I. Overview Relationship between re-selection difficulty and intermediate specific gravity component content δ p ± 0.1 component content (%) Re-election Requirements for re-election methods and operations Typical methods and main equipment Degree of difficulty Equipment sorting efficiency Processing rate Operational control 0-7 easy general Big general Ordinary chute, jig July 10 Easier Higher Big general 1 cone concentrator October 15 Harder high Moderate Good operation 1 shaker, spiral concentrator heavy medium dressing 15-20 difficult high Moderate Skilled in operation Heavy medium dressing 20-25 Hard high Moderate Skilled in operation   Precise control Heavy medium dressing > 5 Extremely difficult very high small Skillful and precise control Heavy medium dressing (with precise density control device) 1 The coarse grain can be used with a jig, and the fine grain can use a centrifugal concentrator and a cross flow belt chute. Particle size composition and metal distribution rate of a sand-tin ore sample Size (mm) 10 -4 -2 -1.5 -1.5 -0.7 -0.226 -0.074 total Yield(%) 1.95 3.14 9.39 25.04 33.42 22.47 4.29 0.3 100 Grade (%Sn) 0.01 0.01 0.02 0.03 0.03 0.07 0.17 0.32 0.044 Distribution rate (%) 0.4 0.7 4.3 17.1 22.8 35.9 16.6 2.2 100 4. Embedding characteristics of useful minerals in ore The embedding characteristics of useful minerals determine the process structure of the beneficiation, including a selection of particle size, number of selected sections, and a series of basic problems in the treatment of minerals. figure 1 If the test shows that from -12mm, a sufficient amount of concentrate can be obtained for each size, it indicates that the selected particle size is basically correct, and if necessary, the coarser sample can be tested to explore the improvement of the selected particle size. The possibility. If the test proves that the selected particle size can be increased, the sample should be replaced for the next test. figure 2 The main tasks of the test are: (1) If the tailings that can be discarded are not thrown at all levels of +2 mm, then the test at this stage should continue to explore the initial particle size of the tailing; (2) determine the final crushed and ground grain size; 3) For materials with -2+0.5mm, sometimes the effect of jigging and shaker selection is compared to determine what equipment should be used for sorting. image 3 If the coarser fraction has been able to tail, it is not necessary to check the finer grade tailings, otherwise the next finer fraction should be checked in turn. (2) Measurement of the number of revolutions and the number of revolutions The number of revolutions of the rotating parts can be measured by a tachometer. The stroke of the reciprocating motion can be measured by measuring the rotational speed of the eccentric. In the absence of a tachometer, a piece of paper can be attached to the moving part to be tested, and then the line is moved perpendicularly to the reciprocating direction of the part by the pencil, or the pencil is fixed on the part to move the piece of paper, and the beginning and end of the underline are recorded. time. At this time, the curve will be a zigzag curve, and the number of vertices on one side of the curve is the number of times the moving parts to be tested reciprocate during the time recorded in the stopwatch, and then converted into the number of reciprocations per minute, which is the desired The number of times or frequency. Figure 5 is a schematic illustration of a float flow meter with a magnetic converter. The main portion of the flow meter is a tube 1 whose inner diameter gradually expands in the direction of flow of the medium and a float 2 having a certain weight. The magnet pair is used to transmit the movement of the float to the adjustment system or to drive the pointer, and generally does not need to be installed. The height h of the float stay depends on the force F w of the fluid on the float, and F w is proportional to the square of the flow rate υ. In either equilibrium position, F w should be equal to the weight F g of the float in the fluid, and Die Cast Aluminium,Led Lamp Housing Parts,Aluminium Die Casting Parts, Led Light Cover Parts Ningbo Best Channel Import & Export Co., Ltd. , https://www.btc-metal.com
Laboratory selective research methods and experimental techniques for various mineral processing processes have the same points and differences.
Compared with other beneficiation methods, the re-election process has lower cost and less environmental pollution. Therefore, in the optional research work, any ore that may be selected by re-election method should first consider the re-election test.
