Dehydration System of Lithium Mica Concentrate Filter Press

Lithium has characteristics such as low melting point, high boiling point, maximum negative potential, and light weight, and is widely used in fields such as new energy vehicles, nuclear industry, aviation, and medical care. Lithium is the most important basic raw material for the new energy industry and is known as the "21st century new energy". In order to accelerate the achievement of the strategic goals of "carbon neutrality and peak carbon emissions", China has vigorously developed the lithium battery new energy industry. The demand for lithium raw materials has been increasing year by year, and the strategic position of lithium has been continuously improved, triggering a new wave of mineral resource competition. Currently, the main sources of lithium resources in China are salt lake lithium and ore lithium. Ore lithium mainly includes spodumene, lithium mica, lithium feldspar, iron lithium mica, lithium muscovite, phosphate lithium aluminate, etc. To ensure the stable market supply of lithium battery raw materials, extracting lithium from lithium mica has become an important way to obtain lithium raw materials. Yichun, Jiangxi Province has the world's largest associated lithium mica mine. In the process of lithium mica beneficiation, belt filters are commonly used for dehydration of lithium mica concentrate. The moisture content of the concentrate is generally greater than 18%, which has the characteristics of high moisture content of lithium mica concentrate, large equipment footprint, and low processing efficiency. A beneficiation plant in Yichun area uses an FFP horizontal fast opening filter press produced by a certain company to dehydrate lithium mica concentrate. It has the characteristics of small equipment footprint, high processing efficiency, and low moisture content of lithium mica concentrate. At the same time, it can reduce the transportation cost of lithium mica concentrate and the drying cost of downstream lithium carbonate plants. This article focuses on the influence of the type of filter cloth, cycle time, working pressure, type of filter aid for lithium mica concentrate, and amount of filter aid on the moisture content of lithium mica concentrate in fast opening filter presses,membrane filter press.

The experimental sample is based on the lithium mica concentrate from a beneficiation plant in Yichun area. The multi-element chemical analysis results and screening analysis results of the lithium mica concentrate are shown in Tables 1 and 2. According to Tables 1 and 2, the lithium mica concentrate has a Li2O content of 1.71%, Al2O3 content of 29.34%, and SiO2 content of 47.60%. The content of lithium mica concentrate with particle size<75 μ m accounts for 32.79%, and<25 μ m accounts for 14.63%. When using traditional belt filters for dehydration, there are disadvantages such as difficulty in the dehydration process and high moisture content in the concentrate. Introduction to 2FFP Horizontal Quick Open Filter Press Quick open horizontal filter press is a high-capacity filter press mainly used for solid-liquid separation. The appearance of the FFP quick opening horizontal filter press is shown in Figure 1. When working, there are mainly the following steps.

1) Feed: The material is pumped to each filtration chamber of the filter press until it is completely filled.

2) Filtration: As the feed pressure increases, the filter cake forms on the surface of the filter press cloth, and the filtrate is discharged through the collection channel.

3) Squeezing: After the squeezing medium enters each chamber, the diaphragm squeezes the filter cake between the filter cloth, forcing the filtrate to pass through the filter cloth.

4) Air drying: Compressed air passes through the filtrate channel on the diaphragm side to blow dry the moisture in the filter cake to the lowest level. During the drying process, the filter cake maintains the squeezed state of the diaphragm, which can keep the filter cake from cracking.

5) Pipeline flushing and blowing: Residual slurry and water in the pipeline are cleaned and treated.

6) Diaphragm release: The compressed air in the diaphragm is completely released.

7) Unloading cake: Within approximately 30 seconds, all filter press cake are unloaded at once. After the filter plate group is fully opened, the filter cloth vibrates to ensure complete cake unloading.

