Introduction Of Ultrafiltration Membranes Cleaning

2022-04-18


Ultrafiltration membrane is the core element of ultrafiltration equipment. One of the first polymer separation membranes developed is used in the middle-end treatment device in the preparation of ultrapure water. Since the Ultrafiltration Membrane is a porous material that removes impurities in the water by means of physical retention, the ultrafiltration membrane should be cleaned regularly to ensure the throughput of the ultrafiltration membrane and extend the service life of the ultrafiltration membrane.

 The cleaning method of the Ultrafiltration Membrane 4040 is generally determined according to the nature of the membrane and the nature of the treated liquid. It is usually similar to reverse osmosis, that is, it is cleaned with water power first, and then different chemical detergents are used for cleaning according to the situation. For example, ion-containing solubilizers can be used for electrocoating materials, and "bridging" type can be used for water-soluble organic coatings. Solvent. Protein precipitation in the food industry can use prion solvents or alkaline detergents based on phosphate and silicate. The precipitate formed by the inorganic salt on the surface of the membrane can be dissolved with a chelating agent such as EDTA or acid or alkali. The cleaning method of ultrafiltration membrane is divided into seven steps:

1. Prepare cleaning fluid

2. Low flow input cleaning fluid

First, mix the cleaning fluid with a cleaning water pump, and use a low flow rate when preheating the cleaning fluid. Then replace the raw water in the element with the lowest possible cleaning fluid pressure, and its pressure only needs to be enough to supplement the pressure loss of the inlet water to the concentrated water, that is, the pressure must be low enough to not produce obvious permeation water. The low-pressure replacement operation can minimize the re-precipitation of dirt on the membrane surface. Depending on the situation, part of the concentrated water is discharged to prevent the dilution of the cleaning solution.

3. Loop

When the raw water is replaced, cleaning fluid should appear in the concentrated water pipeline, allowing the cleaning fluid to circulate back to the cleaning water tank and ensuring a constant temperature of the cleaning fluid.

4. Soak

Stop the operation of the cleaning pump, and allow the membrane element to be completely immersed in the cleaning fluid. Sometimes it is enough to soak the components for about 1 hour, but for stubborn contaminants, it is necessary to extend the soaking time, such as soaking for 10-15 hours or soaking overnight. In order to maintain the temperature of the soaking process, a very low circulating flow rate can be used.

5. High flow water pump circulation

High flow can wash away the pollutants cleaned by the cleaning fluid. If the pollution is serious, please use a flow rate higher than 50% specified in Table 1 to help cleaning. Under high flow conditions, there will be excessive high pressure drop. The problem is that the maximum allowable pressure drop for single components is 1 bar (15 psi), and the maximum allowable pressure drop for multi-element PRESSURE vessels is 3.5 bar (50 psi), which is limited first.

6, Rinse

The pretreated qualified product water can be used to flush the cleaning fluid in the system, unless there is a corrosion problem (for example, static sea water will corrode stainless steel pipes). To prevent precipitation, the minimum flushing temperature is 20oC. Note: During the pickling process, the pH value of the cleaning solution should be checked at any time. When the acid is consumed by the dissolved inorganic salt precipitation, if the pH increases by more than 0.5 a single low pH value, the acid should be added to the cleaning tank. The total circulation time of the cleaning solution should not exceed 20 minutes. After this time, the cleaning solution may be saturated with the cleaned inorganic salt, and the contaminants will be deposited on the membrane surface again. At this time, qualified pretreatment product water should be used Drain the first cleaning liquid in the membrane system and the cleaning system, and reconfigure the cleaning liquid to perform the first acid cleaning operation. If the system must be shut down for more than 24 hours, the components should be stored in a 1% (weight ratio) sodium bisulfite aqueous solution. Before cleaning the Dadian system, it is recommended to take out a membrane element from the system to be cleaned and conduct a test evaluation of the unit cleaning effect.

7. Cleaning the multi-stage system

In the washing and soaking steps of the multi-stage system, all stages of the entire system can be carried out at the same time, but the high-flow circulation must be carried out in stages to ensure that the circulation flow rate is not too low for the first stage and not too low for the last stage. High, this can be achieved by one pump cleaning each section separately or setting different cleaning pumps according to the flow requirements of each section.

Timely cleaning of the Ultrafiltration Membrane Filter can maintain the permeation rate and life of the membrane, and the correct cleaning method can save time and reduce the damage of membrane elements during the cleaning process. For different membrane modules, different cleaning methods can be used. For example, tubular modules can be mechanically cleaned with sponge balls, and hollow fiber modules can be backwashed. For the film used in the food industry, it needs to be disinfected (using NaOH and H2O2, etc.).