June 02, 2020

Iron ore beneficiation test plan example

First, the surface dressing Test Scheme sample preparation step hematite test program are:
(1) Analyze the research data of the ore nature, and formulate alternative schemes based on the ore nature and the production practice experience of the same minerals and its research results.
(2) According to the relevant policies and policies of the state, combined with the specific conditions of the locality and the requirements of the entrusting party, comprehensively consider and determine the main attack plan.
(I) Analysis of ore property research data 1. Spectral analysis and chemical multi-element analysis The spectral analysis results of the sample are shown in Table 1, and the results of chemical multi-element analysis are shown in Table 2.

  Spectral analysis results of a surface hematite










Approximate content


















Approximate content









  Multi-element analysis results of a group of hematite





SiO 2

AL 2 O 3






Burning down













From the results of spectral analysis and chemical multi-element analysis, the main recovery element in the ore is iron. The content of associated elements has not reached the comprehensive recovery standard. The main harmful impurities are not high in sulfur and phosphorus , and only the silica content is very high. Just consider removing the harmful impurity silicon.
The items of TFe, SFe, FeO, SiO 2 , AL 2 O 3 , CaO and MgO in the chemical multi-element analysis table are important items for the analysis of iron ore. The meanings and purposes of each item are introduced below:
(1) TFe total iron (refer to the total iron content metal minerals and non-metallic minerals). The mine's total iron content is only 27.40%. It is a poor iron ore.
(2) SFe soluble iron (refers to the amount of iron that can be dissolved by acid in chemical analysis). [next]
Subtracting SFe from TFe is equivalent to acid-insoluble iron, which is often considered to be the iron content of iron silicate and is used to represent the "non-selectable iron" amount. The mine's “non-optional iron” content is very low, so it is not necessary to consider the recovery of this part of the iron when formulating the plan; the reason for the poor dressing index is not mainly due to “not optional iron”.
In fact, the concept of using acid-insoluble iron as the iron content of iron silicate is not clear enough. It is often the case that iron ore is often symbiotic with several iron minerals, and various iron minerals are dissolved in acid. More complicated, some of the iron silicate minerals are soluble in acid, and some are not soluble in acid, so the specific application must be considered according to the specific circumstances.
(3) FeO ferrous oxide. Generally, the ratio of TFe/FeO (called ferrous ratio or oxidation degree) to FeO and TFe (magnetic ratio of iron ore) indicates the degree of oxidation of magnetite. They are an important indicator of the type of iron deposits classified by the geological department and an important basis for judging the selectivity of iron ore in the preparation of the ore dressing test.
According to the ratio of TFe/FeO and FeO/TFe, iron ore can be divided into the following types:
(FeO/TFe)*100(%)>37%TFe/FeO<2.7 primary magnetite (green mineral) easy magnetic separation (FeO/TFe)*100(%)=29-37%TFe/FeO=2.7~ 3.5 Mixed ore magnetic separation combined with other methods (FeO/TFe)*100(%) <29%TFe/FeO>3.5 Oxidized ore (red ore) Magnetic separation difficulties The ferrous ratio of Tef/FeO=8.43 is oxidized. The type of mine is therefore more difficult to choose.
Practice has proved that the method of dividing the ore type by the above ratio is only applicable to iron. The industrial mineral is magnetite or magnetite with different degrees of oxidation, and the mineral composition is relatively simple. For magnetite deposits with complex mineral composition and various iron minerals, the classification of ore types should be combined with the specific characteristics of the deposit and determined according to the test data.
(4) CaO, MgO, SiO 2 , AL 2 O 3 and the like are main gangue components in iron ore. The ratio (CaO+MgO)/(SiO 2 +AL 2 O 3 ) is generally used to indicate the acidity and alkalinity of iron ore and iron concentrate, which directly determines the ratio of smelting charge in the future.
According to the ratio of (GaO+MgO)/(SiO 2 +AL 2 O 3 ), iron ore can be divided into the following categories:
Ratio <0.5 for acidic ore. Alkaline flux ( limestone ) is required for smelting;
Ratio = 0.5~0.8 for semi-self-fluxing ore. When smelting, it needs to be partially alkaline flux or used in combination with alkaline ore;
Ratio = 0.8~1.2 for self-fluxing ore. No smelting during smelting;
Ratio >1.2 for alkaline ore Smelting requires acid flux ( silica ) or with acid ore.
Due to the high content of SiO 2 , the sample has a ratio of <0.5, which is an acidic ore. A large amount of alkaline flux is required for smelting. Therefore, our task of mineral processing is to reduce the silicon content as much as possible and reduce the consumption of flux. [next]
Based on the above analysis data, the sample belongs to a poor iron ore with low content of harmful impurities such as silicon and sulfur, and its ferrous ratio is 8.43. Due to the high content of SiO 2 , it is an acidic ore, and a large amount of flux is required for smelting.
2. Rock and Mineral Identification The rock ore identification results of this sample are as follows :
(1) Mineral composition The relative contents of the iron minerals contained in this sample are listed in the following table.

