Experimental Study In Catalytic Oxidation Pretreatment Of Cyanide Tailings With NO_x-wide Circulation In Three-phase Fluidized Bed

With increasingly exhausting of easily leachable gold ores,Developments of refractory gold ores and cyanide tailings have attracted extensive attention around the world.According to statistics,80%of the world's gold smelting enterprises to adopt cyaniding,resulting in a large number of cyanide tailings,the tailings contain recoverable gold,silver,copper,lead,zinc,iron and other valuable metal elements.These cyanide tailings are resourced,especially gold,silver, iron and other elements of a comprehensive recycling,it can eliminate the environmental pollution caused by cyanide tailings,but can bring tremendous economic benefits to the alchemical enterprise.It is practically Meaningful to explore better methods to utilize the refractory gold ores and cyanide tailings at present and in the future of china.Most important thing of developing this type of mineral is the choice and application of pretreatment method.This will directly relate to the recovery levels of different elements,cost,environmental protection and so on.According to in checking a large number of documents and the original study of our research group,the innovation of retreating cyanide tailings by the way of the catalytic oxidation system that in a three-phase circulating fluidized-bed with NO_x-wide circulation.In this paper,the cyanide tailings from Zhongyuan Gold Smelter used as the test materials,and NO_x reagent as the oxidant,The factors affecting the pretreatment process were examined,the optimum condition was obtained by study under conditions:Pretreatment temperature is 75℃,oxygenation time is 3.5h, initial concentration of nitric acid is 15%,initial concentration of Sulfuric acid is 5%,gas velocity is 0.5m~3/h,aperture of distribution plate is 1mm-2mm,the distance between the hole and the hole for 4mm-7mm.The results show,on this condition,the leaching rate of Fe reached 94.25%and weight loss reached 55.82%,oxidation effect is very obvious.Under the same conditions, pretreatment of refractory gold,the leaching rate of Fe reached 95.29%and weight loss reached 72.68%,indicating that the method of pretreatment of refractory gold is an effective way.The oxidation mechanism of the reaction was analyzed preliminarily.The X-ray diffraction(XRD),LV scanning electron microscopy(SEM) and Energy Dispersive Spectrometer(EDS) adapted to the cyanide tailings before and after the pretreatment respectively.Through analysis and comparison,this method of pretreatment is effective oxidation of pyrite,so that parcels out of gold exposed to enhance the rate of cyanide gold extraction.The cyanide tailings and oxide slag are cyanided gold under the conditions of the liquid-solid ratio 5:1, PH=9-10,NaCN dosage:2.0-3.0g/L,cyanide time for 24h,gold extraction rate from 66.44%to 99.39%.Can be seen that the pretreatment method to effectively improve the rate of cyanide gold extraction.Finally,Comparison of NO_x recycling and does not cycle on the effects of pretreatment cyanide tailings,the results show that recycling can save a lot NO_x nitric acid,nitric acid concentration in the liquid down to ease and improve the reaction rate and shorten the oxidation time.NO_x is achieved with a self-loop at low temperature and Normal pressure.On this basis,the catalytic oxidation experiments have been enlarged scale in three-phase fluidized bed.The results show that would only add a small amount of nitric acid oxidation reaction can be to maintain continuous in a certain time interval,and the iron leaching rate continued to improve.The pretreatment method studied in this paper,pretreatment effect is good,and effectively raise the rate of cyanide gold extraction.And the NO_x-wide circulation is achieved in reaction process;reduce pollution,environmentally friendly energy-saving emission reduction requirements.It is necessary to further study and improves the response equipment and the materials of equipment.