Pre-selection of lead and zinc heavy medium (1)

Heavy medium beneficiation is based on the difference in specific gravity between minerals (or minerals). Due to advances in modern instrumentation and control technology, the specific gravity of the medium is allowed to remain within a selected value of 0.005; therefore, the difference in specific gravity between minerals (mineral continuum) as small as 0.01 can also be separated.
After the ore is crushed, the useful minerals and gangues are fully dissociated, and then the particle size suitable for heavy medium sorting is screened out. Generally, the maximum blockiness is 100 mm and the minimum is 0.5 mm, and the slime and fine particles are removed.
The media density is usually in the range of 1.3 to 3.8. When using coal washing lowest density, magnetic iron ore as medium; while selected from iron or magnetite, used in the highest density; most other ore sorting (see below densities of between two ).

Pre-selection with heavy medium beneficiation can:
1. Simplified selective mining, can be recovered from the cut-off grade ores of valuable metals.
2. Pre-selection of lean ore and boundary grade ore can effectively utilize industrial lean ore resources. Heavy medium beneficiation can economically recover metals from low-grade ore that was previously considered uneconomical, or from ore that has been stored in the past due to poor processing.
3. Reduce transportation costs. When a large amount of ore is required to be transported over a long distance, such as removing gangue in situ at the mine, it is possible to save a lot of transportation costs.
4. Replace the original beneficiation method. Heavy medium beneficiation can completely replace some of the original beneficiation methods due to its high efficiency and reliable operation.
5. Remove undesirable impurities. The pre-selection of heavy medium excludes harmful impurities such as oxides and heavy metal ions in the ore, mixes the ore and increases the content of useful components, and plays a good role in improving the flotation technical index.
Heavy medium pre-selection has moved from the lead-zinc industry to other sectors of nickel , fluorite and non-ferrous metallurgy. In the eighth and ninth five-year plan of the Soviet Union, the amount of ore processed by heavy medium pre-selection increased from 2% to 35%, and reached 50% in the tenth five-year plan.
At the 14th International Mineral Processing Conference, the Soviet Union reported on the promotion and application of pre-selection technology, which achieved remarkable economic results. The lead ore of Geyenovsk is 0.1-0.2% lead and 0.2-0.3% zinc. The heavy medium dressing pre-selection process produces high-quality products with obvious economic benefits. [next]
When Munro PD of Australia studied the effect of silver -lead-zinc ore heavy medium ore dressing, it was pointed out that heavy medium ore dressing can lose tailings which account for 30~35% of the original ore yield. The recovery rate of lead, zinc and silver in heavy products reaches 96~ 97%; At the same time, due to the heavy medium sorting, a large amount of silicate minerals with small specific gravity and difficult to grind are discarded in advance, so that the grinding work index of the milled materials is reduced by 25%. This can be used to increase the volume of the original ball mill , grinding fineness - 0.074 mm to 87%.
The heavy medium sorting equipment has two types: static (cone sorter, drum sorter) and dynamic (heavy medium cyclone, heavy medium vortex cyclone). Dynamic sorting equipment utilizes centrifugal force and has higher processing capacity than static sorting equipment. Static sorting equipment handles a particle size of typically 100 to 6 mm, and dynamic sorting equipment is suitable for fines of 25 to 0.5 mm and up to 40 mm.
The static heavy media separation process was used in the early 1920s. The basic principle is to use gravity and horizontal force (horizontal flow rate) for sorting, such as cone, cylinder, classifier, drum, Vibrating chute and inclined wheel sorting machine, etc. (see the next two figures)

Figure 1 text <Environmental Technology Company Wimco Division>
Technical description Single media system Two media systems Single drum Two specific gravity: round drum of three products Specifications: diameter 6' ~ 12' Specifications: 6' × 10' ~ 12' × 20'
Production: ~400T / hour Yield: ~325T / hour Power required: 5 ~ 20HP Power required: 10~20HP
Single drum: two overflow products Two specific gravity: four drums Specifications: 6′×11′ to 15′×23′ Specifications: 6′×10′ to 12′×20′
Production: ~500T / hour Production: ~650T / hour Power required: 10 ~ 30HP Power required: 10 ~ 20HP

