1 Multi-element chemical analysis of raw ore
The results of multi-element chemical analysis of raw ore are shown in Table 1.
From the chemical analysis results of the above table, the content of chromium in the ore in the ore is relatively low, only 8.19%, which is a chromium-poor ore. It needs to be enriched in ore before it can be smelted into the furnace. Other metal element content of Mg is relatively high as 36.10%, if present as separate minerals, should be considered comprehensive recycling. The main component of SiO2 gangue, content of up to 30.55%, content of other components is low, Al2O3 content of only 1.78%, but if Al3 + and Cr3 + was isomorphous present, while the chromium enriched in the dressing process, the aluminum It will also be enriched in chrome concentrate. For the purposes of this study, the target element is Cr, and Mg and Si are the main targets that need to be removed in the beneficiation.
2 Ore grindability analysis
The grindability comparison was made with the wine ore as a standard ore sample. As a result, the chromium-depleted iron ore is difficult to grind relative to the iron ore mine. When the new-200 mesh content reaches 40%, the relative wearability is 0.56.
3 dressing test
According to the properties of high specific gravity (4.3 to 4.6) and weak magnetic properties (magnification coefficient 286×10-6 C. GSM cm 3 /g) of chromite, the re-election and magnetic separation methods were used for the beneficiation test.
3.1 Shaker beneficiation test
Shakers are currently the most commonly used equipment for chromite ore. Due to their high precision, many mines are willing to use them. To this end, we first carried out a shaker test for the chrome-poor ore.
3.1.1 Full-Grade Sorting
After grinding to the required fineness, go directly to the shaker to sort. In this test, the grinding size, flushing water volume, stroke, stroke and slope of the selected index were selected. According to the selected conditions, the process test is carried out. The selection process is as follows: Shake rough selection - China mine re-selection two sections. The selection process and results are shown in Figure 1.
It can be seen from the above selection results that a chrome concentrate with a grade of 39.85%, a yield of 11.82% and a recovery rate of 56.83% can be obtained at a grinding particle size of -200 mesh of 60%, and the SiO2 content is 4.32%. The medium ore is re-selected to obtain a chromium concentrate with a yield of 2.68% and a grade of 32.69%. The silicon content is increased to 8.14%, which is combined with the rough concentrate to be the final concentrate. The index is the yield of 14.50% and the chromium grade. 38.53%, chromium recovery rate of 67.40%, silicon content of 5.03%, mineral processing ratio of 6.9 times.
3.1.2 Shaker graded ore dressing test
For the shaker, the narrower the level range of the granularity in general, the more stable the selection index and the higher the sorting efficiency. For this purpose, the grinding products are sieved into five levels of +0.15mm, -0.15 +0.10mm, -0.1+0.074mm, -0.074+0.038mm and -0.038mm by dry screening, respectively. The shaker is sorted under the conditions, and the sorting process of each level is the same as that of Fig. 1, and each grade selection product is combined into a total sorting product. The chromite minerals are mainly present in the 38-100 micron size range. The chromium grades in these grades are relatively high, and the total chromium distribution rate is 79.56%. The grades of coarse and fine grades are lower, the grade of +0.15mm grade is 6.22%, and the grade of grade of -38mm is only 5.93%, which is lower than the original ore, indicating that the gangue composition is in these two. Enriched in the grain size. From the results of separate sorting of each grade, the sorting efficiency of the intermediate fraction (0.038~0.010mm) is higher, and the grade and recovery of concentrate chromium are ideal, especially the grade of 0.074~0.100mm, and the grade of chromium is 39.30%, the recovery rate is 85.25%, both indicators are the highest among the various grades. Relatively speaking, the coarse-grained grade of +0.15mm and the fine-grained grade of -0.038mm are relatively poor. The former has a concentrate grade of only 34.07%, and the operation recovery rate is 52.75%, while the latter concentrate grade is only 26.09%. The recovery rate is also as low as 38.28%, and the grades of the two grades of tailings are also significantly higher than other grades. The reason for the analysis is that the coarse grade is low because the mineral dissociation degree is not enough, the chromite ore and the gangue are not fully dissociated, and the purpose of separation is not achieved, and the difference of the fine-grain grade is due to the selection of the fine mud by the shaker. Don't be inefficient. From the comprehensive results, the final concentrate grade is 36.09%, and the recovery rate is 73.97%. Compared with the whole-grain grade selection result, the concentrate grade is low and the recovery rate is relatively high. If the -0.038mm grain size is not incorporated into the concentrate, the concentrate grade can be increased to 37.22%. If the coarse fraction of +0.15mm or more is removed, the concentrate grade can be further improved. On the whole, the beneficiation efficiency of the whole-grain and grading process is basically the same. The whole-grain selection has the advantages of simple process, no grading, and simple operation. For the ore, the grain size is relatively fine, and the grain size is relatively fine. The level is relatively concentrated, and it is more suitable to use the full-grain level.
