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By Peng Cao, Jimin Su, Yang Li

"Abutment pressure distribution is different when a longwall panel is passing through the abandoned gateroads in a damaged coal seam. According to the geological conditon of panel E13103 in Cuijiazhai Coal Mine in China theoretical analysis and finite element numerical simulation were used to determine the front pressure distribution characteristics when the longwall face is 70 m, 50 m, 30 m, 20 m, 10 m, and 5 m from the abandoned gateroads. The research results show that the influence range of abutment pressure is 40 m to 45 m outby the face, and the peak value of front abutment pressure is related to the distance between the face and abandoned gateroads. When the distance between the longwall face and abandoned gateroads is reduced from 50 m to 10 m, the front abutment pressure peak value kept increasing.When the distance is 10 m, it has reached the maximum. The peak value is located in 5 to 6 m outby the faceline. When the distance between the longwall face and abandoned gateroads is reduced from10 m to 5 m, the front abutment pressure sharply decreases, the intact coal yields and is even in plastic state. The peak value transfers to the other side of the abandoned gateroads. The research results provide a theoretical basis for determining the advance support distance of two gateroads in the panel and the reinforcement for face stability when the longwall face is passing through the abandoned gateroads.INTRODUCTIONFront abutment pressure is the result of rearrangement of in situ rock stress caused by the mining (removal) of the coal seam. Research on the distribution character of face abutment pressure have significant importance in confirming the width of the coal pillar and the distance of advance support in roadways (Liu et al., 2011; Liu, Jiang, and Zhu, 2015). Currently, there is a lot of research on abutment pressure characteristics of traditional longwall coal faces, thick coal seam longwall faces, isolated faces, and extra wide face abutment pressure distribution (Xie et al., 2006). However, theoretical analysis and research on the distribution law of the fully mechanized coal face to abandoned gateroads are relatively less. Abandoned roadways are often from less mechanized or room and pillar mines. Due to the existence of these roadways pre-longwall mining, the in situ stress has already been redistributed around the roadway (Liu et al., 2007). Thus, when the longwall approaches and mines through the roadway, the abutment pressure distribution behaviour has different characteristics than those of traditional solid undisturbed coal. Especially when the face approaches the abandoned roadway, the understanding of face abutment pressure distribution has significant importance to the timing of support installation (Ren and Ning, 2014). This prevents the occurrence of a roof and rib failure ahead of and on the longwall and highly efficient advance of the longwall safely and productivity. This paper analyses the E13103 face of the Cuijiazhai Mine of Wenzhou Mining Co., Ltd of Kailuan Group, as the engineering case study, and uses FLAC3D numerical simulation software to conduct numerical simulated analysis on the abutment pressure distribution mechanism of longwall coal mining face."

Jan 1, 2018

By Hongzhen Yu, Xiaoping Ma, Jiansheng Qian

The paper introduces the design of an Intelligent Managerial Attendance Machine (IMAM) for coal mines. In the system, data communication is carried by Optical fiber communication, including industrial control computer on the ground and the car

Jan 1, 1998

By M. S. Badollet

Introduction Very little fundamental research has been done on asbestos fibre to cake maximum advantage of its properties and to determine in what commercial products it can best be utilized. For the research chemist who is associated with asbestos development work, a thorough study of mineralogical information on asbestos deposits would furnish reliable information on the rock formations and the mineral impurities closely associated with the asbestos. Furthermore, ?he must have an intimate knowledge of the uses of the fibre in various products so that he can visualize the importance of the fibre and the role it plays in industry. Some of the properties of asbestos fibres such as strength, composition, length, harshness or softness, and mineral associates are of considerable importance to the manufacturer because they are responsible for many production difficulties. Fibre Strength It has been known for some time chat asbestos filaments have considerable tensile strength. These strengths have been referred to merely as 'weak' to 'very strong'. Not until recently have numerical values been applied to the strengths of asbestos fibres. But today we can take a thin fibre filament and mount it between two holders and apply a gradually increasing load or pull until the fibre breaks. By measuring the cross sectional area of the filament and the amount of load applied, we can calculate the tensile strength of the fibre in terms of pounds per square inch. This type of test is slow and rather difficult, but the fundamental data obtained furnish important basic information that can be applied to mechanical processing equipment and to certain asbestos products.

