Calcination of phosphoric rock by plasma torch, to obtain thermophosphates fertilizers

Abstract

A plasma torch reactor was used to obtain thermo phosphate fertilizers by subjecting the phosphoric rock (PR) from the central eastern region of the Boyacá Department, Colombia, in the municipalities of Iza and Sogamoso. A plasma torch equipment Victor Cut Master A60^TM, with 7.6 kW as nominal power, reaching temperatures of process higher than 10000 °C, was used. The particle size of mineral treated was 0.075 mm, which was calcined during 30 s and 40 s. The experimental results show a maximum concentrations of total phosphorus and assimilable phosphorus corresponding to 27.0 and 3.07 %  P₂O₅ respectively for Iza sample, while the results for the Sogamoso one were 33.12 and 4.83 % P₂O₅, respectively. The total phosphorus analyses were carried out by X ray fluorescence, while the assimilable phosphorus was determined from the extraction with neutral ammonium citrate solution and quantified by visible ultraviolet spectrophotometry. The main crystalline phase in each sample was determined by X ray diffraction. The results indicate that the samples are constituted mainly by fluorapatite carbonate, ranged between 53.0 and 87.0 wt.% for the Iza one and between 60.6 and 93.7 wt.% for that from Sogamoso. The energy consumption to obtain the thermophosphates was very low, ranged between 0.64 kW-h/Kg and 1.14 kW-h/Kg, for electrical current of 30 A and 45 A, respectively.