Study On The Preparation Of Portland Cement Clinker By Iron Ore Tailings

Portland cement clinker production consumes large amounts of natural resources,the cement industry has for some time been seeking alternative raw materials for Portland cement clinker production.Continuous development of the iron and steel industry has led to the increasing amount of iron ore tailings,but the comprehensive utilization rate of iron ore tailings is still low.The huge amounts of stockpiled iron ore tailings bring a series of environmental and social problems.Utilization of iron ore tailings as raw material for building industry not only consumes large amount of iron ore tailings and realizes zero-emission of iron ore tailings wastes,but also is beneficial to protect natural mineral resources and can provide an alternative alumina-silicate raw material for cement industry.For the high alumina of iron ore tailings from Henan province,it was utilized as alumina-silicate raw material for Portland cement clinker production.The effects of lime saturation ratio?KH?,silica modulus?SM?and alumina modulus?IM?on the sintering process of clinker was studied by XRD,TG-DSC,SEM and hydration heat analysis to seek approriate clinker modulus range.The high C₃S cement clinker was prepared by adding forigen ions,the effect foregin ions on the on the sintering process of clinker and apparent activation energy of C₃S was studied.Two kinds of clinkers were prepared:one was prepared by iron ore tailings;the other was prepared by clay as a reference.The properties of two clinkers were analyzed to investigate the possibility of utilizing iron ore tailings to replace clay as alumina-silicate raw material for the production of Portland cement clinker.The main contents and results are as follows:?1?The burnability results show that theKH and SM should be controlled below0.97 and 2.8,or it will have significant impact on theburnabilty of raw meal,while IM betwween 0.9 and 1.7 has a small effect on the sintering process of clinker.The physical properties of Portland cement clinker perared by iron ore tailings are excellent.When theclinker modulus under the values?KH=0.94,SM=2.50,IM=1.50?,the mechanical performance can reach 52.5 MPa strength grade?2?The liquid phase of clinker sintered at 1350?,the content of free CaO decreased rapidly and large amounts of C₃S formed.The crystal of C₃S developed well,the edge of crystal is clear,and the grain size of crystal is small.The main mineral compositions of clinkerwere C₃S,C₂S,C₃A and C₄AF,which were typical characteristic minerals of Portland cement clinker.The mian hydration product of clinker hydrated for 3 days are Ca?OH?₂,ettringite and C-S-H,the C₃A has hydrated completely,but a small amout of C₄AF and large amounts of C₃S and C₂S has not hydrated.The C₄AF has hydrated completely,large amounts of C-S-H formed,the pores are filled by hydration proudcts gradually and the structure of paste is more and more impact at 28 days.?3?The addition of CaF₂and CaSO₄can lower the decomposing temperature of CaCO₃,promote the sinterring process of clinker,improve the reactivity and burnability of raw meal and lower the apparent activation energy of C₃S,which made the high C₃S cement clinker can be prepared at common sinterring temperature.The effect of CaF₂is better thanCaSO₄,and CaF₂+CaSO₄gives the best effect.?4?Comparing with clay,the use of iron ore tailings is found to improve the reactivity and burnability of raw meal and promote the sintering process.The similar mineralogical,physical and mechanical properties of two produced Portland cement clinker have confirmed that iron ore tailings can completely replace clay as an alternative alumina-silicate raw material for the production of Portland cement clinker.However,the Portland cement clinker prepared by iron ore tailings presents lower hydration heat.