I. Overview
(a) preface
Since the development of deposits of different conditions and manganese ore market, Yi Mini ore manganese ore beneficiation gone through several different stages. The characteristics of the ore deposit are that the grade of the ore produced varies greatly.
In order to meet the needs of the huge growth of the manganese ore market for the Iminian ore, the corresponding beneficiation process must be adopted according to the grade of the ore, and the beneficiation process should be improved according to the change of the ore grade.
This paper attempts to review the history of the mine from the initial stage of mining (1939), the original ore is commercial ore (MnO 2 content of 74% ~ 94%) to the current mineral processing plant treatment of the average ore grade of less than 63% of the historical changes, detailed Describes the mineral processing equipment currently in use.
(2) Geographic location
The Imini manganese mine is located on the road in Ouarzazate in southern Morocco, 160km from Marrakech.
(III) History of mine development
The Imini manganese mine was discovered in 1918. Since then, many investigations and exploration studies have been carried out. Mokta, founded in 1865, has explored mountains in Morocco since 1901 to find manganese and iron deposits.
The prospecting work began in 1929 with the discovery of a manganese deposit consisting of three adjacent horizontal deposits. In 1939, the proven ore was about 6 million tons, and the manganese content was 48%.
Second, the deposit
(1) Geological conditions
The Iminini Manganese deposit is located in the pre-African fold area between the Upper Atlas Mountains and the Southern Atlas-Atlas Mountains. Mineral carrier layer Late Cretaceous - Turonian of dolomite rock. The ore belt is divided into three layers: the first and second layers are separated from each other, and some parts are separated by only one interlayer, which is almost superposed. The third layer is north of the first and second layers and is located approximately 5 m above the second layer (Fig. 1). Mineralogical studies have shown that pyrolusite is mainly present in the third layer, while hard manganese ore and iron oxide mainly occur in the northern boundary of the deposit.
Figure 1 Xiaobai Yuji-Tulunpan Formation
(2) Ore classification
The Iminian ore is all manganese oxide (pyrox ore, hard manganese ore, manganese earth, lithium hard manganese ore), and iron oxides (goethite, limonite, magnetite) are associated with the northern boundary of the deposit.
Pyrolusite: Pyrolusite is the most important ore in the deposit, and its form of occurrence varies greatly, and it is symbiotic with manganese or manganese-manganese, or even symbiotic with iron oxide.
Hard manganese ore: amorphous or cryptomorphic, with different shapes: massive, layered or coagulated, belonging to the implicit isomorphous system. The main minerals of the isomorphic system are manganese ore, lead hard manganese ore and manganese antimony ore.
Manganese soil: Manganese is an earthy mineral of hard manganese ore, which is a brown-black light mineral.
Lithium manganese ore: Lithium manganese ore is a typical cryptocrystal, and sporadic tuberculosis is rarely seen in hard manganese ore.
Iron oxide: present in manganese ore at a low grade, with iron oxides only present at the northern edge of the deposit.
Third, the beneficiation process
(1) Primary test
The current beneficiation process is not studied and determined at the beginning of the mining process. It is developed and evolved as the deposit changes and the needs of the manganese ore market.
A lot of research work has been done on the wet selection and washing process tests, and the main facilities have been installed.
The test did not yield results due to the fragility of the ore and the lack of water in the area. Moreover, the test turned to the dry selection process.
(II) Initial beneficiation process
In the early mining, manganese ore in the world market situation is very favorable for the development of metallurgical industry. The Iminian manganese ore is powdery (50% < 2mm) and its market demand for manganese dioxide is very small. Based on this situation, the initial beneficiation process as shown in Figure 2 was selected.
Figure 2 Initial beneficiation process
The four types of ore mined in the mine were sorted, two of which were directly converted into commercial ore, and the other two were re-selected. The difference between the two groups of ore is that the content of pyrolusite is different. These two groups of ore are called "chemical ore" (more content of soft manganese ore) and "metallurgical ore" (the content of soft manganese ore is less, this name is not accurate). To this end, two sets of beneficiation (or pre-selection) equipment were installed. One set is used for beneficiation of direct commercial ore, and the other is used for enrichment and selection of ore.
