Experimental Study On Magnetic Iron In Pyrolysis Furnace Slag

The high oxygen potential converting technology has been widely applied in copper pyrometallurgy process, which can improve the copper matte grade and make the content of magnetite in slag increase. In order to improve the recovery of copper, the magnetite must be reduced to make the viscosity of copper molten slag decrease so that accelerate the settling and separation of copper droplet from slag. Aiming at cutting the carbon emission in copper smelting process, a new technology is proposed that using waste cooking oil as the reductent to reduce the magnetite in copper smelting slag. The main contents are as follows.1. The elements, chemical composition as well as the physical and chemical properties of waste cooking oil are analyzed. The major elements of waste cooking oil are carbon, hydrogen and oxygen. The fatty acids in waste cooking oil are oleic acid, linoleic acid, palmitic acid and stearic acid, et al. The waste cooking oil shows the characteristics of large density, high viscosity and acid value as well as high water content.2. The pyrolysis characteristics of waste cooking oil are investigated by the thermogravimetric analysis coupled with fourier transform infrared spectroscopy (TG-FTIR) and the kinetic parameters are calculated through Coats-Redfern method under linear temperature increase condition. The distribution of the pyrolysis products of waste cooking oil under constant temperature conditions are researched in a fixed bed pyrolysis system. The results show that the pyrolysis of waste cooking oil under non-isothermal conditions can be devided into three steps including the volatilization of light components below 180℃, the pyrolysis of heavey components at the temperature of 180-200℃, the polymerization and crack of the residues over 450℃. The products of waste cooking oil pyrolysis under linear temperature increasing include hydrocarbons, ethers, aldehydes, carboxylic acids, H2O and CO2. The pyrolysis of waste cooking oil is a second order reaction according with three dimensional diffusion model. Under constant temperature conditions, the products of waste cooking oil pyrolysis contain tar, coke, H2, CH4, CO, C2H4 and C2H2 at the temperature range of 600-900℃ while coke, H2 and CO at that of 1000-1300℃.3. The reduction characteristics of magnetite in copper electric furnace slag using waste cooking oil are investigated. The phase transitions before and after reduction are researched by XRD and SEM. And the reduction kinetic model of magnetite in copper electric furnace slag by waste cooking oil is built using experimental data and the accuracy of the model is verified. The results show that the magnetite content in copper slag decreased with the reduction time increasing and raising temperature is conducive to the reduction of magnetite in slag. The magnetite in copper slag gradually transform to fayalite and the viscosity of copper molten slag reduced with the magnetite content decreasing in the process of reduction. The reduction of magnetite in copper molten slag using waste cooking oil is a first order reaction and the reaction rate limiting step is the mass transfer of Fe3O4 through the liquid boundary layer. The reduction ratio of magnetite in copper smelting slag using waste cooking oil can be expressed as...