Jan 1, 1948

The molybdenum ores currently utilized in China are mostly molybdenum sulfide ores whereas oxidized molybdenum ores, being finely disseminated and difficult to process, have not been exploited and utilized effectively. In this article the beneficiation process of a molybdenum ore occurred in an oxidized ore zone was investigated in order to provide a new way for the development and utilization of the oxidized molybdenum ores in China. The molybdenum mineral in the ore was mainly wulfenite and the associated minerals included barite, limonite, quartz and small amount of cerusite. Limonite in the ore occurred in a crust and honeycomb-like colloidal state and composed the framework for the formation of the other minerals in the ore, which filled the pores in the framework. Wulfenite was mainly fine-grained and occurred in the fine porous crust and honeycomb-like framework. The finely disseminated ore structure made the separation and recovery of the molybdenum mineral in the ore very difficult. On the basis of the mineralogical study of the ore, experiments were conducted to compare the various mineral processing methods for the beneficiation of the ore, including single gravity concentration, single magnetic separation, single flotation, and a combination of high intensity magnetic separation and gravity concentration. The results indicated that with single gravity concentration a molybdenum concentrate containing 5.85 % Mo with a yield of 11.76 % and a Mo recovery of 43.5 % was produced. With single high intensity magnetic separation it was very hard to obtain a molybdenum concentrate product. With single flotation process a molybdenum concentrate containing 7.06 % Mo with a yield of 15.14 % and a Mo recovery of 62.63 % was produced. With a combination of high intensity magnetic separation and gravity concentration a molybdenum concentrate containing 6.46 % Mo with a yield of 11.81 % and a Mo recovery of 42.11 % was produced. In conclusion, compared to the other methods the flotation process can produce more reasonable technological and economical results and is the best process for the exploitation and utilization of the finely disseminated oxidized molybdenum ore.

Jan 1, 2014

By X. Q. Ma

The beneficiation test on low grade phosphate ore from a state of Russia is carried out. The rougher-cleaner ? re-cleaner system is used in the flotation process, The fineness of grind is 39.07% minus 200 mesh. The result indicates that concentrate containing 31.25% P2O5 can be obtained from the flotation feed assaying 6.18% P2O5, with 93.54% P2O5 recovery. The test result is also a guideline for further development of some currently operated phosphate beneficiation plants.

Jan 1, 2014

By Chuan-liu Wang

The bionic non-smooth surface has the characteristics of anti-wear, and reducing resistance. Based on bionic non-smooth surface?s characteristics, a bionic drill bit was developed. When the bionic drill bit is used, a bionic non-smooth surface forms on the crown of bionic drill bit. This surface can be used to extend the life of drill bit and improve drill efficiency. The bionic unit diameter and arrangement were researched in this paper to determine the optimal bionic non-smooth surface for further improving the life and efficiency of drill bit. Four bionic samples having the same structure size, materials and arrangement were designed and manufactured. After being sintered, the abrasion ratios of the four bionic samples were tested, and the results show that the abrasion ratio of Nos. 3 and 2 were similar (only 2% difference) and higher than that of No. 1 and 4. Therefore, the optimal diameter of bionic unit is 1.5 and 2.0 mm. Small diameter bionic drill bits were designed and manufactured, and tested in the laboratory. The results show that not all bionic structure bodies are better than normal diamond bits, except the bionic unit arranged in a reasonable range. When the angle was 24° and 30°, the arrangement of bionic unit were more reasonable, which shows the superiority of the bionic coupling bit.