In the various wet sorting processes, the materials selected for re-election are relatively coarse, and the particle size range is relatively wide. Different particle sizes—materials require different equipment, even materials that can be treated with the same type of equipment are often classified. In addition, in order to avoid the adverse effects of over-smashing on re-election, the stage selection process is often used, resulting in a complex combination of re-election processes and more types of equipment used. Therefore, the main problem that must be considered first in the re-election test is the process. And equipment. It is also important to mention that the work efficiency of the re-election equipment itself is often the primary factor determining the efficiency of the re-election process. The major changes in the re-election of production in history are inseparable from the improvement and creation of equipment. In the optional experimental research work of specific mineral application problems, the development of new equipment is also often required.
On the other hand, the operational factors of re-election are relatively simple. Various sorting equipments, as long as the specific gravity composition and particle size composition of the selected raw materials are basically the same, the selection conditions are basically the same, and some physical phenomena occurring during the re-election process are relatively macroscopic, and most of them can be directly observed by the naked eye. Judgment, therefore, in the re-election study, the number of conditional tests required to find the optimal process parameters is generally small.
However, due to the coarse selection of the sample and the complicated process combination, the amount of sample and the amount of work required for each process test are large, which determines that the re-election test cannot arrange a large number of comparative tests like the flotation test. It must be carefully thought out beforehand. According to the research results of ore material composition characteristics, carefully select the test process and try to avoid mistakes.
The difficulty of re-election separation of minerals of different specific gravity can be roughly judged by equal ratio:
δ 2 — △
e = —————
δ 1 — △
Where δ----the specific gravity of light minerals;
δ----the specific gravity of heavy minerals;
Δ----the specific gravity of the sorting medium;
e is greater than 5, which is an easily re-selectable ore. Except for fine fine (less than 5~10um) fine mud, materials of various sizes can be sorted by re-election method;
e is less than 5 but greater than 2.5, which is an easy-to-select ore. According to the current re-election technology level, the effective lowering of the lower particle size may reach 19um, but the sorting efficiency of 38-19um is lower;
e is less than 2.5 but greater than 1.75, which is easier to select ore. At present, the lower limit of effective particle size may reach 38 μm , but the selection of 75~38um has been difficult;
e is equal to 1.75 ~ 1.5 is a more difficult to choose ore, the effective selection of the lower limit of the particle size is generally about 0.5mm;
e is equal to 1.5 to 1.25 is a refractory ore, the re-election method can only deal with materials not less than a few millimeters, and the sorting efficiency is generally not high;
e is less than 1.25 is extremely difficult to select ore, it is not appropriate to use re-election method to choose.
In the process of heavy medium dressing, if Δ≈δ1 is taken, then e will tend to infinity, indicating that the heavy medium beneficiation method can be used to sort minerals with very small specific gravity in principle. In theory, the particle size should be small, but technically For economic reasons, it can only be used to process materials of not less than 0.5 to 3 mm.
Most metallic mineral gangue minerals with a specific gravity not smaller difference, gravity separation by sorting are not difficult, but the separation between each associated minerals is more difficult. For example, the e value of scheelite separated from quartz is 3.1, and the value of e is only 1.4 when separated from stibnite . As another example, cassiterite with quartz: e = 3.8, and cassiterite TONGHUI bismuth: e = 1.05, cassiterite with pyrite: e = 1.56. It can be seen that the above criteria for re-election difficulty mainly considers the difference in the specific gravity of the light and heavy minerals to be sorted, and then gives the lower limit of the effective separation size when different e values ​​are given according to practical experience, without specifically considering the ore. The effect of symbiotic combinations of medium minerals, inlaid grain size and continuous nature. In fact, in the re-election, there are always mainly useful minerals and gangues, as well as associated minerals with intermediate proportions; both monomers and continuous organisms. The difficulty of re-election depends not only on the difference in specific gravity of the useful minerals and gangue, but also on the specific gravity component distribution of the ore particles (see next section). Considering the confounding phenomenon in the re-election process, it is mainly caused by the part of the ore particles whose specific gravity is close to the sorting specific gravity δp, regardless of whether they are continuous or associated minerals with intermediate specific gravity, in order to obtain a single-valued quantitative judgment. According to some suggestions, it is recommended to re-select the difficulty of using the weight percentage of the component with a specific gravity of δp ± 0.1 in the ore, and judge the applicability of various re-election methods and equipment, and the accuracy of operation control. Requirements (see Table 1 below). The disadvantage of this method is that if the intermediate component is mainly composed of associated mineral particles, its content can only indicate the possible degree of concomitant minerals mixed with the main useful minerals and gangue, but it cannot explain the separation of the main useful minerals from the gangue. Degree of difficulty. [next]
In practice, various sand mines belong to the first and second categories. Tungsten, tin and rare metal veins belong to the third category. The pre-selection operations and the proportion of useful minerals are not high.
