Experimental Research On Dephosphorization Of Converter Slag By Microwave Heating And Carbon Thermal Reduction

Integrated utilization of resources is an important strategy to achieve sustainable development of environment and promote cyclic economy. The steel slag has a problem of phosphorus enrichment. There will be a limit on steel slag recycling for steel plant. In terms of environment protection, it's necessary to develop the technology of dephosphorization, as well as recycle Fe,Mn. The microwave heating is an effective way of heating high dielectric consuming raw materials.With microwave heating,the converter steel slag is reduced by carbothermic reduction. Under different processing conditions, it studies the reductive kinetics of iron oxides and phosphorus, which are generated by carbothermic reduction with microwave heating; and also the distribution of phosphorus in gas, slag and iron.The microwave heating can promote the redction of steel slag. It achieves low temperature reduction dephosphorization within 1000~1400℃. The maximum dephosphorization rate of converter slag is up to 91.5%, with more than 85% of phosphorus removed by gasifying. The microwave-heating carbothermic reduction of slag can produce compact Fe-C alloy spheres. The maximum diameter of these alloy spheres is up to 18mm. So, it is easy to extract these big one from the slag. The rest Fe-C alloy spheres, which diameter is under 3mm, are dispersed equably in slag. And they will be separated from the slag by screening.Within 1100~1400℃, the dephosphorization rate increases with temperature increment. At 1100℃, the dephosphorization rate is 80%, while at the temperature of 1400℃, the dephosphorization rate will rise up to 87.5%. If the warm-keeping time is extended properly, then the reduction will be much better. Keeping the reducting materiel warm for 30 minutes will make the dephosphorization rate increase to 89.5%.The reducing agent has a large influence on the reduction of steel slag. The metal retrieving rate and dephosphorization rate increases with the increment of carbon equivalent Ceq. When Ceq is 1, the dephosphorization rate is 67%, when Ceq increases to 3, the dephosphorization rate will rise to 86.9%. The finer the granularity is, the better the reduction effect is.SiO2 can increase the dephosphorization rate. Adding SiO2 can also prevent sintering in reductive products and make the condition of slag loose and fine. So, it is very easy to separate mental from slag. Under the condition that granularity is 100 mesh, triple carbon equivalent, temperature is 1300℃, keeping warm for 20 minutes and adding SiO2, the highest dephosphorization rate of steel slag is up to 91.5%.