Yixian fluorite selection plant grinding process determination example

I. Introduction

China's fluorite ore resources are relatively abundant, and the fluorite mineral production industry has a long history and occupies an important position in the international market. With the development of iron and steel, aluminum refining and chemical industries, fluorspar consumption is also increasing, particularly acid grade fluorspar broad in the chemical, aluminum industry market prospects. Fluorite ore and fluorite are traditional non-metallic mineral products of our country, accounting for about 60% of the international market, good market conditions. Yixian fluorite ore reserves based on the consideration of external construction conditions, environmental conditions and other factors, determine the date Yixian build processing capacity of 300 t fluorite ore dressing plant, designed to produce concentrate volume 41760 t, of which: export firefly The stone concentrate powder is 33718 t, the domestic sales of fluorite concentrate powder is 8042 t, and the export rate accounts for 80% of the output. Since the products are mainly exported, the quality requirements of the products are strict, and the design concentrate grades CaF ₂ >97% and SiO ₂ <0.8%.

The quality standards of fluorite powder at home and abroad are shown in Table 1.

Table 1 Fluorite powder quality standards

The production indicators of Yixian fluorite mine are shown in Table 2.

Table 2 Yixian fluorite mine production indicators

Second, the nature of the ore

(1) Ore types and contents

The fluorite ore in Yixian is a fluorite ore with quartz as the main associated mineral. The mineral type and structure are relatively simple. The content of fluorite and quartz accounts for 94.23% of the total ore. The other minerals are less. See the results of mineral types and contents. table 3.

Table 3 Mineral types and contents (%)

(2) Structure and structure of main minerals

1, fluorite

Fluorite is ubiquitous in ore and is the main mineral in ore. Fluorite cleavage is relatively developed, and often exists in the ore as a granular or granular aggregate, and the local crystal form is intact. The fluorite and quartz in the ore are closely related, followed by barite. Quartz is distributed around the fluorite or between the granules. Sometimes quartz is also produced in the fluorite particles. Sometimes the quartz is aggregated to surround the fluorite particles. At this time, the quartz is generally in the form of crystal clusters and horse-shaped, with a particle size of 0.07. Between ~0.14 mm, the larger one is about 0.2mm. The contact surface of fluorite and quartz is relatively straight, a small number of small particles of fluorite and quartz are interdigitated, and some fluorite particles are interspersed with plate-like barite.

2, quartz

Quartz is widely distributed in ore and is irregularly granular. Quartz is closely related to fluorite. The aggregates of siliceous or chalcedony are produced at the edges, intergranular or fissures of fluorite. Quartz is mostly contaminated with iron and partially brown. Fine quartz particles are often carbonated. Salt and sericite and a small amount of kaolin are filled. Since quartz particles are mostly in the form of aggregates, the boundary between quartz and fluorite is clear.

3, barite

The barite is mostly plate-like and strip-shaped between fluorite or quartz particles. The barite is not closely related to fluorite. In the ore, the crystal form is relatively intact and the particles are larger. The cleavage is more developed.

4, calcite

Calcite is less distributed in the ore, and the particle size is very fine, and it is irregularly filled between fluorite and quartz.

5, sericite

Sericite is rare in ore and is distributed in fine flakes or flakes between fine particles of quartz.

6, kaolin

The content of kaolin in the ore is also very small, and the soil cryptocrystalline is distributed between the quartz particles or the crack.

Third, the determination of the grinding process

The products of Yixian Fluorite Mine are mainly for export. The requirements for CaF ₂ grade and the content of impurities such as SiO ₂ are very strict, which adds certain difficulty to the beneficiation process. From the nature of ore, fluorite has a relatively simple relationship with most quartz and other minerals. The symbiotic relationship between minerals is not complicated. The primary particles of fluorite minerals are also coarser. This is the selection of fluorite minerals among other minerals. Create favorable conditions. However, a small part of fluorite minerals are closely related to quartz and barite, which is not conducive to monomer dissociation and affects the selection effect. The impurity that affects the quality of fluorite concentrate is mainly SiO ₂ . The main reason for the difficulty in the SiO ₂ content is that quartz and fluorite do not have sufficient monomer dissociation. To achieve monomer dissociation, it must be finely ground; and over-grinding will definitely affect the flotation index. Fluorite is more brittle than quartz. When the grinding is too fine, the fluorite is over-grinded, and the grinding is slightly thicker and cannot achieve sufficient monomer dissociation. Using a reasonable grinding process to determine the appropriate grinding fineness is the prerequisite for obtaining high quality fluorite powder. Grinding fineness test is shown in Table 4.

