Chun-hua Gao, Xiao-bo Yuan, "Development of the Shaking Table and Array System Technology in China", Advances in Civil Engineering, vol. 2019, Article ID 8167684, 10 pages, 2019. https://doi.org/10.1155/2019/8167684
Shaking table is important experimental equipment to carry out antiseismic research. Research, conclusion, comparison, and analysis concerning the developmental history, constructional situation, performance index, control algorithm, and experimental technique of the internal shaking table were reviewed and compared. Such functional parameters as internal shaking tables table-board size, bearing capacity, working frequency, and maximum acceleration were given. Shaking tables constructional status quo and developmental trend were concluded. The advantages and disadvantages of different control algorithms were contrastively analyzed. Typical shaking table test, array system tests, and experimental simulation materials were induced and contrasted. Internal existing shaking table and array system tests structural type, reduced scale, and model-material selection were provided. Analysis and exposition about the developmental tendency of shaking tables enlargement, multiple shaking tables array, full digitalization, and network control were made. The developmental direction, comparison of technical features, and relevant research status quo of shaking table with high-performance were offered. The result can be reference for domestic or overseas shaking tables design and type selection, control technique, and research on experimental technique.
At present, the structural seismic research methods include the pseudostatic test, pseudodynamic test, and shaking table test. The test method of the shaking table test can recreate the structural response and seismic oscillation in the lab accurately and reproduce the whole process of seismic oscillation effect or artificial effect in real time. The development of shaking table provides an accurate and effective way to study structural elastic-plastic seismic response .
Japan and the United States are the first two countries to establish shaking tables in the world. And, China initially built a shaking table in 1960  when Institute of Engineering Mechanics, Chinese Academy of Sciences, built one-way horizontal vibration  with a specimen size of 12m3.3m. So far in China, there are a lot of shaking tables ; some were made in China, some were systematically remodeled from imported parts, and some were totally imported. In recent years, many scholars [8, 9] and Wang et al.  conducted abundant research on the development and control technology of Chinas shaking tables and also got some research achievements. However, such results are mostly summaries of the test technologies or control technologies of shaking table , while there are few summaries concerning the construction history and usage of domestic shaking tables. This paper makes a comprehensive summary of the development and application of domestic shaking tables and array test technologies in terms of the development, control technology, test application, and development trend of shaking table and array system based on current collected information, so as to provide some reference and basis for the construction and development of domestic shaking table.
The development of shaking table in China came relatively late [1, 3, 1114]. It can be roughly divided into four stages. In 1960s, the mechanical shaking table was the main stream with a working frequency of 1Hz40Hz, of which the characteristics of the specimens in low segment are difficult to be controlled [2, 10, 11]. Electrohydraulic shaking table was then rapidly developed with its high frequency. In 1966, departments of machinery and electronics collaborated with each other to build Chinas first exclusive shaking table for national system of defense in three years [2, 10, 13]. Thereafter, many domestic colleges and universities as well as scientific research institutes also begun to conduct researches. For example, Tongji University brought in the 4m4m two-horizontal dimensional identically dynamic electrohydraulic shaking table developed by American MTS, which has been transformed into three- to six-degree-of-freedom identically dynamic shaking table . At the beginning of the 70s, the research on shaking table in China was continuously carried out and quickly developed. Our country also started to develop one-way electrohydraulic servo shaking table but rarely hooked into multiaxis shaking table . And, foreign shaking tables were introduced only when the test was demanding, so the introduction quantity of shaking tables was sharply decreased. Domestic institutes that conduct researches on shaking table mainly include China Academy of Building Research, Xian Jiaotong University, HIT (Harbin Institute of Technology), Institute of Engineering Mechanics, and Tianshui Hongshan Testing Machine Co., Ltd. [21, 22]. The shaking table construction situation in China is shown in Table 1.
The work frequency of electrohydraulic shaking table in the early stage of our country was about 50Hz. At present, at home and abroad, the work frequency of high-thrust shaking table with over 50t can reach more than 1000Hz. For instance, the work frequency of Y2T.10c shaking table developed by 303 Research Institute of China Aviation Industry Corporation is as high as 1000Hz, and the wide band random vibration control precision is 2.0dB  within the frequency range of 20Hz1000Hz.
In 2006, Beijing University of Technology built a nine-sub-building block array system with a size of 1m1m, which along with the original 3m3m single-array system composed the 10-subarray system, which can be used to constitute testing systems with any several subarray systems and many optional positions; at the end of 2006, Institute of Electro-Hydraulic Servo Simulation and Test System of Harbin Institute of Technology (HIT) developed successfully the first domestic multiaxis independent intellectual property rights (the hydraulic vibration test system with shaking table system is shown in Figure 1) and got identification, which changed the history of depending on importing shaking tables . In 2012, Jiangsu Suzhou Dongling Vibration Test Instrument Co., Ltd. successfully developed the worlds largest single electromagnetic shaking table test system (http://www.cnki.net/kcms/detail/11.2068.TU.20130124.1608.001.html) with a thrust of 50 tons.