Since the application of the re-election method is limited by the particle size of the material, even for minerals with a large difference in specific gravity, the fine-level sorting efficiency is always inferior to the coarse grade. In addition to the difference in specific gravity between useful minerals and gangues, the embedding properties of useful minerals in ores are another major factor in determining whether ore can be re-elected. Only in the coarser fractured sizes can most of the useful minerals be dissociated. The ore can be selected by re-election to get satisfactory results. The re-election of alternative research work is usually carried out by studying the distribution characteristics of useful minerals in different fractions and different specific gravity fractions, and judging the possible inclusion granularity and selection index.
Second, the re-election test process In the re-election selectivity study, the most important task is to select and determine the selection process.
The re-election test process is usually based on the nature of the ore and is determined by reference to the production practices of similar ores. However, the test process is more flexible than the production process, because at the beginning of the test we can only understand the general rules of this type of mineral dressing, and the special laws of the ore beneficiation to be tested need to be gradually understood in the test process. Therefore, the content of the process test itself also includes an examination of many undetermined factors.
(1) The main reason for deciding the re-election process is that the internal cause of the ore sorting process is the nature of the ore, the most important of which are the following.
1. The degree of muddyness and washability of ore The ore that is high in mud and can be broken by washing can be washed first. According to the study of the metal distribution rate in the slime, it can be initially determined whether the washed sludge can be discarded or should be sent to the sorting. Some ferrous metal ores, such as manganese oxide ore and some limonite, enriched in non-argillaceous useful component part, it is possible to get more crude concentrate rich even by washing qualified concentrate. Generally, argillaceous ore can improve the crushing, grinding and sorting conditions of lump ore by washing and de-sludge, and avoid over-crushing of useful mineral particles and reduce the loss rate of metal in mud ore. Therefore, "washing into the mill" plus "mud sand sorting" is one of the basic experiences of China's re-election practice.
The disadvantage of the mechanical washing method is that it has a grinding and stripping effect on the ore and produces secondary slime. The ore produced by artificial washing is usually about 5 to 6% less than the mechanical washing method, which is one of the reasons why the laboratory test results are difficult to match the industrial production index. The slime obtained from the washing is usually sent to the classification, and the finest part is discharged into the overflow, and the sand part (rough mud) is sent to the sorting. [next]
The selectivity of the ore is not only related to the content of the shale portion of the ore, but also to a greater extent depending on the nature of the clay material contained in the ore, including plasticity, swelling and permeability. The plasticity of clay refers to the property of clay containing certain moisture that does not crack after compression and produces fixed deformation. It can be measured by plasticity index K (%):
K = B h -B 1
Where B h ———the upper limit of clay plasticity, ie the water content (%) when the clay begins to flow;
B 1 ———The lower limit of clay plasticity, that is, the water content (%) at which clay can be crushed.
According to the value of K, which is >15.15~7.7~1<1, the plasticity of clay can be divided into high, medium, low and no four types. Correspondingly, the washability of ore is divided into the most difficult, difficult, medium, Easy four categories. The swelling property of clay refers to the extent to which the volume of the clay is increased after being wetted, and the larger the swelling property, the easier it is to wash. Permeability refers to the ability of clay to penetrate water. The greater the permeability, the easier it is to wash. Obviously, in connection with these properties, the efficiency of the washing depends not only on the intensity and time of the scrub, but also on the time of the pre-wetting of the ore. For some difficult-to-wash ores, it is also possible to strengthen the washing process by adding chemicals or even pre-drying. Pre-study of ore washability allows us to carefully consider these issues as we develop our process plan.
