Fundamental Research On Lime Preparation By Microwave Heating

For the purpose of sulphur and phosphorus removal from the steel bath and theirtransfer into the slag, active lime is added during the steelmaking process. The activelime is mainly produced by shaft kiln and rotary kiln on about1200℃, and its quality hasdirect influence on the quality of steel. By using active lime, converter blowing time canbe decreased by10percent, steel yield increased by1percent, lime consumptiondecreased by more than30percent, fluorite saved about25percent, scrap ratio of rawmaterials increased by2.5percent, in addition, Using active lime is beneficial to improvethe life of the converter lining. Therefore, improving the quality of lime is very importantfor the metallurgical industry.As a new efficient way of heating, microwave has lots of advantages such as clean,efficient, low energy consumption and uniform heating, so it has a broad applicationprospect in the field of metallurgy. Compared with the traditional heating methods,microwave heating has characteristics of volumetric heating, selective heating, non-contact heating, real-time heating. The microwave heating can achieve the samemetallurgical purpose with lower temperature and shorter time. The experiments study onthe feasibility of active lime production by microwave heating and especially focus onthe factors influencing lime activity and the microstructure comparison of the calcinedlime under different conditions.The results show that high activity lime can be produced with microwave heating,the influence of the microwave heating temperature, holding time and the particle size oflimestone on lime activity is increased first and then decreased. Effect of temperature andtime on the lime activity is restraint, when the heating temperature is a constant, there isan optimum time for the active lime activity, otherwise, under-sintering or post-sinteringwill reduce the activity of lime. Under the best conditions(treating temperature ofmicrowave heating is1000～1050℃and the holding time is30～40min) for thelimestone of20～30mm, the highest lime activity can achieve up to410mL and the50～80mm can up to435mL. The microstructure of active lime is porous structure and madeup with tiny CaO grain.