3.2 Spiral chute tailing-shaker beneficiation test shaker
It has the advantages of high sorting precision, but at the same time has the disadvantages of large floor space and low processing capacity. For the ore, due to the low grade of raw ore chrome, a large amount of dissociated gangue minerals enter the shaker, which greatly increases the burden of the shaker. Therefore, it is necessary to explore the pre-spinning process and use a large amount of processing after grinding. Low-cost equipment throws out qualified tailings, which reduces the amount of minerals entering the shaker, saves the number of shakers, and reduces the interference of gangue, especially fine-grained gangue, creating favorable conditions for shaker sorting. For this purpose, the spiral chute tailing-shaker sorting test was carried out. The spiral chute can remove the tailings with a yield of 43.91% and a chrome grade of 4.47%. The amount of minerals entering a shaker and a two-stage shaker after tailing is greatly reduced. It can save nearly half of the shaker equipment and floor space, and the efficiency of the shaker sorting after tailing is obviously improved. The same shaker sorting process as the full grain grade and graded sorting is adopted, and the final concentrate grade is finally adopted. It can be increased to 39.54%, but the recovery rate index is relatively low. The main reason is that when the spiral chute is thrown tail, a small part of fine-grained chromite ore enters the tailings due to centrifugal force, resulting in a slightly higher grade of tailings. The spiral chute has the advantages of large processing capacity per unit area, simple structure and no need of power, but the lower limit of the recovery particle size is about 30 microns. When the grinding particle size is fine, it is easy to cause the loss of useful minerals of fine particles.
3.3 Magnetic separation tailing - shaker beneficiation test
According to the high specific magnetic susceptibility of chromite, a magnetic separation tailing-shaker selection test was carried out.
The magnetic separation equipment adopts the pseudo- Jones wet magnetic separator, and the strong magnetic separation tailing test is carried out under the condition of grinding grain size - 200 mesh 60% and magnetic field strength 5000 Oe. Because the magnetic separation tailings grade is low, it can be used as qualified tailings. Therefore, the magnetic separation is used for rough selection and tailing, and the shaker is used for selection to improve the grade. The test procedure and indicators are shown in Figure 2.
From the results of Figure 2, the strong magnetic separation can remove the qualified tailings with a yield of 50.21%, and the tailings grade is only 2.19%, which reduces the amount of minerals entering the shaker by half, greatly reducing the number of shakers. After the tailing, the favorable conditions for the sorting of the shaker were created, and the selection index was further improved. Finally, the ideal index of grade 39.98%, recovery rate 64.74% and SiO2 content 4.07% was obtained, and the spiral chute tailing-shaker process In contrast, the strong magnetic separation process has a large throwing amount and a low grade of tailings, and the final concentrate recovery rate is relatively high.
