Research On Physicochemical Properties And Resource Utilization Of Conerter Slag

With the development of iron and steel industry,the output of steel increased year after year.It brought us a mass of steel slag,which is not reproducible and will bring lots of environmental pollutions.It is necessarily for people to reuse the steel slag comprehensively turning the waste into useful material.At current time,the steel slag is used as component of cement and construction aggregate material.Deep research on physicochemical properties should be carried out to find new recycle way.Micro-structures of slag samples from 3 steel plants were observed by the back scattered electron images of SEM.The element composition was determined by energy dispersive X-ray analysis,in order to ascertain mineral category the composition,data of the mineral phases with the same morphology characteristics was analyzed by statistics.And the possibility of extracting silicate phase from steel slag by Salicylic Acid Methanol(SAM) Solution was studied,and effect of specific surface area of steel slag, dissolving period of samples,concentration of salicylic acid on the extraction mass of silicate phase were analyzed.Furthermore,the basic extraction theory was also studied.With the grinding process,the ease of grinding of steel slag was investigated,and the comparison of grinding performance between steel slag and the slag was made.The cementitious behavior of the steel slag activated by mechanical and alkaline process was also studied.With the study of micro-structure and the mineral phases of Converter Slag,the characteristic conformation,the form of solid solution and representative composition were determined.The results show that morphology of C₂S in high alkalinity slag is round or leaf shape,C₃S is hexagonal,and the phase of Fe₂O₃-Al2O₃-CaO and MgO-FeO all are irregular. The main phases in the slag are C₂S,Fe₂O₃-Al₂O₃-CaO and MgO-FeO solid solution,the minor mineral is C₃S,f-CaO and MgO.It was found that the representative composition of the Fe₂O₃-Al₂O₃-CaO phase is calcium aluminoferrite,the chemical formula of which is Ca₂(Al,Fe)₂O₅,the RO phase, which has been unknown for a long time,is MgO-FeO solid solution,its representative composition is MgO·2FeO.The possibility of extracting silicate phase from steel slag by SAM was studied,and the SAM solution showed good ability for extraction of silicate phases.One way for the determination of the cementitious performance of the steel slag was offered by the measurement of extraction amount of the silicate phases.The results show that,with the extraction for 3h at ordinary temperature,the silicate phase in 5g steel slag(600m²/kg)can be totally extracted out,and only silicate phase was dissolved in SAM.It is in point that silicate phase extraction is due to forming the complex between legend of salicyclic acid and Ca²⁺on the surface of mineral,which weakens the stability of Si-O bond,then decreases the activation energy of silicate phase.The grinding results showed that:the grinding performance of steel slag was influenced by metal grains and compact configuration of some mineral, instead of the steel slag itself,the ease of grinding performance listed in descending order is RO,C₂S,Ca₂(Al,Fe)₂O5,MgO and Ca(OH)₂,the different grinding performance of which provide us a effective way for the separation of the steel slag.The grinding performance of steel slag was much better than that of slag.The cementitious ability of steel slag,from which preparation of high activation pozzolanic materials,was studied by several ways.And its cementitious performance improved a lot with the mechanical process. However,the mechanical activation effect of steel slag is inferior to the slag. For the lower amount of glass state contained in steel slag,it was difficult to activated than slag.Cementitious performance improved by mixing into the stag in evidence,as a result of compound function of hydrate process.And the compressive strength for 28d of 2×2×2cm specimen with 50%steel slag was 48.6Mpa.