Aug 1, 2013

By Feng Chen, Lirong Chen, Yufeng Guo, Wenjie Weng, Tao Jiang

"In this paper, the carbonthermal reduction behavior and the influencing factors of Panzhihua ilmenite under the condition of carbon-burdened were systematically investigated. The results show that the ilmenite forms into titanium nitride during the reduction process at 1200 °C under the condition of carbon-burdened. Carbon-burdened is beneficial to the reduction of iron oxide, but less favorable for the growth of iron grain.IntroductionThe titanium ferrous resources are very rich in Panzhihua-xichang area, accounting for about 38.85% of the world's proved reserves [1]. However, TiO2 grade of this kind of ilmenite is low and calcium magnesium content is high, it generally requires preconcentration to titanium-rich material—titanium slag or synthetic rutile.Chlorination process is an advanced method for production of titanium dioxide, which should takes high quality titanium-rich material with low content of calcium and magnesium as raw materials (the content of MgO and CaO are less than 1.0%). Ilmenite in Panxi area, however, contains high calcium and magnesium; it is not suitable as a raw material for chloride process. Methods of producing titanium-rich materials which have been applied in industry are electric smelting, various acid leaching and reduction rust [2-5]. There still exist some problems such as CaO and MgO removed not thoroughly, low resource utilization, high energy consumption and environmental pollution."

Jan 1, 2012

By Q. Chen, J. H. Zhang, M. Zhang, F. M. Zheng, Y. J. Zhang

The characteristics of air bubbles and gas dispersion in KYF flotation cell are studied using the method of the point conductivity probe and CFD simulation. With increasing of speed, the velocities of air bubbles increase slowly and the distribution of diameters exhibits little change. With increasing of aeration rate, the gas holdup is increased. However, the velocities and diameters of bubbles have no great change. The CFD predictions on gas holdup have good agreement with the experiment results. The gas holdup distribution in the center section is revealed. The gas dispersion in the middle and upper part of flotation cell is uniform. It would be helpful for bubbles and solid particles collision. The gas holdup of the lower part of flotation cell is scarce, and it agrees with the observation in experiment. The gas would accumulate at the suction side of impeller blades, and it would decrease the power consumption. The rotating speed and aeration rate have great effect on gas dispersion. With increasing of aeration rate, the gas holdup of flotation cell will increase. The increasing of speed would improve gas dispersion. The results are expected to help to optimize the performances of KYF flotation cell.

Jan 1, 2015

By Chaojun Fan, Du Wenzhang, Sheng Li, Hong-Hong Shi

"Coal and gas outburst is an extremely complex dynamic disaster in coal mine production process which will damage casualties, equipment facilities and disorder the ventilation system by suddenly ejecting a great amount of coal and gas into roadway or working face. This paper analyzed the interaction among the three essential elements of coal and gas outburst dynamic system. A stress-seepage-damage coupling model was established which can be used to simulate the evolution of the dynamical system, and then the size scale of coal and gas outburst dynamical system was investigated. Results show that the dynamical system is consisted of three essential elements, coal-gas medium (material basis), geology dynamic environment (internal motivation) and mining disturbance (external motivation). On the case of C13 coal seam in Panyi mine, the dynamical system exists in the range of 8-12 m in front of advancing face. The size scale will be larger where there are large geologic structures. This research plays an important guiding role for developing measures of coal and gas outburst prediction and prevention. INTRODUCTIONCoal and gas outbursts are a complicated mine gas dynamic phenomenon that pose a serious threat to coal mine safety production. Since the first recorded coal and gas outburst occurring in Isaac coal mine of the Lule coal field in 1843, more than 40,000 outbursts have occurred in the world. China ranks first in outburst frequency and intensity. In recent 20 years, China on average increases 37 pairs of coal mines and more than 280 times outburst accidents every year (Yan, 2013). The coal and gas outburst occurred on Oct 20, 2004 in Daping Coal Mine, Zhengzhou Coal Group, caused serious gas explosions and ejected 1,894 tons of coal into the face, causing 148 fatalities. In recent years, despite implementation of numerous control measures, coal and gas outburst still occur frequently ash mining depth and mining intensity increase. The outburst mechanisms can be summarized in the following four aspects: the gas leading role hypothesis, the geostress leading role hypothesis, the chemical effect hypothesis, and combination hypothesis. The last hypothesis has won the acceptance of most scholars who consider that an outburst is the result of combined effect of stress, gas and coal (Yu, 1992).Numerous experimental measurements and numerical simulations were conducted to investigate the permeability and damage development process in coal seam. Sobczyk, et al (2011) carried out a laboratory research of the influence of sorption processes on gas stresses leading to coal and gas outbursts. Wang, et al (2013, 2015) conducted laboratory experiments to investigate the rapid decompression and desorption induced energetic failure in coal using a shock tube apparatus. Xu, et al (2006) developed a coupled gas flow and solid deformation numerical model and applied to simulate the coal and gas outbursts in underground coal mines using RFPA2D-Gasflow. An, et al (2013) and Xue (2014) analyzed major parameters and the effect of gas desorption on outburst initiation and established a model of gas migration and mechanical processes during excavation."

