Research On The Fundamental And Process Of Smelting Bismuth Concentrate With Oxygen In Bath

Abstract:The traditional pyrometallurgical processes of bismuth smelting from bismuth concentrates are generally as following sintering roasting and smelting in a blast furnace, reverberatory furnace or converter and then fire refining. But this processes have such disadvantages as low valuable metal recovery, less effective use of sulfur, pollution of sulfur dioxide and long smelting flowsheet. To solve these problems, a new process that directed smelting bismuth concentrate with oxygen in bath is put forward in this work, which bismuth alloys and slag containing lead and bismuth are produced in the oxidizing smelting and then lead and bismuth alloys ate got from the slag in the reduction smelting.Firstly thermodynamic calculation of some basic reactions between bismuth and lead on the smelting was carried out. Then the mechanism of the direct bismuth smelting process was discussed.Last, experiments of the two stage smelting (oxidation smelting&reduction smelting) were done. Based on the analysis and characterization of the products by XRD,TGA and ICP, it can be concluded as follows.(1) Bismuth can be precipitated by lead just similar to the precipitation smelting of iron.The metal is obtained finally by the interactions between the sulfide and the oxide of lead and bismuth under high temperature. The direct smelting process of bismuth are feasible in theory by the analysis of oxygen and sulfur potential graph between lead and bismuth. And the oxides of lead, bismuth and copper can be reduced very thoroughly with carbon in theory.(2) Bath are helpful to reduce the volatile metal and increase the metal yield. Also using oxygen enrichment is beneficial to improve metal recovery and the efficient utilization of elemental sulfur. So it is necessary to adopt two stage smelting for bismuth sulfide concentrate.(3) On the oxidation smelting experiments, the appropriate smelting conditions are:(?)FeO/siO2by1-1.25,(?)caOisiO2by1, the temperature for1200℃, the proportion of bismuth concentrate to water granulated slag is75g/125g, oxygen gas, oxygen flow rate by0.81/min, depth of vent pipe is35cm, blowing time of7to10min, the precipitation time of45min. Under the optimum condition, the direct metal yield of bismuth and lead are80%-90%,40%-70%respectively.(4) On the Reduction Smelting, the suitable smelting conditions are: coal consumption by4%,(?)FeO/SiO2of0.9,(?)CaO/SiO2of0.8, reduction time of75min, smelting temperature of1200℃. Under the optimum condition, the metal recoveries of Bi, Pb, Cu and Ag respectively are78.9%,72.5%,87.7%and96.5%.The problems existed on the traditional pyrometallurgical processes of bismuth can be solved by this new technology, such as difficult to make acid with low sulfur dioxide and not effective to use heat from sulfur. Even this technology also have such advantages as high comprehensive recycle of valuable metals, short flowsheet and high productivity. Thus it is feasible and suitable.