2. The depletion rate of ore is to reduce the cost of ore dressing and increase the on-site production capacity. For the ore with high depletion rate, it should first be pre-selected by pre-selection (pre-enrichment) using heavy medium beneficiation and photo-selection and hand-selection methods. To discard the surrounding rock and stone that are mixed in during mining. The amount of waste rock pre-selected by the heavy medium beneficiation method should generally be no less than 20%, and the grade of waste rock should be significantly lower than the grade of the total tailings, otherwise it may not be cost-effective.
Some ferrous metal ores sometimes meet the smelting requirements according to their geological grades. However, due to the depletion of the mining process, the ore grade is lower than the smelting requirements. At this time, the main task of sorting is to discard the waste rock to restore the geological grade. In addition to the heavy medium beneficiation method, other high-efficiency re-election methods such as jigging can also be used for sorting.
For ores that mainly use flotation, magnetic separation and other mineral processing methods to recover useful minerals, when the ore depletion rate is high, it should also be considered to be pre-selected by the heavy medium beneficiation method.
The possibility of pre-selection of ore by heavy medium beneficiation method can be determined by the method of analyzing the specific gravity of the sample. Under the condition that the specific gravity of the surrounding rock is greater than the specific gravity of the gangue, if the useful mineral is high in price, low in content, and finely embedded, That is, it is difficult to separate the surrounding rock by the heavy medium beneficiation method. At this time, only other methods such as photoelectric selection and hand selection can be considered for pre-selection.
3. The grain size composition of the ore and the metal distribution rate of each grain grade are particularly important for sand deposits, because in most sand mines, useful minerals are mainly concentrated in each intermediate grain size; coarse and fine mud, especially The content of useful components in large gravel is very low, so it is generally possible to use waste washing and sieving to separate waste rock. The particle size composition and metal distribution rate of a certain sand mine are listed in the table below. As can be seen from the table, the level of +4mm can be screened as waste rock.
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Since the efficiency of the re-election process is significantly reduced as the particle size of the material becomes smaller, the ore of unequal granules embedded in the thickness should generally be adopted according to the principle of “accepting early harvest†and “can lose earlyâ€. Stage selection process. Naturally, economic principles must also be considered when deciding on the number of segments. If the useful mineral value is high and it is easy to muddy, or the size of the plant is large, more sorting segments can be used; for base metals or small plants, a simpler process should be adopted.
Generally speaking, the sorting granularity of the first stage, that is, the selected particle size, should be selected so that the metal recovered by the sorting section is not less than 20%, or the tailings yield of the thrown is not less than 20%.
The inlaid particle size characteristics of the ore are usually provided by microscopically identified data. It should be recognized that although the particle size of the dissociation of useful mineral monomers is primarily dependent on its inlaid particle size in the ore, it is not completely equal. Therefore, in order to determine the ore size of the ore, it is better to have the analysis of the specific gravity of the ore under different crushing sizes, which can directly tell us about the separation of mineral monomers under different crushing sizes. It is only because heavy liquid with a specific gravity of more than 3.2 is difficult to prepare. At present, the analysis of specific gravity components of ore is mainly limited to the case where the separation specific gravity does not exceed 3.2, such as heavy medium dressing. In order to separate the heavy minerals with higher specific gravity, the crushing granularity necessary before the selection can only be determined directly on the basis of the rock identification data, and the basic task of the re-election process test is to determine the ore. Incorporate the granularity and number of segments.
