Introduction to the working principle of vacuum filter

Vacuum filter is a device that uses vacuum negative pressure as a driving force to achieve solid-liquid separation. It is widely used in chemical, mining, food, environmental protection and other fields (such as sludge dehydration, mineral concentration, etc.). Its core principle is to form a pressure difference on both sides of the filter medium (such as filter cloth) by vacuuming, so that the liquid (filtrate) is sucked away, and the solid (filter cake) is retained on the surface of the medium.

1. Main components

- Filter medium: filter cloth, filter screen, etc., used to intercept solid particles.

- Filter plate or drum: carries the filter cloth and forms a sealed filter area.

- Vacuum system: vacuum pump or vacuum generator, providing negative pressure suction.

- Filtrate collection system: stores or discharges separated liquid.

- Scraper or unloading device: peels off the filter cake to complete solid-liquid separation.

2. Workflow (taking the rotary drum vacuum filter as an example)

(1) Immersion and suction filtration

- The drum is partially immersed in the slurry tank, and the filter cloth absorbs the slurry.

- The vacuum pump forms negative pressure inside the drum. The liquid is sucked into the filtrate tube, and the solid is trapped on the surface of the filter cloth to form a filter cake.

(2) Filter cake formation

- The drum rotates, and the filter cake continues to be dehydrated under the action of vacuum, and the thickness gradually increases.

(3) Filter cake drying

- After the drum leaves the slurry tank, the vacuum continues to act to further remove the moisture in the filter cake.

(4) Unloading

- A scraper or compressed air stripping device peels the dried filter cake off the filter cloth to complete a cycle.

3. Key influencing factors

| Factors | Influence |

|------------------------|-------------------------------------------------------------------------|

| Vacuum degree         | The higher the vacuum degree, the faster the filtration speed; however, excessively high vacuum degrees may cause the filter cloth to become blocked or increase energy consumption. |

| Filter cloth pore size  | The smaller the pore size, the higher the filtration accuracy, but the flow rate may be reduced. |

| Slurry concentration  | The higher the concentration, the faster the filter cake forms, but excessive concentration may cause blockage. |

| Drum speed               | Low speed → thick filter cake, more complete dehydration; high speed → large processing volume, but the filter cake may be thinner and have a high moisture content. |

4. Advantages and disadvantages

✅ Advantages

- Continuous automatic operation, high efficiency.

- Suitable for a variety of materials (fine particles, sticky substances, etc.).

- The moisture content of the filter cake can be adjusted (controlled by vacuum degree and speed).

❌ Disadvantages

- High energy consumption (depending on the vacuum pump).

- The filter cloth is easy to clog and needs to be cleaned or replaced regularly.

- Cavitation problems may occur when filtering volatile liquids.

The vacuum filter achieves solid-liquid separation through negative pressure adsorption and is suitable for continuous, large-scale dehydration needs. Its efficiency depends on the vacuum degree, filter cloth performance and material characteristics. When selecting a model, it is necessary to ｓｅｌｅｃｔ the appropriate type (drum, belt, disc, etc.) according to the material properties (particle size, viscosity) and processing capacity.