Waste to Wealth Strategy: Preparation and Properties of Lightweight Al2O3-SiO2-Rich Castables Using Aluminum Dross Waste

Aluminum dross is a well-known industrial waste generated in the aluminium industry, and its recycling and reuse is still a worldwide issue. Herein, aluminum dross waste (ADW) was recycled to progressively replace the aggregate fraction of clay at 70, 75, 80, 85, and 90 wt% for the fabrication of Al2O3-SiO2-rich porous castable refractories. Their physical properties and mechanical behavior were assessed by the measurement of linear shrinkage rate, bulk density, apparent porosity, cold crushing strength, and thermal conductivity. The microstructure and phase evolutions were analyzed via scanning electron microscopy (SEM) and X-ray diffraction (XRD). The incorporation of 85 wt% of ADW allowed the development of a waste-containing conventional refractory castable with improved properties as compared to those of the other samples. The sustainable refractory castable exhibited decent thermal conductivity and physical and mechanical characteristics, and is suitable for application as reheating furnace lining. It is a “green” practice to partially replace the traditional raw materials with industrial waste in the manufacture of conventional refractory castables and provides environmental and economic benefits.

Research on the Preparation Parameters and Basic Properties of Premelted Calcium Aluminate Slag Prepared from Secondary Aluminum Dross

Secondary aluminum dross is a byproduct of the electrolytic aluminum industry, whose main components are Al2O3, AlN and Na3AlF6. Secondary aluminum dross is a type of hazardous waste, with a tremendous yield every year. Realizing the harmless treatment or resource utilization of secondary aluminum dross has important economic and social benefits. In the present research, the process of preparing premelted calcium aluminate slag used for molten steel refining from secondary aluminum dross was studied in detail. Firstly, the chemical composition and phase component of secondary aluminum dross were analyzed systematically. Then, according to phase diagram analysis and melting point measurement, the appropriate mixing ratio of CaO and secondary aluminum dross and the appropriate calcination temperature were determined. On this basis, an experiment of premelted calcium aluminate slag preparation was carried out in a tubular resistance furnace. The phase component and micromorphology of the premelted slag were analyzed by XRD and SEM. The results show that the main component of the premelted calcium aluminate slag is 11CaO·7Al2O3·CaF2 phase with a low melting point. The original Na3AlF6 phase, which is the cause of leachable fluoride in secondary aluminum dross, disappears totally, and there is no water-soluble fluoride detected in the leaching toxicity detection. The research indicates that the process of preparing premelted calcium slag from secondary aluminum dross is feasible, which provides a helpful reference for the resource utilization of secondary aluminum dross.