Table 4 Grinding fineness test results

When the fineness of grinding is -0.074mm and 75%, the analysis of raw ore screening and the determination of fluorite mineral monomer dissociation are shown in Table 5.

Table 5 Raw ore screening analysis and monomer dissociation measurement results

As can be seen from Table 4, as the fineness of the grinding increases, the loss of fluorite in the tailings gradually decreases. When the grinding fineness 0.075mm reaches 25% or more, the fluorite loss rate in the tailings is less than 6%. From the selected results, as the fineness of the grinding increases, the final concentrate grade also increases, and The recovery of fluorite in the final concentrate is significantly improved. This indicates that when coarser fineness is used, more continuous particles are inhibited in the selected tailings in the selection. It can be seen from Table 5 that when the grinding fineness is -0.075mm and 75%, 50.21% of the fluorite is distributed in the -0.038mm particle size, and the monomer dissociation degree can reach 97.84%. According to the sieving analysis, the content of SiO _{2 in the} grain size of more than 0.038mm is less than 1%, and the content of SiO _{2 in the} grain size of -0.038mm is less than 1%. From this, it can be seen that more than 0.038mm of the grain in the concentrate is mainly composed of continuum and inclusions. . Because fluorite has a simple relationship with most quartz and other minerals, it is easy to dissociate, and coarse grinding can be tailed, but some quartz is wrapped in fluorite with fine particles. A qualified concentrate having a SiO _{2 of} less than 1% is obtained. From the above analysis, it can be concluded that the process structure using a single-stage grinding for flotation will not achieve the intended purpose, and fine grinding is a necessary means to obtain high-quality concentrate powder.

Because fluorite has a simple relationship with quartz and other minerals, it is easy to dissociate, and rough grinding can be tail-tailing. Therefore, it is reasonable to use coarse concentrate re-grinding, which not only reduces power consumption, but also avoids excessive pulverization of fluorite. When the regrind fineness is -0.038mm, which is 66%, the concentrate grade is over 99%, the SiO ₂ content is 0.70%, and the fluorite recovery rate is 90.75%.

The fine product size of the coarse concentrate after re-grinding is -0.038mm 66% is shown in Table 6.

Table 6 Concentrate product granularity

The results of analysis of concentrate impurities are shown in Table 7.

Table 7 Concentrate analysis results of concentrate

In the design, Φ1500×3000 overflow ball mill and Φ1200 single spiral sunken classifier are used to form a closed-circuit grinding. The grinding fineness is -200 mesh, accounting for 75%, so that the coarser-grade fluorite mineral is obtained earlier. . The designed fine concentrate has a regrind fineness of -400 mesh and 66%. How to ensure the fineness requirements, it is also difficult to ensure the classification effect. Four Φ125 hydrocyclones are used in the design, two of which are used in series, and a Φ1500×3000 overflow ball mill constitutes closed-circuit grinding, thus ensuring the requirements of grading fineness and meeting the selected optimal grain size requirements. .

Fourth, the conclusion

(1) Fluorite has a simple relationship with most quartz and other minerals, and is easy to dissociate.

(2) The beneficiation process adopts rough grinding and rough selection, coarse grain tailing, and coarse concentrate re-grinding, which can reduce power consumption and reduce fluorite over-pulverization. This design process is more suitable.

(3) Yixian Fluorite Ore Concentrator is a site design carried out under tight time. After the production, the qualified concentrate products with the index of CaF ₂ greater than 97% and SiO ₂ less than 1% were obtained, which proved that the formulation of the process was reasonable and the equipment selection configuration was suitable.

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