Precision filters are the most commonly used filters in industrial water treatment equipment, which can effectively remove suspended substances in liquids and can withstand high filtration pressure. This type of filter has a small shape, a relatively large filtration area, and a relatively long service life on average. The precision filters launched by Xinxiang Lifelt Filter come in various models and sizes to meet the various needs of customers. So what are the factors that affect the precision filter during operation?
1. Feed flow rate: Increasing the flow rate of feed liquid is beneficial to prevent concentration polarization and improve equipment processing capacity. However, increasing the pressure increases the energy consumption of the process, resulting in increased costs. Generally, the flow velocity in a turbulent system is 1-3m/s. In a spiral modular system, it usually operates in the laminar flow region. Turbulence-promoting materials can be provided on the liquid flow channels, or diaphragm mounts can be used to generate pressure waves on the flow channels to improve flow regimes and control concentration differences. To ensure the normal operation of ultrafiltration components.
2. Working pressure: The relationship between ultrafiltration membrane permeation flux and working pressure depends on the properties of the membrane and the boundary layer. In the actual UF process, the latter usually controls the same amount of UF permeation. When using the osmotic pressure model, the permeate flux of the membrane is proportional to the pressure, while using the gelation model, the permeate flux of the membrane is independent of the pressure. The permeate flux at this time is called the critical permeate flux. In fact, the ultrafiltration operation should be carried out near the critical permeate flux. At this time, the working pressure is about 0.5-0.6MPa. In addition to overcoming the resistance of the permeable membrane, the pressure loss of the fluid across the membrane surface must also be overcome.
3. Temperature: The working temperature mainly determines the chemical, physical properties and biological stability of the liquid being processed. It should be operated at the highest temperature allowed by the membrane equipment and the treated substance, because high will reduce the viscosity of the feed liquid, thereby increasing the mass transfer efficiency and improving the flux. The relationship between temperature and diffusion coefficient can be seen from the above formula, the higher the temperature T, the smaller the viscosity μ, and the larger the diffusion coefficient D. For example, the maximum temperature is 25°C for enzymes and 30°C for electrocoating. , 55°C for protein, 50-55°C for milk industry, and 85°C for PVA in textile industry desizing wastewater.
4. Operating time: As the ultrafiltration process proceeds, concentration polarization forms a thick gel layer on the membrane surface, thereby reducing the ultrafiltration flux. The decay of its transfer flux over time is related to the hydraulic characteristics of the membrane module, the properties of the feed liquid and the characteristics of the membrane. After the ultrafiltration has been running for a period of time, it needs to be cleaned. This period of time is called the operating cycle. Of course, changes in the operating cycle are also related to cleaning conditions.
5. Pretreatment of feed liquid
In order to improve the permeate flux of the membrane and ensure the normal and stable operation of the ultrafiltration membrane, the feed liquid needs to be pretreated before ultrafiltration. Although the pretreatment process of UF is not as rigorous as that of reverse osmosis, this pretreatment is also the key to ensuring the proper operation of the UF process.
