Study On The Kinetics Of CO₂ Capture By Steel Slag With Cold-rolling Wastewater And Carbonated Slag Resource Utilization

In order to solve the steel slag stacking,large CO₂emission and difficult cold-rolling wastewater（CRW）treatment,this paper intends to establish a three-waste closed system to analyze the steel slag carbonation reaction in CRW to achieve CO₂emission reduction and subsequent steel slag resources utilization.The effects of key factors on steel slag carbonation and wastewater desalination were studied,the kinetics model suitable for the reaction system and strengthening effect of carbonated steel slag on cement materials were also explored.The results show that wastewater carbonation reaction has an intensifying effect on CO₂capture,and has a positive significance for improving steel slag resource utilization.The main results are as follows:This paper firstly studied the use of the wastes produced in steelmaking process to construct a closed system thereby collaboratively capturing CO₂.It can be considered that the composition of wastewater is fluctuating,the effect of water composition,temperature,liquid to solid ratio and reaction time on steel slag carbonation and wastewater desalination was studied.The results showed that carbonation degree and decalcification rate eventually reached 38%and 97%when CRW composition was of 300.00 ppm Ca²⁺,304.00 ppm Na⁺,350.00 ppm Cl^-,400.00 ppm SO₄^2-and 170.00 ppm OH^-at 60℃,20.00 L/kg,200 rpm and CO₂partial pressure of 3 atm for 120 min.The kinetics model suitable for the three-waste system was secondly studied.The reaction system process temperature,liquid to solid ratio and wastewater composition were discussed.Then,the adaptive analysis of shrinking core model and surface coverage model for description of the system was compared.The results showed that shrinking core model can better predict the reaction system,the process was controlled by calcium diffusion.The highest carbonation conversion was 41±1%under 80℃,CRW composition was of 300.00ppm Ca²⁺,304.00 ppm Na⁺,350.00 ppm Cl^-,400.00 ppm SO₄^2-and 170.00 ppm OH^-at 10.00L/kg for 120 min.Finally,the resource utilization of carbonated steel slag was considered.The effects of different steel slag carbonation degree,L/S ratio,S/C ratio and curing time on the compressive strength,water absorption and soundness changes were discussed.Moreover,the quantitative modelling relationship between material properties and various influencing factors was explored to be popularized for actual production by responding surface methodology（RSM）.The compressive strength increased from 47.51 MPa to 69.24 MPa,water absorption increased from 0.15 to 0.27 g,H₂O/g,Solid and soundness decreased from±4.24 to±1.35 mm when steel slag carbonation degree increased from 3-7%to 23-27%,S/C ratio was 0.11,L/S ratio was 0.20 L/kg and curing time was 28 d.The mathematical model between compressive strength and influencing factors was obtained by the response surface method.The calculation showed that the highest compressive strength should be 75.85 MPa when steel slag carbonation degree was 35%,the liquid to solid ratio was 0.15 L/kg,the slag to cement ratio was 0.04,and the curing time was 70d.