ABSTRACT
U. S. Borax Inc. is upgrading its primary ore crushing system at its open pit mine and refinery near Boron, California. The new crushing system as developed and tested by the U. S. Borax Technology Department will include two reduction steps using MMD toothed double roll sizers. The system will reduce run-of-mine tincal and kernite ore from 1.25 meter lump size to 9 centimeter top size. Pilot and field tests results, that are confirmed with operation of full size units in temporary installation, show that improved granulometry and material handling characteristics for the ore can be achieved with the MMD sizing method. The new primary crushing system replaces a single stage 54×72 Jeffrey Slugger impact crusher that was installed in-pit in 1961. Replacement became necessary due to mining of ore near the primary crushing location, and also the impact system had also reached the end of its useful life resulting in increased maintenance costs and other operational problems.