4 Comparative analysis of indicators
From the selection indicators of the above processes, the final concentrate grade and recovery rate indicators are quite different. In comparison, the magnetic separation tailing-shaker selection process results are ideal. The concentrate grade is significantly higher than other processes, and the recovery rate index is not much lower; the spiral chute tail-shake sorting process can also obtain high-grade chromium concentrate, but due to the spiral chute equipment for the recovery efficiency of fine-grained chromium minerals The low grade makes the tailings grade slightly higher, which makes the concentrate recovery rate relatively low. The index of the full-scale sorting process of the shaker is middle, and the classification index is relatively poor, mainly in the concentrate chrome grade. Low, if the concentrate belt width is further adjusted, the concentrate grade may increase, but the recovery rate will drop significantly. It is expected that the final indicator will not exceed the magnetic separation-shaker process indicator (for example, 0.038 in the classification process) A section of the selected grade concentrate of ~0.15mm is combined, the chromium grade is 38.74%, and the recovery rate is only 59.78%).
From the process point of view, the number of shakers required for the full shaker selection is large, occupying a large area of ​​the plant. If the classification is selected, it is necessary to control the classification granularity more strictly; for the ore, due to the finer grain size of the ore, the granularity The range is small, and from the perspective of ease of management and operation, a full-grain selection process can be used. The spiral chute and strong magnetic separation tailing process can pre-delete the tailings with a yield of more than 43%, which creates favorable conditions for the next sorting of the shaker, and greatly reduces the number of shakers. The two tailing equipments operate reliably and have a large processing capacity. Can be considered for use. Magnetic separation is the most suitable process. Due to the large processing capacity of the equipment, only a small number of units can be used to complete the workload of a large number of shakers, and the operation is simple, the operation is reliable, the index is stable, and the management is convenient. The disadvantage is that the equipment price is high. A single device consumes a lot of power. The above test procedures have their own advantages and disadvantages. The selection process that is suitable for the actual and low cost should be selected according to the construction conditions and economic comparison.
In this test, in order to recover as much chromite as possible, in the middle ore re-election of each sorting process, the amount of medium ore intercepted is large, so that the amount of minerals that are re-selected into the shaker is also large. From the selection index, the re-selected concentrate yield is very low, and most of the ore reserves re-enter the tailings, so in the actual production, the amount of minerals in a shaker can be reduced, thereby reducing the burden of the second-stage shaker.
5 Product Analysis
Multi-element chemical analysis was performed on the concentrate of the magnetic separation tail-shake full-grain process. The results are shown in Table 2. It can be seen that the main gangue components in the concentrate are Al2O3 and MgO, and the total content of the two is as high as 25.11%, which seriously affects the concentrate grade. The content of MgO in the ore is higher, and there is a large decrease in the chromium concentrate after beneficiation, indicating that most of the Mg is present in the chromite ore as a separate mineral, which can be separated from the chromite by beneficiation. Al2O3 is abundantly enriched in chrome concentrate, and the enrichment ratio is as high as 5.8 (the content in the ore is only 1.78%), indicating that Al is likely to enter the chromite ore crystal, which is in phase with chromium. It cannot be separated from the chromium by mechanical means.
6 Conclusion
6.1 The content of Cr2O3 in a chrome-poor iron ore is only 8.19%. After proper process selection, a qualified product with a Cr2O3 content of more than 39% can be obtained, indicating that the chrome-poor iron ore is optional.
6.2 Using the shaker selection process, the selection index of yield 14.50%, grade 38.53%, and chromium recovery rate 67.40% can be obtained at the full-grain level. When the fractionation grade is selected, the selection index of the yield of 16.91%, the grade of 36.09%, and the recovery rate of 73.97% can be obtained. Comprehensive comparison, the full-scale inclusion index is relatively better. The advantage of the full shaker process is that the sorting precision is high, and the disadvantage is that the processing amount is small, the number of equipment required is large, and the floor space is large.