5. The nature and content of symbiotic heavy minerals in ore and its mosaic relationship with the main useful minerals are currently mainly relying on the re-election method to select some of the main useful minerals. The difference in specific gravity from the gangue is generally large enough. The method is easier to separate; but when it contains symbiotic heavy minerals, the difference in specific gravity between symbiotic heavy minerals is often small, it is difficult to completely separate them during the re-election process, and only the re-election of coarse concentrates can be recovered together. In the wool concentrate, the next step is to separate and recover by the combined processes of magnetism, electricity, floatation, re-election and chemical treatment. The interweaving relationship between the symbiotic heavy minerals determines the treatment method of the ore in the beneficiation. Sometimes due to the dense symbiosis of heavy minerals, in the process of sorting, a part of the so-called “difficult-selected oreâ€, which is mainly composed of symbiotic heavy minerals, will inevitably be produced. It cannot be sorted by ordinary mechanical beneficiation methods, but can only be directly Send it to the smelter for processing. For example, the cassiterite ore and residual slope sand deposit in a mining area in Yunnan is a severely weathered cassiterite polymetallic sulphide deposit containing a large amount of iron sulfide. The ore contains 15-25% iron and is in the form of iron hydroxide (brown). In the presence of iron ore, etc., these iron minerals contain fine cassiterite, as well as lead , zinc , copper , arsenic , antimony , indium , cadmium, etc. in the state of fine mineral particles or ion adsorption, which can only be used as a middle in the beneficiation process. The output of the mine is then separated and recovered by the smelter.
(II) Example of re-election test flow Take the test procedure of tungsten-tin primary vein re-election as an example.
It is found that the degree of dissociation of 20~12mm monomer is <10% when the ore is broken to 20mm, and 10~30% for 12~6mm, and 0.5~0.3mm when the ore is broken to 20mm. Up to 90% or more. Therefore, it is initially determined that the selected particle size is 12 mm, and the final crushing particle size is 0.5 mm. Considering the high value of tungsten and tin minerals, the brittleness and easy muddy, it was decided to adopt a multi-stage sorting process. The first section was crushed to 12mm, the second section was ground to 2mm, and the third section was grounded to 0.5mm.
In the exploratory test phase, the first step can be carried out according to the process shown in Figure 1. The test has two tasks: (1) further determining whether the selected inclusion particle size is reasonable; and (2) examining the granularity at which the tailings can be started. 
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If the test shows that qualified concentrates can be obtained from -6mm, the -12+6mm grade fine, medium and tailings should be combined, crushed to -6mm and then incorporated into the original -6mm sample. One step test. It is also possible to take another sample from the ore and crush it to -6 mm and then retest it.
In the case of the study of ore embedding characteristics and the determination of monomer dissociation, the actual inclusion particle size and the estimated value do not differ greatly. After clarifying what particle size can start the problem of concentrate, Should be transferred to examine the tailing granularity.
If the sample is not pre-selected, and the -12+6mm jigging can be used to obtain a considerable yield of waste tailings, a sample of -25 (50) mm should be taken from the ore to carry out the heavy medium. A beneficiation or jigging test to examine the possibility of pre-selected tailing of the sample using heavy medium dressing. Under normal circumstances, the effect of coarse-grained grades with heavy medium beneficiation should be better than jigging.
Regardless of the size of the grading, if the tailings are not available, the medium and tail mines should be combined as a “jigging tailings†for the next selection. If you can throw out the abandoned tailings, you can just send the middle mine to the next section. The test flow of the next paragraph is shown in Figure 2.
In order to check whether the -2+0.5mm grade tailings can be disposed of, the following methods can be used: (1) comparison with the current production specifications of similar ore; (2) inspection of the number and nature of the connected bodies in the tailings under the microscope; 3) 2~5kg sample is diverted from the tailings, ground to less than 0.5mm, and then checked with a shaker to see if it can recover some of the monomeric useful minerals. If it can, it indicates that the tailings cannot be discarded. It should be re-selected. When the amount of sample is small, heavy liquid separation can be used instead of shaker inspection; (4) If necessary, the branching process shown in Figure 3 can be used for comparison test, that is, half of the sample is tail-flow process of -2 mm, and the other half of sample is -2 mm. Process test without tailing. [next]
In order to check whether the final grinding fineness is sufficient, it is necessary to inspect the mine in the -0.5+0.2mm shaker. The content and properties of the continuum can be examined first by microscopy. If the distribution rate of the metal in the middle ore is not high, and there are not many organisms, it indicates that the fineness of the grinding is sufficient; if the metal distribution rate in the middle ore is high, If the direct re-election cannot recover more monomeric useful minerals, it should be re-grinded and re-selected (ie, reduce the final grinding fineness); if it is re-grinded, it can not recover more monomeric useful minerals. The mine conducts detailed material composition studies to find out the cause.
