Permanent magnets for water-scale prevention

Abstract

Anti-scale magnetic treatment (AMT) is discussed with the emphasis on the construction of magnetic devices and the mechanism of AMT influence on scale formation. Two field cases are reported of mineral-fouling reduction during water heating by using permanent magnets. Instead of hard encrustation on the heated surfaces a powdery deposit was formed because of modified crystal morphology (observed by X-ray powder diffractometry and scanning-electron microscopy). In order to find a proper design for magnets regarding the influencing parameters (a magneticfield distribution with alternating lines orthogonal to the water-flow and minimal density peaks 0.2 T), costeffective for actual water-flow capacities, several models with NdFeB magnets were simulated by the finiteelement method using the OPERA 15R1 computational program. Two optimized models are presented for moderate capacities: a model with a rectangular gap (a two-row set of rectangular magnets) for capacities from 0.5 m3/h to 3 m3/h, and a model with annular gap (annular magnets on a pipe and disk magnets within a cylindrical kernel) for 3.5 m3/h to 5.5 m3/h.