Steel slag powder-CO2 contact state in static or rotary process of carbon fixation

•The different steel slag carbon fixation process were simulated and calculated.•The gas–solid interaction effect of steel slag carbon sequestration was evaluated.•The effect of microorganisms on the gas–solid interaction was studied. The carbon fixation of steel slag can effectively improve its soundness and activity, increase its utilization rate, and reduce the emission of CO2, which has a significant development prospect. Currently, the effects of different carbon fixation processes for steel slag need further exploration. In this study, the ‘static-pressure’ and the’rotary’ process of the carbon fixation by steel slag powder were simulated, using the gas–solid contact between slag and CO2 as the indicator. The influence of different parameters was investigated, and experimental validation was conducted under optimized conditions. The results indicate that in the ‘static-pressure’ process, reducing the stack thickness and applying pressure to accelerate CO2 transfer are beneficial for gas–solid contact. In the ‘rotary’ process, reducing the filling coefficient to below 20.0 % and increasing the rotation speed to 1.0 rad/s are conducive to gas–solid interaction. Under the optimized conditions, the carbon fixation rate for the ‘static-pressure’ process after 2 h is approximately 6.4 %, while the carbon fixation rate for the ‘rotary’ process is approximately 9 %, indicating better carbon fixation performance in the latter. The addition of microorganisms can further accelerate carbon fixation and enhance its effectiveness. Under the ‘rotary’ process, the carbon fixation rate of microorganism-treated samples reaches 10.21 % after 1 h, surpassing the carbon fixation rate of 7.8 % in the’static-pressure’ process. A satisfied carbon fixation effect is achieved when the contact duration between steel slag particles and CO2 reaches 12.6 min.