8) Filter cloth flushing: After unloading the cake, the filter cloth is flushed by the spray pipe installed at the top of the filter plate group. This can ensure the removal of residual filter cake on the surface of the filter cloth and ensure good operating conditions for the next cycle. The quick opening horizontal filter press has the following advantages:

1) Has high equipment operating efficiency and short technical time for opening and closing plates (<30s);

2) Equipped with a weighing system, it can measure the feeding amount at any time and automatically adjust the operating parameters;

3) The filter plate follows European quality standards, with reliable quality and easily worn edges that can be disassembled and replaced without the need to replace the entire filter plate;

4) After unloading the cake, the filter cloth automatically vibrates to help unload the cake and remove residual cake residue, without the need for manual assistance in unloading, avoiding residue getting stuck between the filter plates and causing spraying or deformation of the filter plates;

5) High degree of automation, on-site PLC can be connected to DCS system, enabling observation of equipment operation status and remote start stop in the central control room;

6) Low operating costs, fully automatic operation of the equipment, and basically unmanned on-site operation can save customers more labor costs.

3 Results and Discussion: Taking the lithium mica concentrate from a beneficiation plant in Yichun area as the research object, the lithium mica concentrate has a particle size<75 μ m, a content of 32.79%, and a slurry concentration of 55%. The slurry concentration determines the feeding time of the filter press. When the slurry concentration remains constant, the feeding time remains constant.

3.1 Filter cloth type condition test Filter cloth is a crucial component in filter press equipment, as the materials filtered by the industry have different requirements for the filter cloth, resulting in many types of filter cloth. This article determines a suitable filter cloth for dewatering lithium mica concentrate through on-site industrial experiments. The effect of different filter cloth types on the moisture content of lithium mica concentrate is investigated under the conditions of a FFP horizontal fast opening filter press cycle time of 900s (including feeding time of 180s, extrusion time of 330s, and drying time of 360s) and a constant working pressure of 1MPa. The experimental results are shown in Table 3 and Figure 2. According to Table 3 and Figure 2, it can be seen that the filter cloth with a nylon monofilament permeability of 300L/(m2 · min) has the lowest moisture content in the lithium mica concentrate, which is 15.89%. In the experiment, it was found that the nylon monofilament filter cloth has good peeling performance and the filter cake peels quickly. The main reason is that the nylon monofilament filter cloth has high filtration accuracy and precision, which can filter out small particles with a diameter of 1 μ m. This will be beneficial for extending the service life of the filter cloth and improving the efficiency of the mining filter press.

3.2 Test of Filter Press Cycle Time Conditions: The horizontal quick opening filter press adopts a nylon monofilament air permeability of 300L/(m2 · min) filter cloth and a constant working pressure of 1MPa to investigate the effect of filter press cycle time on the moisture content of lithium mica concentrate. The experimental results are shown in Table 4 and Figure 3. According to Table 4 and Figure 3, as the slurry concentration is relatively consistent, the feed and filtration time are the same. As the extrusion time and drying time increase, the moisture content of the lithium mica concentrate decreases. When the total cycle time exceeds 930 seconds, the moisture content of lithium mica concentrate does not decrease significantly. Taking into account all factors, a cycle time of 930 seconds is chosen as the working parameter for the filter press, at which point the moisture content of the lithium mica concentrate is 15.32%.

3.3 Working pressure condition test of fast opening filter press FFP horizontal fast opening filter press adopts nylon monofilament air permeability 300L/(m2 · min) filter cloth, with a circulation time of 930s (including extrusion time of 345s and drying time of 375s) unchanged, to investigate the effect of filter press working pressure on the moisture content of lithium mica concentrate. The experimental results are shown in Table 5 and Figure 4. According to Table 5 and Figure 4, as the working pressure increases, the moisture content of lithium mica concentrate decreases. When the working pressure of the filter press exceeds 1.1 MPa, the moisture content of the concentrate decreases slowly. Taking into account all factors, the working pressure of 1.1 MPa is determined as the working parameter of the filter press. At this time, the moisture content of the lithium mica concentrate is 15%.

