Study On The Synergistic Preparation Process And Properties Of Ceramsite By Bayan Obo Tailings And Blast Furnace Slags

The Bayan Obo Mine is a polymetallic associated deposit,which is rich in niobium,thorium,fluorite and other resources in addition to iron and rare earths.Among them,the reserves of rare earth are the first in the world,and the reserves of niobium and thorium are the second in the world.For a long time,the mining and utilization of Bayan Obo Mine has adhered to the policy of"mainly iron,comprehensive utilization",resulting in a large amount of industrial solid waste such as waste rock,tailings,and slag.Facing the major national strategic needs of ecological civilization construction and ensuring the safe supply of resources,adhere to the strategic positioning of"ecological priority and green development".In the process of development and utilization of Bayan Obo Mine,the selecting and smelting solid waste(tailings,blast furnace slag),which is produced in large amount,has low resource utilization rate and has serious ecological environment impact,is taken as the research object.To carry out the development and research on the technology of synergistic preparation of ceramsite from selecting and smelting solid waste,so as to realize the resource utilization of selecting and smelting solid waste in Bayan Obo rare earth ore.According to the chemical composition and mineral characteristics of Bayan Obo tailings and Baotou Steel blast furnace slag,and based on the synthesis rule of yellow feldspar phase,the method of preparing ceramsite is adopted to realize the harmless and large-scale utilization of the the selecting and smelting solid waste of Bayan Obo mine.By measuring and analyzing the basic properties of Bayan Obo tailings and Baotou Steel blast furnace slag,it is found that the main mineral composition of Bayan Obo tailings is dolomite and quartz,and the phase composition of Baotou Steel’s water-quenched blast furnace slag is mainly glass phase.A large amount of coal-based solid waste(coal gangue)in Inner Mongolia was selected as the pore-forming agent,and the raw material ratio of 60%Bayan Obo tailings,35%Baotou blast furnace slag,and 5%coal gangue was clarified through the calculation of the phase diagram.The process flow of the roasting method was selected to prepare ceramsite,and the influence of different process regimes on the properties of ceramsite was explored.The results show that with the decrease of the particle size of the mixture,the porosity and water absorption of the ceramsite decrease,and the compressive strength increases.With the increase of compaction time in the compaction stage of pelletizing,the compressive strength of ceramsite was significantly improved,and the porosity and water absorption decreased less.The method of cooling with the furnace can make the ceramsite have more abundant internal pores.The process system of ceramsite is determined by experiments as follows:the particle size of the mixture is ground to below 75μm,the amount of water added is 10%,the pelletizing time is 10min,the preheating temperature is 350℃,the preheating time is 12min,and the holding temperature is 750℃,the holding time is 1h,the roasting temperature is1130℃,the roasting time is 20min,the heating rate is 5℃/min,and the cooling method is cooling with the furnace.The physical properties of the ceramsite are obtained under this process system as follows:the compressive strength is 1.89MPa,the porosity is 51.31%,the water absorption rate is 31.42%,and the bulk density is 1.94g/cm~3.When the calcination temperature is higher than 1050℃,the phase composition of the ceramsite has basically not changed,which indicates that the temperature of the phase transformation reaction of the ceramsite is lower than 1050℃.Combining with the microstructure of ceramsite at 1050℃,1130℃and 1170℃,it can be seen that when the sintering temperature is 1130℃,obvious feldspar structure can be observed inside the ceramsite,and no obvious large pores appear.In addition,the pores penetrate each other and present a three-dimensional appearance.These pores and the cooled liquid phase constitute a loose and porous ceramsite skeleton.The porosity and water absorption of ceramsite prepared by roasting method meet the requirements of water treatment ceramsite,the detection of leaching toxicity meets the national standard,and it also has certain purification ability for ammonia nitrogen wastewater.