in 2009, the highest loss for the analysed period, was about US$ 0.937 million and during the whole evaluated period was US$ 2.46 million.

Jan 1, 2014

By H. Y. Ran

Magneto-flotation is a recently developing technology of mineral processing. This technology combines the traditional magnetic separation with flotation and provides a magnetic and buoyant force compound field to separate different minerals based on the differences of magnetism and floatability between useful minerals and gangue minerals. Magneto-flotation is applicable to separate ferromagnetic from nonmagnetic minerals, especially to separate magnetite from floatable gangue minerals. This magneto-flotation column is equipped with pulse electromagnetic field in the middle upper part, a bubble producer and upwell water inlet in the bottom. The pulse time of electromagnetic field in the column can be optionally adjusted and the maximum intensity of pulse magnetic field can reach 35mT. Pulse magnetic field can not only restrain magnetic minerals from entering into the froth layer, but also destroy the magnetic agglomeration to ensure a higher recovery and a higher concentrate grade. The results of experiments with magnetite show that pulse magnetic field has remarkable influence on flotation process. Compared with single flotation, magneto-flotation column can improve the recovery of magnetite by ten percent. After one time?s magneto-flotation processing, the grade of iron concentrate can increase from 65.4% to 69.5%, the content of silicon oxide in iron concentrate decreases from 7.4% to 2.8%, and the total recovery is above 96%.

Jan 1, 2014

By Evgeni Visariev

In Copper smelter Aurubis Bulgaria, the copper in slag from the Flash furnace and the Converters is recovered by flotation. The scheme of slag processing is crushing, two stage grinding (autogenous and ball) and flotation. Till 2010 the grinding cycle in the plant was in two stages ? the first stage was AG Mill 70?23 working with a classifier and the second stage was ball mill 3.6/5.5 working with a hydrocyclone. In 2010 a new AG Mill 65x78 with hydrocyclone was put in operation in order to increase throughput of the plant. The second stage of the grinding cycle is with the same ball mill. The Old AG mill processed 55-60 t/h slag with particle size -0.071 mm 75% or over 75 t/h with particle size -0.071 mm 35-40 %. The new AG Mill was designed for throughput 105 t/h with particle size -0.071 mm over 70 %. After the start up there were some problems with the equipment ? block up of AG Mill?s grate and pumps for feeding of the hydrocyclone. For optimization of the process a lot of general tests were made. One of the main problem was a wearing of the sand nozzles. Different materials (rubber, ceramic, metallic) for the sand nozzles were tested. The openings of the grate were changed. This paper presents: ? the optimal technological parameters of the old and the new working scheme; ? how the technological parameters of the new working scheme change when the hydrocyclone works with different nozzles; ? the effect of the change of the grate openings; ? the problems with the increase of the circulating load; ? a final decisions for improvement of the grinding cycle work. Keywords: spigot, wearing, classification, effectiveness, circulating load, autogenous, mill

Sep 1, 2012

Incomplete liberation of mineral particles is one of the key factors limiting the performance of industrial flotation circuits. This work aims to quantify the relationship between different breakage modes and how these affect mineral liberation properties. A copper porphyry (bornite) ore sample was subjected to breakage using a piston-die compression unit and an impact mill. The particles produced as a result of each mode of breakage were then characterised using Mineral Liberation Analysis (MLA) to quantify the mineralogical and liberation properties of the progeny particles. The impact mill was found to produce bornite that was finer grained relative to the host particles. In con-trast, bornite discharged from the piston-die unit closely followed the size distribution of the host particles and was retained to a greater extent in the larger/intermediate size fractions. The results provide insight into what breakage methods are optimal for the purposes of downstream separation.

Jan 1, 2014

By Subrata Roy

The slag produced in metallurgical smelting processes contains considerable amount of valuable metals. The present work focuses on recovery of copper value by froth flotation from the copper smelter slag. The slag samples are subjected to detailed characterization including automated quantitative mineralogy using Mineral Liberation Analyzer (MLA). The MLA results indicate that a part of copper is present in sulphide form in fayalite (iron-silicate) matrix and very poorly liberated. SEM-EDX analyses also reveal that a certain part of the copper is present within the fayalite (Fe-Ca-Si) matrix, perhaps either as lattice impurity or very fine grain. The copper smelter slag is ground in wet mode in a ball mill, to particle size distribution suitable for flotation. Subsequently, the slurry undergoes froth-flotation in lab-scale Denver-type flotation cell. Various combinations of sodium iso-propyl xanthate (SIPX) and alkyl hydroxamate collectors are used along with pine oil as frother. A multiple collector dosage is required for effective flotation of non-sulphide copper phases associated fayalite and alkyl hydroxamate is identified as one of the effective collector for non-sulphide minerals. The copper recovery can be enhanced by 7-10% with a combination of collectors as compared to conventional sulphide flotation using only xanthate type collectors. However, the grade decreases to some extent. Keywords: flotation, copper slag, hydroxamate collector