With the 9-subarray system of Beijing University of Technology as an example, this paper introduces the construction situation of shaking table array system. In 2003, The State University of New York built the first set of two-subarray systems. In the same year, the University of Nevada-Reno built the three-subarray system with three movable two-direction shaking tables. The size of the table and the maximum bearing capacity of the shaking table are introduced. The array system (shown in Figure 3) is suitable for experimental research on spindly space structure.
In 2004, Chongqing Jiaotong Institute of our country completed the constitution of the two-subarray system with a specimen size of 6m3m, of which one is fixed and the other is movable (shown in Figure 4). And, in 2008, National Key Laboratory of Bridge Dynamics was established.
In 2011, Beijing University of Technology began to prepare to construct nine-subarray system (shown in Figure 5) and has built 12 sets of actuator building block array systems till 2006, which was increased to 16 sets in 2009 and is now the array system with the largest number of single-array system in the world. Each single shaking table is composed by mesa, 5 connecting rods, a vibrator, and a base. The array system can be made into various combinations by 16 sets of vibrators and connecting rods to conduct varied shaking table array tests with different layouts and forms. The performance indicators of nine-subarray system are shown in Table 2. The system uses four piston pumps to offer oil. The rated oil supply pressure of the seismic simulated shaking table system is the same as the maximum oil supply pressure. In addition to 4 oil pumps, the system also has energy storage to supplement the oil supply when the oil supply of the oil supply pump is insufficient.
There are two main types of traditional shaking table control technology: one is PID control based on displacement control and the other is three-parameter feedback control (also known as the three-state feedback control) synthesized by the displacement, velocity, and acceleration . It is essential for feedback theory to adjust the system after making the right measurement and comparison. In 1950, the PID control method mainly composed of unit P proportion, integral unit I, and differential unit D was developed. The traditional PID control method is simple in control algorithm, good in stability, and high in reliability and thus has been widely applied in the practical engineering. The PID control method is especially suitable for deterministic control system. Yet, as the target signal of shaking table is acceleration signal, high-frequency control performance is poorer when the displacement PID control is adopted, while the mesa cannot be located if acceleration PID is used. Meanwhile, in the process of control, nonlinear behavior exists in every specimen; thus, the effect of traditional PID control is not ideal due to the large waveform distortion [24, 2629]. As the structure sets higher requirement for control accuracy, three-parameter feedback control synthesized by the displacement, velocity, and acceleration was put forward in 1970s (the control principle is shown in Figure 6), which makes up for the narrow frequency band and the inability to realize acceleration control of single displacement control. Acceleration feedback can improve the system damping, and velocity feedback can improve the oil column resonance frequency. Adopting the displacement to control low frequency, speed to control midfrequency, and acceleration to control high frequency plays an important role in improving the dynamic behavior and bandwidth of the system. The introduction of three-parameter control technology greatly improved the playback accuracy of seismic time history, but due to the complexity of transfer function in the system, the correlation of input and output waveform is still not high. Power spectrum emersion control algorithm modifies drive spectrum utilizing system impedance and the deviation of the reference spectrum and the control spectrum, so as to get a relative high consistency of response spectrum and reference spectrum of the system [30, 31]. Power spectrum retrieval principle diagram is shown in Figure 7. This method belongs to the nonparametric method, which has nothing to do with any model parameters. But the matching degree of estimated power spectral density and real power spectral density is very low, so it is an estimation method with low resolution.
Another kind of the parametric estimation method, using the parameterized model, can give a much higher frequency resolution than period gram methods. The power spectrum control method based on the parameter model has high resolution and can improve the system control convergence speed and power spectrum estimation precision, yet it is sensitive to noise with higher computation requirements. Therefore, in the vibration test control, it has not reached practical stage .
