Thermal regeneration of waste foundry phenolic sand in a lab scale fluidized bed

ABSTRACT Improper disposal of sand used in molding processes after casting increases logistical costs and environmental impact because of the presence of the phenolic resin in its composition. The regeneration process of waste foundry phenolic sand (WFPS) aims to recycle this material. As mechanical regeneration methods are not efficient to guarantee 100% cleaning of the sand grains and their use again in the molding process, this work investigated the efficiency of a method of thermal regeneration of this type of residue that can be employed as a complementary procedure. A laboratory-scale fluidized bed reactor was designed and built to regenerate WFPS that was previously treated by a mechanical method. The methodology used to design and construct the fluidized bed prototype is described, as well as the characterization of the residual, the standard clean sand and the regenerated sand. The results of the thermal regeneration in the fluidized bed were very satisfactory with respect to the regeneration efficiency. For the nine process conditions tested, loss on ignition values were reduced when compared to standard clean sand. This study presents the advantages of a combination of two processes, mechanical and thermal regeneration, which allows to reduce the time and eventual temperature of resin removal due to the partial removal of the resin layer or its weakening during the mechanical regeneration process. Of the nine process conditions tested, six had loss on ignition values below the CSS. Thus, the thermal regeneration in the fluidized bed results was quite satisfactory in relation to the regeneration efficiency. RESUMO A disposição inadequada de areia de processos de moldagem após vazamento do metal fundido aumenta os custos de logística e impacto ambiental por causa da presença da resina fenólica na sua composição. O processo de regeneração de resíduos areia fenólica de fundição (RAFF) objetiva a reciclagem deste material. Como os métodos de regeneração mecânica não são eficientes para garantir 100% de limpeza dos grãos de areia e sua utilização novamente no processo de moldagem, este trabalho investigou a eficiência de um método de regeneração térmica deste tipo de resíduo que pode operar de forma complementar. Um reator de leito fluidizado em escala de laboratório foi projetado e construído para regenerar RAFF que foi tratada anteriormente por um método mecânico. A metodologia utilizada para projetar e construir o protótipo de leito fluidizado é de