# Application of Waste Tire Carbon for Iron-Containing Dust Reduction in Industrial Processes
## 4 Discussion  
This study employed a custom vertical furnace reactor to closely simulate the high-temperature conditions of a blast furnace. It focused on the influence of varying oxygen concentrations caused by blast air on the reduction efficiency of Fe. The optimal conditions for reducing SMTD using WTC were explored, and the reduction performance of different heating methods and feedstocks was compared. Heavy metal leaching from the residues was also examined to assess potential environmental impacts. The conclusions are as follows:  
1. Reduction conditions: The optimal conditions for reducing Fe to MFe are 1000 \({}^{\circ}\)C, with a mass ratio of SMTD to WTC of 2:1, and 0% O\({}_{2}\), for a reaction time of 45 min. Under these conditions, the replacement of IBD with SGD ensures that all Fe phases detected by XRD are in the MFe form, without affecting Fe reduction under typical blast furnace oxygen injection rates of 0-8%;
2. Effects of reductants: The reduction efficiency follows the order: WTC > CC > WT. Although WTC has 20.66% lower carbon content than CC, its higher saturation, smaller TG weight loss, and a surface tar E\({}_{\text{a}}\) of only 5.79 kJ/mol contribute to a faster reaction rate. Additionally, the carbon black structure is more three-dimensional;
3. Effects of heating methods: The three heating methods (PH, FH, MH) have little impact on Fe reduction. Among them, the higher heating rate of FH results in a faster carbon gasification rate, making the FH residue more uniformly loose. MH exhibits a more concentrated reaction zone, leading to larger metal particle sizes;
4. TCLP results: Sufficient carbon thermal reduction significantly suppresses the leaching of Mg and Zn while promoting the leaching of Ca and Al. It also promotes the Cr leaching of 117.60%. The reduced residues require further processing to remove Cr to meet environmental safety standards.  
Conceptualization, F.L. and M.Z.; methodology, M.Z.; formal analysis, M.Z.; investigation, C.L.; resources, F.L.; data curation, M.Z.; writing--original draft preparation, M.Z.; writing--review and editing, M.Z.; supervision, F.L. All authors have read and agreed to the published version of the manuscript.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & **Limiting Value** & **CC-A1** & **CC-A2** & **SGD-A1** & **SGD-A2** & **FH1** & **FH2** & **PH2** & **MH2** \\ \hline Zn & 100 & 4.05 & 248.71 & 261.77 & 16.08 & 257.32 & 3.41 & 7.57 & 6.96 \\ \hline Cr & 1 & 1.15 & 3.45 & 2.04 & 4.22 & 1.27 & 2.53 & 2.58 & 2.25 \\ \hline Cu & 100 & 0.27 & 1.44 & 0.50 & 1.49 & 0.30 & 0.36 & 0.62 & 0.43 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Leaching quantity of Zn, Cr, Cu (mg/L).  
**Funding:** This research was supported by the National Natural Science Foundation of China (52376205) and Young Scientific and Technological Talents (Level Two) in Tianjin (QN20230228).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
**Conflicts of Interest:** The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.