Multi-material circulation optimization of the calcification-carbonation process based on material balance and phase transformation for cleaner production of alumina

The calcification-carbonation process is a novel cleaner production method to recover alkali and alumina from bauxite residue and obtain harmless residue with low aluminum content and no alkali. At present, this method is only limited to laboratory research and has not been put into industrial application. The reason is that the existing research only focuses on the mineral transformation of the solid phase, but lacks consideration of the concentration and availability of the extract in the liquid phase. The calcification-carbonation process is a complex hydrometallurgical series process. Without a complete continuous production line, it is difficult to evaluate the reliable concentration distribution in the system. In order to obtain the concentration distribution of Na₂O and Al₂O₃ in the whole calcification-carbonation process, this paper adopts a combined research method of metallurgical process simulation and experimental research based on the existing solid phase transformation theory. This method turns out to be effective and inexpensive to develop new technology at present. On the basis of the previous experimental results of solid structure transformation and parameter optimization, this study employs the material balance analysis module of METSIM software to analyze the distribution and concentration of Na₂O and Al₂O₃ in the calcification-carbonation process. Combined with the concentration characteristics of input and output and the experimental verification of the key steps, a multi-material circulation optimization scheme of the calcification-carbonation process through the integration of liquid material flow resources is proposed to realize the effective recovery of low-concentration Al₂O₃ and the circulation of alkali liquor in the system. It promotes the recycling of resources and cleaner production of alumina.