Calcified Roasting Process And Reaction Path Of Low-Nickel Matte

With the rapid development of industrial economy,the contradiction between supply and demand of nickel resources is increasingly prominent.Therefore,the efficient utilization of nickel mines is of great importance.However,the traditional process of pyrometallurgy has a large energy consumption and low metal recovery rate,while the hydrometallurgy requires high cost equipment and difficult technique.On the other hand,the combination of pyrometallurgy and hydrometallurgy process,which is of less energy consumption and less pollution,has strong adaptability to raw materials and gradually becomes a hotspot of metallurgy research.Therefore,this project uses the combination of pryrometallurgy and hydrometallurgy process to extract valuable metals from low-nickel matte.Low-nickel matte,which is a preliminarily intermediate product obtained by matte smelting process of nickel sulfide concentrate,has less impurities and was much more enriched in valuable metals compared to raw ore and concentrate.Taking low-nickel matte as the research object can not only simplify the technological process,but also reduce energy consumption,minimizing costs and diminish the loss of valuable metals.Thus,in this study,we selected low-nickel matte as the subject and CaO/CaCO₃ as the additive to elucidate the metal extraction process and related mechanism.The main contents are as follows:?1?With the addition of CaO as calcified agent,the influences of calcified temperature,calcified time,CaO addition amount,sulfuric acid concentration and leaching time on the extraction of metals were investigated.The results showed that under the optimal conditions,the extraction of Ni,Cu,Fe and Co were 94.20%,98.10%,91.32%,92.21%,respectively.In the process of calcified roasting,CaO firstly reacted with Fe₂O₃ to produce CaFe₂O₄,which can effectively inhibit the formation of ferrites.As a result,the target metals would exist in the form of oxides in the roasting product,and could be transferred to the liquid phase in the subsequent acid leaching process.?2?To further improve the roasting effect,CaCO₃ was chosen to replace CaO as the roasting agent,and the valuable metals were extracted by calcified roasting-acid leaching process.The results showed that under the optimal conditions,the extraction of Ni,Cu,Fe and Co were 95.10%,99.21%,91.75%and 93.32%,respectively.It was found that for low-nickel matte containing several valuable metals,the direct calcified roasting-acid leaching requires a high temperature?1100 ^oC?.Therefore,the ball-milling was introduced to pretreat the mixture of low-nickel matte and CaCO₃,which can reduce the calcified temperature to 850 ^oC,and the corresponding extraction of Ni,Cu,Fe and Co were 94.41%,99.01%,90.75%and 93.02%,respectively.?3?The removal of iron from the leaching solution was carried out by goethite process.The influences of pH,temperature,time and crystal species on iron removal efficiency were studied.The losses of target metals?Ni,Cu,Co?in the process of iron removal were analyzed.The results showed that under the optimal conditions,99.60%of Fe could be removed in the form of goethite,and the concentration of iron in the solution was 3.84 mg/L.Due to the coprecipitation of metal ions and adsorption of hydrolysates in the process of iron removal,1.20%of Ni,0.91%Cu and 1.80%Co will be lost,but the final recovery of Ni,Cu and Co still reached 93.28%,98.11%and91.34%,respectively.In this paper,low-nickel matte was taken as the research object,and calcified roasting-acid leaching method was used to extract valuable metals,which achieved high extractions.This process is of low energy consumption and friendly to environment,which can be used as an effective method for the extraction of valuable metals in China.It is of great importance to the research and development of low-nickel matte as raw material.