The grinding fineness of phosphate ore determines whether the phosphate ore can be dissociated from the monomer and separated from the gangue mineral, and further affects the flotation efficiency of phosphate ore, which in turn affects the final concentrate grade and recovery rate.Therefore, the determination of the fineness of phosphate ore grinding is an important topic worth studying.This paper discusses the factors that affect the fineness of phosphate ore grinding and the methods for determining the fineness of grinding.

Factors affecting the fineness of phosphate ore grinding

1. Ore properties

Different types of phosphate rock have different inlay particle sizes and structures, and different requirements for grinding fineness.The types of phosphate ore are summarized, and the fineness of the grinding of each type of phosphate ore can be roughly summarized as follows：

(1) Coarse-grained and leached phosphate rock: Coarse-grained leached phosphate rock generally refers to crystalline apatite ore, and the leached particle size of phosphorus-containing minerals is 0.3-0.4mm.When grinding, it is necessary not only to ensure the full dissociation of phosphorus-containing minerals, but also to meet the particle size requirements of flotation, which requires rough grinding and rough selection.

(2) Medium-grain leached phosphate rock: The leached particle size range of medium-grain leached phosphate rock is generally 0.1-0.2mm.When processing this kind of ore, a grinding process is generally selected, and the specific grinding fineness needs to be based on the results of the mineral processing test.

(3) Fine-grained dip-dyed phosphate rock: Those with a dip-dyed particle size of 0.05-0.1mm are called fine-grained dip-dyed phosphate rock. Generally, colloidal phosphate ore or fine-grained apatite belongs to this kind of ore.When grinding ore, this kind of grinding needs to be ground to a very fine particle size before the phosphorus-containing minerals can be fully dissociated.

(4) Complex leaching and dyeing of phosphate rock: The leaching and dyeing particle size of this kind of ore is generally uneven, and the dissociation particle size of the mineral needs to be carefully studied.Stage grinding and stage flotation processes can also be used to process this kind of ore.

2. Flotation process requirements

The fineness of the grinding ore needs to meet the requirements of the flotation process to ensure the effective separation of minerals.It was mentioned in the experimental study of mineral processing of a phosphate mine in Yunnan that when the fineness of the grinding ore is about 75% of -0.074mm, the recovery rate of concentrate obtained by the flotation collector is low, so a plan to adjust the fineness of the grinding ore and replace the flotation collector is proposed.

3. Energy consumption and cost

The improvement of grinding fineness is often accompanied by an increase in energy consumption and an increase in costs.Therefore, under the premise of ensuring the mineral processing effect, an economical and reasonable grinding fineness should be selected as much as possible.

How to determine the fineness of phosphate ore grinding?

The fineness of phosphate ore grinding is determined through a series of experimental studies and process mineralogical analysis, mainly considering factors such as mineral dissociation, flotation effect and economic benefits.The following are some key steps and methods to determine the optimal value of the fineness of phosphate ore grinding：

1. Determination of mineral dissociation: Use equipment such as mineral dissociation analyzer (MLA) to study the chemical composition, elemental distribution, mineral composition, dissociation and symbiotic relationship of phosphate rock.Through the determination of the dissociation degree of minerals under different grinding fineness conditions, the appropriate grinding fineness can be determined.

2. Single-factor conditional test: Better test parameters are obtained through single-factor conditional tests, such as anti-flotation demagnetization agent conditions, anti-flotation desilicon agent conditions, etc., to determine the best grinding fineness.

3. The relationship between grinding fineness and flotation effect: The influence of grinding fineness on flotation effect is studied experimentally to determine the best grinding fineness.For example, with the increase of the fineness of the grinding ore, the grade of the concentrate first remains stable and then gradually increases, and the recovery rate is higher when the fineness of the grinding ore reaches a certain proportion.

4. Economic benefit considerations: Under the premise of meeting the mineral processing effect, consider the impact of grinding fineness on energy consumption and cost.Suitable grinding process parameters can improve the effective phosphorus content and solubility of phosphate ore powder, while reducing energy consumption.

5. Experimental research: Determine the appropriate grinding fineness of the ore through experimental research.For example, a low-grade phosphate mine in Malian, Sichuan, has been determined by a series of conditional experiments that the ore is suitable for grinding with a fineness of -0.074mm65%.

6. Flotation closed-circuit process flow and parameters: While determining the fineness of the grinding ore, it is also necessary to consider the flotation closed-circuit process flow and parameters to ensure that the best flotation effect is obtained under the condition that the raw ore contains P2O5.

7. The relationship between grinding time and fineness: The experimental results show that the grinding time is short and the fineness of the grinding is small. With the extension of the grinding time, the fineness of the grinding increases.According to the flotation experiment, it was determined that the grinding time was 7 minutes and the fineness of the grinding was 8.5%.

In short, the determination of the fineness of phosphate ore grinding requires comprehensive consideration of many factors, and through the grinding test of the ore sample, the fineness that can dissociate the monomer and separate it from the gangue mineral is the suitable fineness.It should also be noted that the fineness of phosphate ore grinding is not as fine as possible. In the process of grinding, the serious problem of mudification caused by over-grinding should be avoided. This will definitely increase hidden dangers for subsequent flotation, so it is very important to master the scale well.