The traditional control algorithm is based on the linear model of vibration table and specimen , and the parameters in the process of test are assumed unchanged, but the actual test object is very complex. The components experience elastic-plastic phase and then the failure stage in the process of the test, and the parameters that were assumed to be unchanged turn out to have been changed in the process of test. The change of the parameters influences the accuracy of the input seismic signal, which is the biggest defect in the traditional control technology. From the 1970s to 80s, intelligent control is a new theory and technology with strong control ability and great fault tolerance. The introduction of the adaptive control improved the robustness and control precision of the system, such as adaptive harmonic control theory (AHC), adaptive inverse function control theory (AIC), and the minimum control algorithm (MCS) . At present, the fuzzy control algorithm of the structure control attracted the attention of more and more scholars with its advantages of powerful knowledge expression ability, simple operational method, and the adoption of fuzzy language to describe the dynamic characteristics of the system. As early as 1996, some scholars abroad has carried out the induction and comparison of structural seismic control methods and summarized the advantages and disadvantages of various control methods, particularly expounding that the fuzzy control and neural network control algorithm could better solve the problem of nonlinear. The application of domestic intelligent control algorithm in the engineering structure control is relatively late. In 2000, Ou  and other scholars proposed the control algorithm which can realize fuzzy control according to the control rules and fuzzy subset, which greatly improved the practicability and efficiency of fuzzy control algorithm.
Most of the fuzzy control rules are established based on experience, leading to great difficulty in structure control. In view of this, Wang and Ou , in 2001, put forward the method of extraction, optimization, and generation of fuzzy control rules with the basis of structural vibration fuzzy modeling and genetic algorithm. Qu and Qiu  came up with a kind of active feed forward control method based on adaptive fuzzy logic system method, which better solved the nonlinear control problems of reference signal and external interference in the feedforward control. Wang  for flexible structure completed the application of the fuzzy PID control method in the structural vibration and conducted the active control experimental verification of beam vibration.
The efficiency of fuzzy control depends on the selection of function parameters and the establishment of the fuzzy control rules. Therefore, the adaptive fuzzy control is of great research significance for the nonlinear structure system. Because of the functions of self-adaptation and self-study of artificial neural network, the application of neural network in seismic control in civil engineering began in the 60s, which adopts a simple neural network controller to control the movement of the inverted pendulum, and achieved good effect. In 2003, Mo and Sun  implemented numerical simulation of active vibration control on the beam vibration control model by using genetic algorithm with the minimum energy storage structure as the goal, compared with the exhaustive method, and achieved good control effect. Chen and Gu  carried out simulation research on the application of frequency adaptive control algorithm based on the least square method in the domain of vibration control, and the simulation got the damping effect of about 50db. Li and Mao  achieved evolutionary adaptive filtering algorithm with strong instantaneity and applied it into the vibration control of structures to conduct simulation calculation based on genetic algorithm and moving least mean square algorithm of transient step, and the simulation obtained the damping effect of about 30db.
To solve the limit bearing capacity of shaking table for large structure test, scholars from all over the world conducted a wide variety of researches. The combination of substructure technique and shaking table test is an effective way to solve this problem . Hybrid vibration test divides the structure into test substructure and numerical substructure. Test substructure is the complex part in experiment on shaking table, while numerical substructure is the simple part to carry out numerically simulation. Test substructure can carry out full-scale or large-scale model test, avoiding the influence of the size limit of shaking table with large-scale structure, and thus was widely used in the study of the engineering seismic test. The domestic researchers Chen and Bai  implemented preliminary exploration into structural seismic hybrid test technique on account of the condensation technology. In 2008, Chen and Bai  also embarked on the hybrid vibration test on the hybrid structural system of commercial and residential buildings, of which the bottom commercial district was put into a full-scale experiment on shaking table and other parts were involved in numerical simulation.
In 2007, Mr. Wu Bin from Harbin Institute of Technology applied the center difference method into the change of the acceleration calculation formula in hybrid real-time test which takes consideration of the quality of test substructure and analyzed the stability of the algorithm. The test results show that the stability of the center difference method in real-time substructure application is poorer than that of the standardized center difference method. Such scholars as Yang  in the same year made the numerical simulation analysis on the shaking test substructure test, and the analysis results show that the integral step change is sensitive to the influence of experimental stability. At the same time, he verified the validity of the theoretical research results.
In recent years, the structural styles of shaking table test research were developed from masonry structure, frame structure, tube structure to bridge structure, structures with the consideration of some isolation and damping measures, and structural foundation interaction experiment. The application of shaking table tests on the structure seismic resistance made it possible to establish structure nonlinear model with various structural styles . Many shaking table tests have been carried out in recent years in China, which, according to the testing purpose, can be roughly divided into three categories: the first type is to determine structural earthquake-resistance performance as the test purpose; the second type is to determine the dynamic characteristics of structure, obtain such dynamic parameters as the natural vibration period and damping of structure, seek for weak parts of the structure damage, and provide the basis for super high-rise and supergage designs; the third type is to verify the applicability of certain measure or design theory in the structure. This paper drew a conclusion of typical shaking table tests in recent years in terms of building types, model dimensions, and so on (shown in Table 3).
