Study On The Process Of Microwave Strengthening CO₂ Sequestration With LF Waste Slag

Waste slag is an unavoidable by-product of the steelmaking process.Ladle furnace?LF?slag,which is one of the metallurgical slag,contains high basicity and large amounts of Ca O,and can be used to fix CO₂.This reaserch studies on the microwave strengthening indirect aqueous fixation CO₂ process using ammonium salt and LF slag as a leaching agent and raw material,respectively,simultaneously,high purity precipitated calcium carbonate is prepared in order to reuse resource,reduce CO₂ emission and create economic benefits.In this paper,the basic characteristics of the LF slag were investgated by ICP,XRD,TG/DSC and SEM.The specific surface area,morphology and phase compositions were also investgated with and without microwave processing.The feasibility of chemical reactions between the ammonium salts and LF slag was calculated with the Factsage thermodynamic software.In the self-made microwave experiment device,the leaching rates of the calcium and impurity elements in the LF slag were studied in different process conditions,such as types of ammonium salts,microwave power,stirring speed,initial volume of leaching agent,initial concentration of leaching agent,liquid-solid ratio and particle size.Moreover,the leaching ratio of calcium ion from LF slag in the conventional heating condition was compared to explore the optimum leaching condition.In the self-made microwave experiment device,the optimum carbonation conditions,such as microwave power,CO₂ flow rate,the volume of ammonia and stirring speed,were studied with the leachate in the optimum leaching conditions.In addition,the recycle of the ammonium salt as new leaching agent was preliminary explored.The results show that the main phases of LF slag are calcium-bearing minerals.After microwave processing,the internal and surface of LF slag particles have some micron cracks,and there are no obvious change in phase composition.In the leaching process,the optimum leaching conditions of LF slag are the microwave power of 385W,2mol/L NH₄Cl as a leaching agent,the strring speed of 300rpm,the solid-liquid ratio of1:20,and the reaction time of 60min.The leaching rate of calcium ion from LF slag can be more than 62%in the optimum leaching conditions.To reduce the granularity can improve the calcium leaching rate,however,the volume of NH₄Cl solution is not significantly to the leaching ratio of calcium ion.In the carbonation process,the optimal parameters to carbonate are the microwave power of 120W,CO₂ flow rate of 130m L/min,1/15 of the volume of ammonia to the volume of leachate,the stirring speed of 300rpm,and the reaction time of 20min.The precipitation rate of calcium could reach?98%.In the process of leaching agent recycling,the concentrations of the impurity ions tend to concentrate,and the leaching rate of calcium reduce.