Kinetics and synthesis of formation of phosphate composites from low-grade phosphorites in the presence of phosphate–siliceous shales and oil sludge

Abstract The purpose of this work is to study the kinetic features of the formation of phosphate agglomerates from low-grade phosphorites in the presence of phosphate–siliceous shales (PSSs), coke, and oil sludge. The selection of the Yerofeyev–Kolmogorov equation characterizing heterogeneous processes is justified by a comparative analysis of the Aravi equation used for the crystallization processes. The PSS/coke–oil sludge system has been studied in the temperature range of 1,073–1,373 K in the air environment, typical for agglomeration firing. Thermogravimetric analysis, X-ray fluorescence analysis, scanning electron microscopy, and IR spectrometry were used to study the features of oil sludge and the physicochemical characteristics of the phase composition and mineralogical structure of the firing products. The effect of the modulus of acidity and temperature on the strength parameters of phosphate agglomerate was studied for charges of 0.7–0.83, providing mechanical strength of 3.3–3.4 MPa at temperatures of 1,313–1,318 K of the onset of deformation. The calculation results of the apparent energy corresponding to 4.15–22.99 kJ·mol −1 indicate complex diffusion–reaction characteristics of the agglomeration process in the presence of PSS and oil sludge.