Jan 1, 2016

By Walter Knox, J. D. Doherty

IN 1939, at the request of The Koppers Coal Co., the Koppers Company Research Department established a Stoker Coal Research Laboratory for the purpose of investigating the performance characteristics of stoker coals in typical domestic stoker installations. Fig. I is a photograph of part of the laboratory. The material in this paper deals with the performance of one coal in a single installation. Presented are details of this installation, mechanical characteristics of the stoker, and the results of a series of burning tests in which adjustments were systematically varied. SUMMARY OF RESULTS Mechanical Features I. A large percentage of the total power consumed by a domestic stoker is used to operate the gear case and motor (Fig. 3). 2. The power consumption per ton goes down with an increase in rate of coal feed (Fig. 4). 3. The automatic air control in this stoker showed advantages over manual control (Fig. 5). 4. The air velocities through the retort tuyeres were uniform around the retort, but varied between the rows of tuyere rings (Fig. 6). 5. The crushing of coal with this stoker increased the minus 1/8-in. from 1 1.6 per cent to 19.2 per cent. There was a noticeable segregation of coal as it came from the retort and distribution was not uniform (Fig. 7). 6. Measurement of air entering over the fire showed that with some not uncommon adjustments this air may he a high percentage of the total air supply (Fig. 8 and Table I). Operating Performance I. The removal of clinker was shown to give a period of poor performance characterized by a high fuel-bed resistance and a high percentage of carbon monoxide in the flue gases (Fig. 10). 2. The fuel-bed resistance was found to decrease as the fuel bed built up in a normal response to heat demand after a prolonged hold-fire (Fig. II). 3. With intermittent operation the burning rate was almost always less than the feeding rate. The wide variations were found to be greatly dependent upon the length of the On period and the length of the intervals between On periods (Fig. 12). 4. The maintenance of a low furnace draft led to less fly ash, better clinker formation, and higher efficiencies (Fig. I3). 5. The maintenance of a minimum of excess air also resulted in less fly ash, better clinker formation, and higher efficiencies (Fig. 14). GUIDING PRINCIPLES In planning the investigations, the following principles were adopted: Selection of Healing Equipment.-Use only standard models of stokers and furnaces representative of those widely used.

Jan 1, 1942

By Jianwen Yang, Yucai Zhou, Yanhong Dong, Daixiong Chen

"The study of combined depressants for flotation separation of lead from copper has been carried out to solve the copper-lead separation problem. Test results show that the depressant of CMC (Carboxyl Methyl Cellulose) or sodium sulfite plays an important role on the selective depression of galena flotation. When the two reagents above are combined, the selective depression effect on galena is further enhanced. When the mass ratio of CMC to sodium sulfite is 1:4, galena was best depressed, with the lowest lead content in the copper concentrateClosed-circuit tests indicate that under a certain pH value of the slurry, with the best ratio of CMC to sodium sulfite as depressants, the copper concentrate with the grade of 28.23% copper and 4.12% lead is obtained, and the copper recovery is 84.87%; the lead concentrate with 68.12% lead and 0.86% copper is obtained, and the lead recovery reaches to 92.20%. An efficient separation of copper and lead is achieved with the combined depressants. INTRODUCTIONComplex copper-lead-zinc sulfide ore is abundant in China. With the rapid increase of mineral consumption, it has become one of the important sources to produce copper-lead-zinc metals. However, it is difficult to achieve effective separation of copper and lead, due to the complicated ore properties, such as fine dissemination, low copper grade, complex symbiotic relationship and similar floatability of copper and lead.Poisonous reagents of bichromate and cyanide are often used as depressants for copper lead separation. They have good separation efficiency, but pose serious pollution issues. As the environmental protection is becoming more and more important, it is a trend to replace traditional toxic reagents with new nontoxic efficient chemicals. Organic depressant FCLS studied by Liu has strong selectivity against galena, and does not depress chalcopyrite. A new type of galena depressant of CLS-01 discovered by Jin-lin Yang shows good results in the separation a mixed copper and lead concentrate. In addition, dextrin, chitosan and some other natural organic compounds (Drzymala, 2003; Huang, 2012; Qin, 2013) have also been studied to separate copper and lead."

