Study On Preparation Of Si-Fe Alloy From Crystal Silicon Cutting Waste

With the rapid development of the photovoltaic industry,the global demand for silicon is growing rapidly.The wafer manufacturing industry is located in the middle of the photovoltaic industry chain.Production of single crystal silicon rods or polycrystalline silicon ingots by using a silicon material from upstream,using a single crystal silicon growth furnace or a polycrystalline silicon ingot furnace.Then,under the action of the diamond wire and the cutting fluid,it is cut into a single crystal silicon wafer or a polycrystalline silicon wafer for producing solar cells and components.During the cutting process,30%-40%of the high-purity silicon material becomes sawdust into the cutting slurry.At present,the recovery technology of cutting fluid in cutting slurry is relatively mature,but the recycling of silicon powder with higher value is still under study.Due to a certain proportion of the iron in the waste,most of the regeneration routes require a system of pickling and iron removal.In order to simplify the regeneration process and reduce the processing cost,this study used the waste as raw material to prepare Si-Fe alloy,mainly studied the content of silicon's detection method,the physical properties and chemical analysis of raw materials,the pelleting process and the fusion preparation method to prepare Si-Fe alloy.At present,there is no uniform national standard for the determination of elemental silicon content in cutting waste.In this study,the principle of reacting silicon with sodium hydroxide solution to generate hydrogen is used,and the detection device is self-made,and the optimal test conditions are obtained:the reaction temperature 60?70?,the concentration of sodium hydroxide solution is 4-6 mol/L,the reaction time is 40 min.The material properties and chemical analysis of crystalline silicon cutting waste are carried out,the composition of which is w[Si]=65%,?[SiO2]=9%,?[water]=21%,?[organic matter]=4%,w[other]=1%.The crystal powder has a median diameter of 1.475 ?m after drying and simple grinding,and 90%of the particles have a particle size of less than 5.419?m.The pellets are pressed using a high pressure roller press.The optimum conditions for the formation of crystalline silicon cutting waste pellets are the amount of water,bentonite and modified water glass accounted for 40%,3%and 8%of the quality of crystalline silicon cutting waste,dehydration at 70? for 7.25 h,desorption of organic matter at 250? for 45 min,sintering at 500? for 7 h.A pellet having a dry bulb drop strength of 3.5 times/0.5m and a w[Si]=71.63%can be obtained,which can be utilized as a preferred silicon-containing pellet.The pellets are used as raw materials,and the Si-Fe alloy is prepared by fusion bonding.The preferred process conditions are determined by three high graphite crucible.Under the protection of N2 atmosphere,m(Fe):m(pellet)=15:100,the heating time is 30 min,reaction temperature is 1500?,and the holding time is 60 min.A Si-Fe alloy having a w[Si]=70.46%can be obtained.