Shaking table experiment diversifies the structural styles in experiment, makes it possible to establish the nonlinear damage model, and provides a reliable basis for all kinds of structures to establish the corresponding destruction specification. But large span structure tests on bridges, pipes, aqueduct, transmission lines, and so on may produce traveling wave effect under the action of earthquake due to large span, and a single shaking table will not be able to simulate the real response of the whole structure under seismic action. Array system can better solve these problems. For example, the State University of New York-Buffalo did damper damping effect research on Greek Antiliweng Bridge using 2-subarray system; conducted shaking table array test research on two continuous steel plate girder bridge and concrete girder bridge by using the 3-subarray system of University of Nevada. Many domestic scholars also carried out shaking table array test research on different structures of array systems. For instance, in 2008, Gao Wenjun made shaking table array test research of organic glass model on Chongqing Chaotianmen Bridge with the 2-subarray system of Chongqing Traffic Academy; conducted a multipoint shaking table array test research on concrete-filled steel tubes arch bridge with the 9-subarray system in Beijing University of Technology.
According to the size of mesa, shaking tables can be divided into large, medium, and small ones; in general, specimen size less than 2m2m for the small, 6m6m for the medium, and over 10m10m for the large. Due to the size limitation of a small seismic simulation vibration table, it can only do small-scale tests, and there is a certain gap with the prototype test. In the seismic simulation vibration table test of scale model, all parameters are required to meet the similarity principle, but it is difficult to do in practical engineering. For some important structures, especially the important parts of large structures, to accurately reflect the dynamic characteristics of the structure, within the permitted scope of the condition of capital, it is necessary to increase the specimen size and the maximum load as much as possible to eliminate the size effect of the model, so the large full-scale test must be the development trend of shaking table. China Academy of Building Research developed a shaking table with a mesa dimension of 6.1m6.1m and the maximum model load of 80t.
Due to the great investment, high maintenance cost, and test fees as well as long production cycle of large-scale shaking table, infinite increase in size of shaking table is obviously unreasonable, and likewise, it is not possible to fully meet the actual requirements only by increasing the size of shaking table. For large-span structure tests on bridges, pipes, aqueduct, transmission line, and so on array systems composed of many sets of small shaking table can be adopted. Shaking table array can either conduct a single test or make seismic resistance test on the structure of large-scale, multidimensional, multipoint ground motion input with varied combinations according to various needs. Therefore, the array system composed of many sets of small shaking tables must be the development trend of shaking table.
In terms of control mode, power spectral density control was mostly adopted before 1975. After 1975, Huang Haohua and other scholars used the time-history playback control to finish the seismic wave control research in a broad band. In the mid-1990s, digital control and analog control are widely used in the shaking table control, of which digital control is mainly applied in the system signal and compensation and the analog control is the basis for the control, whose control mode is complicated in operation with too much manual adjustment. After 1990s, Fang Zhong and other scholars developed a full digital control technology which has been widely used in the hydraulic servo control system with the rapid development of digital technology. Other than the valve control device and feedback sensor which adopt analog circuits, the rest utilize digital software to fulfill implementation. This control method can make up for some flaws in the analog control with simple test operation, being able to improve the accuracy, reliability, and stability of the system. Full digital control is the inevitable development trend of hydraulic servo system control.
With the appearance of slender and shaped structures and the application of new materials in building engineering, the seismic test methods of structures are put forward with higher and higher requirements. To meet the requirements of actual engineering and seismic research, scholars from all over the world are active in exploration and attempt and put forward some new testing methods. In recent years, countries around the world greatly invest in seismic research. From 2000 to 2004, the United States Science Foundation Committee spent eighty million dollars of research funding on the NEES plan; Europe established a collaborative research system European Network to Reduce Earthquake Risk (ENSRM); South Korea established a virtual structure laboratory using grid technology, which includes the wind tunnel, the shaking table, and other scientific research equipment. Furthermore, Internet ISEE Earthquake Engineering Simulation System in Taiwan of China was the earthquake engineering research platform developed by National Earthquake Engineering Research Center of Taiwan, China, with the Internet. The platform not only allows several laboratories to interconnect each other to implement large-scale shaking table test but also permits different laboratory researchers around the world to observe the test simultaneously and synchronously.
In China, Hunan University firstly put forward the structure network synergy test research and cooperated with Vision Technology Co., Ltd in 2000 to develop the network structure laboratory (NetSLab is shown in Figure 8). The main module and interface are shown in Figure 8. Thereafter, Hunan University cooperated with Harbin Institute of Technology to accomplish secondary development to establish the network collaborative hybrid test system and conducted a structure remote collaborative test along with Tsinghua University, Harbin Institute of Technology. Three domestic universities firstly completed remote collaboration pseudodynamic test, which is shown in Figure 9.
