Study On Ring-forming Of Oxidized Pellet Rotary Kiln At Baotou Iron And Steel(Group)Co

The grate-kiln oxidized pelletizing process was adopted by Baotou Iron andsteel(Group)Co western district1.2million t/a pelletizing line with Baiyunebo Barun oresas raw material,the ring have formed frequently since the process went into operation,whenthe ring-forming problem got serious,it formed basically four to five times a month,and thethickest ring accretions reached up to one meter,which severely hindered the smoothproduction in Baotou Iron and steel(Group)Co.In view of the rotary kiln ringing seriousproblems during production process of Baotou Iron and steel(Group)Co1.2million t/agrate-kiln pelletizing line,the ring-forming causes have been investigated systematicallyaccording to the series of ring accretions characteristics,material condition andtechnological parameters.The ring accretions in kiln head,kiln middle and kiln feed endwere sampled,the mineral composition and microstructure of which were studied by acombination of metallographic microscope and scanning electron microscope,especiallythe distribution characteristics of elements K,Na and F;The soft melting performanceincluding DT and ST of ring accretions were measured by ash melting point test;Theconsolidation strength of ring accretions was tested with pellets consolidation strengthtester;The raw materials was made as crude pallet with uniform particle size by pelletizingmethod,whose consolidation strength was tested after roasting in different technologicalparameters of rotary kiln,then investigating the influence rule of roasting temperature andtime on the ring-forming performance of rotary kiln;The thermodynamical data based onthe thermodynamics and dynamics of desulfurization in the process of pellets oxidizingroasting were studied by thermodynamic software Factsage,then analyzing the impact ofdesulfurization on magnetite oxidation,grate technological parameters and preheatedpellets crushing strength.By synthesizing the above study contents,the effects of Baiyunebospecial Barun ores on oxidized pellets kiln-ringing were studied,what is more,we shouldnot only reveal the ring-formation causes and influencing factors but also propose effective measures for the prevention and inhibition of ring-forming in Baotou Iron andsteel(Group)Co oxidized pellets rotary kiln.The study shows that, the rings in kiln head are caused by powder materials bondedby liquid phase which comes from the melting of coal ashes and aluminosilicate ganguecontaining elements K and Na in Baiyunebo Barun ores;The rings in kiln middle arecaused by hematite crystal concretion,what is more,that the liquid phase which comes fromthe mineralization of coal ashes and silicate gangue containing elements Ca and Mg inBaiyunebo Barun ores and binds the powder materials has aggravated ring-forming;Thering accretions in kiln feed end are caused by powder materials bonded by liquid phasewhich comes from the melting of low-melting-point minerals formed by aluminosilicategangue containing elements K and Na in Baiyunebo Barun ores and the reaction betweenFeO and the gangue.