In order to judge whether the material of -2+0.5mm should be selected by jigging or shaker, the branching process can also be adopted. The sample of this grade is reduced into two parts, which are separately sorted by jig and shaker, and the results are compared. .
After the selected particle size, the final grinding grain size, and the medium-mine processing method are determined, the basic structure of the process is also determined. The remaining problem is the problem of slime treatment.
-0.075mm slime, can be graded by cyclone, +0.038mm coarse mud, can be directly selected by grooved shaker, -0.038mm part, generally using centrifugal concentrator rough selection, belt chute selection process. When the particle size distribution of the slime is heavier than the coarser grade, it can also be (graded or not graded) using the automatic chute or the common flat chute rough selection, the selection process of the grooved shaker.
At the end of the exploratory test, a larger number of samples should be taken and a formal test conducted in accordance with the established procedure to obtain a formal selection index and sufficient re-election of the concentrate for the next test. A rough test procedure for a tungsten-tin-quartz vein ore is an example of a formal test procedure. The sample has a particle size of 12mm, the final crushing particle size is 0.5mm, the starting tailing particle size is 6mm, and the main segment (12, 2, 0.5mm) is selected separately. The other jigging tailings are treated separately, not in the same ore. Fine particles are combined. That is, the process of “stage grinding, grading, and poor and poor sorting†is adopted. It should be noted that there are still different views on whether there is a need for the distribution of rich and poor. At least for small factories, the process of sorting between rich and poor may not be used. [next]
Third, test operation and testing technology (A) process factors and adjustment re-election test, before the system flow test, usually must first use a small number of samples to examine and adjust the process affecting the efficiency of various equipment selection Factors to find out the most suitable process conditions.
1. Contents of the examination The working principles of various types of re-election equipment have their own characteristics, but there are also many commonalities, so the process factors can be summarized as follows:
(1) Load (feed) This includes the amount of dry ore to be fed, the concentration of the ore and the volume load (the volume of the slurry to be fed). Obviously, the three are interrelated, and after any two of them are determined, the third quantity is determined. However, for different equipment, the focus is different. The jig and washing equipment are mainly used to control the dry ore volume, while the film casting equipment mainly controls the volume load.
When the fed slurry is a pressure flow, the feed pressure must also be checked and adjusted. For example, the swirling pressure of the cyclone is one of the most important factors affecting the operation of the cyclone.
(2) Water quantity In the wet re-election process, water quantity is also an important process factor. In addition to the feed water related to the load, there are various supplementary waters, including the sieve of the jig and the heavy medium vibration tank. The water is replenished and the rinse water used in the film dressing process. The importance of replenishing water is not the same for different equipment. For example, shakers, spiral concentrators, cross-flow belt chutes, etc., wash water is fed laterally along the direction of the main or concentrate ore flow, directly affecting the zoning of minerals, so it must be adjusted when selecting An important factor is that the washing water of ordinary plane chutes and belt chutes is fed longitudinally along the direction of the movement of the ore flow, and only serves as a cleaning effect. The ore dressing effect is mainly adjusted by controlling the amount and concentration of the ore.
(3) Medium and bed In the wet re-election process, the most basic selection medium is water and a suspension of water and solid material.
In the re-suspension beneficiation, the required separation specific gravity is first determined, and then the weighting agent is selected to adjust the composition and rheological properties of the suspension.
In the jigging process, the bed is also a medium. In the fine jigging, in addition to the natural bed formed by the selected materials, it is added to the workbed stone. (Natural) bed thickness, artificial bed thickness, bed stone material and particle size are all factors that may affect the selection of the jig.
In the heavy medium vibration tank, the heavy medium layer is the bed layer.
(4) Equipment structural parameters Equipment structural parameters, some are only examined during the development of the equipment, and some must be adjusted in the optional test. The second category is now mainly discussed.
Jigs generally do not adjust structural parameters during the optional test.
The common flow film beneficiation equipment selected in the gravity field such as the shaker, the plane chute and the belt chute, the structural parameters to be adjusted are mainly the slope (inclination angle). The tapered chute sometimes needs to adjust the torsion ratio.
