Building iron ore stockpiles to target grade and composition

Abstract

An iron ore mine prepares pre-crusher stockpiles, feeding the processing plant with ore at target composition, in grade (iron and multiple contaminants) and physical and source characteristics. Weekly, ore blocks to be mined are allocated to the previous stockpile, or to a new stockpile. By week end, the previous stockpile is completed. The new stockpile becomes the starting stockpile for the following week. An Excel-based program using Visual Basic macros allocates ore to the stockpile builds, selecting mining blocks to build the stockpiles, so completed stockpiles are close to target grade and composition. It sequences the stockpile builds, so the stockpile has consistent grade and composition throughout its build, maintaining control under early termination of stockpile build or reclamation. Initial solution using the Excel add-on ‘Solver’ exceeded the integer variable limit, so was replaced by a greedy algorithm solving the problem much faster, without the limitation on the integer variables.