Physico-chemical features of acid decomposition and production of extraction phosphoric acid based on moroccan phosphorites

The results of research on the establishment of physicochemical features of acid processing of North African (Moroccan) phosphorites, as well as their influence on the technological process and technical and economic indicators of extraction phosphate acid (EPA) production are presented. Significant differences have been established in the nature of the acid decomposition process, syngony and the size of the formed calcium sulfate crystals for different grades of phosphorites, which is due to a significant influence on the decomposition process not only of the technological mode of the process, but to a large extent differences in the mineralogical composition of phosphate ores. Thus, the increased content of carbonate apatites in phosphorites of the K-9 and K-10 grades led to a higher reactivity in the region of low concentrations. At the same time, the high reactivity of carbonateapatites leads to a number of negative processes, in particular, abundant foaming and passivation of grains of phosphate raw materials with fine-crystalline calcium sulfate precipitate, formed due to the rapid supersaturation of the system, which in turn leads to a sharp decrease in the degree of decomposition. A significant difference in the nature of calcium sulfate crystallization for the conditions for obtaining EPA from the known data was established, which made it possible to conclude that the rate and nature of the process of calcium sulfate recrystallization in the CaO-P₂O₅- H₂O system is determined not only by temperature, sulfate regime and P₂O₅ content in the liquid phase, but also by the nature and composition of phosphate raw materials. Based on experimental data, conclusions were drawn about a decrease in power during the transition from apatite to phosphorites from 21.89 to 24.23% (depending on the brand of Moroccan phosphorite), a significant increase in the load on filters and a decrease of 1.5–2 times in the amount of fluorine compounds released into the gas phase during decomposition.

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