Long-term production scheduling in open-pit mines with special emphasis on processing plant feed constraint (Case study: Saheb Saghez iron ore mine of Iran)

摘要

The issue of production planning optimization (conceptual, long-term, mid-term, short-term and daily schedules) in open pit mines is to find optimum sequence of extracting blocks from ore zone during mining cycle. In this regard, maximizing the Net present value (NPV) and minimizing required energy, especially in processing plants, play major role in productivity and effectiveness of mining operation. The role of long-term production planning optimization is very sensitive for the mine and will reduce investment risks, leading to a capital return with a logical rate in a short period. In this paper, the long-term production planning is optimized for Saheb Saghez iron ore mine located in Kurdistan Province of Iran. Considering the block modelling of ore resources based on gathered data, the economic model was first prepared. In this regard, sensitivity analysis was carried out on the ultimate pit slope for achieved economic model and 42 degree slope was selected as the appropriate and optimized slope for mine walls. Then, the final working area was determined according to the data. In the following, the geometric parameters of excavation area were estimated and the final area was designed using Studio 3 software. To optimize the production planning aiming to meet the required energy for the primary crusher, push-backs were designed to obtain proper production planning. Optimized production planning is then presented according to the objective constraints analyzed by NPV Scheduler program. Results showed that there are 864 thousand tons of economic and minable reserves with average grade of 40 percent in the final extraction area. Accordingly, the production planning, achieved using NPVS, the 200 thousand tones annual extraction of minerals to supply for the primary crusher with average grade of 40 percent, less than 1 percent sulfur for a 5-year mining period.