Introduction to the principle of ultrafiltration membrane filtration

Ultrafiltration is a screening process using membrane separation technology. The pressure difference between the two sides of the membrane is the driving force, and the ultrafiltration membrane is used as the filter medium. Under a certain pressure, when the original liquid flows through the membrane surface, the ultrafiltration membrane Many tiny pores on the surface only allow water and small molecules to pass through and become permeate, while the material in the original solution with a volume larger than the pore size of the membrane surface is trapped on the inlet side of the membrane and becomes a concentrated solution, thus realizing Purification, separation and concentration of the original liquid.

There are about 6 billion 0.01 micron micropores on the wall of the ultrafiltration membrane per meter long. Its pore size only allows water molecules, beneficial minerals and trace elements in the water to pass through, and the smallest bacteria have a volume above 0.02 microns. Therefore, bacteria, as well as colloids, rust, suspended solids, silt, and macromolecular organic matter that are much larger than bacteria can be intercepted by the ultrafiltration membrane, thereby realizing the purification process.

1. Water production process of ultrafiltration membrane

The tap water first enters the ultrafiltration membrane tube. Under the action of the water pressure difference, the densely packed many 0.01 micron micropores on the membrane surface only allow water molecules, beneficial minerals and trace elements to penetrate and become purified water. Bacteria, rust, colloids, silt, suspended matter, macromolecular organic matter and other harmful substances are trapped in the ultrafiltration membrane tube and discharged when the ultrafiltration membrane is flushed.

2. ultrafiltration membrane flushing process

After the ultrafiltration membrane is used for a period of time, the trapped bacteria, rust, colloids, suspended solids, macromolecular organic matter and other harmful substances will adhere to the inner surface of the ultrafiltration membrane, causing the water production of the ultrafiltration membrane to gradually decrease, especially for tap water. When the quality pollution is serious, it is more likely to cause the clogging of the ultrafiltration membrane. Regular flushing of the ultrafiltration membrane can effectively restore the water production of the membrane.

3. ultrafiltration membrane filter element

The bundled ultrafiltration membrane filaments are cast into an ultrafiltration element as shown in the figure below. The filter element is composed of an ABS shell, an epoxy head at both ends of the shell, and a bundle of ultrafiltration membrane filaments. The epoxy head fills the gap between the membrane filament and the membrane filament to form a separation between the original liquid and the permeate. The original liquid first enters the pores of the ultrafiltration membrane, and becomes the permeate after being filtered by the ultrafiltration membrane, preventing the original liquid It enters the permeate directly without filtering.

4. Calculation of the total area of ​​the membrane filament of the ultrafiltration membrane filter element:

Under the circumstance that the water production volume per unit area of ​​membrane filament remains unchanged, the larger the membrane area filled by the filter element, the more the total water production volume of the filter element.

Its calculation formula is:

S (inner)=πdL×n, S (outside)=πDL×n

where: S inner is the total inner surface area of ​​the membrane filament, d is the inner diameter of the ultrafiltration membrane filament;
S is the total external surface area of ​​the membrane filament, and D is the outer diameter of the ultrafiltration membrane filament;
L is the length of the ultrafiltration membrane filament;
N is the number of ultrafiltration membrane filaments.
Internal pressure type and external pressure type hollow fiber ultrafiltration membrane

An ultrafiltration membrane is composed of hundreds to thousands of tiny hollow fiber filaments. Generally, the ultrafiltration membrane with the inner diameter of the hollow fiber membrane between 0.6-6mm is called the capillary ultrafiltration membrane. The capillary ultrafiltration membrane is due to the inner diameter of the ultrafiltration membrane. Larger, not easy to be blocked by large particles.

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Further reading:

CPI1080 Inside-out UF Filter

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