This paper drew a conclusion of the construction, history, and status quo as well as application and research of shaking table and array. The main conclusions are as follows:(i)On account of factors of actual application demand and economy, the size of the shaking table is between 1m and Xm, among which 3m6m are the majority. For large span structures such as bridges and pipes many sets of small array mode of vibration table can be used.(ii)Shaking table mesa acceleration and speed are about and 80cm/s, respectively. Through statistics, the remarkable frequency of previous ground motion records is mainly within 0.1Hz30Hz, and the frequency range of medium shaking table should be in 0Hz50Hz according to the requirements of the similar rule. Moreover, tests with special requirements need to be above 100Hz.(iii)With the appearance of slender and shaped structures and the application of new materials in building engineering, the seismic test methods of structures are put forward with higher and higher requirements.
The authors acknowledge the support from the Science and Technology Breakthrough Project of the Science and Technology Department of Henan Province ( 9), the Key Scientific Research Projects in He Nan Province (No. 18B560009), and Nanhu Scholars Program for Young Scholars of XYNU in China. The authors thank Xin Yang Normal University School of Architecture and Civil Engineering Laboratory and would also like to thank teachers and students of the team for collecting data.
Copyright 2019 Chun-hua Gao and Xiao-bo Yuan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
After crushing, grinding, magnetic separation, flotation, and gravity separation, etc., iron is gradually selected from the natural iron ore. The beneficiation process should be as efficient and simple as possible, such as the development of energy-saving equipment, and the best possible results with the most suitable process. In the iron ore beneficiation factory, the equipment investment, production cost, power consumption and steel consumption of crushing and grinding operations often account for the largest proportion. Therefore, the calculation and selection of crushing and grinding equipment and the quality of operation management are to a large extent determine the economic benefits of the beneficiation factory.
There are many types of iron ore, but mainly magnetite (Fe3O4) and hematite (Fe2O3) are used for iron production because magnetite and hematite have higher content of iron and easy to be upgraded to high grade for steel factories.
Due to the deformation of the geological properties, there would be some changes of the characteristics of the raw ore and sometimes magnetite, hematite, limonite as well as other types iron ore and veins are in symbiosis form. So mineralogy study on the forms, characteristics as well as liberation size are necessary before getting into the study of beneficiation technology.
1. Magnetite ore stage grinding-magnetic separation process The stage grinding-magnetic separation process mainly utilizes the characteristics of magnetite that can be enriched under coarse grinding conditions, and at the same time, it can discharge the characteristics of single gangue, reducing the amount of grinding in the next stage. In the process of continuous development and improvement, the process adopts high-efficiency magnetic separation equipment to achieve energy saving and consumption reduction. At present, almost all magnetic separation plants in China use a large-diameter (medium 1 050 mm, medium 1 200 mm, medium 1 500 mm, etc.) permanent magnet magnetic separator to carry out the stage tailing removing process after one stage grinding. The characteristic of permanent magnet large-diameter magnetic separator is that it can effectively separate 3~0mm or 6~0mm, or even 10-0mm coarse-grained magnetite ore, and the yield of removed tails is generally 30.00%~50.00%. The grade is below 8.00%, which creates good conditions for the magnetic separation plant to save energy and increase production.
2.Magnetic separation-fine screen process Gangue conjoined bodies such as magnetite and quartz can be enriched when the particle size and magnetic properties reach a certain range. However, it is easy to form a coarse concatenated mixture in the iron concentrate, which reduces the grade of the iron concentrate. This kind of concentrate is sieved by a fine sieve with corresponding sieve holes, and high-quality iron concentrate can be obtained under the sieve.
There are two methods for gravity separation of hematite. One is coarse-grained gravity separation. The geological grade of the ore deposit is relatively high (about 50%), but the ore body is thinner or has more interlayers. The waste rock is mixed in during mining to dilute the ore. For this kind of ore, only crushing and no-grinding can be used so coarse-grained tailings are discarded through re-election to recover the geological grade.
The other one is fine-grain gravity separation, which mostly deals with the hematite with finer grain size and high magnetic content. After crushing, the ore is ground to separate the mineral monomers, and the fine-grained high-grade concentrate is obtained by gravity separation. However, since most of the weak magnetic iron ore concentrates with strong magnetic separation are not high in grade, and the unit processing capacity of the gravity separation process is relatively low, the combined process of strong magnetic separation and gravity separation is often used, that is, the strong magnetic separation process is used to discard a large amount of unqualified tailings, and then use the gravity separation process to further process the strong magnetic concentrate to improve the concentrate grade.
