In environments such as mine slurry dewatering, chemical purification, and environmental wastewater treatment, vacuum disc filters are a commonly used high-efficiency solid-liquid separation equipment, which mainly relies on "vacuum suction and rotating filter discs" for operation.

The mixture that needs to be processed is first loaded into the slurry tank, with some filter discs submerged in it. When the device is started, the vacuum pump creates negative pressure inside the filter disc, and the mixed hydraulic liquid is sucked into the filter disc and discharged. Solid particles are intercepted by the filter cloth and slowly accumulate into a filter cake.

The filter disc continues to rotate. After discharging the slurry tank, if purification is needed, washing water will be sprayed first to wash away impurities on the surface of the filter cake. Then, the vacuum pump will continue to filter and further absorb the moisture from the filter cake. Finally, the filter disc is turned to the top and the vacuum is disconnected. Some will blow compressed air in conjunction with a scraper to scrape the filter cake into the collection tank.

Working principle of vacuum disc filter

The vacuum disc filter is actually operated by the pressure difference created by the vacuum system, which is the key driving force for separating solids and liquids.

The mixed liquid that needs to be filtered can pass through the filter cloth and enter the gas-liquid channel inside the filter disc under the suction force generated by vacuum, and then be pumped away by the vacuum pump. However, the solid particles in the mixture are larger than the pore size of the filter cloth and are trapped on the surface of the filter cloth, gradually forming a thick layer of filter cake.

Whether the entire process can proceed smoothly and efficiently depends on whether the pressure difference between the mixture and the filter disc is large enough; Secondly, whether the pore size of the filter cloth can match the solid particles. The larger the pressure difference and the more suitable the pore size, the faster the filtration speed and the better the effect.

The key structure of vacuum disc filter

Workflow

When the filter disk rotates around the central axis, it will complete the four processes of filtration, washing, dehydration, and cake unloading in sequence with the change of position. The specific steps are as follows:

Filtering stage (core separation process)

Position: Lower part of the disc, immersed in the suspension in the slurry tank.

Process: The central distribution valve connects the filter disc to the vacuum system, creating negative pressure inside the filter disc. The liquid is sucked into the filter disc and enters the gas-liquid separator through the pipeline (the filtrate can be recovered or processed later); Solid particles are intercepted and stacked into a uniform filter cake due to their larger particle size than the filter cloth aperture (the thickness of the filter cake can be controlled by adjusting the speed or vacuum degree).

Objective: To achieve preliminary solid-liquid separation and form a filter cake that can be further processed.

Washing stage (optional, to enhance solid purity)

Location: The first drying area after the disc is rotated out of the slurry tank, not completely detached from the vacuum.

Process: When it is necessary to improve the purity of the filter cake (such as mineral purification in mines), washing water/liquid is sprayed in this area. The washing liquid penetrates the filter cake under vacuum and is extracted together with the residual filtrate to remove surface impurities.

Objective: To reduce the impurity content in the filter cake and improve the purity of solid products.

Dehydration stage (reducing the moisture content of the filter cake)

Location: After washing and before unloading the cake, the filter disc is still connected to the vacuum system.

Process: The filter cake is transferred away from the spray area, and the vacuum continues to draw negative pressure to remove residual moisture/washing solution inside, reducing the moisture content to 15% -30% (depending on industry requirements).

Objective: To reduce the moisture content of the filter cake, facilitate subsequent transportation and drying, and reduce drying energy consumption.

Unloading stage (solid recovery)

Position: Rotate the disc to the top and escape from the vacuum (connected to atmosphere or compressed air).

Process: Cut off the vacuum of the central distribution valve, introduce a small amount of compressed air (or connect to the atmosphere), and "blow back" to separate the filter cake from the filter cloth; Then use a scraper/high-pressure airflow to scrape the filter cake onto the conveyor belt/collection tank.

Goal: Thoroughly peel off the filter cake to achieve recycling, while restoring the filtering ability of the filter cloth to prepare for the next round.

The core advantages and applicable scenarios of vacuum disc filter:

1. Continuous homework and large processing capacity:

2. The moisture content of the filter cake is low, and the subsequent processing cost is low;

3. High degree of automation and simple operation;

4. Strong adaptability, capable of handling high concentration, large particles, or corrosive suspensions.

Applicable scenarios:

Mining such as iron concentrate, copper concentrate dewatering, chemical industry (such as catalyst recovery, salt crystallization separation), environmental protection (such as sludge dewatering, solid slag recovery in wastewater treatment) and other fields.

The vacuum disc filter adopts the design of "vacuum negative pressure drive+multi disc rotation+multi process synchronization" to achieve efficient and continuous solid-liquid separation, and is one of the key equipment for processing large-scale suspensions in industrial production.