Jan 1, 2016

By Jianhang Hu, Li Yang, Yonggang Wei, Kongzhai Li

"In this paper, the pyrolysis of biomasses including bamboo, sawdust and walnut shell were performed in a tube furnace under temperatures between 400? and 600? to obtain biomass carbon, gas, and tar. Textural parameters analysis revealed the caloric value of biomass carbons between 32 MJ/kg and 34 MJ/kg. It also indicated that the surface of biomass carbon consists of mesopore and macropore structures. By using GC analysis, it was determined the main ingredients of pyrolysis gas are CO, H2, CO2, CH4, C2H4 and C2H6. Calculation states that the density of pyrolysis gas is roughly between 1.0 kg/m3 and 1.7 kg/m3, while the calorific value of pyrolysis gas is between 12000 kJ/m3 and 16500 kJ/m3, illustrating that pyrolysis gas is a median gas. The calorific value of biomass tar was found to be between 32 MJ/kg and 34 MJ/kg, with more than 80 compounds in the biomass tar identified by GC-MS method.IntroductionBiomass as a renewable source is the world's largest and most sustainable energy resource [1].The conversion of biomass has the potential to be a renewable and carbon neutral method of producing fuels and chemicals [2-4]. Pyrolysis is a thermo-chemical process defined as applying heat to degrade biomass in an inert atmosphere. It transforms unstable biomass and other organic materials into biomass carbon, gas, and tar [5]. Biomass carbon can be stored or transported much easier as compared to parent biomass or be converted to value added products such as activated carbons[6]; gas is a relatively low-energy-density fuel; tar can be considered as a source of useful chemicals[7].The characterization of biomass pyrolysis will lead to its increased understanding and utilization as a source of solid, liquid and gaseous products which can be used as fuels and petrochemical feedstock[8,9].In recent years, many researchers studied the effect of temperature on biomass pyrolysis product distribution characteristics in a variety of pyrolysis reactor[10]. Ramin Azargohar's paper [11] presents the results of characterization for biomass and investigates the effects of pyrolysis temperature on the pyrolysis products obtained by fast pyrolysis of four different types of biomass."

Jan 1, 2014

By X. Xu

This paper presents the research on comprehensive recovery of copper, gold, silver and iron from tailings from high-intensity magnetic separation in Tonglushan Mine. By comparison of experimental results of three flowsheets?regrinding of tailings-conventional sulphidizing flotation, water heating enhanced sulphidizing flotation and acid leaching-sulphidizing precipitation flotation, it is concluded that regrinding of tailings-conventional sulphidizing flotation flowsheet has the best economical and technical performance and practicability. Regrinding and using the mixture of sodium hydroxamate and sodium xanthate are two of the notable technical characteristics of this best flowsheet. The system for comprehensive recovery of tailings has been put into production. It not only can recover the valuable minerals from tailings in Tonglushan Mine, but also can reduce the environmental pollution, resulting great economic and social benefit.

