Synergistic pyrolysis with Refuse-Derived Fuel (RDF) can neutralize bauxite residue

It is estimated that approximately 1.2 tons of bauxite residue (BR) was generated per tonne of alumina produced, and less than 3 % of the annual generation is used. The high alkalinity makes it technically and economically challenging to reuse this material. The study investigated the alkaline neutralization of BR through synergistic pyrolysis with products from Refuse-Derived Fuel (RDF). Two types of RDF, from different producers, were used and BR (pH 12) was generated by an alumina refinery in Brazil. Different mass proportions (0, 10, 20 and 50 % w/w) of RDF were used for synergetic pyrolysis. A pyrolysis was performed at 200, 400, 600, and 800 degrees C using muffle furnace and crucibles with a residence time of 20 min. The pH of the mixtures after pyrolysis, decreased as the proportion of RDF increased. The results showed that the neutralization of the BR occurred at temperatures of 200 and 400 degrees C. However, as the temperature increases (600 and 800 degrees C) the pH neutralization is reduced. The best performance was observed for 50 % RDF at 400 degrees C with a final pH 8 (33 % reduction). Synergistic pyrolysis of BR and RDF was effective in promoting reduction in the alkaline content of the bauxite residue.