Structural parameters are important when separating in a centrifugal force field. The most prominent of these is the cyclone. Almost all of its structural parameters can be adjusted, but some should be determined by designing and manufacturing laboratory equipment. The optional test elbow is just how to select its specifications according to the nature of the work. Dimensions, such as the diameter and height of the barrel, the taper angle and the size of the feed port, etc.; others are often adjusted during routine optional tests, such as the size of the grit and the overflow. Sometimes in the optional research work itself, including the development task of the equipment, there will be a lot of projects to be examined. For example, for the study of a sample using a heavy medium cyclone preselection, all structural parameters of the cyclone were examined.
The structure of the centrifugal concentrator is relatively simple. The structural parameters to be examined are mainly the slope; the structural parameters of the spiral concentrator - the pitch and the section shape, are sometimes adjustable, and sometimes it is not necessary to adjust.
(5) Equipment motion parameters For reciprocating equipment, such as jigs and shakers, and heavy medium vibration grooves, it refers to stroke (amplitude) and stroke (vibration); for rotary motion equipment, Refers to the speed, such as the drum speed of a centrifugal concentrator. [next]
(6) Working time For the intermittent feeding and operation equipment, it is necessary to check the working time, such as the feeding and rinsing time period of the centrifugal concentrator and the automatic chute.
2. Examination method When examining the process factors of the re-election process, the characteristics of the re-election process must be considered. In the process of re-election, many sorting phenomena are macroscopic phenomena. Through visual observation, the quality of the sorting effect can be judged. This is a favorable factor for our experimental work and must be fully utilized.
The most typical is the shaker, and the sorting effect can be judged by the visual observation of the ore banding. Thus, in the optional study, the operating conditions of the shaker were temporarily adjusted with a small amount of sample before the formal test, and special conditional tests were rarely arranged for this purpose.
The stroke, stroke and replenishment of the jig can be judged mainly based on the looseness and undulation of the bed. When the conditions are right, the water surface is undulating. If the bed is detected by hand, a intermittent and uniform suction effect will be felt. The palm cannot be inserted all at once, but it can be tight with the bed. Gradually insert to the bottom, in which case the useful minerals and gangue will stratify quickly. Conversely, if the bed is too tight or too loose, or the water surface is splashed, the bed is disordered, indicating that the operating conditions are not appropriate. Only when it is not possible to make a final judgment based on visual observations, it is necessary to arrange a small number of special conditional tests to finally select the process conditions.
Many re-election equipments, although they cannot directly select operating conditions based on visual observation, can make some preliminary judgments based on macroscopic phenomena to reduce the blindness of the test work and save the test workload. For example, various types of chutes, especially centrifugal chutes, if the distribution of the ore layer is uneven, and the phenomenon of "ditching" occurs, it can be concluded that the sorting effect is not good, and it is not necessary to blindly sample the test.
In short, because the re-election phenomenon is relatively macroscopic, the workload of conditional testing is small, and not all equipment needs to be arranged for special conditional testing. Equipment that requires conditional testing, and not every factor needs to be arranged for special tests. In the course of the test, we should be good at grasping the main contradictions and conducting tests in a targeted manner.
The test method for seeking optimal conditions, in combination with the characteristics of the re-election test, can be prioritized by using the tuning operation or the steepest slope method. An example of the steepest slope method in this section is an example of a jigging condition test.
3. Determination of certain process parameters (1) Determination of stroke After adjusting the stroke of the equipment to a certain size, in order to measure the actual length of the stroke, the following methods can be used: on the part to be tested, perpendicular to the plane of movement of the part, fixed A pencil, then put a piece of paper under the tip of the pencil, then turn the pulley with your hand to make the part to be tested reciprocate, the pencil will follow the reciprocating motion, and the paper should be fixed, then the pencil is A line is drawn on the paper, the length of which is equal to the length of the stroke. Generally, the measurement should be repeated several times and the average value should be taken.
