Filtering impurities from liquid using mineral wool fiber material

Claim 1

A process for filtering liquid for removing impurities therefrom which comprises passing said liquid through a filter body of mineral wool fiber material cut from a fiber material web with a thickness of at least 5 cm, of fibers prepared from a melt of fibers with a thickness of essentially from 1 to 20 microns, by depositing said fibers on a surface and bonding the fibers with a binder at a substantial number of points at which the fibers contact each other, said fibers, at least along a main part of a total fiber length, being directed in a direction which deviates less than 45% from a main direction plane formed by said surface, said mineral wool fiber material having a density of from 50 to 150 kg/m 3 and a stiffness, expressed as compressibility under a load of 0.05 kp/cm 2 on an upper surface of a cylinder of said mineral wool fiber material with diameter 100 mm and height 100 mm of at most 40%, in which filtering process the liquid is brought to penetrate into said body of mineral wool fiber material through an inflow surface area comprising a major part of said body of mineral wool fiber material and is removed from said body through an outflow surface area formed by at least one outlet opening nozzle urged against a cut surface of said body of fiber material cut in a direction transverse to a direction of said web, with said nozzle arranged at a distance of at least 1 cm from a peripheral line of said cut surface of said body, the ratio of said inflow surface area to said outflow surface area of said body of fiber material being at least 10, said inflow surface area being at least 90% of the total surface area of said body, said body extending in a direction perpendicular to said outflow surface area at least 5 cm, and passing said liquid through said filter body with a flow speed, calculated on said outflow surface area of said filter body of above 10 meters/hour.