Neutralização da alcalinidade de resíduo de bauxita por pirólise sinérgica com produtos provenientes de resíduos sólidos urbano

Abstract

Large-scale use of bauxite residue, a byproduct generated during the refining process of the ore used for aluminum production, has been a challenge for more than a century. The large mass continuously produced, associated with its high alkalinity, makes it technically and economically challenging to use the material in the production of other products. It is estimated that there are more than 1.5 billion tons of bauxite residue stored globally, and less than 3% of the annual generation is used, mainly for cement production. Given the expected growth in aluminum production and the consequent increase in bauxite residue generation, finding new ways to process and use this material is even more relevant. The pH neutralization of bauxite residue with CO2 and organic acids is well-known and has been published by several authors. However, recent studies show that bio-oil produced from different types of biomass pyrolysis and synergistic pyrolysis of biomass with bauxite residue are capable of promoting bauxite residue neutralization. The aim of the study was to investigate the alkaline neutralization of bauxite residue through synergistic pyrolysis with products from municipal solid waste (MSW). Two types of MSW were used in the form of refuse-derived fuel (RDF) from different producers, and bauxite residue was generated by the alumina refinery from Companhia Brasileira de Alumínio (CBA). Different mass proportions of RFD were used: 0, 10, 20, and 50%. A pyrolysis test was performed using muffle and crucibles, with a residence time of 20 minutes at four different temperatures: 200, 400, 600, and 800 oC. The results indicated that neutralization of the bauxite residue occurred at temperatures of 200 and 400 oC when 50% of RFD was used in the blend. The best performance was observed at 400 oC, with a final pH of 8. Synergistic pyrolysis of RFD and bauxite residue was effective in promoting a reduction in the alkaline content of the latter.