Aluminium Recycling in Single- and Multiple-Capillary Laboratory Electrolysis Cells

This work is a contribution to the approach for Al purification and extraction from scrap using the thin-layer multiple-capillary molten salt electrochemical system. The single- and multiple-capillary cells were designed and used to study the kinetics of aluminium reduction in LiF–AlF3 and equimolar NaCl–KCl with 10 wt.% AlF3 addition at 720–850 °C. The cathodic process on the vertical liquid aluminium electrode in NaCl–KCl (+10 wt.% AlF3) in the 2.5 mm length capillary had mixed kinetics with signs of both diffusion and chemical reaction control. The apparent mass transport coefficient changed from 5.6∙10−3 cm.s−1 to 13.1∙10−3 cm.s−1 in the mentioned temperature range. The dependence between the mass transport coefficient and temperature follows an Arrhenius-type behaviour with an activation energy equal to 60.5 J.mol−1. In the multiple-capillary laboratory electrolysis cell, galvanostatic electrolysis in a 64LiF–36AlF3 melt showed that the electrochemical refinery can be performed at a current density of 1 A.cm−2 or higher with a total voltage drop of around 2.0 V and specific energy consumption of about 6–7 kW.kg−1. The resistance fluctuated between 0.9 and 1.4 Ω during the electrolysis depending on the current density. Thin-layer aluminium recycling and refinery seems to be a promising approach capable of producing high-purity aluminium with low specific energy consumption.

Analytical and Experimental Studies of Rapid Cloth Drying for Technological Innovation

This paper presents analytical and experimental studies of a rapid cloth drying process. The mathematical models are developed from mass diffusion of wet clothes under hot and dry air conditions There are three critical factors: air temperature, air humidity, and the mass transport coefficient. Experiments of outdoor cloth drying are investigated as a benchmark. It is found drying duration is about 2-3 hours for satisfactory drying states under sunny weather. To reduce drying period, the mass transport coefficient is the highest sensitive factor while it can be adjusted by air speed through clothes. Experimental results of a rapid cloth drying heat pump show that the drying period can be reduced to 12 minutes with COP of 5.4. This understanding is able to strengthen development of rapid cloth drying for technological innovation.

Mathematical Modeling of a DMFC Cathode with a Double Catalyst Layered Structure Membrane Electrode Assemblies

Membrane electrode assemblies (MEA) is the key component of a direct methanol fuel cell (DMFC) and its structure and fabrication technology influenced the performance of DMFC a lot. A novel structured MEA including a hydrophilic inner thin catalyst layer and a traditional outer catalyst layer, provide higher performance. To optimize the combination of the two catalysts layer a mathematical model based on Tafel type kinetics and semi-empirical mass transport coefficient was applied. The simulation of cathode overpotential results showed a DMFC with a 5μm thick inner Pt Blk catalyst layer and an 8μm thick outer 40wt%Pt/C catalyst layer as cathode electrode was the best.