Process Of Curing Roasting-Cyanide Leaching Gold From Refractory Metallurgical Ore

With the global large-scale exploitation of gold resources, easy melt gold ore resources have been dwindling, and therefore refractory metallurgical ore would become the most important source of gold resources in future. According to statistics, there was about1/3of the gold from refractory metallurgical ore all around the world nowadays. China had rich in refractory gold resources, metallurgical mineral resources were about1/4of the proven reserves, total reserves about1000tons. The key to develop refractory metallurgical ore was to select the appropriate pretreatment method, which would directly affect the production cost, environmental protection and the final recovery of gold and so on.In this thesis, the refractory metallurgical ore as research goal, its structure and chemical compositions were characterized and tested by X-ray diffraction(XRD), X-ray fluorescence spectroscopy(XRF), scanning electron microscopy(SEM), atomic absorption spectrometry(AAS), flame atomic fluorescence spectrometry(AFS) and elemental analyzers and other test and analysis methods. So curing roasting additives cyanide leaching gold was the final choice. The optimum parameters microwave furnace and electric resistance furnace for the fine ore roasting were investigated. Through a comprehensive comparison the best pretreatment method was chosen. The curing effect of arsenic sulfur in the ore samples after curing agent NaOH and CaO joined and the gold leaching rate were investigated. The factors of NaCN amount of the slurry liquid-solid ratio, pH value, the gold leaching time and help infusion CaO2on the gold leaching rate were also researched. The main findings were as follows:(1)Through test analysis shows that:the concentration of sulfur and arsenic in fine ore was high, but also containing carbonaceous materials. The content of sulfur、 arsenic and carbonaceous materials was36.85%、7.45%and1.04%respectively. The main metallic minerals of ore were pyrite and arsenopyrite, which was the main gold- bearing mineral; the content of which was about68%. Non-metallic minerals were mainly quartz and feldspar. Precious metal minerals were native gold, the content of which was59.32g/t. The gold leaching rate was6.43%by conventional cyanidation of the concentration leaching. Therefore the ore was typical refractory metallurgical ore rich of Arsenic and sulfur.(2) The factors that calcination temperature, calcination time and additives on the test results were investigated by resistance furnace for roasting of fine ore. The final roasting conditions:calcination temperature was750℃, calcination time was2h, the amount of KMnO4was5%, the amount of curing agent CaO was60%. Not only did the leaching rate of gold reached as high as92.05%, but the curing rate of the harmful elements of As and S was up to83.92%and60.04%respectively. The pretreatment of the results are satisfactory under this condition to roast the fine ore.(3)The leaching rate of gold was improved previously with using microwave radiation on the fine ore. But it was constrainted by the microwave radiation temperature, microwave irradiation time and in Mineral additives. The gold cyanide leaching rate was up to84.39%with the conditions that the roasting temperature was400℃, calcination time was20min, dosage of KMnO4was0.2%in microwave oven. Adding a curing agent NaOH to ore sample could reduce the pollution of the environment and short the heating time, but the gold cyanide leaching rate decreased significantly. Compared with the resistance furnace pretreatment, the traditional roasting pretreatment was more practical and more controlling the roasting conditions.(4)In the gold leaching test, the infusion agent CaO2added in the slurry, which enhanced the gold cyanide leaching rate about3%and saved the amount of of sodium cyanide about20%and short leaching time for12h.The optimal experimental leaching process as follows:concentration of NaCN wasl.6g/L, the dosage of the help infusion CaO2was4.5g/L, the ratio of slurry liquid to solid was3:1, the leaching time was24h, the pH value was11, the final leaching rate of gold was as high as94.39%.A comprehensive analysis of the test and the results show that the process of refractory ore using roasting-auxiliary cyanidation had important practical significance and guidance for the future industrial production. A number of theoretical references were offered by the technology of microwave pretreatment of refractory metallurgical ore.