Pre-selection methods for various types of iron ores

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With the rapid development of social economy, my country's demand for iron ore resources will continue to rise. However, the average iron content of iron ore in my country is less than 30%, and lean ore accounts for 98.8% of all iron ore reserves. If you want to effectively recycle this type of iron ore, iron ore pre-selection is essential. Pre-selection follows the principles of "early disposal when possible" and "energy saving and consumption reduction". Through iron pre-selection technology, impurities are removed from the ore dressing process in stages, which effectively improves the recovery rate of iron concentrate and reduces the investment cost of enterprises. Let's take a look at the different methods for pre-selection of lean iron ore.

1. Preselection method of ultra-lean magnetite

The boundary grade requirement of ultra-lean magnetite is generally MFe>6%, and the industrial grade requirement is MFe>8%. Its beneficiation ratio can reach 8~15, but the unit beneficiation cost is high. Therefore, it is necessary to focus on the principle of "more crushing and less grinding, coarse grain discarding, and discarding as early as possible". At present, the preselection can be carried out by stage crushing-stage dry preselection process or high pressure roller mill-classification preselection process.

Stage crushing-stage dry preselection: Use suspended dry preselection magnetic separator to preselect and discard the -25mm fine crushed product and the high pressure roller mill ultra-fine crushed product (-3mm) of the first stage preselected concentrate, and the cumulative yield of the two stages of discarding is 83.30%.

High-pressure roller mill-classification pre-selection: The +2 mm particle size is discarded by the traditional drum dry separator, and the coarse concentrate returns to the high-pressure roller mill to form a closed-circuit crushing; -2 mm is discarded by a boiling dry magnetic separator with a vibrating aerated chute, and the dry concentrate is then discarded by wet magnetic separation and then enters the grinding system. The wet tailings are dehydrated and combined with the dry tailings and sent to the tailings dry yard for storage. This process can discard more than 85% of tailings, solving the problems faced by mining companies, such as the hardening of the mined ore and the decrease in iron grade, which caused the insufficient processing capacity of the crushing and grinding system and the decrease in concentrate production. At the same time, the dry stacking of tailings can extend the service life of the tailings pond.

2. Pre-selection method for fine-grained magnetite

For fine-grained magnetite, the conventional dry magnetic pre-selection equipment is not ideal for its selection effect. The main reason is that strong magnetic minerals such as magnetite will have strong interaction forces after magnetization, which makes it easy to form magnetic agglomerates between particles and contain gangue. To improve this problem, the pre-selection method of high-pressure roller mill-3mm dry screen-dry magnetic pre-selection-middling ore circulation dissociation can be adopted. The 360° rotating alternating magnetic field and eccentric roller are used to construct a unique alternating gradually weakening sorting magnetic field, which can greatly reduce fine-grained magnetic inclusions and mechanical inclusions.

3. Vanadium-titanium magnetite pre-selection method

Titanium magnetite and ilmenite are the main target minerals for vanadium-titanium magnetite recovery, mostly produced in aggregates, and micro-fine ilmenite and titanium magnetite are co-embedded in the gangue. For this type of weak vanadium-titanium magnetite, the new ZCLA gravity magnetic concentrator can be used. This equipment uses a semi-closed external magnetic system and an inner cylinder structure to make the magnetic minerals in the material subject to the combined effects of magnetic force, gravity and centrifugal force, thereby achieving efficient separation from non-magnetic minerals. Compared with the cylinder-type weak magnetic separation coarse grain tailing process, the process is simpler, the operating cost is low, and the concentrate yield and metal recovery are higher.

4. Preselection method of lean hematite ore

For mixed lean hematite ore, the preselection process of coarse-grained dry strong magnetic preselection tailings discarding-fine-grained wet strong magnetic preselection desludging can be adopted. When the magnetic induction intensity is 0.70T, the -2 mm particle size lean hematite is preselected to obtain a better iron concentrate with a recovery rate of 79.56% and a tailings discarding yield of 47.17%; the lean hematite wet preselection process can also be adopted. When the TFe grade of the selected ore is 18.34%, the preselection feed particle size is -3 mm, the magnetic field intensity of the permanent magnetic drum magnetic separator is 191kA/m, and the background magnetic induction intensity of the vertical ring pulsating high gradient magnetic separator is 796kA/m, which can effectively obtain high-grade iron concentrate with a recovery rate of 86.31%.

5. Preselection method for weakly magnetic and difficult to select lean iron ore

For weakly magnetic and difficult to select hematite, the metal loss rate is high when a single strong magnetic preselection process is used. With the rapid development of science, intelligent photoelectric sorting technologies such as surface radiation, transmission technology, laser induction and image color sorting have emerged. Therefore, preselection can be performed by combining the above process with magnetic separation to improve the recovery rate of iron concentrate, such as intelligent photoelectric preselection-strong magnetic dry preselection: the preselection equipment is XNDT-104 X-ray intelligent sorting machine and T-QCG dry strong magnetic separator. When the particle size of the processed material is When the diameter of the iron ore is 45-15mm, when the belt speed of the intelligent pre-selection equipment is 3m/s and the magnetic induction intensity is 0.85T, the tailings with a total yield of 24.12% can be discarded, and the grade of TFe concentrate is increased by 3.85 percentage points.

The above is an introduction to the process of pre-selection of lean magnetite ore. In actual ore dressing plants, iron ore pre-selection is an important means to improve the grade of iron concentrate. How to choose the pre-selection method depends on the properties of the iron ore. Therefore, it is recommended to conduct ore dressing test analysis first, and design and customize suitable iron ore pre-selection workers and iron ore dressing process solutions according to actual conditions.