A new spin on reducing membrane-filtration fouling

Last month at Filtech (Wiesbaden, Germany; October 13–15), Fil Max Inc. (Brea, Calif.; www.fmxfiltration.com) exhibited a new application for its FMX vortex-generating, membrane-filtration technology — treating wastewater from a biogas plant. Fil Max installed its first commercial system — three KFS units with 220 m2 of filtration surface area — for this application in August at a 6-MW biogas facility in Europe. The system integrator of the plant had experienced considerable problems due to clogging of the previous tubular ultrafiltration system, explains Fil Max director Tzu-Lung Lin. Pilot trials (conducted in March) demonstrated FMX technology’s ability to not only meet EU water-quality standards, but also to increase methane production in the biogas-plant digester.

FMX consists of a stack of membrane filters with a vortex-generating blade sandwiched between the membranes. The blade — jointly developed by the Korean Institute of Machinery and Materials (Daejeon; www.kimm.re.kr) and Fil Max — is spun by a variable-speed drive creating a swirling pattern known as Kármán vortices, which generate a strong turbulence with minimum energy. This turbulence dislodges foulants from the membrane surface, enabling the foulants to be carried away by the feed stream (diagram, top). In contrast, conventional membrane filtration systems, which rely on a cross flow to remove the boundary layer built up by foulants, are less efficient because the shear force is often weakest near the membrane surface (diagram, bottom).

FMX made its commercial debut in 2005 for treating wastewater from a methyl cellulose plant of Samsung Fine Chemicals. Since then, the technology has found applications in the oil-and-energy, chemical and environmental industries. Units are available with membrane areas of 10 to 100 m2, and the modular design enables stacking as many membranes as needed to meet the required capacity, says Lin.