Due to the complexity, large-scale mixed iron ore and hematite ore adopt stage grinding or continuous grinding, coarse subdivision separation, gravity separation-weak magnetic separation-high gradient magnetic separation-anion reverse flotation process. The characteristics of such process are as follows:
(1) Coarse subdivision separation: For the coarse part, use gravity separation to take out most of the coarse-grained iron concentrate after a stage of grinding. The SLon type high gradient medium magnetic machine removes part of the tailings; the fine part uses the SLon type high gradient strong magnetic separator to further remove the tailings and mud to create good operating conditions for reverse flotation. Due to the superior performance of the SLon-type high-gradient magnetic separator, a higher recovery rate in the whole process is ensured, and the reverse flotation guarantees a higher fine-grained concentrate grade.
(2) A reasonable process for narrow-level selection is realized. In the process of mineral separation, the degree of separation of minerals is not only related to the characteristics of the mineral itself, but also to the specific surface area of the mineral particles. This effect is more prominent in the flotation process. Because in the flotation process, the minimum value of the force between the flotation agent and the mineral and the agent and the bubble is related to the specific surface area of the mineral, and the ratio of the agent to the mineral action area. This makes the factors double affecting the floatability of minerals easily causing minerals with a large specific surface area and relatively difficult to float and minerals with a small specific surface area and relatively easy to float have relatively consistent floatability, and sometimes the former has even better floatability. The realization of the narrow-level beneficiation process can prevent the occurrence of the above-mentioned phenomenon that easily leads to the chaos of the flotation process to a large extent, and improve the beneficiation efficiency.
(3) The combined application of high-gradient strong magnetic separation and anion reverse flotation process achieves the best combination of processes. At present, the weak magnetic iron ore beneficiation plants in China all adopt high-gradient strong magnetic separation-anion reverse flotation process in their technological process. This combination is particularly effective in the beneficiation of weak magnetic iron ore. For high-gradient strong magnetic separation, the effect of improving the grade of concentrate is not obvious. However, it is very effective to rely on high-gradient and strong magnetic separation to provide ideal raw materials for reverse flotation. At the same time, anion reverse flotation is affected by its own process characteristics and is particularly effective for the separation of fine-grained and relatively high-grade materials. The advantages of high-gradient strong magnetic separation and anion reverse flotation technology complement each other, and realize the delicate combination of the beneficiation process.
The key technology innovation of the integrated dry grinding and magnetic separation system is to "replace ball mill grinding with HPGR grinding", and the target is to reduce the cost of ball mill grinding and wet magnetic separation.
HPGRs orhigh-pressure grinding rollshave made broad advances into mining industries. The technology is now widely viewed as a primary milling alternative, and there are several large installations commissioned in recent years. After these developments, anHPGRsbased circuit configuration would often be the base case for certain ore types, such as very hard, abrasive ores.
The wear on a rolls surface is a function of the ores abrasivity. Increasing roll speed or pressure increases wear with a given material. Studs allowing the formation of an autogenous wear layer, edge blocks, and cheek plates. Development in these areas continues, with examples including profiling of stud hardness to minimize the bathtub effect (wear of the center of the rolls more rapidly than the outer areas), low-profile edge blocks for installation on worn tires, and improvements in both design and wear materials for cheek plates.
With Strip Surface, HPGRs improve observed downstream comminution efficiency. This is attributable to both increased fines generation, but also due to what appears to be weakening of the ore which many researchers attribute to micro-cracking.
As we tested , the average yield of 3mm-0 and 0.15mm-0 size fraction with Strip Surface was 78.3% and 46.2%, comparatively, the average yield of 3mm-0 and 0.3mm-0 with studs surface was 58.36% and 21.7%.
These intelligently engineered units are ideal for classifying coarser cuts ranging from 50 to 200 mesh. The feed material is dropped into the top of the classifier. It falls into a continuous feed curtain in front of the vanes, passing through low velocity air entering the side of the unit. The air flow direction is changed by the vanes from horizontal to angularly upward, resulting in separation and classification of the particulate. Coarse particles dropps directly to the product and fine particles are efficiently discharged through a valve beneath the unit. The micro fines are conveyed by air to a fabric filter for final recovery.
Air Magnetic Separation Cluster is a special equipment developed for dry magnetic separation of fine size (-3mm) and micro fine size(-0.1mm) magnetite. The air magnetic separation system can be combined according to the characteristic of magnetic minerals to achieve effective recovery of magnetite.
After rough grinding, adopt appropriate separation method, discard part of tailings and sort out part of qualified concentrate, and re-grind and re-separate the middling, is called stage grinding and stage separation process.
According to the characteristics of the raw ore, the use of stage grinding and stage separation technology is an effective measure for energy conservation in iron ore concentrators. At the coarser one-stage grinding fineness, high-efficiency beneficiation equipment is used to advance the tailings, which greatly reduces the processing volume of the second-stage grinding.