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Dynamic heavy medium sorting is performed by using centrifugal force greater than 20 times gravity. The heavy medium sorters currently in production include the widely used DSM heavy medium cyclones, the NCM vortex type heavy medium cyclones, the Japanese inverted vortex cyclones, and the DWP heavy medium vortex sorters.
The following highlights several new dynamic sorting devices.
1.DWP (Dyna Whirlppl Process) Dina vortex cyclone
2
Dyna (DYNA) Vortex Sorter (DWP) is a cylindrical dynamic sorter with a particle size of 1吋 (or 1-吋) to 65
1
Head.
The ratio of length to diameter of the sorter is 4:1 or 5:1. There is a tangential inlet and a tangential outlet at both ends, and approximately 90% of the circulating medium is pumped from the lower end to the inlet into the separator, and the heavy product is discharged through the tangential outlet at the upper end. Both ends of the cylinder are covered by a cover drilled with an axial hole.
The upper end axial hole is provided with a feeder, and the mine pipe is inserted into the container; the lower end is provided with a discharge pipe, the discharge pipe and the feed pipe are inserted into the container to have the same depth, and the light product is discharged from the lower discharge pipe. The figure below shows the department view of the DWP. 90% of the medium enters the sorter from the media inlet (5) at a tangential direction with a pressure of about 15 pounds. The medium is divided into two parts and discharged through the sinker port (7) and the float port (3). The difference in specific gravity between sinking and floating media is generally between 0.2 and 0.5. The remaining 10% of the medium is fed by gravity from the ore.

The DWP vortex separator is operated at an angle of 15 to 45 degrees from the horizontal. If the installation position of the equipment is close to horizontal, it will cause difficulty in feeding the mine; if its position is close to vertical, the ore will pass directly through the cylinder without any sorting action. Generally used for coal preparation, the installation angle is 15 degrees, and the installation angle is 25 degrees for metal ore selection. [next]
The static pressure of the DWP sorter is 0.6-1.8M, the diameter of the test-type vortex sorter is 150-460 mm, the processing is given the particle size of -50 mm to 210 μm, the ore amount is 100 ton / hr, and the lower limit of the processing fraction can be reached. 500 microns. It takes about 10 tons of medium (about 4m ³ ) to process one ton of ore.
DWP vortex separators have the following characteristics compared to other types of heavy medium cyclones:
(1) The moment the ore reaches the DWP sorter in the passenger shop is always separated from the medium; and most heavy medium cyclones are pumped into the cyclone after the ore is mixed with the medium in the pump pool. Therefore, it is determined that the feeding pressure of the medium has nothing to do with the feeding amount and the feeding, and the medium and the ore can be separately controlled and adjusted to meet the requirements of the system change in time. In addition, the process can be allowed to penetrate easily. Porous ore, temporary contact between the ore and the medium limits the penetration of the medium into the ore, reduces the contamination of the light product by the medium, and reduces the tendency of light products to enter heavy products.
(2) The static head of the DWP sorter is 2 to 6 feet, so the centrifugal force is small, the speed is low, and the surface of the container is worn little. The heavy product falls through the medium and is immediately discharged through the heavy product discharge port. The portion of the light product in the ore supply is not in contact with the metal, and only the portion near the heavy material moves along the wall of the container, so wear occurs only in a small range of the heavy product discharge.
(3) The sorting particle size range is wide, the lower limit particle size can reach 0.2 mm, and the pre-selected throwing rate is high; the metal and mineral contact in the sorter is less. Therefore, the brittle mineral is less muddy.
(4) The DWP separator has a mineral ratio of about 4, which is lower than that of the ordinary heavy medium cyclone (6-8), and the medium circulation is small.
(5) The equipment is small in size, simple in structure, light in weight, easy to manufacture, and requires a small plant area per unit throughput.
The mineral processing process and equipment are shown in the figure below.

1—pre-slide screening, 2-DYNA vortex sorter, 3-fixed media screen, 4-de-packing and rinsing screen, 5-washing liquid pump, 6-magnetic separator, 7-main media warehouse, 8- Media pump, 9-medium concentration spiral, 10-demagnetization line, 11-sewage pump, 12-sink phase fixed sieve, 13-sink phase vibrating screen, 14-media distributor

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