6.3 The use of spiral chute and strong magnetic separation process can remove more than 43% of tailings in advance, creating conditions for shaker selection, and greatly reducing the number of shaker equipment and plant floor space. In comparison, the strong magnetic separation tailings have a low grade and can be directly discarded as qualified tailings, while the grade of the spiral chute tailings is relatively high. Both tailing devices have large processing capacity and reliable operation.
6.4 Adopting strong magnetic separation and throwing tail - shaker selection process
A chromium concentrate having a yield of 13.28%, a grade of 39.98%, and a recovery rate of 64.74% can be obtained, and the SiO2 content in the concentrate is 4.07%. The spiral chute tailing-shaker sorting process can obtain the index of concentrate grade 39.54%, yield 12.50%, and chromium recovery rate of 60.28%. The SiO2 content in the concentrate is 4.15%. The former has a relatively good selection index.
Since chromium is the most versatile metal, it ranks first in the “strategic metalâ€. The world today has chrome resources
Countries or countries with scarce resources are stepping up research on chrome ore beneficiation, and their selection methods are;
(1) Re-election: such as jigging, shaker, spiral chute, heavy medium cyclone, etc.
(2) Magnetic power selection: including high-strength field magnetic separation and high-voltage electric selection.
(3) Flotation and flocculation flotation.
(4) Joint election: such as re-election.
(5) Chemical beneficiation: It is difficult to treat extremely fine grains and choose chromium-poor ore.
In the above chrome ore beneficiation method, the re-election method is mainly used in production, and the shaker and the jig are often used for sorting. Sometimes heavy
The concentrate is selected by weak magnetic separation or strong magnetic separation to further improve the grade and ferrochrome ratio of the chromium concentrate. An ore with a high iron content or a dense symbiosis with magnetite, a concentrate obtained after ore dressing, a chromium grade and chromium. The iron ratio is low, and it can be considered as an ingredient for the production of ferrochrome by fire method, or by hydrometallurgy. For example, sodium dichromate method, chromium hydroxide method, reduction rust method, chlorination roasting acid leaching or electrolysis method. The production practice of low-grade ferrochrome concentrate by hydrometallurgy.Platinum deposits (platinum, palladium , rhodium , iridium , ruthenium and rhodium ), cobalt , titanium , vanadium , nickel and the like are often associated with chromium deposits. When the platinum content is greater than 0.2-0.4g/t, the cobalt content is greater than 0.02%, and the nickel content is greater than 0.2%, comprehensive recovery should be considered. Chromite ore in associated form, such as PGE sulfide, arsenic compound or sulfur arsenide state, can be recovered by flotation. Olivine and serpentine ore, can be considered comprehensive recovery, for the production of refractory materials, calcium magnesium phosphate fertilizer diabase or the like. In the shallow part of the ultrabasic rock mass, there is sometimes an amorphous magnesite that is caused by weathering and leaching, and it is also a good raw material for refractory materials.
Solenoid Valve
Brando is a Solenoid Valve manufacturer and exporter in Ningbo, China, which has more than 10 years experience.
According to different valve body materials, solenoid valve is divided into:
1. Brass Solenoid Valve
2. Stainless Steel Solenoid Valve
3. Plastic Solenoid Valve
4. Aluminum Alloy Solenoid Valve
According to different working meidum, solenoid valve is divided into:
1. Water Solenoid Valve
2. Steam Solenoid Valve
3. Gas Solenoid Valve
According to different application, solenoid valve is divided into:
1. Dust Collector Solenoid Valve
2. Refrigeration Solenoid Valve
3. Pneumatic Solenoid Valve
4. Air Compressor Solenoid Valve
5. RO Water Solenoid Valve
6. Fountain Solenoid Valve
7. Irrigation Solenoid Valve
8. Truck Solenoid Valve
9. Automobile Solenoid Valve
10. Medical Solenoid Valve
Solenoid Valve 24VDC, Solenoid Valve 220VAC, Solenoid Valve 12VDC, Solenoid Valve 110VAC
NINGBO BRANDO HARDWARE CO.,LTD , https://www.brandopneumatic.com