Xueming Lv

Thermal Analysis Kinetics of the Solid-State Reduction of Nickel Laterite Ores by Carbon

Non-isothermal multiple scanning rate analysis method was used to analyse the solid-state reduction of nickel laterite by carbon. According to the TG curves, the activation energies were calculated and the most probable mechanism functions were determined by the Malek method. The results show that the process can be divided into three stages according to the reaction degree (α): 0–40%, 40–70%, 70–100%, respectively. In the stage of 0 ≤ α ≤ 0.40, the most probable mechanism function fits the chemical reaction order function. In the stage of 0.40 ≤ α ≤ 0.70 and 0.70 ≤ α ≤ 1.0, the process may not be exactly described by one mechanism function.

Drying kinetics of Philippine nickel laterite by microwave heating

ABSTRACT In this study, microwave heating was used to dry nickel laterite, which contains significant quantities of free water, crystal water, and hydroxy water. The results show that the main phase of crystal water is Ca3Al6Si10O32(H2O)13, and the main phases of hydroxy water are FeO(OH) and Mg5(Al, Cr)AlSi3O10(OH)8. The microwave drying process of nickel laterite can be divided into two stages: the removal of free water and the coupled removal of free water, crystal water, and hydroxy water. The effect of particle size and microwave power output were studied, and these indicate that the drying time and specific energy consumption decrease with increasing particle diameter and microwave power. The effective diffusivity and activation energy were calculated, and these are larger in the second stage than that in the first stage. The activation energies are 27.66 and 32.80 W/g for the first and second stages, respectively. The phase transition of the product, schematic drying mechanism, and feasibility analysis of the microwave drying process are also discussed.

Analysis of Microwave Drying Behavior of Nickel Laterite

In this study, microwave heating was used to dry the nickel laterite which contains plenty of free water, crystal water and hydroxy water. The results showed that compared with the conventional drying process, the microwave drying greatly improved the drying efficiency of nickel laterite. The whole microwave drying process can be divided into three stages according to the drying rates, namely, the rising stage, stable stage and declining stage. The effects of microwave power output and particle size were also studied in the range of 0.8–2.0 KW microwave power and 3–6 cm of particle size. The results showed that the drying time significantly decreased with the increase of microwave power and decrease of particle size. The phases transition of the sample during the microwave drying process were also discussed.

Preparation of Ferronickel from Nickel Laterite Ore via Semi-molten Reduction Followed by Magnetic Separation

The rotary kiln-electric furnace (RKEF) process is the main method for producing ferronickel from nickel laterite ore. However, this process is energy intensive as it involves several high temperature steps. Therefore, a novel process is proposed to directly produce ferronickel from nickel laterite ore by semi-molten reduction, which is expected to be realized in a rotary hearth furnace (RHF). The RHF process is able to shorten the flow sheet, decrease the reaction temperature as well as reduce energy consumption. In this study, the influence of basicity on reduction of nickel laterite ore was investigated. The results showed that it is possible to produce the ferronickel nugget directly at 1400 °C when the quaternary basicity [(mCaO + mMgO)/(mSiO2 + mAl2O3)] was fixed at 0.60. Under this experimental condition, the grade and the recovery ratio of nickel reached 11.53% and 98.59%, and the grade and recovery ratio of Fe were 84.16% and 68.72%, respectively.

Non-isothermal kinetic studies on the carbothermic reduction of Panzhihua ilmenite concentrate

ABSTRACT In this study, the kinetics of reduction of Panzhihua ilmenite concentrate by graphite under an argon atmosphere using the non-isothermal method was investigated by thermogravimetric analysis and mass spectrometry at heating rates of 10, 15, and 20 K·min−1. Both the reactants and products were analysed by X ray powder diffraction (XRD) and scanning electron microscopy (SEM) to identify their phases and morphologies, respectively. The Málek method was used to analyse the reaction mechanism and model function. The results show that the reduction of ilmenite concentrate proceeded in three stages: mixed control, chemical reaction, and three-dimensional diffusion in that order. The Starink method was used to calculate the activation energy. The average apparent activation energies for the carbothermic reduction of raw ilmenite concentrate were 478, 617, and 468 kJ mol−1 for the first, second, and third stage, respectively. The oxygen potential of tail gas during the reduction process was also obtained.