Jan 1, 2014

By Li Xibing

The In order to mine safely with reasonable cost, it is necessary to research the fracture characters of backfill and its matches with rock mass. Four kinds backfill with cement-tailing ratio of 0.250, 0.125, 0.100 and 0.083 respectively were tested, and basing on stress-strain curves tested, the deformation characters and fracture laws as well as the damage constitutive equations investigated with damage mechanics whose calculating results are coincided with experiment results well were proposed. The results of damage analysis show that there have different damage characters in different backfill, e. g. the lower the ratio of cement to tailings the lower the damage values when stresses reach to peak value; the lower the content of cement the more rapid in damage and the more abrupt in breakage process. In addition, using catastrophe theory, an energy model was proposed for backfill and rock mass acted each other in mechanics, and the unstable condition of the system was obtained. Research results show that the higher is the stiffness of rock mass the more stable the system, and the lower is the ratio of cement to tailings, the more unstable the system will be. Further more, according to the catastrophe model proposed, the reasonable matches between backfill and rock mass were researched, and a calculation formula that designs reasonable strength of backfill during mining was put forward. It has been proved by practice that the model and theory researched in this paper can guide filling design in mining. Keywords: Cemented tailings backfill, constitutive equation, catastrophe theory, match of backfill and rock mass

May 1, 2007

By Zhenyang Wang, Yiran LIU, Xiangdong Xing, Jianliang Zhang, Zhengjian Liu

Basic characteristics of marine placer were systematically studied by chemical analyze, scanning electron microscope and X-ray diffraction in this paper. It could be found that the marine placer mainly consists of titanomagnetite and titanohematite. A series of experiments were performed to investigate reduction-magnetic separation for Fe and Ti from the marine placer. Effects of reduction temperature, reduction time, carbon ratio, magnetic density, and grinding fineness on the reduction-magnetic separation process were investigated. And the optimal process parameters were obtained as follows: the reduction temperature 1300, the reduction time 30 min, the carbon ratio 1.1, the magnetic density 50mT, and the grinding fineness of 0.074μm 86.34%. Under such conditions, the metallization rate, iron grade of magnetic substance and iron recovery reached to 94.23%, 97.19% and 90.28% respectively, and the titanium grade in non-magnetic substance and recovery of was 57.94% and 87.22% respectively. The effective separation of iron and titanium could be achieved in reduction-magnetic separation process.

Jan 1, 2015

By Z. C. Zhen

Basing on character of fine ores, and employing all the advantage of dissolved-air flotation, the study within the dissertation put forth the methods of superfine metal mineral flotation with dissolved-air flotation equipment, and constructed a full set of laboratory flotation system. Experiments both in water and in slurry were respectively carried out by means of this flotation equipment. Further study was also fulfilled on mechanism of air-dissolved released devices, and the key components of system including ejector, releaser and saturator were designed. Optimizing devices parameters were chosen by taking ideal performance of the devices into consideration, according to orthogonal experiments and tests on bubbles factors, those performance factors were called air release rate, air release efficiency. The results with some minerals are better than JJF flotation machine with 30 litres bulk. The Dissolved-air Flotation(DAF) machine shows great potentiality in treating super-fine metal mineral concentration. The research indicates the Dissolved-air Flotation(DAF) system has superiority over mechanical flotation machine in fine flotation. Air-dissolved released bubbles appear on the surface of hydrophobic minerals in priority, solving collision probability less in the tradition fine mineral separation, such that the metallurgy technology of fine metallic minerals are improved. The exploratory research is a foundation for industrial pilot, commercial test and equipment maturity in the future.

Jan 1, 2014

By Lama RD

The paper outlines the development in the control of dust in Australia over the last 20 years. Factors influencing dust make at the faces are discussed. The effect of high production systems is analysed. Changes in dust standards and results of dust sampling on longwalls and continuous miner panels are given. Research conducted on air curtains and water infusion on dust control on longwall faces is presented along with recommendations for future research. It is found that both dust curtains and water infusion can cut dust mak by 50" each when applied separately.

