Research On Selective Leaching Of Calcium-based Active Components Of Converter Steel Slag

As a big country of iron and steel consumption and CO₂ emission,China is facing serious environmental problems and huge pressure to reduce emissions.Use of converter steel slag rich in calcium carbonate CO₂ fixation,and can realize the carbon dioxide of fixed in position,produce high stability at the same time,the value-added of calcium carbonate products,realize the resource and value-added utilization of solid waste,emissions of carbon dioxide has played a positive role.In this paper,the leaching behavior of calcium and its main elements in converter steel slag under conventional and ultrasonic intensification conditions is systematically studied.The main contents are as follows:?1?The phase composition of the converter steel slag was analyzed and characterized.The converter slag is mainly composed of calcium oxide?CaO?,calcium ferric acid?CaFeO₂?,ferrous oxide?FeO?,two calcium silicate?Ca₂SiO₄?,calcium titanate?Ca TiO₃?and RO phase.?2?The effects of leaching time,reaction temperature,solid to liquid ratio and initial acetic acid concentration on the leaching behavior of calcium,iron and magnesium were investigated in a single factor experiment.It is found that the rate of calcium ion leaching is very rapid,the concentration of initial acetic acid is increased,and the solid to liquid ratio and the reaction temperature are reduced,which is beneficial to the leaching of calcium and the increase of the leaching rate of calcium ions.It is also found that prolonging the reaction time,increasing the solid-liquid ratio and reducing the initial acetic acid concentration are beneficial to remove the impurity ions in the solution,and the selective leaching rate of calcium is increased.When the leaching time is 60 min,the leaching temperature is 70oC,the ratio of solid to liquid is 1:3,the concentration of acetic acid is 2 mol/L,the concentration of calcium ion in the leaching solution of steel slag with 0⁹6?m is as high as 25.82 g/L,the selectivity of calcium ion is up to 99.8%,but the leaching rate of calcium is only 27.11%.?3?The effects of leaching time,leaching temperature,solid-liquid ratio,initial acetic acid concentration and ultrasonic power on the leaching behavior of calcium,iron and magnesium in steel slag were investigated.It is found that reducing the particle size and solid to liquid ratio of steel slag,increasing the concentration of acetic acid and ultrasonic power are beneficial to increase the leaching rate of calcium.Reducing the size of steel slag,solid-liquid ratio and initial acetic acid concentration are beneficial to increase the selectivity of calcium leaching.At the same time,improving the leaching temperature is beneficial to improving the filtration performance of the leach liquor.When the leaching time is 60 min,the leaching temperature is 60oC,the ratio of solid to liquid is 1:3,the concentration of acetic acid is 2 mol/L,the ultrasonic power is 600 W,the concentration of calcium ion in the slag leaching solution of 0⁹6?m is as high as 31.1 g/L,compared with the conventional leaching,the leaching rate of calcium is increased by 5.55%.At the same time,the selectivity of calcium ion is higher than 99%.?4?The kinetics of calcium in the converter steel slag in the leaching process is analyzed.It is found that the slag is controlled by the internal diffusion of the solid product layer in the conventional leaching process.The apparent activation energy of the calcium leaching process is 8.714 kJ/mol.The reaction progression of the initial acetic acid concentration and the steel slag particles is respectively obtained by fitting.1.582 and 1.0816,a kinetic equation for the conventional leaching process of steel slag was established.