Mechanism of Fe crud deposition by membrane electrification in hollow fiber membrane filter

The hollow fiber membrane filter (HFF) applied to the condensate polishing system in BWR plants occasionally experiences a greater pressure drop due to fouling of the membrane inner surface. Then a mechanism for fouling and its countermeasures were studied from simulated laboratory experiments. The HFF made of polyethylene polymer which has a dielectric property became negatively charged on its surface when pure water, such as condensate, flowed through the filter. The degree of the negative charge depended on the water electrical conductivity and flow velocity through the membrane. The amount of Fe hydroxide deposits on the membrane surface depended on the Fe and Cu ion concentrations. Then a crud precoating method was confirmed as an effective and practicable means to restrict deposits. (author)