Nurila Sagindikova

The purpose of this study is to develop a multiphysical model of agglomeration of low-grade phosphorites with the addition of phosphate-siliceous shales and oil sludge. To achieve these tasks, a numerical approach was used in the COMSOL Multiphysics environment, based on solving the related problems of heat transfer and hydrodynamics during heat treatment of the material. A laboratory vertical tubular furnace made of heat-resistant quartz glass with electric heating was used to study the effect of the temperature field and the velocity of gases on the degree of sintering and the dynamics of phosphorous agglomerate formation under various technological conditions. It has been established that the optimal temperature for the agglomeration process is a layer temperature of 950–1000 °C at a gas flow rate of 1.5–2 m/s, which ensures the formation of durable granules and minimizes sintering heterogeneity. The maximum sintering layer height of the test charge reaches 210–230 mm at pressures of 0.015–0.027 MPa. A comparison of the numerical simulation results with experimental data showed a good agreement, which confirms the practical significance of the proposed model for the design and optimization of industrial processes of agglomeration of phosphorous raw materials. Modern physical and chemical analyses have established the phase, microstructural, and element-by-element characteristics of the studied phosphate-siliceous shale and the product of agglomeration firing. The results of modeling the hydrodynamics of the charge agglomeration process can be recommended to increase the efficiency of processing phosphate-containing waste and reduce energy consumption.

The article presents the results of physico-chemical and thermodynamic studies of the use of petroleum coke obtained from oil refining waste for use in agglomeration of phosphate raw materials as fuel.Using the method of thin-layer chromatography and IR spectroscopy, groups of organic compounds in the composition of heavy waste used for slow coking of petroleum coke were determined. The obtained results of the analysis of heavy oil waste showed a high content of strong aromatic groups 35.1-54.1%, resin groups 12.0-25.7%, paraffin groups 3.0-41.4%. All these indicators indicate the suitability of heavy oil waste for the production of petroleum coke.The element composition and microstructure of the resulting petroleum coke, which contains C-78.56%, Te-4.05%, Al-12.14%, Si-1.18%, were identified using a scanning electron microscope JSM-6490LV.The results of thermodynamic studies of reactions characteristic of agglomeration firing of a working mixture of phosphorite-phosphate-siliceous shale - neftekox composition are presented, performed using the HSC-5.1 Chemistry software package developed by Outokumpu Research Oy. The results of calculating the Gibbs energy change from the temperature of decarbonization reactions indicate the thermodynamic probability of all studied reactions occurring in the high-temperature region. Moreover, the probability of 5.6 reactions is possible only above 1200K. Thermodynamic modeling of decarbonization of the working systems СаСО_з – С – С₆Н₆ –О₂ и СаСО₃ – С – С₆Н₅О – О₂ were performed in the temperature range 500-1500 K and pressures 0.1-0.01MPa, typical for the agglomeration process using the Astra-4 software package.The results of graphical dependences of the equilibrium distribution of the main components of calcium and carbon depending on temperature and pressure are of the same type. Moreover, as the pressure decreases, the possibility of formation of CaO and CO₂ per 100 K moves to a low-temperature region.