1. Direct mineral ore dressing
Metallurgical mine: The quality requirements of this ore must first be sieved to 12mm. The coarse particles on the sieve are hand-selected by hand selection and stored as metallurgical commodity ore. The fines under the sieve are sent to a large belt sintering machine on the outskirts of Casablanca. The plant is equipped with a Dwight-Lloyd belt conveyor and the full set of unloading equipment required.
The ore was all broken to 4 mm and then mixed with 2 mm of coke from the hot pull. The proportion of coke is 1200kg of raw ore mixed with 150kg of coke. The output of the sinter plant is 20t/h, and a sintered ore containing 55% to 56% of Mn can be obtained.
Chemical ore: The same beneficiation process is used at the Imini smelter, and the ore is first sieved to 12mm. The fine particles under the sieve are stored as chemical ore. The coarse particles on the sieve are first selected by hand and then stored as commercial ore.
The above two ores, rich ore blocks are sorted on the hand-selected stage, and then crushed by a selective crusher to obtain a very rich commercial ore powder (92% MnO 2 ) for sale.
2, the need to enrich the processing of selected ore
The plant can also select metallurgical and chemical grade ores. After the ore is sorted on the hand selection stage, it is sieved to 1.5 mm. The parts below 1.5mm are all used as commercial ore, and the ore larger than 1.5mm is divided into 4 layers (1.5~2.5, 2.5~5.5, 5.5~8 and 8~15mm), and 4 Birtley pneumatic gravity beneficiation stations are supplied to obtain concentrate. And tailings. The first plant (concentration plant I) was built in the center of Butazurt and was put into operation in 1951. Another identical factory (Planter II) was built in the city centre of Timkit in 1961.
Fourth, technical transformation
As mentioned earlier, the beneficiation equipment was modified according to the situation of the manganese ore market and the changes in the Iminian manganese deposit.
The Iminian manganese ore was originally used in the metallurgical industry and was converted to natural manganese dioxide due to the drop in metallurgical manganese prices.
Due to the presence of fine-grained products on the market for manganese dioxide, several grinding equipments have been installed to develop the production of such products.
Due to the decline in several grades of raw ore, the grades of several commercial products (pellets, fines, magnetic concentrates) have also declined, so the beneficiation process has been modified to recycle these products and reprocess them.
(1) Powder processing
The metallurgical ore market is mainly represented by the worldwide competition in which the ore market declines and the sintering cost rises. It is urgent to carry out powder ore processing tests. Since 1966, a set of equipment has been put into operation in Tijukit, and an industrial trial of fines processing has been carried out on the Birtley pneumatic dressing station (Selection III).
Due to the friability of the ore and the high proportion of high-humidity particles in the ore, the efficiency of the equipment is not high, and the fine ore dressing station is finally eliminated.
In 1967, a new method of processing powder ore, namely dry high-strength magnetic separation, was studied. A large amount of research work in the laboratory was carried out on a Sime concentrator, through which the basic parameters of the size and adjustment of the industrial equipment were established.
The powder ore magnetic separation processing equipment was put into operation in 1970, and its main components are as follows (Fig. 3).
Figure 3 Initial process of fine ore dressing
The fine ore produced by the Concentrator II was sieved through a 750 μm Mogensen screening machine with a grade of ≥74% MnO 2 as a bulk product. The sieved material was first passed through a Kestner fuel drying oven to lower the temperature to facilitate 50 μm sorting in the next two parallel Alpine sorters.
The fine ore below 50 μm is called ultrafine powder ore and contains a large amount of MnO 2 ) MnO 2 is 74% to 94% depending on the adjustment of the ore and equipment.
The powder mine larger than 50μm is called coarse Alpine powder ore and is directly supplied to two three-stage magnetic separators. The content of MnO 2 in the manganese concentrate powder is 72% to 80%, and the content of MnO 2 in the tailings is 35% to 45%.
The powder processing equipment has undergone several technical transformations. For example, a third-stage Alpine sorting machine was installed in 1975. The sorting machine was connected in series with two other original sorting machines to recover the high proportion of poles. Fine powder ore. Because the first, very fine fine ore is a commercial ore, and secondly, very fine fine ore will seriously hinder the normal progress of the magnetic separation process.
