Our diaspore bauxite mainly sedimentary type and accumulation type categories month, it was reported, sedimentary bauxite accounted for about 86% of the country's total reserves of bauxite ore accumulation-type accounting of total reserves 13%. China's bauxite is mainly composed of sedimentary diaspore-type bauxite, but the stacked diaspore-type bauxite is a unique bauxite resource in China. The obvious differences in the properties of these two types of ore make their beneficiation methods different.

I. Deposited diaspore-type bauxite ore properties and de-smelting of ore dressing

The stacked diaspore type bauxite is mainly produced in Guangxi, Guizhou, Yunnan and other places in southern China, and the representative mining area is Guangxi Pingguo bauxite. Chemical composition characteristics Pingguo bauxite is aluminum, low silicon, low-sulfur, high-speed rail, Al 2 O 3 content of Fe 2 O 3 content was a negative correlation, a correlation coefficient of -0.92; major ore mineral is a diaspore, followed goethite, hematite, kaolinite, chlorite, anatase like.

The ore-bearing bauxite ore-bearing layer is composed of clay and bauxite clastics, and has a wide range of crumb size distribution. Grain size screening results of the ore in each typical mining area of ​​Pingguo bauxite: The ratio of aluminum to silicon ratio varies with grain size. The finer the particle size, the lower the ratio of aluminum to silicon. The ratio of +1mm grain size aluminum to silicon is >8, -0.3mm grain size aluminum silicon. Ratio <2, silicon is enriched at the fine fraction. As long as the -1mm grain size or even -0.3mm grain size is removed, the aluminum to silicon ratio of the ore can be made to meet the alumina production requirements. Therefore, washing and de-sludge, ore as the raw material for the production of alumina by Bayer process is a typical process of sedimentary bauxite ore dressing. China Pingguo Aluminum Co., Ltd. has been using the washing-Bayer process to produce oxidation with stacked bauxite. aluminum.

2. Sedimentary type diaspore-type bauxite ore properties and de-siliconization of ore dressing

China's bauxite mining areas are concentrated, and the four provinces of Shanxi, Guizhou, Guangxi and Henan account for more than 90% of the country's reserves. Among them, Shanxi and Henan bauxite deposits are sedimentary, and Guizhou bauxite deposits are mainly sedimentary.

Sedimentary bauxite has the characteristics of high aluminum, high silicon and low iron. It is the main treatment target for desiliconization of ore dressing. The research on desiliconization of bauxite ore should also focus on this type of bauxite. So far, there have been many research reports on de-siliconization of mineral processing, involving positive flotation, reverse flotation, selective grinding-grading, selective flocculation, re-election and other mineral processing methods, as well as some basic research.

The difference in properties of aluminum and silicon minerals is the basis of the de-siliconization method of beneficiation. The structural structure of bauxite ore, the embedding characteristics of aluminum and silicon minerals determine the ease and feasibility of bauxite ore dressing.

The useful mineral in the sedimentary bauxite bauxite is a diaspore, the main silicon-containing mineral is aluminosilicate, including kaolinite, illite and pyrophyllite. The content ratio of the three kinds of silicon minerals varies depending on the place of production and the mining area.

The difference in density between diaspore and aluminosilicate minerals is small and the hardness difference is significant (Table 1). The dilperite has a finer natural particle size in bauxite, and the silicon mineral is even worse. However, in bauxite, diaspore is often present in the form of aggregates such as columns, granules, soybean meal, plate, and spindle. The diaspore aggregate has a high hardness and a large difference in hardness from the aluminosilicate mineral. The grinding products of diaspore-type bauxite exhibit the characteristics of grain-level enrichment. Therefore, it can be considered that the diaspore can be separated from the silicon-containing mineral in an enriched form, thereby making the bauxite disintegration process selective. The more diaspores present in the bauxite in the form of rich aggregates, the more selective the disintegration.

Table 1 Differences in physical properties of aluminum and silicon minerals
mineral
Bauxite
Kaolinite
Illite
Pyrophyllite
Moh's hardness
6~7
1 to 3
1 to 2
1 to 2
Density / (g / cm 3 )
3.3 to 3.5
2.61~2.68
2.6 to 2.9
2.65~2.90

The selective disintegration characteristics of diaspore-type bauxite is an important basis for desiliconization of bauxite ore and a criterion for the selectivity of ore. Selective grinding-grading desiliconization is the direct application of the selective disintegration characteristics of bauxite, and various re-electing desiliconization methods are mainly based on the difference in particle size between the aluminum and silicon minerals after grinding, rather than the density difference. Silicon. If the diaspore type bauxite must be ground to the natural grain size of aluminum and silicon minerals to be effectively dissociated, gravity field, centrifugal force field sorting, screening and classification methods are difficult to apply to bauxite ore dressing desiliconization. The flotation method and the selective flocculation method may also achieve better sorting results.

The choice of bauxite with different structural structures is different, and the main reason for this is that their selective disintegration is different. Common bauxite ore structures are rough (earth-like), crumb-like, soybean-like, and dense. In the years of bauxite ore dressing practice, the author found that dense bauxite is difficult to select, and the denser the ore is, the more difficult it is to choose. The surface of the dense bauxite is smooth and compact, and the fracture is shell-like. The color is mostly gray and blue-gray. The selective disintegration of the grinding product is not obvious or even selective. Zhao Ping’s test results also show that the selective grinding of bauxite in dense cryptocrystalline structure is not obvious. Therefore, the reason why the dense bauxite is difficult to be selected is that it is difficult to dissociate between aluminum and silicon minerals under the fineness of conventional grinding. If the dissociation between aluminum and silicon minerals is achieved by fine grinding, it is difficult to ensure suitable candidates. granularity.

The difference in surface properties of diaspore and aluminosilicate minerals makes flotation desiliconization the main method of beneficiation and desiliconization, as well as research reports on selective flocculation and desiliconization. In view of the good floatability of diaspore, so far, the technical and economic indicators of positive flotation desiliconization are the best, and the industrialization has been successfully realized. The floatability of three kinds of silicon minerals, kaolinite, illite and pyrophyllite, makes the reverse flotation more difficult than positive flotation. Pyrophyllite has a certain natural floatability. Therefore, the reverse flotation index of the silicon-containing minerals with pyrophyllite is better than that of the other two minerals, while the positive flotation index is opposite.

In summary, the alumina production process does not require high aluminum-to-silicon ratio of raw materials, while bauxite has selective disintegration characteristics, and aluminum is enriched in coarse-grained grades. Therefore, the nature of de-siliconization of bauxite ore dressing It is to remove the fine-grained silicon-containing minerals, or to remove the siliconite mud. The beneficiation method capable of effectively separating fine-grain grade aluminum and silicon minerals can obtain excellent sorting indexes. Among the many bauxite ore dressing methods, bauxite ore flotation desiliconization can successfully achieve industrial application is a good evidence.

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