Experimental investigation and computer simulation of the continuous flash converting process of solid copper mattes

Experimental tests and mathematical modeling were conducted to elucidate the main features of the processes taking place in the shaft of the continuous flash converting furnace for solid copper mattes. The experiments were performed in a large laboratory furnace. Input variables tested included matte grade, oxygen concentration in the feed gas, particle size of the feed material, oxygen-to-matte mass ratio, solid feed rate, and two types of burner configurations. Output variables included fractional conversion of the oxidation reactions, fraction of sulfur remaining in the particles, quality of conversion, change in copper-to-iron atomic ratio, size distribution, mineralogy, and morphology of the reacted particles.; The mathematical formulation was made incorporating the turbulent transport of mass, momentum, energy, and gas-particle kinetics. In the formulation, the gas phase is treated in an Eulerian framework, whereas the particle phase is viewed from a Lagrangian framework. Key features include the use of the k-ϵ model for gas-phase turbulence, the particle cloud model to treat particle dispersion, the discrete-ordinates method to solve the radiation field, and a kinetic model for the oxidation of matte particles. The mathematical model is fully three-dimensional and set up in Cartesian coordinates.; The experiments showed substantial differences in the oxidation behavior of high-grade (72% Cu) and low-grade (58% Cu) matte particles. Low-grade matte particles reacted more evenly throughout the furnace, increased in size, and experienced no substantial fragmentation during oxidation. High grade matte particles tended to be oxidized unevenly and experienced severe fragmentation with the generation of dust. The order of effect of the input variables was found to be: oxygen-to-matte mass ratio > particle size > oxygen concentration. Microscopic examination revealed that copper and iron oxides were the major oxidation products, with little elemental copper produced in the flash converting furnace shaft.; The results of the mathematical model showed reasonable agreement with the experimental values of fractional conversion and sulfur remaining in the particles. The fields of gas velocity, temperature, and composition in the laboratory furnace showed that the converting reactions were mostly completed within 40–60 cm below the burner tip. The paths of particle clouds in the laboratory furnace were tracked in terms of their location, temperature, and composition. The simulation of an industrial flash converting furnace was performed. Results showed that particle radiation scattering can be neglected for most modeling purposes, and that high oxidation rates, even distribution of particles, and an efficient use of the reactor volume is obtained with a burner having a distributor cone.