红土镍矿氯化离析过程研究

【作者】 张琏鑫；

【导师】 李新海；

【作者基本信息】 中南大学 ， 冶金物理化学， 2011， 硕士

【摘要】 随着高品位硫化镍矿日益枯竭,低品位红土镍矿的利用随之受到越来越多的关注。本论文以国外某一地区的低铁高镁红土镍矿为原料,在本课题组所进行的工艺研究基础上,对红土镍矿氯化离析过程进行研究。通过热力学计算,绘制了气相组成热力学平衡图。应用FactS age软件以及其相图数据库,研究了M-C-O系相图、MO-SiO2系相图、Ni-Fe-O系相图、Ni-Fe合金磁性相图和混合氯化物相图,结果表明要得到好的离析效果必须要控制体系为弱还原性气氛和较高的温度,在850℃出料水淬,应控制镍铁合金中镍的质量分数≥5%。为了研究氯化氢的生成过程,研究了SiO2与CaCl2的反应过程：在200℃以下,二水氯化钙发生脱水反应；温度在200℃到750℃之间,体系无有效反应发生；温度在750℃到800℃之间,体系SiO2和CaCl2的摩尔比为2：1和1：1时,生成了Ca2SiO3Cl2,随温度升高Ca2SiO3Cl2与水反应放出氯化氢气体,摩尔比为1：2时,生成了Ca3SiO5·CaCl2,但是随着温度升高,其并不分解,过量的氯化钙会因蒸汽压降低而以气体的形式挥发。对金属氧化物的氯化过程进行研究,结果表明：在600℃左右,蛇纹石分解,脱羟基,增大了氯化过程的反应界面,而温度在700℃,热力学上需要更高的氯化氢气体分压,从而造成了镍的氯化率随着温度从600～1000℃升高,先降低然后升高。对氧化镍氯化过程动力学计算,反应符合气固反应的“收缩核模型”,属于内扩散控制,表观活化能为32.42 kJ-mol-1。对金属颗粒的生成及长大过程进行研究,结果表明：随着水蒸气分压的升高,精矿品位逐渐降低,镍的收率逐渐升高。镍铁合金颗粒可以在碳表面和粗糙的硅酸盐表面离析,在碳表面离析的合金颗粒容易长大,而在硅酸盐表面离析的颗粒难以长大。在1000℃～1100℃下,颗粒的长大机制是小的镍合金颗粒向更加有利位置即两颗粒的接触点迁移的过程；在1100～1350℃条件下,颗粒的长大机制是小的镍铁合金颗粒熔化蒸发吸附到大的镍铁合金颗粒表面的过程。对红土镍矿离析过程物相变化进行研究,结果表明：在400℃～600℃之间,随着温度的升高,碳酸镁分解；600℃～700℃之间,蛇纹石相分解消失,取而代之的是富铁和富钙的橄榄石相。降温过程中红土镍矿的矿相并没有发生明显改变,红土矿氯化离析的过程是不可逆的过程。更多还原

【Abstract】 As the high grade nickel sulfide ores are depleted, more and more attention has been put on low grade nickel laterite. In this paper, based on the process study of our lab team, the process of chloride segregation of laterite with the low Fe and high Mg ore from an area of foreign as raw materials was studied.By thermodynamic calculation, the thermodynamic equilibrium diagram of vapor composition was drawn. Applying FactSage software and database, phase diagram of the M-C-O, MO-SiO2, Ni-Fe-O, Ni-Fe alloy, Ni-Fe alloy magnetic and mixed chloride have been studied. In order to achieve good segregation effect, the system must be weak reducing atmosphere and high temperature. The production, water quenching at 850℃, should control the nickel mass fraction of nickel-iron alloy≥5%.To study the generation of hydrogen chloride, the reaction process of SiO2 and CaCl2 was studied:below 200℃, CaCl2·2H2O was dehydration. Between 200℃to 750℃, there was not valid reaction. Between 750℃to 800℃, with the ratio of SiO2 and CaCl2 2:1 and 1:1, the Ca2Si03Cl2 was generated, as the temperature increases, Ca2Si03Cl2 decomposed with hydrogen chloride gas released; with the ratio 1:2, Ca3Si05-CaCl2 was generated, as the temperature increases, it did not break down, however, excessive calcium chloride volatilized due to vapor pressure decreased.The researches of chlorination process of metal oxide indicated that at about 600℃, serpentine decomposed, which increased the reaction interface of the chlorination process. After 700℃, a higher HCI partial pressure was needed. This Causes the rate of nickel chloride decreased first and then increased as the temperature increased from 600℃～1000℃. Based on kinetics calculations of chlorination of nickel oxide, the reaction accords with the "shrinking core model" of gas-solid reactions, which was controlled by the internal diffusion, the apparent activation energy value was 32.42kJ·mol-1.The results of the formation and growth process of metal particles showed that with the increase of steam pressure, the concentrate grade decreased and the yield of nickel increased gradually. Nickel-iron alloy particles can segregate on the carbon surface and rough surface of silicate. The growth of particles was easy on the carbon surface, but on the surface of silicate particles, it was very difficult. At low temperature, the particles growth mechanism is small nickel-iron alloy particles move to a more favorable position which is the contact point of two particles; At high temperature conditions, the particles growth mechanism is the small melting particles evaporated and adsorbed to the surface of large one.The studies to phase transformation of chloride segregation revealed that with the increase of temperature, between 400℃and 600℃, magnesium carbonate decomposed; Between 600℃and 700℃, the serpentine phase decomposes and disappeared, replaced by the Fe-rich and Ca-rich olivine phase. It was apparent that the phases formed were stable and the process was not reversible during reduction at elevated temperatures.更多还原