The residue and smoke remaining after pyrite is roasted to make acid are collectively referred to as pyrite cinder and sulfuric acid cinder, namely cinder. The main component is iron, whose content is generally between 40% and 55%, and some cinders also contain a certain amount of non-ferrous metals. Therefore, cinder is a valuable raw material worthy of comprehensive utilization. The gold content in the cinder is very low, except that the gold content of the cinder used to make acidic pyrite from gold concentrate is high. The gold content is generally below 2~0.5 g/t, and the slightly higher is 5~10 g / T. It is difficult to recover low-grade gold from pyrite cinder, and its technical indicators are generally not high. At present, this part of low-grade gold ore mainly adopts the final treatment of cyanide in the beneficiation process, so that it is possible to achieve economic benefits. However, before cyanidation, gravity separation (shaking table, flannelette chute), flotation and other methods are generally used to further improve the enrichment rate of gold ore and reduce the amount of cyanidation to achieve the purpose of economic rationality.
Gold bearing pyrite cinder is the product of roasting and desulfurization of gold bearing pyrite, and its structure and occurrence state of gold are different from that of gold bearing pyrite. Therefore, the cyanide extraction of gold from cinder is also different from that of general gold ore or gold concentrate. Usually, after the slag is discharged from the roasting furnace, it is cooled with water first, so the slag must be dehydrated; After roasting the insoluble gold bearing sulfur concentrate, in addition to the preparation operations such as cooling and grinding of the cinder, it also needs strong washing and chemical treatment.
The purpose of flushing the slag is to remove copper sulfate, acid, base metal oxide and iron salt in the slag. Mixing these impurities or compounds into cyanide operation will increase the consumption of cyanide and lime, the dissolution of passivated gold and complicate the process of gold precipitation. Due to the different characteristics of cyanide consuming substances and other active ingredients in the slag, the intensity of flushing is also different. Washing operation includes hydrocyclone classification, concentration, filtration and other steps. Although this makes the process of treating cinders more complicated, it can greatly reduce the consumption of cyanide in the future gold leaching operation and improve the gold leaching rate. Therefore, it is economically cost-effective to compare the two.