Process and system for eliminating the potential for LD and EAF steel slag expansion

A process for eliminating the expandability of steel-plant slag, the process comprising the steps of:

• a) separating the steel-plant slag by size difference and transporting the steel-plant slag to a processing unit;
• b) feeding a primary crusher with the steel-plant slag and crushing the steel-plant slag depending on their grain size, wherein natural moisture of the steel-plant slag facilitates the crushing of the steel-plant slag into slag material;
• c) collecting the slag material processed by the primary crusher and transporting the slag material to a magnetic separator and removing metallic fragments bigger than a determined grain size;
• d) drying the slag material received from the magnetic separator in a rotary dryer to produce dry slag;
• e) feeding the dry slag to an impact mill that fragments and discharges the dry slag;
• f) performing aero-classification with disaggregation and fragmentation of the dry slag in the impact mill by means of a static classifier that provides a depression inside the impact mill, so as to drag fine and superfine particles of the dry slag that are smaller than a predetermined grain size;
• g) feeding the dry slag particles bigger than the predetermined grain size, after the step of aero-classification with disaggregation and fragmentation, to a cooler in which cooling is provided by means of an aero-classifier, which makes the heat exchange and removes fine and superfine particles that were not collected in the aero-classification step in the impact mill, leaving cooled material;
• h) disposing the cooled material on a vibrating sieve having two or more decks provided with screens with predetermined sizes to sieve the cooled material into fractions separated according to their grain sizes;
• i) magnetically separating the fractions of cooled material in low-intensity magnetic separators, to separate non-magnetic slag fractions, which are free from metallic iron (Fe0) and from iron monoxide (FeO), and magnetic fractions, which are composed by metallic iron (Fe0) and iron monoxide (FeO or Fe+2);
• and
• j) reprocessing said magnetic fractions in low-intensity magnetic separators to concentrate high metallic iron contents and generate a product with high concentration of iron monoxide (FeO or Fe+2).