The primary crusher is an important part of the mining process, taking the run of mine (ROM) ore and reducing it to a size which can be processed by the downstream operations. However, mining operations frequently have issues related to the primary crusher: low throughput, low utilization and high wear rate of liners. Changes in fragmentation and breakage characteristics of the feed are sometimes difficult to observe and consequently, difficult to control. The presence of oversized ore boulders in the feed is readily apparent since the throughput immediately decreases and typically causes blockages in the crusher cavity. These blockages can damage the crusher and take time to clear, resulting in a serious bottleneck for the entire process.
In order to prevent this type of bottleneck, one key element that needs to be analysed is the mine’s existing drill and blast program. There are three critical things that need to be looked at to ensure that your feed does not contain oversized rocks which can cause unplanned downtime.
1. Difficulty detecting changes in ore type and ore mass characteristics
Problem: The mass of material that you are blasting (blasting polygon), appears to be the typical ore type, therefore the blast design was unchanged. After blasting, an unusual quantity of oversized ore is found in the muckpile.
Solution: Even though ore types can appear to be similar, only the details from a true drill and blast program can eliminate guesswork. A trained geologist with local experience is a necessity and can predict the correct joint system parameters needed to optimize the program. In the design phase, input from the site geologist is a valuable resource to achieve good fragmentation results as only an experienced geologist can distinguish ore types and alterations with the naked eye. For the same ore type, changes in ore mass structure will induce changes in fragmentation of the blasted material. An area with big preformed blocks in the ore mass sometimes cannot be detected during drilling.
Information related to ore mass structure can be used to adapt the drill and blast design to local conditions. Maintaining a drill and blast database to record conditions for each blast, design and results will contribute to continuous improvement in blast outcomes when blasting in adjacent or similar areas. The best way to deal with variation in rock mass structure is to define ore domains based on blastability and have an adequate drill and blast design for each area.