When the vibration frequency (frequency) exceeds 960 times, the stroke length can be measured by visual residual phenomenon. To this end, you can use the mm coordinate paper to draw a triangle on the paper with a certain length, for example 10mm (this value should be significantly larger than the maximum stroke length of the device), and then divide the triangle into equal parts with horizontal lines along the height, and The horizontal distance between the sides of the triangle at different heights is placed next to the horizontal line at the corresponding height. Then, the indicator paper is attached to the moving part to be tested so that the bottom edge of the triangle coincides with the moving direction. Start the device to vibrate the part to be tested according to the specified vibration. If the two extreme positions of the triangle in the reciprocating motion are abc and a Ìb Ìc Ì, the shadow will appear in the range of the entire ab Ìc Ìc due to the visual residual, but the overlapping portions of the two triangles will A small triangle with a darker color, a Ìbo, corresponds to the distance between the sides of the large triangle at the height of the apex of the small triangle, which is the stroke of the reciprocating motion (5 mm in Fig. 4).
Figure 4 stroke indicator paper [next]
(3) Determination of slope (inclination) For the membrane separation equipment, it is usually necessary to measure the inclination of the bed (groove) surface. In the case of an inclinometer, the inclinometer should be used as directly as possible. In the absence of an inclinometer, the protractor can be used for measurement. Since the surface of the frame or the floor is not necessarily horizontal, it is preferable to hang a string with a heavy object at the upper end of the slope to represent the plumb line, and then determine the angle β between the slope and the plumb line, and the remaining angle a=90 ̊ -β is the angle of inclination sought. When the angle of inclination is very small, the protractor will not be easy to measure. At this time, the height difference between the two ends of the slope can be measured, and then the inclination angle can be calculated by using a trigonometric function relationship.
(4) Measurement of flow rate At present, in the batch test of the ore dressing laboratory, the determination of various water quantities is still accustomed to the direct meter measurement—measuring the amount of water flowing out within a certain period of time and then converting it into the flow rate per unit time. The size of the flow is controlled by a gate or a water stop clamp. Since the amount of water has a great influence on the re-election effect, it is generally necessary to install a constant pressure water tank instead of directly using the water of the water pipe, and it is preferable to install a flow meter and a water pressure gauge.
Flowmeters are mostly based on the use of energy conversion between the flow medium and the measuring element. The most commonly used flow meter is to measure the pressure drop of a fluid as it flows through a flow blocking element or the force acting on a flow blocking element. Among the former categories are various instruments with throttle plates or nozzles, such as the Wenqiuli flowmeter, and the latter representative is a variety of float flowmeters. In addition to the above two categories, electromagnetic flowmeters are commonly used, and ultrasonic flowmeters have appeared in recent years.
Because the float flowmeter is particularly suitable for small and medium flow measurements, it is extremely useful in beneficiation laboratories. It measures a minimum flow rate of 0.1 L/h for gas and 0.02 L/h for liquid; maximum flow rate is 4000 m 3 /h, gas and 200 m 3 /h, liquid. In addition, the float flowmeter is simple in construction, relatively not afraid of pollution, and can be directly read when using a glass tube, which is also the reason why it is widely used.
Figure 5 float flowmeter
1—conical tube; 2—float (with magnet); 3—slave magnet
Ï f Ï… 2
F g = V s g(Ï S - Ï i )= C w A·———
2
Where V S is the volume of the float;
g----gravity acceleration;
Ï S and Ï f ---- float and fluid density;
C w ---- resistance coefficient;
A----maximum flow area;
Ï… ------ flow rate;
In the throttle type flowmeter, the flow area of ​​the fluid is constant, and as the flow rate increases, the pressure drop is correspondingly increased; in the case of the float type flowmeter, the pressure drop is always a constant. After the flow rate increases, the float suspension position will move up, so that the flow area will gradually increase, and the FW will gradually decrease to the equilibrium condition expressed by the re-satisfaction formula (the upper formula), so the float height of the float is the direct flow rate. measure.
For smaller flow rates and common fluids, a transparent tube is typically used, and the flow scale can be directly marked on the tube surface to make it easy to read directly. In other cases, a metal tube can be used and a magnetic pointer can be mounted as shown in FIG. When measuring liquids other than water and air, the flow rate must be converted using the flowmeter characteristic curve provided by the manufacturer.