Abstract: In a largescale lowgrade gold copper mine,the flotation process is used to enrich the highgrade copper ore,while the biological heap leaching process is used to produce cathode copper for the lowgrade copper ore.With the increase of the heap height,the leaching rate of iron in the mine keeps increasing,but the copper leaching rate decreasing.With regard to the biological heap leaching of lowgrade copper ore,the preclassification and smelting combined process was adopted,and the original heap leaching process was optimized.The leaching rate of the +2 mm sieve products in the column leaching test was 75.22%,which was 5.08 percentage points higher than the original leaching rate,and the iron cumulative leaching rate decreased by 2.75 percentage points.2 mm products can finally obtain copper concentrate containing 20.20% copper,with recovery rate of 87.21%,associated gold grade of 3.6 g/t,gold recovery rate of 5874%,associated silver grade of 83.7 g/t,silver recovery rate of 68.28%,and sulfur concentrate containing 47.12% sulfur with recovery rate of 33.00% through flotation process.So by using pregrading and metallurgy process,not only the comprehensive recovery rate of copper reaches 79.55% which is 10.41 percentage points higher than that of 69.14% by the original bioleaching process,but also get some associated gold,silver and sulfur concentrate.What's more,the new process will increases about RMB 116 million profits.In conclusion,the new process will bring a large number of benefits,including raising the utilization efficiency of resource,reducing the leaching of ferric acid,achieving remarkable economic benefit,and greatly saving the environmental protection cost.

Key words: Low grade copper mine, Leaching rate, Resource utilization, Environmental protection cost