Quantitative Determination Of Light Burned Magnesia Activity And Its Effect On Properties Of Sintered Magnesia

Light burned magnesia has reactivity and is widely used in steel metallurgy,building materials,chemical industry,agriculture,light industry,environmental protection and other industries.More than 80% of them are used for the production of two-step calcined magnesia.The activity of light burned magnesia is an important symbol of its physical absorbability and chemical reactivity,which is closely related to the quality of light burned magnesia.At present,there are two industry standards for the determination of the activity of light burned magnesia.The first method is citric acid time method.This method can only indirectly characterize the activity of light burned magnesia by color changing time.It can not measure the specific content of active magnesia and distinguish samples with little activity or high activity.The second method is hydration method.Although it can quantitatively measure the content of active magnesia and the operation is simple,it takes long time and is poor in reproducibility.There are few reports about the effect of the activity of light burned magnesia on the performance of two-step calcined magnesia.The purpose of this study is to obtain a rapid,simple and accurate method for the quantitative determination of the activity in light burned magnesia and the effect of its activity on the performance of two step calcined magnesia.Determining the content of active magnesia in light burned magnesia by citric acid dissolution-EDTA complexometric titration is researched.The best experimental conditions were obtained by comparing with hydration method.The phase composition,grain size and microstructure of light burned magnesia were analyzed by X-ray diffraction and scanning electron microscope.The relationship between the phase composition and microstructure and the activity of light burned magnesia was studied.The light burned magnesia with different activity is prepared.Sintered magnesia is prepared by two-step calcined method with above different activity light burned magnesia.The influence of activity of light burned magnesia on particle volume density and grain size of periclase and microstructure of sintered magnesia is studied.The results are as follows:1.Titration end point of Citric acid dissolution-EDTA complexometric titration is sensitive.The operation is simple and rapid.The results are stable and reproducible and basically consistent with the industry standard hydration method.The best reaction conditions at normal temperature are sample mass 1g,sample size-200 mesh,citric acid solution dosage 200 m L,stirring time 5 minutes.2.The magnesite decomposition rate and the content of active magnesia increased gradually with the increasing of calcined temperature.At 850~1050?,the grain size of periclase increase slowly,the active magnesia content changes unobviously(higher than 80 mass%).At 1050~1200?,the grain size of periclase increase rapidly,and the active magnesia content reduce quickly.3.Because active magnesia content is high the internal mass transfer resistance is increasesed in the process of calcining.The final sample density is relatively low and periclase grain size is relatively small.The density of the sintered magnesia prepared with the low activity light burned magnesia calcined at 650? and 1200? is higher and the periclase grain size of the sintered magnesia is larger.The sintered magnesia prepared with the light burned magnesia at 1200? has better performance.