After determining the equipment parameters such as filter cloth type, cycle time, and working pressure of the EntrateFFP horizontal quick opening filter press, the influence of filter aid type and dosage on the moisture content of lithium mica concentrate will be studied. Firstly, investigate the effect of filter aid type on the moisture content of lithium mica concentrate. Select inorganic filter aid polyaluminum chloride, organic filter aid 840, and organic filter aid 320 for comparative filtration experiments. Under the same dosage of 500g/t, investigate the effect of filter aid type on the moisture content of lithium mica concentrate. The experimental results are shown in Figure 5. As shown in Figure 5, under the same dosage of 500g/t, when using polyaluminum chloride, the moisture content of lithium mica concentrate is 13.79%. The filtration effect of polyaluminum chloride is higher than that of organic filter aid 320 and organic filter aid 840. This is because the molecular chains of polyaluminum chloride are fixed on the surfaces of different fine or extremely fine particles, forming polymer bridges between them to form aggregates. During the filtration process, the aggregates will not cause blockage of the filter holes of the filter cloth. At the same time, the cake has good peelability and the service life of the filter cloth is longer.

3.5 Experimental study on the dosage of filter aid for lithium mica concentrate. The FFP horizontal quick open plate & frame filter press was used with a nylon monofilament air permeability of 300L/(m2 · min) filter cloth, a cycle time of 930s, a working pressure of 1.1MPa, and a filter aid of polyaluminum chloride to investigate the effect of polyaluminum chloride dosage on the moisture content of lithium mica concentrate. The experimental results are shown in Table 6 and Figure 6. From Table 6 and Figure 6, it can be seen that as the amount of polyaluminum chloride increases, the moisture content of lithium mica concentrate decreases. When the dosage of polyaluminum chloride is greater than 450g/t, the rate of moisture reduction in lithium mica concentrate is relatively small. Considering factors such as cost, a dosage of 450g/t of polyaluminum chloride is selected, and the moisture content of lithium mica concentrate is 13.80%. Comparative analysis of 3.6FFP horizontal quick opening filter press and traditional belt filter press. According to the selection calculation of 743.75t/h (dry ton) lithium mica concentrate, the comparative analysis of FFP horizontal quick opening filter press and traditional belt filter press is shown in Table 7. According to Table 7, the FFP horizontal quick opening filter press has the characteristics of small equipment footprint, high dehydration efficiency, high degree of automation, and cost savings in transportation.

4 Conclusion

1) Taking the lithium mica concentrate from a beneficiation plant in Yichun area as the research object, this study investigated the types of filter cloth, circulation time, working pressure, lithium mica concentrate filter aid type, and filter aid dosage of the FFP horizontal quick opening filter press. The experimental results showed that when using a nylon monofilament air permeability of 300L/(m2 · min) filter cloth, circulation time of 930s, working pressure of 1.1MPa, and filter aid of 450g/t polyaluminum chloride, the moisture content of lithium mica concentrate in the FFP horizontal quick opening plate and frame filter was 13.80%.

2) In the experiment of filter aid conditions for lithium mica concentrate, polyaluminum chloride had the best effect on reducing the moisture content of lithium mica concentrate, with polyaluminum chloride>organic filter aid 320>organic filter aid 840 showing the best filter aid effect. This is because the molecular chains of polyaluminum chloride are fixed on the surfaces of different fine or extremely fine particles, forming polymer bridges between each fine or extremely fine particle to form aggregates. During the filtration process, the aggregates will not cause blockage of the filter holes of the filter cloth, and the cake has good peelability, resulting in a longer service life of the filter cloth. 3) Compared with belt filters, the FFP horizontal quick opening filter press used in a certain beneficiation plant in Yichun area has the characteristics of small equipment footprint, high dehydration efficiency, high degree of automation, and saving transportation costs. It solves the industry problem of high moisture content in lithium mica concentrate in Yichun area and is the first large-scale successful application in the lithium mica beneficiation industry. It has important demonstration significance in the industry sludge dewatering machine and has broad prospects for future application.