  Relative content of various iron minerals

Iron mineral








It can be seen from the above table that iron minerals mainly exist as hematite, followed by magnetite and limonite. Magnetite is easily selected by weak magnetic separation, mainly to solve the problem of ore dressing of hematite and limonite.
Gangue minerals dominated by quartz, sericite, chlorite, black and white female, muscovite, followed pyrite, iron and containing a certain amount of shale impurities. The gangue-bearing minerals are mainly chlorite, followed by biotite and a small amount of pyrite.
(2) The grain size characteristics of iron minerals under the microscope are shown in the following table by the straight line method.

  Inlaid grain size characteristics of iron minerals

Size (um)




According to 12um









The measurement results show that the ore is a type of fine particles and microparticles, which needs to be finely ground before being selected. However, the grain size of magnetite, hematite, limonite, etc. is not exactly the same. The magnetite is relatively coarse and relatively uniform, mostly in the range of -200+20μm; the hematite is the finest. Most of them are -20+2μm, most of them do not exceed 50μm, and very few are up to 100μm; limonite is somewhere in between. Since the main selection object is hematite, the inlay is fine, so it is difficult to select. [next]
The mosaic relationship between the magnets, hematite, and limonite in the ore is advantageous for weak magnetic separation. According to the mineral phase report, most of the magnetite is magnetite-hematite crystals, accounting for about 50% of the total iron minerals. Due to the weathering effect of the surface, some of the magnetite is oxidized to limonite, and partially produced by magnetite-limonite. Magnetic--erythro-magnetic--brown crystals have strong magnetic properties (weaker than magnetite, but stronger than hematite and limonite). This mosaic relationship of iron ore is a very favorable factor for weak magnetic separation, but it is necessary to control the fineness of grinding and prevent the destruction of magnetic--red and magnetic-brown crystals.
The results of rock ore identification show that: according to the magnetite content of the sample is 14% and the magnetite-hematite crystals account for about 50% of the total iron minerals, the beneficiation process should have weak magnetic separation. . Since the main iron-bearing mineral is hematite, it is not possible to use a single magnetic separation process and must be combined with other methods.
In addition, due to the serious weathering effect of the surface, resulting in more mud, it is necessary to increase the mud removal operation.
(2) Selection of test plan
Based on the results of the above ore properties, the sample is a single iron ore of the type of high-silicon, low-sulfur and low-phosphorus impregnated with hematite. The options for selecting such ores are:
(1) Direct reverse flotation, including cationic collector reverse flotation and anionic collector reverse flotation;
(2) Selective flocculation--anionic collector reverse flotation;
(3) recovering the ferromagnetic iron oxide mineral by weak magnetic separation, and then recovering the weak magnetic iron oxide mineral by re-election;
(4) Weak magnetic separation - positive flotation, or positive flotation - weak magnetic separation;
(5) Weak magnetic separation--strong magnetic separation--strong magnetic separation concentrate re-election;
(6) Weak magnetic separation--strong magnetic separation--strong magnetic separation concentrate reverse flotation;
(7) roasting magnetic separation;
(8) Direct reduction method.
Among the above methods, the roasting magnetic separation index is the most stable, and the mature production experience in China is available for reference, but the cost is high, especially the fuel consumption is large, and the fuel resources of the mine area are lacking, so it is not considered. The positive flotation scheme has a simple process, but the hematite inlay size is too fine and the effect is not good. The main disadvantage of strong magnetic separation is that it is difficult to obtain qualified concentrates. Therefore, there are only three main attack options selected, namely (1) selective flocculation-reverse flotation; (2) weak magnetic-reselection (centrifuge) (3) Weak magnetic--strong magnetic--strong magnetic concentrate re-election (centrifuge). [next]
The initial test results show that among the three schemes, the selective flocculation-reverse flotation scheme has the highest index, and the concentrate grade exceeds 60%, but the technical problems to be solved are also the most – the ore needs to be finely ground to -38 μm; The wastewater needs to be purified; the source of the drug should be solved and the cost is high. The weak magnetic "re-selection scheme has the lowest cost, but the index is not good, especially the concentrate quality is low (average not exceeding 55%), the centrifuge has low production capacity and large area. The weak magnetic-strong magnetic-centrifuge is used. The advantage of the scheme is that it can use a strong magnetic separation to discard a part of the tailings and reduce the amount of ore that needs to be sent to the centrifuge, but it can not solve the problem of low quality of the concentrate. Finally, the schemes are complemented by weakening and strengthening. -- Centrifuge, plus selective flocculation and desliming scheme, obtained better indicators, basically meeting the requirements of the design department, but still need to further solve a series of industrial fine grinding, slime sedimentation and backwater utilization. Technical problems. Compared with the flocculation reverse flotation scheme, the cost of the medicament can be greatly reduced, and thus the production cost is low.
Second, the main scheme of other types of iron ore beneficiation test The above examples belong to relatively simple iron ore. The difficulties encountered in the test are mainly due to the fine embedding, and the material composition is not complicated, neither under the current conditions. The associated useful elements for comprehensive recovery, the harmful elements such as sulfur and phosphorus are not high, so the process combination is not very complicated.
