Applied Basic Research Of Stainless Steel Pickling Sludge As Sintering Ingredients

Pickling sludge,containing 38%of CaO and CaF₂,and 20-22%valuable metals including oxygen,include Fe,Ni and Cr etc.Aiming at the harmless and recylable sludge,pickling sludge was used as sintering ingredients by returning back to sintering process.FactSage was used to predict the amount of pickling sludge,temperature and basicity on the the quantity of liquid phase during the sintering process,characteristic temperature of liquid phase formulation,the amount of calcium ferrate and liquid area in CaO-SiO₂-Fe₂O₃-MgO-Al₂O₃-CaF₂ system.Also the distribution of S,F and Cr in sintering process were simulated and calculated.The results of thermodynamic calculation showed that the shape of liquid area of CaO-SiO₂-Fe₂O₃-MgO-Al₂O₃-CaF₂ system is strap-like.The sintering characteristics and characteristic temperature were improved and the aomunt of liquid area has increased at centain amount of pickling sludge and basicity.In the temperature range of 1200-1300?,0-15%of sludge and basicity 1.5-2.0,the sintering temperature was easied governed resulting in the increasing of the liquid phase andthe amount of calcium ferrite and the decreasing of the temperature of liquid phase During the pickling process,Sulfur is most commonly presented in the form of sulfur dioxide.Fluorine in the form of cuspidine and Chromium in the form of chromic oxide.With the increasing of sludge basicity and sinering temperature,the production of cuspidine would be restrained and chromic oxide transformed into liquid sintering.The experiment of basic sintering characteristics results showed that the basic sintering characteristics has improved,and the fluidity of liquid phase has deteriorated and intensity of bonding phase increases in the temperature of 1200-1300?,5-10%sludge and basicity of 1.5-2.0.The formula of liquidity index?y?and the aomut of sludge?x?,y=18.40305-0.09139x-0.02644x²+9.07734x³,is consistent with the thermodynamic calculations.The experimental result indicates that there are distinct grain boundary between the phases of hematite,magnetite and calcium ferrite,which is happening at1300?,240min,5-10%and basicity 1.5.the content of hematite and magnetite has increased,and the number of silicate and pores has decreased,and the shape of calcium ferrite gradually has changed from granular to needle-like or flaky to needle-like.During the pickling process,Sulfur,Fluorine and Chromium exit in the form of FeSO₄?Ca₄Si₂F₂O₇ and Cr₂O₃.With the help of SEM,Sulfur was dispered in the view of SEM,and Fluorine was enriched in the light grey area and Chromiumconcentated in the white area.The above results demonstrate the feasibility of using pickling sludge as sintering ingredients could enrich the way of its resource utilization,and provide a reference for the utilization of pickling sludge in the internal of metallurgical enterprises.