If the crystal grain size is relatively coarse, the stage grinding, stage magnetic separation-fine sieve self-circulation process is adopted. Generally, the product on the fine sieve is given to the second stage grinding and re-grinding. The process flow is relatively simple.
If the crystal grain size is too fine, the process of stage grinding, stage magnetic separation and fine sieve regrind is adopted. This process is the third stage of grinding and fine grinding after the products on the first and second stages of fine sieve are concentrated and magnetically separated. Then it is processed by magnetic separation and fine sieve, the process is relatively complicated.
At present, the operation of magnetic separation (including weak magnetic separation and strong magnetic separation) is one of the effective means of throwing tails in advance; anion reverse flotation and cation reverse flotation are one of the effective means to improve the grade of iron ore.
In particular, in the process of beneficiation, both of them basically take the selected feed minerals containing less gangue minerals as the sorting object, and both use the biggest difference in mineral selectivity, which makes the two in the whole process both play a good role in the process.
Based on the iron ore processing experience and necessary processing tests, Prominer can supply complete processing plant combined with various processing technologies, such as gravity separation, magnetic separation, flotation, etc., to improve the grade of TFe of the concentrate and get the best yield. Magnetic separation is commonly used for magnetite. Gravity separation is commonly used for hematite. Flotation is mainly used to process limonite and other kinds of iron ores
Through detailed mineralogy study and lab processing test, a most suitable processing plant parameters will be acquired. Based on those parameters Prominer can design a processing plant for mine owners and supply EPC services till the plant operating.
Prominer has been devoted to mineral processing industry for decades and specializes in mineral upgrading and deep processing. With expertise in the fields of mineral project development, mining, test study, engineering, technological processing.
Download this complete Project material titled; Up-Grading Of Agbado-Okudu Iron Ore Using Magnetic Separation And Shaking Table Techniques with abstract, chapters 1-5, references, and questionnaire.Preview Abstract or chapter one below
The beneficiation of the Agbado Okudu iron ore deposit located in Kogi State, Nigeria was investigated. The investigation involved determining the chemical composition and mineralogical characteristics of the run-of-mine. Followed by determination of the work index of the ore and then separation tests using shaking table, magnetic technique and a combination of the two techniques. The results of the tests carried out revealed that the Agbadu okudu iron ore contained on the average a total iron content (38.82% FeT), 49.10% (Si02) and other element. Thin sections of the ore sample examined under polarized light revealed that the iron bearing minerals are predominantly magnetite and hematite with a combined average percentage distribution of 69% and the mineral in abundant after the iron bearing minerals is quartz. The grindability test reveals that the Agbado Okudu iron ore has and average work index of about 4.32 kwh/tonne. The results of gravity separation shows that a concentrate with a maximum grade of 55.81% (FeT), and a recovery of 66.40% at particle size fraction -56 + 45m could be produced. While magnetic separation alone produced a concentrate with an optimum grade of 57.43% (FeT), and a recovery of 82.12% at particle size fraction of 80+63m. However, combination of gravity separation technique (shaking table) followed by magnetic separation technique could only produce a concentrate with an optimum grade of 57.17% (FeT), and a recovery of 80.85% at a particle size fraction of 63+53m. Hence, based on the results obtained from the concentration tests, the Agbado Okudu iron ore deposit can be best beneficiated using magnetic technique to produce a concentrate that can serve as feed for pig iron production by conventional blast furnace route.
