Wenju Tao

Equivalent conductivity and its activation energy of NaF-AlF3 melts

Electrical conductivity of NaF-AlF3 melts was measured by continuously varying cell constant (CVCC) technique. Relationships between equivalent conductivity at 990-1030℃ and temperature and composition, and relationship between equivalent conductivity activation energy and composition of the melts were then studied on the basis of two-step decomposition mechanism of AlF6(superscript 3-). According to the changes of molar fractions of different anions in NaF-AlF3 melts, courses of dependence of equivalent conductivity and its activation energy on composition were analyzed. The results show that the influence of temperature on equivalent conductivity of the melts is small in the researched temperature range, and equivalent conductivity increases with increasing the molar fraction of AlF3; there is a minimum point in the activation energy-composition curve when molar fraction of AlF3 is 0.29.

Study on the thermal decomposition of aluminium chloride hexahydrate

ABSTRACT This paper presents a preliminary study on the thermal decomposition process of aluminium chloride hexahydrate (AlCl3·6H2O) crystal with non-isothermal thermal kinetic analysis and static calcination experiments. The ‘kinetic triplets’ including activation energy, pre-exponential factor and mechanism function for the decomposition reaction were determined through thermal analysis from Differential Scanning Calorimetry–Thermos Gravimetric Analysis results. It is found that the average activation energy and pre-exponential factor were 59.668 kJ mol−1 and 6.67 × 105 min−1, respectively, and the most suitable conversion function was . The emission rates of the gaseous products, water (H2O) and hydrogen chloride (HCl), were calculated from the chlorine content evolution obtained from the static calcination tests, respectively. The phase transformation and the change of particle morphology during the decomposition process were also investigated through X-ray diffraction and scanning electron microscope technologies.

Thermo-electric field analysis on heat recovery aluminum reduction cell

The distribution of the electricity and the thermal field directly affects the stability, current efficiency and energy consumption of electrolysis cells. In this paper, by using finite element software ANSYS, the thermoelectric field of 2000 A heat recovery aluminum reduction cell model was built. Through the use of APDL, a parametric model was established and then the thermoelectric field was simulated. The results indicate that the model is accurate. On the basis of the established model, the thermoelectric field was further analyzed.

Finite element analysis of thermo-electric coupled field in 400kA large-scale aluminum reduction cell

In order to apply non-grid-connected wind power to the aluminum electrolysis industry, it is necessary to describe and study characteristics of temperature field of present cell. In this paper, a thermo-electric mathematical model was built up by using ANSYS finite element analysis software, and the 3D coupled thermo-electric field of 400kA aluminum electrolysis cell was analyzed. It is concluded that if applying non-grid-connected wind power to the large-scale industrial aluminum reduction cell, some structural improvement should be made in order to make thermo field more stability against current change. The results obtained provide a basis for the further structural improvement of the cell.

Discussion on Alumina Dissolution and Diffusion in Commercial Aluminum Reduction Cell

Dissolution model for smelting grade alumina (SGA) in the commercial reduction cell should take into account both thermodynamic and kinetic factors because of the specific dissolution environment in the cell referring to bath chemistry condition and feeding strategy. Earlier dissolution model are mainly focused on the dissolution mechanism and laboratory kinetics, while few considerations on the effects of industrial dissolution kinetics. This paper presents measurements on the velocity (by adding traceable element—strontium ‘Sr’) of the bath were carried out on two 400 kA commercial cells, and the effects on the SGA dissolution rate are discussed to support an initial investigation for the establishment of an advanced dissolution model for alumina.

Impact of Anodic Large Bubble on Horizontal Current Distribution in Metal Pad of an Aluminum Reduction Cell

In this paper, the effects of anodic large bubble including bubble position and coverage on horizontal current (HC) in the metal pad in an aluminum reduction cell have been investigated using a three-dimensional electric model. Results show that the HC, the maximum HC, and inward HC flow are greatly influenced by the large bubble position and coverage. It is necessary to take the large bubble into account when we study the horizontal current in a cell.

Research on form of Nd-F-O complex ions in NdF3-LiF-Nd2O3 melts

It is important to study the ionic structure of NdF<inf>3</inf>-LiF-Nd<inf>2</inf>O<inf>3</inf> melts. In this paper, dissolution mode of O^2- in LiF-NdF<inf>3</inf> melts in which the concentration of NdF3 was lower than 20mol% was studied by cryoscopic method. It was thought that O^2- dissolved as the equation: NdF<inf>4</inf>^-+ O^2- +F^- = 3D NdOF<inf>5</inf>^4- with Flood model on the basis of hypothesis of ideal mixing of the ions in the melts.