Experimental Study On Preparation Of Composite Iron Coke Low Carbon Iron-making Charge With Steel Slag

Based on the background of carbon peak,carbon neutral and green low-carbon development direction of China’s iron and steel industry,composite iron coke low carbon ironmaking charge is an effective way to achieve low carbon ironmaking of blast furnace.In order to expand the source of raw materials for the preparation of composite iron coke and to enrich the resource utilization of steel slag solid waste,a process of preparing steel slag composite iron coke(SCC)from steel slag and mixed coal was proposed in this paper.Firstly,the effects of process parameters on the compressive strength,reactivity(CRI)and post-reaction strength(CSR)of SCC were studied,and the appropriate preparation parameters were obtained.Then,the effects of CaO,MgO,Fe3O4 and their coupling on the gasification reaction behavior of SCC were investigated,and a kinetic model was established to obtain the kinetic parameters and kinetic equations.Based on the change of activation energy and phase structure,the catalytic mechanism of gasification reaction was discussed.Finally,in order to evaluate the droplet performance of steel slag composite charge used in blast furnace ironmaking,the influences of steel slag ratio of SCC and SCC ratio in place of coke on the soft melting,air permeability and dropping property of the comprehensive charge were studied,and the suitable ratio of steel slag and coke ratio in SCC were obtained.The main conclusions are as follows:(1)When the ratio of steel slag increases from 5%to 25%,the compressive strength of SCC decreases from 4236 N to 3214 N;When the steel slag ratio increases from 5%to 15%,the CRI increases from 53.7%to 60.64%,and when the steel slag ratio increases to 20%,the CRI decreases to 57.2%.The ratio of steel slag increased from 5%to 15%,and the CSR decreased from 82.35%to 57.24%.(2)CaO、MgO、Fe3O4 effectively catalytic gasification of carbon,SCC gasification reaction kinetics consistent with nuclear model(SCM).The catalyst can weaken the C=C bond strength of aromatic hydrocarbons.With the decrease of graphitization degree,carbon disorder and active sites of gasification reaction increase,the activation energy of gasification reaction decreases and the energy barrier decreases.When the content of CaO,MgO and Fe3O4 is 3%,the corresponding activation energies are 121.26,130.78 and 142.3 kJ/mol,respectively.The catalytic capacity is CaO>Fe3O4>MgO.Coupling effect is more effective than single component for gasification reaction catalysis,and the catalytic capacity is CaO&Fe3O4>CaO&MgO>MgO&Fe3O4.(3)With the addition of SCC,the softening interval of the composite charge becomes wider,the melting zone becomes thinner and decreases,and the melting property of the composite charge is improved.Droplet characteristic value S decreases,which improves the column permeability.The suitable SCC steel slag ratio is 15%,and the suitable SCC ratio is 20%.