Polymetallic iron ore, with many types of minerals and complex material composition, in order to fully utilize national resources, it is generally necessary to adopt more complicated processes, as follows:
1. magnetite ores containing copper and cobalt content of iron sulfide minerals according dissemination size and sulfides may be employed the following scheme:
(1) If the sulfide content is small and the magnetite is coarsely embedded, the magnetite concentrate can be selected by dry magnetic separation and wet magnetic separation, and then the tailings are ground to the necessary fineness. Select copper and drill sulfide by flotation.
(2) If the sulfide content is high and the iron mineral is finely embedded, the ore can be directly ground to the necessary particle size, firstly flotation of the sulfide, and then iron minerals from the flotation tailings.
2. Iron ore containing fluorite and rare earth minerals This type of ore is a comprehensive deposit of rare earth and iron. Since fluorite and rare earth minerals are highly floatable, they are usually selected by flotation. Therefore, the basic selection scheme for such iron ore is:
(1) Weak magnetic--flotation--strong magnetic (or re-election, flotation), that is, first select the magnetite with weak magnetic separation, then use flotation to recover fluorite and rare earth minerals, and finally use flotation, Strong magnetic separation and re-election methods are used to select weak magnetic iron minerals.
(2) Weak magnetic--strong magnetic--flotation, first select all iron concentrates by weak magnetic and strong magnetic, and then use tailings to recover fluorite and rare earth minerals by flotation.
(3) Weak magnetic--reverse flotation--positive flotation, the first selection of ferromagnetic iron sputum by weak magnetic separation, the selection of fluorite and rare earth minerals by reverse flotation of magnetic separation tailings, and the products in the reverse flotation tank Positive flotation separates weak magnetic minerals and gangue. [next]
(4) Roasting magnetic separation--flotation, that is, all the iron concentrates are selected by roasting magnetic separation, and the tailings are used to recover fluorite and rare earth minerals by flotation.
(5) First flotation of fluorite and rare earth minerals, and then using selective flocculation (or reverse flotation) method to decalcify the iron concentrate.
3. Phosphorus-containing iron ore According to the existence form of phosphorus and iron, it can be divided into the following two cases:
(1) Phosphorus exists in the form of apatite, which is the main form of phosphorus in iron ore. Iron is mainly in the form of magnetite or magnetite-hematite. In this case, the flotation method is commonly used. Out of apatite, possible solutions are:
1 re-election--reverse flotation, re-election method to select iron concentrate, and then iron concentrate to reverse the flotation method to remove apatite; 2 weak magnetic--flotation--strong magnetic separation, first weak Selecting magnetite by magnetic separation, selecting apatite by flotation by tailings, and finally selecting hematite by strong magnetic separation for flotation tailings; 3 magnetic separation--flotation or flotation--magnetic separation, When the main mineral in the iron ore is magnetite and apatite, the apatite is selected by flotation, and the magnetite is selected by weak magnetic separation. It is also conceivable to flotation of apatite in a magnetic field.
(2) Phosphorus is in the form of colloidal phosphate ore, and iron ore is dominated by braided structure. This ore is a difficult ore. The current promising solution is:
1 roasting magnetic separation; 2 re-selection - direct reduction - magnetic separation, re-election of iron concentrate by direct reduction roasting, roasting products after grinding, using weak magnetic separation to recover metal iron powder.
4. Vanadium- containing titanium magnetite ore The vanadium-bearing magnetite is a ferromagnetic mineral. The ilmenite is a weak magnetic mineral, but the specific gravity is large and can be recycled by re-election. If the ore contains sulfides and apatite, it is necessary to consider the flotation of titanium concentrate to remove sulfur and phosphorus, or to preferentially float sulfur and phosphorus before titanium is selected. If the symbiotic minerals in the ore are very finely embedded, densely symbiotic or similar, it is often necessary to directly use metallurgical methods or separation processes. Therefore, the selection scheme for such ores is:
(1) The magnetite is recovered by weak magnetic separation, the ilmenite is recovered by re-election, and the cobalt and nickel sulfide are removed by flotation of ilmenite concentrate.
(2) Recovering magnetite with weak magnetic separation, selecting cobalt and nickel sulfide by flotation, re-election-flotation combined process or re-election (selecting coarse particles)--strong magnetic separation (selecting fine particles)-- The ferromagnetic concentrate flotation combined process selects ilmenite.
(3) Recovering magnetite by weak magnetic separation, selecting cobalt and nickel sulfide by flotation method, reselecting-strong magnetic separation-flotation combined process to select titanium, and finally selecting titanium concentrate by electro-selection method, Improve the grade of titanium concentrate.
At present, magnetic separation and magnetic separation-flotation are mainly used in foreign countries. A single magnetic separation process produces a vanadium-containing titano-magnetite or vanadium-bearing magnetite concentrate. The magnetic separation-flotation combined process can produce three concentrates: vanadium-bearing iron concentrate, ilmenite concentrate and pyrite-based sulphide concentrate.
Because vanadium is similar to iron, iron and titanium are densely symbiotic, and cannot be separated by mechanical ore dressing. Chemical methods are needed.

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