Installation of the "Zigzag" sorter
The method used to limit the size of the ore on the screen, here is the Mogenson screening machine. Due to the high humidity of the ore powder and the large ore particles (750 μm, and the particle size specified by magnetic separation is 500 μm), the ore dressing effect is not satisfactory.
In 1978, after several tests, the above screening machine was replaced by an updraft sorter. This sorting machine is called the "Zigzag" sorting machine. It was put into production in 1979 and can be adjusted to ensure the sorting of the particle size of 350-500 μm. The undersize product is about 5% to 8%. In addition to the best sorting effect, this sorting machine has the following two advantages:
The production capacity of the "Zigzag" sorting machine can reach more than 25t∕h, and the average normal production capacity is 18t/h.
The sorted tailings are enriched by gravity beneficiation (up to 70% to 80% MnO 2 depending on the original ore).
Development of magnetic separation method
The good test results obtained in the laboratory were not used in industrial production. The biggest obstacle is the fragility and obstruction of the ore. It is because people have not been able to solve the problem of magnetic separation of ultrafine powder ore, and there is no guarantee that the supply site has a thin and uniform material layer. In addition, there is another important technical problem (rotor winding) due to the decline of the magnetic separation concentrate market and the long-term shutdown of equipment.
In 1979, the equipment was forced to stop operating. In order to re-determine the specifications of the equipment, research work was carried out in 1980. In 1981, a new set of four secondary conveyor belts was put into production. In 1984, due to the replacement of the rotor and the equipment could not be operated for a long time, the magnetic separation concentrate was no longer commercialized. Considering that the magnetic separation equipment is finally eliminated, it is replaced by the grinding scheme described below.
(2) Recycling of pellets
On Birtley mineral processing platform from MnO 2 high grade ore shipped region, produces ≧ 80 percent of MnO 2 grade concentrates containing about 74% of the MnO 2 mixed ore and MnO 2 content of 50% of tailings. The ore transported from the low-grade marginal zone of MnO 2 failed to produce a concentrate of 84% to 92% of pellets, with a product yield of 80%.
The recycling efficiency was improved by the installation of 2 sets of secondary processing equipment for the grain division.
Grinding of 2~15mm pellets
The problem that needs to be solved most is how to recycle the mixed material on the platform because the grade of the compound (<74% MnO 2 ) does not meet the commercial requirements. In 1973, a set of grinding equipment was installed, and its working circuit is shown in Figure 4.
Figure 4 2 ~ 15mm pellet process
The pellet mixture of the beneficiation platform is first stored in the commercial material platform and then sent to the receiving silo, which feeds the Dragon Hammer Mill. The product is ground to 2 mm, the sieve material (tailing) is returned to the grinding, and the sieved product is transported to the supply bin of the zigzag sorting machine. This equipment not only guarantees the recovery of all the mix on the platform, but also ensures that all concentrates and tailings are recovered for professional production.
Grinding of small pellets (0.5~2mm)
For the same reason, in the new case of granule recycling, RZZ pellets are not commercial pellets (Dragon chose to mine to obtain lean ore pellets), and a new RZZ grinding equipment was installed in 1981. The simplified working circuit of this new device is shown in Figure 5.
Figure 5 Small material process
Like pellets, RZZ pellets are typically stored in a commercial pallet or recycled as soon as practicable. There is a PALLA50U vibrating rod mill for grinding. The ground minerals are sent to the 4th concentrator.
The above two sets of equipment can be used for the following various mineral processing:
Recycled pellets and low grade pellets for the production of high grade UF;
92UF is produced by selecting the concentrate and enriching the RZZ material;
Re-election of low grade magnetic separation concentrates and SMMI unprocessed Alpine coarse minerals.
(3) Current process
The current processing flow is shown in Figure 6. In this figure, the mineral material does not automatically enter the same processing line. The route taken by the mineral material depends first on the quality of the UF to be produced and the quality of the ore to be processed, and secondly on The quality of the intermediate product to be recycled.
Figure 6 Flow chart of the Yimini concentrator
V. Results
To illustrate the problem, the processing results for the Imine manganese ore are listed in the table below.
Table Imini manganese ore processing results (%)
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