ultrafiltration membrane It is a key element of ultrafiltration equipment. It is one of the polymer material membrane separations initially developed and designed, and is used as a mid-range solution equipment in pure water production. Because the ultrafiltration membrane is a raw material with multiple empty ends, and the residues in the water are removed by physical interception, the ultrafiltration membrane should be cleaned on time to ensure that the service life of the ultrafiltration membrane is increased according to the amount.

The cleaning method of ultrafiltration membrane is generally determined according to the characteristics of the membrane and the type of solution. Generally, it is similar to ro reverse osmosis, that is, the water power generation is used for cleaning first, and then different organic chemical cleaning agents are selected according to the specific situation. For example, solubilizers containing anions and cations can be used for electric coating materials, and "bridge bond" organic solvents can be used for water-soluble organic chemical architectural coatings. Protein deposition in the food industry can use prion enzyme solution or polyphosphate, silicate materials as the basic acidic detergent. Deposits on the membrane surface generated by inorganic substances can be dissolved with antioxidants such as EDTA or acids and bases. The cleaning method of ultrafiltration membrane is divided into seven processes

1. Configure detergent

2. Low flow keying detergent

First mix the cleaning solution with the cleaning centrifugal pump, and heat the cleaning solution with low flow rate. Then replace the source water in the element with the lowest working pressure of the cleaning solution. The working pressure only needs to be enough to make up for the pressure damage caused by water seepage to concentrated water, that is, the working pressure must be low enough not to cause significant water seepage. The actual operation of low-voltage replacement can minimize the re deposition of stains on the membrane surface. Depending on the situation, part of concentrated water is discharged to avoid diluent of cleaning solution

3. Circulation system

When the source water is replaced, the cleaning solution should be produced in the concentrated tap water pipeline, so that the cleaning solution circulation system can return to the cleaning water storage tank and ensure that the ambient temperature of the cleaning solution is stable.

4. Soak

Stop the operation of the cleaning pump and allow the membrane element to be completely immersed in the cleaning solution. Sometimes it is sufficient to soak the components for about one hour, but for stubborn pollutants, the soaking time must be increased, such as soaking for 10-15 hours or soaking for overnight stay. In order to better maintain the ambient temperature during the whole soaking process, a very low flow rate of the circulating system can be selected.

5. High flow centrifugal pump circulation system

The high flow rate can clean the pollutants cleaned by the cleaning solution. If the environmental pollution is relatively serious, please select a flow rate higher than 50% of the explicitly specified flow rate in Table 1, which will be conducive to cleaning. Under the high flow rate standard, the problem of too high pressure drop may occur. The larger allowable loss of a single component is 1 bar (15 psi), and the larger allowable pressure drop for a multi element high-pressure vessel is 3.5 bar (50 psi), It shall be exceeded first.

6. Cleaning

The qualified filtrate prepared for treatment can be used to clean the cleaning solution in the system software, unless there is an erosion problem (for example, the stainless steel pipeline will be corroded by the stationary sea surface). To avoid deposition, the minimum cleaning ambient temperature is 20oC. In the process of acid treatment, the pH value change of cleaning solution should be checked in time. When acid is consumed in the process of dissolving carbonate deposits, if the pH increase exceeds 0.5 pH value, the acid should be filled into the cleaning box. The total circulation system duration of acid and alkali cleaning solution should not be longer than 20 minutes. After this time, the cleaning solution is likely to be saturated by the washed carbonate, The pollutants will accumulate on the surface of the membrane again. At this time, the first cleaning solution in the membrane system software and cleaning system will be discharged by using the qualified preliminary treatment filtrate, and the cleaning solution will be redeployed to carry out the actual operation of the first acid-base cleaning. If the system software must be shut down for more than 24 hours, the components should be stored in 1% (net weight ratio) sodium bisulfite solution. Before cleaning the software of the grand ceremony system, it is proposed to remove a membrane element from the system software to be cleaned, and carry out the experimental evaluation of the actual effect of cleaning the unit parts.

7. Clean multi segment system software

In the cleaning and soaking process of the two-stage system software, all sections of all systems can be carried out at the same time, but the circulation system with high flow rate must be carried out in sections to ensure that the flow rate of the circulation system is not too low for the first section and not too high for the final section, This can be accomplished by cleaning each section of a pump each time or setting a different cleaning pump according to the flow regulation of each section.