Sep 1, 2012

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 M. M. Yahyaei

The Sarcheshmeh new concentration plant uses a 32 ft×16 ft constant speed (10.5 RPM) SAG mill with two 5500 hp motors which could rotate in two directions. The mill liners are chrome-molybdenum steel casting type with a Brinnell hardness between 325 and 375 with the lifter face angle of 14° and lifter height of 152 mm. The shell liner consists of 120 (two 60 rows) pieces with a High-High configuration in a rail design. A specially designed liner wear profile measuring device enabled fast and accurate measurements inside the mill during the mill shut-down periods. The measurements indicated that the liner wear profile along the liner length is non-uniform and the highest wear occurs between 1.25m and 2.75m of the mill length. The average weight of liners at the time of removal was 47% of the original weight indicating a significant metal loss. The modification of liner shape was undertaken with the aim of having a uniform profile at the liner removal time. The proposed liner unlike the pervious type did not have a uniform shape with a lifter height of 187mm at the section where the wear rate was high. It was believed that this new profile could arrive at a uniform profile at the liner change out time. A study was also directed to the possible change of charge motion due to the liner profile modification. The dynamic behaviour of charge was investigated through the analysis of forces acting on a single ball using mill characteristics such as mill diameter, rotational speed, lifter height and release angle. The simulation of charge motion with this method and Milltraj TM software indicated that the impact position of charge will change only one degree due to the maximum increase of 35 mm in the lifter height. This assured that the installation of the modified liner would not have any adverse effect on the mill because of ball impacting the mill shell. It was predicated that the amount of scrap metal will reduce to 30% from the current value of 47% beside 1500 h increase in the liner life time.

Jan 1, 2014

By G. R. Forbes

Flotation froth machine vision systems provide consistent real-time measurements pertaining to the state of the flotation cell being monitored. Typical measurements include froth velocity, froth colour, froth texture and froth stability. This paper presents the results from test work conducted on the molybdenite rougher circuit at the Kennecott Utah Copper Concentrator during February 2006. Machine vision results show that it is not possible to accurately determine bubble size distribution information for the molybdenite froth, despite using state-of-the-art methods. Instead, it is necessary to make use of texture measurements to classify the various different froth states. Numerous combinations of texture measurements and classifiers are used to determine the best combination. Results show that the Fourier ring based texture measurements perform the best when both K nearest neighbour and Gaussian mixture model classifiers are used. The concentrate grade of the flotation cell is modelled using combinations of froth velocity and froth texture descriptors. The results show that by using a linear combination of these descriptors rather than either one by itself it is possible to account for a much larger percentage of the variation observed in the concentrate grade data. Adjusted R2 values of 92% and 84% are achieved when modelling the copper and the molybdenite concentrate grade respectively.

Jan 1, 2014

By G. F. Zhang

Yunnan mineral is a kind of containing Ta-Nb rare earth deposit, the most potential economic valuable element in it is Sc, and raw mineral has 17.0 g/t Sc. Take the character of Sc into account, the key problem in producing scandium chloride molten salt by adaptive technology is how to man-ufacturer anhydrous scandium chloride molten salt. During the course above, the key problem is that preventing Scandium chloride from being hy-drolyzed into ScOCl. The ScOCl content of molten salt not only affect purifying scandium but al-so do harm to the production of Mg-Al alloy. In order to restrain the creation of ScOCl, add ammo-nium chloride into molten salt. As long as ScOCl is created, it would be chloridized. Thus, during the course of dehydrating anhydrous chloride molten salt this method prevents scandium from hydrolyzing. Accordingly, the key phase of this producing course is eliminate ammonium chloride and the surplus crystal water, and the most crucial of it is restrain scandium chloride from being hydrolyzed into ScOCl. This research analyzed the theory that ammonium chloride is trend to be hydrolyzed into ammo-nium chloride, and propose the research scheme of restraining this process from creating ScOCl. The new process of restraining the generating of ScOCl and dehydration for crystal water rare earth chloride is adopted: Inert gas temperature increases rapidly to a certain degree to eliminate ammonium chloride and crystal water. The experimental research were done such as : the temperature of eliminating ammonium chloride and crystal water, amount of ammonium chloride, time, temperature growth speed, influence of inert gas flow toward to scandium percent hydrolysis, whereby, we conclude the optimal process condition in this period: Temperature: 400°C, proportion of oxidized scandium and ammonium chloride is 1:1.5(Proportion of oxidized scandium and additional salt is 1:5.4), time is 120minute, temperature growth speed is 10?/min inert gas flow is 5L/min.

Jan 1, 2014

By F. Q. Cheng

As the important potash, the product yield of KCl in winter is low and the resources waste is serious according to the deficiency of collectors, which can be used in this condition currently. This paper studied on the change of contact angle, turbidity, and flotation recovery of KCl particles when different chain lengths, ratios of amines were used as collectors in KCl flotation process to get a new mixed collector. The contact angle values of KCl crystal in its brine solution added different amine collectors were first measured by captive bubble method. The turbidity of brine solutions were then measured by the laboratory turbidimeter at room temperature when different amine collectors were contained. In the end micro-flotation experiment using mixed amine with fixed ratios and ODA as collectors respectively at 5 °C, 23 °C were performed. The results show when the ratio of the mixed amine is DDA- 20%, ODA-60%, C20-20%, the contact angle at KCl surface is the maximum and the hydrophobic state is best. Meanwhile the result of turbidity measurement indicates that the dispersion of mixed amine colloids is better than the ODA collector due to the addition of DDA, which plays the role of frother. The flotation results also prove that the mixed amine is not only fit for the KCl flotation at room temperature but also fit for its flotation at low temperature. This study provides strong technical support to extend the production time of potash business in Chaerhan areas in China.

Sep 1, 2012