Jan 1, 1988

By Z. G. Li

The large-scale vibrating screen has been applied widely in coal industry and other industrial areas as a kind of important device. As vibration mechanical device, it works very hardly and works in very bad environment so that the structure of screen is damaged easily. Therefore, it is very important that how to detect the fault of structure as early as possible to make the repair schedule reasonably and economically and to avoid the body hurt and device damage. As a kind of important structure of vibrating screen, the lower crossbeam is the main carrying structure and it is easily damaged, so it is regarded as a researched object in this thesis and it is tested under the load in the laboratory. Based on the test, acoustic emission wave signals can be got-ten by modern acoustic emission testing technique. Then, the ?wavelet packet - energy? from the characteristics of acquiring signals is used as neural network input vector. In the BP network structure design, the design of a hidden layer with variable number of BP network is established. Based on the error by contrast, the best nerve number can be identified in the hidden layer. Through integrated analysis, using Levenberg-Marquard BP study algorithm, network-training errors are relatively small, the acoustic emission signal is used in BP neural network as a pattern of recognition. In Matlab6.5, neural network model identification is created and taking advantage of nonlinearity and the ability of learning and memory of Neural Network, this model is fixed by training structure of network with training samples. The work presented shows that acoustical emission signal processing and research on early fatigue fault diagnosis based on the wavelet and the neural network is viable.

Jan 1, 2014

By Jinxia Nie, Yunnen Chen, Dachao Zhang

"Rare earth resources are strategic and non-renewable resources. But disordered exploitation on rare earth metals leads to resources waste, environmental pollution and ecosystem destroyed. In this paper, soil collected from garden was cultured in thermostated incubator. Adding exogenous rare earth to the soil and the effects of recombination action of rare earth lanthanum, cerium and yttrium on soil enzymatic activities were studied. The results showed that single metal La and Ce can increase urease activity, but Y inhibits its. Coexist La/Y or La/Ce in soil inhibit the urease activity, coexist Y /Ce or coexist three metals promote its. Single metal La, Y and Ce can promote catalase activity, and that of coexist three metals. Pairwise coexist La, Y, Ce in soil inhibit catalase activity. With certain concentration of rare earth recombination action, urease activity in soil has been very significant direct proportion to ionic impulse, but catalase activity been insignificant inverse proportion to its.1. IntroductionThe increase of rare earth element content due to anthropogenic inputs frequently takes place in agro-industrial areas, leading to soil pollution episodes that may cause serious environmental problems because of their potential toxicity to microorganisms, plants, animals and human beings [ 1]. China is abundant in lanthanides resources. Rare earth metals are used in many frontier technologies such as photic devices, magnetic materials, and fine ceramics, and the amount of the rare earth metals used in these industries has been increasing. In addition to their use in industry, rare earth metals are more widely applied to cropland as microelement fertilizers due to their ability to promote growth and productivity of some crops [2]. As a result, more and more rare earth metals are moving into the ecosystems. While a permanent contamination of soils results in populations of micro-organisms with high resistance to rare earth metals, a short-term burden of contaminants at high concentrations could exert inhibitory effects on microbial carbon [3]. They accumulate in soils, bioaccumulate in crops, and enter the food chain, causing a potential problem of rare earth metals environmental pollution in China [4]. This contamination may also severely influence organisms and soil activities [5]."

Jan 1, 2011

By G. Y. He

The large-scale 8.53m×3.96m (28?×13? F/F) SAG mills was first applied in Donggua Hill Copper Mine which processes 13,000 tons ore per day. The crushing and grinding circuit went into operation in the Donggua Hill plant in October 2004. However, at the beginning, the productivity of grinding only reached 58% of the capacity expected and some indexes of the crushing and milling circuit didn?t meet the requirements. Especially, the total load of the 8.53m×3.96m (28?×13? F/F) SAG mills was up to 34%~41% (25%~30% designed)and some hard rocks with the size of 25~70mm, which can?t be treated as a medium or even would be crushed and make larger ores or steal balls necessary, were seriously accumulated in the SAG mills. Consequently, they occupied the effective mill volume which in turn reduced the efficiency of the SAG mills and increase the energy consumption. In order to solve the problem of accumulation in the SAG mill and increase its productivity, some measures were taken, such as passing more hard pebble through the grate at mill dis-charging end, changing the type of steal balls and so on. And the results showed that these measures functioned well and had good effects, which is that the filling percentage of the SAG mills has been reduced to 26%~29% from 34%~41% with the composition of particle sizes improved a lot and the productivity increased by 77.4% reaching up to 13,380 tons per day.

Jan 1, 2014