PAGE DECLARATION- iii CERTIFICATION- iv DEDICATION- v ACKNOWLEDGEMENT- vi ABSTRACT- vii TABLE OF CONTENTS viii LIST OF TABLES- xi LIST OF FIGURES xiii CHAPTER ONE Introduction- 1 CHAPTER TWO 2.0 Literature Review- 4 2.1 Nigeria Iron Ore Deposits- 4 2.1.1 Agbado-Okudu Iron Ore- 5 2.1.2 Mineralogy of Agbado-okudu Iron Ore- 6 2.2 Study of some Nigerian Iron Ores Characteristics- 7 2.2.1 Iron Ore Beneficiation Process- 9 2.2.2 Gravity concentration process- 9 2.2.3 Magnetic separation- 11 ix 2.2.4 Froth flotation- 13 2.3 Methods for the Beneficiation of Iron Ore- 13 2.3.1 Beneficiation route for the Itakpe Iron Ores- 14 2.4 Procedures for development of conceptual flow sheet for a newly discovered ore- 17 2.5 Particles Size Analysis 19 2.6 Size/Assay Analysis 20 2.7 Determination of liberation size of the valuable Minerals in the Ore 20 2.8 Work index Determination 23 2.8.1 Standard bond method- 23 CHAPTER THREE 3.0 Materials and methods- 26 3.1 Samples collection and equipment used- 26 3.2 Methods- 26 3.2.1 Preparation of the bulk sample for chemical analysis- -26 3.2.2 Chemical analysis- 26 3.2.3 Microscopy- 27 3.2.4 Size/Assay analysis- 28 3.2.5 Work index Determination- 29 3.2.6 Separation test using shaking table technique- 29 3.2.7 Separation test using Magnetic Separator- 30 x 3.2.8 Shaking table separation followed by Magnetic Separation techniques 31 CHAPTER FOUR 4.0 Results and Discussions- 32 4.1 Results 32 4.2 Discussions 32 4.2.1 Chemical analysis- 32 4.2.2 Mineralogical analysis- 33 4.2.3 Size/Assay Analysis of the Head Sample 34 4.2.4 Work index Determination- 35 4.2.5 Concentration test using Shaking Table 36 4.2.6 Magnetic separation technique- 40 4.2.7 Results of concentration test using shaking table followed by magnetic Separation Techniques 43 CHAPTER FIVE 5.0 Conclusions and Recommendations 46 5.1 Conclusions- 46 5.2 Recommendations- 46 References- 58
NTRODUCTION Iron is one of the most common elements on earth. Nearly every structure put on by man contains at least a little iron. It is also one of the oldest metals and was first fashioned into useful and ornamental objects about 3,500 years ago (Lambert and Mark, 1988). One of the most important determining factors for establishing Iron and steel plants is the availability of iron ore deposit with good geological, mineralogical and metallurgical properties. There is an estimated 2,707 million tonnes of iron ore deposit in the country out of which 200 million tones are in the proven reserve (Umunnakwe, 1988). Iron ore is simply the largest single raw material input in iron and steel making process and the country is endowed with abundant reserves of it but with varying characteristics. The deposits abound in different parts of the country as shown in Table 2.1. Most of the iron ores discovered in the country are however, low grade (their iron content in the crude ranges between 28-45% FeT). This meant that for them to be used in iron and steel production they have to undergo substantial beneficiation and upgrading. (Also and Yakubu, 1995). The Itakpe iron ore had been the most intensively studied and exploited deposit with a proven reserve of 200million tones with an average iron content of 36% FeT. This is presently being up-graded to obtain a 2 concentrate of 64% FeT for use at Ajaokuta and Aladja steel plants. Apart from the Itakpe iron ore deposit there are other deposit which reserves are estimated at over 2.3 billon tonnes as shown in (Table 2.1) within 150km radius of the Ajaokuta steel plant. To ensure security of supply of the iron ore for the nation Steel industries, further research and development need to be carried out on these new founded deposits to enable their full exploitation. With these reserves, conservative estimates indicate that the nation could be self-sufficient in iron ore for a period ranging between 100- 150 years (Umunnakwe1988). The role of iron and steel in the national economy is enormous. One cannot name an economic branch where iron and steel find no application and to some extend the economic power of a country is determined by its consumption and output of steel products. It is on this basis, that the Federal Government of Nigeria in 1971 launched the country into a new era of iron and steel technology by the establishment of the Delta and Ajaokuta steel projects. Though, the establishment of these projects was laudable inadequate attention was given to the development of local raw materials to feed the plants thus, making the plants on commissioning to import iron ore concentrate form countries like Brazil, Liberia and Guinea. Recently there has been renewed interests on the souring of locally available raw materials to feed these plants because the Itakpe iron ore project and the total iron ore requirement of Ajaokuta at 1.3 million tonnes of steel per 3 annum is about 2.135 million tones of iron concentrate and at this rate the Itakpe iron ore project is conservatively estimated to last for about 25 years, (Also and Yakubu, 1995). Also, the Itakpe iron ore plant commissioned on the 80s to deliver iron concentrate to Ajaokuta and later closed and now concessioned to Indians. Would not be able to meet the demand of Ajaokuta Steel plant when it finally takes off fully. It is therefore, important that these types of studies be conducted so as to increase the source of Iron Ore for Ajaokuta plant. And through such studies the technology for the beneficiation of various Nigerian iron ore deposits for onward supply to Ajaokuta and Delta steel plants will be developed. Since the goal of every beneficiation process, mineral-processing operation in particular, is to effectively separate the valuable material from the gangue with minimum loss to the tailings; the need to develop and employ a sustainable, effective and relatively economical method of separation is imperative. The concentration of the valuable minerals from the gangue involves exploitation of the differences in physical, chemical and electrical properties of the ore after effective comminution Akande et al (2000). This work, therefore, is aimed at developing a process route for the beneficiation of the Agbado- Okudu iron ore deposit located close to Jakura village in Kabba, Kogi State for its possible utilization in Ajaokuta and Delta Steel Plants.
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