The large-scale manipulation of small particles

High gradient magnetic separation is a new technique which provides a practical means for separating weakly paramagnetic materials down to colloidal particle size on a large scale and at flow rates over one hundred times faster than the flow rates possible in ordinary filtration. The technique is also applicable to non-magnetic materials which can be made to associate with magnetic seed materials. HGMS has already been applied industrially to the purification of kaolin for paper coating, and is also applicable to the beneficiation of many minerals which are too finely divided to be economically separable by any existing method. Other potential applications include the desulfurization and de-ashing of pulverized and liquefied coal, the decontamination of water, industrial waste and municipal sewage, and even the decontamination of rivers and lakes. HGMS is based on the use of matrices of finely divided filamentary ferromagnetic material containing 95% void space, such as felted or woven steel fabric, compressed steel wool, expanded steel lath, etc. It requires sophisticated magnets capable of generating high intensity fields in large volumes of empty space at lower cost and energy expenditure than was previously possible. Superconducting magnets will ultimately be used for larger applications.