An optimization journey: from blasting, dry AG milling to regrind HPGR and everything in between

Author(s) W. Valery, K. Duffy, R. Valle, R. Hayashida, A. Jankovic, P. Holtham, E. Tabosa, B. Andrade
Presented at Procemin-Geomet 2019 in Santiago, Chile, from November 20-22, 2019.


In late 2017, Hatch was engaged to conduct a Mine to Process Optimization project for a large iron ore operation. The operation consists of five iron ore mines, of which three currently feed seven processing lines contained within three plants. The operation also includes hematite recovery and a pelletizing plant. The processing lines have three different flowsheets and include some different applications of comminution equipment compared to many iron ore operations, such as dry AG milling and an HPGR in regrind duty.

The objective of the Mine to Process Optimization project was to develop integrated mining and processing strategies to increase production and improve the quality of the pellet plant feed while minimizing costs. The operation aimed to increase concentrate production from 14 Mt/y to over 17 Mt/y. Hatch conducted and supervised detailed mine and process plant audits, full surveys with sampling of the plants, ore characterization testing, data collection, mathematical modeling, simulations and integrated analysis and recommendations for optimization of the three active mines and all processing lines. The Hatch blast fragmentation model, process models, energy/power-based models, extensive database and industrial experience were used to develop, calibrate and integrate the site-specific models for blasting, comminution and magnetic separation, which included some interesting challenges with dry AG milling and HPGR in regrind application.

Numerous opportunities were identified to increase production and improve the quality of pellet feed with the existing equipment. Several changes in operating strategy were recommended including increasing and better distributing blasting energy according to ore characteristics, tightening crusher gaps and screen apertures where appropriate, changing mill internals and operating conditions, HPGR product recycle and cobbing, redirecting magnetic separation streams, etc. Where these improvements would be insufficient to meet the specified production targets, expansion options were proposed and evaluated.