An ultrafiltration membrane is used in the process of artificial membrane filtration. It is generally made of high molecular materials such as cellulose acetate, cellulose acetate ester, polyethylene, polysulfone, and polyamide. Various forms of membrane components, such as tube-shaped, plate-shaped, roll-shaped, and capillary-shaped, are usually prepared in advance and then assembled together for application to increase the filtration area and facilitate maintenance.
Nowadays, the utilization rate of ultrafiltration membranes is very high, such as in the mineral water industry, food and beverage industry, etc. As the main production line process system, if its performance declines, it will inevitably affect the production efficiency. Therefore, in order to help everyone better use ultrafiltration membranes, we will now understand which factors will affect the normal operation of ultrafiltration membranes.
Increase in material liquid flow rate Although increasing the material liquid flow rate is beneficial to reducing concentration polarization and increasing permeate flux, it requires an increase in material liquid pressure and energy consumption. The flow rate in turbulent systems is generally controlled at 1-3m/s.
Operating pressure The relationship between permeate flux and operating pressure of ultrafiltration membranes depends on the properties of the membrane and gel layer. The ultrafiltration process is a gelation model, and the membrane permeate flux is independent of pressure. At this time, the flux is called the critical permeate flux. The actual operating pressure should be around the ultimate flux, which is about 0.5-0.6mpa.
Temperature The operating temperature depends mainly on the chemical and physical properties of the material being treated. Since high temperatures can reduce the viscosity of the material liquid, increase mass transfer efficiency, and improve permeate flux, it should be operated at the highest temperature.
Operating cycle As the ultrafiltration process proceeds, a gel layer gradually forms on the membrane surface, causing the permeate flux to decrease. When the flux reaches a certain minimum value, it is necessary to flush it, which is called the operating cycle. The change of the operating cycle is related to the cleaning situation.
Feed concentration As the ultrafiltration process proceeds, the concentration of the main liquid flow gradually increases. At this time, the viscosity increases, the thickness of the gel layer increases, and the permeate flux is affected. Therefore, a maximum concentration should be determined for the main liquid flow.
Pretreatment of material liquid In order to increase the membrane permeate flux and ensure the normal and stable operation of ultrafiltration membranes, the material liquid should be pre-treated as required.
Ultrafiltration membranes must be regularly flushed to maintain a certain permeate flux and extend the life of the membrane. Under specified material liquid and pressure, within the allowable pH range, and at a temperature not exceeding 60 degrees, ultrafiltration membranes can be used for 12-18 months. If the ultrafiltration membrane is not cleaned properly, its life will be shortened.