Study On The Distribution Of The Elements In Nickel Laterite Smelting Process With Low Lime

With the development of Chinese economy, the demand of stainless steel and manufacturing for nickel has been increasing. Sulfide ore and laterite ore are two main sources of nickel raw material over the world. As nickel sulfide ore has good quality and mature technology on beneficiation and smelting, especially Jinchuan mining area has rich reserves of nickel sulfide ore in china, nickel sulfide ore has been used as raw materials to produce nickel alloy for a long time. However, the nickel sulfide ore resources become exhausted with continuous mining, the difficulty is increasing for mining and smelting the remained sulfide ore. People began to pay attention to the laterite ore which account 72% of the world's total land-based nickel resource. And as the progress of the technology of beneficiation and smelting for nickel lateritic ore, the proportion of nickel alloy produced from laterite ore increases year by year.Currently the most widely used process for nickel laterite ore smelting in the world is the rotary kiln- electric arc furnace smelting reduction(RKEF) process which is usually used for smelting garnierite ore. The high content of Si O2 in the raw ore, results in high melting point, large viscosity, poor fluidity and low natural basicity of the slag, which is not conducive to the removal of harmful elements. It is necessary to add lime to increase the basicity and fluidity of the slag in the smelting process, but it will increase the amount of slag, increasing the power consumption and the loss of nickel. It is required to reduce the addition of Ca O even without Ca O addition for economic considerations. The basicity of slag can be changed by adding different laterite ore with different composition, controling reducing conditions so that iron partially reduced, leaving the other iron in the slag as Fe O to improve slag fluidity.The low calcium content slag system Mg O-Si O2-Fe O-Ca O-Al2O3 of nickel laterite electric furnace smelting process was studied in this thesis. Calculation model was deduced through the analysis on the thermodynamic properties of slag system, theoretically exploring the effect of the basicity, oxidizing property and smelting temperature of the slag on the distribution of the main elements Ni, P and S between the slag and ferronickel alloy. The calculation model was validated combined with the results calculated by Factsage and the data come from the relevant literature, and obtained the following conclusions:(1) The calculation model about the distribution ratio of nickel,sulfur and phosphorus was deduced.(2)The nickel distribution ratio between slag and alloy decreases when the temperature and the Fe O content in the slag increases, while it firstly increases then decreases with the slag basicity increasing and obtains maximum when Mg O / Si O2 = 0.6. This trend becoming increasingly obvious as the temperature increases. But the effect of temperature is not significant when the Fe O content in the slag is low. The sulfur distribution ratio between slag and alloy increases when the temperature increases, while it decreases with the Fe O content increasing. And it firstly increases then decreases when the slag basicity increases and achieves the maximum value when Mg O / Si O2 = 0.6. The phosphorus distribution ratio between slag and alloy decreases when the temperature increases, while it increases with the Fe O content increasing. And it firstly increases then decreases when the slag basicity increases and achieves obvious peak when Mg O / Si O2 = 0.6. But the peaks of the curves are reduced so that they are not outstanding any more with the temperature improving.(3) Validated by the calculation results of Factsage and the experimental data come from the relevant literature, the results of the calculation model deduced in this thesis close to the practical producing process since the mass action concentration model based on the coexistence theory of slag structure can better reflect the composition and properties of the slag. Therefore, it can be more convenient to calculate the distribution ratio of elements like nickel, sulfur and phosphorus between slag and metal and the results were analyzed to study the behavior of elements like nickel, sulfur and phosphorus in order to provide theoretical support for the realization of smelting process with low lime addition.