Application of Wedge Wire Filter in Nuclear Power Plant
Water treatment is divided into physical treatment and chemical treatment. The wedge wire filter is a new type of filter material used in the physical treatment process.
Different from the traditional process, the wedge wire screen filter adopts the resistance welding process, which can realize automatic numerical control processing, with high filtration accuracy and structural strength, and can be backwashed and cleaned.
Wedge wire filter application background
Nuclear power generation requires large amounts of water to be drawn from the ocean, and water quality treatment is crucial.
Seawater needs to undergo multiple chemical and physical treatments before it can be used for power stations. Physical treatments include adsorption, precipitation or barrier methods to purify the water. The barrier method is to pass the water through the filter material, so that the larger impurities cannot pass through, and then get a cleaner Power station water.
As a new type of structural filter material, wedge wire filter screen has higher filtration precision and structural strength than other filter materials such as metal braided filter screen, powder sintered filter element and laminated filter screen. It is easy to backwash and clean, and has formed mature standardized series products in petrochemical industry, food industry and other industries.
Application analysis of wedge wire filter element in nuclear power plant
At present, the commonly used filter materials in nuclear power plant include metal woven filter screen, powder sintered filter element and laminated filter screen.
Metal woven filter screen is widely used in nuclear power plant. It is generally used in water intake filter equipment of nuclear power plant for preliminary filtration. It is usually aimed at impurities with large volume such as aquatic grass and shell, and has large flow area, while wedge wire filter screen is more suitable for high-precision filtration.
Metal powder sintering filter element is a porous filter material made of metal powder through powder classification, molding, sintering, mechanical welding and other processes. However, due to the bending and crisscross of internal pores, impurities cannot be cleaned after entering the filter element, after a long time of use, the system pressure will be increased due to fouling, which needs to be replaced regularly.
Sintering filter element is widely used in power plant sampling equipment, but the maintenance interval of nuclear power equipment is long, and Johnson screen filter has been gradually used on high-pressure filter, which can be backwashed and online blowdown under the same filtering accuracy, which is more favorable for equipment maintenance.
The laminated filter screen is mainly used in the nuclear power plant desalter equipment. The desalter is an important equipment for the chemical treatment of water quality in the nuclear power plant. The H-type cation resin and oh type anion resin inside the filter are exchanged with various anions and cations in the water to achieve the purpose of purifying water quality.
The inlet and outlet of the desalter will be equipped with filter screen to filter water quality and prevent resin leakage. The diameter of resin particles is very small, generally 0.3-0.7mm. Moreover, the system pressure is high and the working conditions are complex, so there are strict requirements for the pressure drop resistance of the filter screen.
The filter accuracy of laminated filter can meet the requirements of desalter equipment, but the effect is not good after it is put into use. Because of the serious abrasion of boss, easy leakage of resin, short working life and high requirements for machining accuracy, laminated filter screen has been gradually replaced by wedge wire filter.
Although the wedge wire filter can meet the requirements of desalinizer equipment in terms of filtration accuracy and structural strength, its initial promotion is not smooth, because the pressure drop resistance value generated in the container has not been tested, and it is impossible to judge whether it meets the requirements. Desalter system design requirements, which require relevant theoretical calculations as a basis.
In a nuclear power desalter equipment renovation project, a large number of theoretical calculations proved that the pressure drop of the wedge wire filter satisfies the design requirements.
Through calculation, the theoretical pressure drop loss of the wedge wire filter in this desalinizer system is about 0.003MPa, which is far less than the allowable pressure drop of the system. In actual use, it has been proved that the performance of the wedge wire filter meets the design parameters.