High Iron Red Mud Calcification-Iron Extraction And Tailings To Prepare Cement Clinker

In China,the annual discharge of high iron red mud produced by the Bayer process exceeds 75 million tons,and its treatment method is mainly dry storage.High red mud will cause serious pollution to the soil and water sources near the storage yard due to its high alkalinity.Once a dam break occurs,it will seriously threaten the surrounding ecological environment.The Mass fraction,fraction of TFe in the high iron red mud is mostly between 40%and 50%,which has great extraction value.However,due to the high alkalinity of the high iron red mud,its average utilization rate in the past ten years is less than 4%.In order to realize the harmless and comprehensive utilization of high red mud,this research group proposed a new process for preparing cement clinker by calcification of high red mud and iron extraction from tailings.This paper focuses on the comprehensive utilization of high iron red mud for calcification iron extraction,calcification iron extraction tailings to prepare aluminate cement,and high iron red mud iron extraction tailings to directly prepare sulfoaluminate cement.The main research contents and results are as follows:(1)The chemical composition analysis and mineralogical analysis of high iron red mud after calcification show that the mass fraction of Fe2O3 in the calcified slag of high-iron red mud is 42.70%,and the mass fraction of Na2O is reduced from 3.10%in the original red mud to 0.54%.The main mineral phases in the high-iron red mud calcification slag are hematite,hydrated garnet,calcium alumina spinel and a small amount of ilmenite.(2)The smelting reduction experiment was carried out with high iron red mud calcification slag as the raw material,and the optimal reduction conditions were determined to be 1550℃,alkalinity 1.1,carbon ratio 1.1,holding time 30 min,and the amount of CaF2 added was 3%of the mass fraction of calcification slag,the recovery rate of iron is 90.06%,and the mass fraction of MFe in the metal is 93.76%.(3)Directly prepare aluminate cement under melting conditions using high iron red mud calcification iron extraction tailings as raw materials.At 1550℃,the holding time is 10 min,and the chemical composition of aluminate cement obtained under air cooling conditions is 33.87%CaO,53.05%Al2O3,4.64%SiO2 and 0.43%Fe2O3,3.03%TiO2,calcium aluminate(CaO·Al2O3)Mass generation.(4)The physical properties of aluminate cement prepared under air cooling and quenching conditions are tested in accordance with GB/T 201-2015.The specific surface area of aluminate cement after grinding under air cooling is 293.2 m2/kg,which does not reach 300.0 m2/kg.The flexural strength of 3 d age does not meet the CA50 I standard,and the compressive strength and flexural strength of the remaining ages Both are higher than the strength of CA50I aluminate cement mortar under GB/T 201-2015.The compressive strength and flexural strength of aluminate cement under quenching conditions for 1 d,3 d,and 28 d are higher than the strength of CA50I aluminate cement mortar under the GB/T 201-2015.(5)Finally,an exploratory experiment to prepare sulphoaluminate cement by direct iron extraction tailings from high iron red mud was carried out.The raw material components were adjusted to 40.00%CaO,32.00%Al2O3,8.00%SiO2 and 2.00%Fe2O3,4.20%TiO2,8.30%SO3,at 1350℃,holding time 1 h,the main crystalline phases in the sulfoaluminate cement clinker obtained under air cooling are calcium sulfoaluminate(3CaSO4·3Al2O3·CaSO4)and β-dicalcium silicate(β-2CaO·SiO2).