An Investigation into EAF Burner Preheating and Melting Characteristics: CFD Model Development and Experimental Validation

Abstract

The scrap preheating stage performed before the main scrap melting stage has a growing significance in the modern electric arc furnace (EAF), which utilizes the coherent jet burners to preheat and melt the scrap to improve the overall energy efficiency within the furnace, but the corresponding computational fluid dynamics (CFD) modeling and analysis of this process were still very limited. The present paper developed a fully integrated and self-consistent CFD model to simulate the multi-physics during the burner preheating and melting process in a full-size industrial EAF, including combustion flame, interphase heat transfer, scrap melting, and liquid steel re-solidification. The innovative dual-cell approach and stack approach were proposed to simulate the porous scrap preheating/melting and its dynamic collapse process. The immersed scrap preheating experiment was first time designed and implemented in an industrial EAF for model validation with an average difference of 12.7 pct. The model was used to gain fundamental insights into the scrap preheating stage and evaluate the effects of different factors on the burner preheating and melting characteristics. The guidance was provided to achieve optimal operational efficiency and energy utilization in the industrial furnace.

Appendix A

The experimental evaluation index layer matrix (M₁): assuming there are i factors in total for the optimization and each factor has m levels, the average value of the evaluation index at the j level of factor ${A}_{i}$ is denoted as ${K}_{ij}$. In the present study, the larger the evaluation index, the better the burner preheating and melting results, thus establishing the matrix ${M}_{1}$ as follows:

$${M}_{1}=\left[\begin{array}{ccc}\begin{array}{c}{K}_{11}\\ {K}_{12}\\ {K}_{13}\end{array}& \begin{array}{c}0\\ 0\\ 0\end{array}& \begin{array}{c}0\\ 0\\ 0\end{array}\\ \begin{array}{c}0\\ 0\\ 0\end{array}& \begin{array}{c}{K}_{21}\\ {K}_{22}\\ {K}_{23}\end{array}& \begin{array}{c}0\\ 0\\ 0\end{array}\\ \begin{array}{c}0\\ 0\\ 0\end{array}& \begin{array}{c}0\\ 0\\ 0\end{array}& \begin{array}{c}{K}_{31}\\ {K}_{32}\\ {K}_{33}\end{array}\end{array}\right]=\left[\begin{array}{ccc}\begin{array}{c}0.817505502\\ 0.785586825\\ 0.744814524\end{array}& \begin{array}{c}0\\ 0\\ 0\end{array}& \begin{array}{c}0\\ 0\\ 0\end{array}\\ \begin{array}{c}0\\ 0\\ 0\end{array}& \begin{array}{c}0.850963786\\ 0.783095242\\ 0.713847823\end{array}& \begin{array}{c}0\\ 0\\ 0\end{array}\\ \begin{array}{c}0\\ 0\\ 0\end{array}& \begin{array}{c}0\\ 0\\ 0\end{array}& \begin{array}{c}0.794552541\\ 0.78206593\\ 0.77128838\end{array}\end{array}\right]$$

(A.1)

The factor layer matrix (${F}_{1}$): the elements in the matrix can be then determined through $1/\sum_{j=1}^{m}{K}_{ij}$ from the values in ${M}_{1}$:

$${F}_{1}=\left[\begin{array}{ccc}\frac{1}{{K}_{11}+{K}_{12}+{K}_{13}}& 0& 0\\ 0& \frac{1}{{K}_{11}+{K}_{12}+{K}_{13}}& 0\\ 0& 0& \frac{1}{{K}_{11}+{K}_{12}+{K}_{13}}\end{array}\right]=\left[\begin{array}{ccc}0.425911275& 0& 0\\ 0& 0.425911275& 0\\ 0& 0& 0.425911275\end{array}\right]$$

(A.2)

The level layer matrix (${L}_{1}$): the elements in the matrix can be then determined through ${G}_{i}/\sum_{i=1}^{i}{G}_{ij}$ based on the range analysis results to compute the ratio of the extreme difference of factor ${A}_{i}$ to the total of all extreme differences:

$${L}_{1}=\left[\begin{array}{c}\frac{{G}_{1}}{{G}_{1}+{G}_{2}+{G}_{3}}\\ \begin{array}{c}\frac{{G}_{2}}{{G}_{1}+{G}_{2}+{G}_{3}}\\ \frac{{G}_{3}}{{G}_{1}+{G}_{2}+{G}_{3}}\end{array}\end{array}\right]=\left[\begin{array}{c}0.311883272\\ \begin{array}{c}0.588301002\\ 0.099815726\end{array}\end{array}\right]$$

(A.3)

The weight matrix (${\omega }_{1}$): the weights of three factors within all three levels can be determined by multiplying three matrixes above:

$${\omega}_{1}={M}_{1}{F}_{1}{L}_{1}=\left[\begin{array}{c}0.108593018\\ 0.104353113\\ \begin{array}{c}0.098937141\\ 0.213220915\\ \begin{array}{c}0.1962155\\ 0.178864587\\ \begin{array}{c}0.033778529\\ \begin{array}{c}0.03324769\\ 0.032789508\end{array}\end{array}\end{array}\end{array}\end{array}\right]$$

(A.4)

For the evaluations of scrap porosity and initial scrap temperature, the same procedure can be performed to calculate ${\omega }_{2}$ and ${\omega }_{3}$:

$${\omega }_{2}={M}_{2}{F}_{2}{L}_{2}=\left[\begin{array}{c}0.23631742\\ 0.307823259\\ \begin{array}{c}0.397359412\\ 0.007309772\\ \begin{array}{c}0.007285178\\ 0.007372853\\ \begin{array}{c}0.012210119\\ 0.012282225\\ 0.012039761\end{array}\end{array}\end{array}\end{array}\right]$$

(A.5)

$${\omega }_{3}={M}_{3}{F}_{3}{L}_{3}=\left[\begin{array}{c}0.121763051\\ 0.153180371\\ \begin{array}{c}0.191400643\\ 0.148217997\\ \begin{array}{c}0.125294203\\ 0.102858986\\ \begin{array}{c}0.049123841\\ \begin{array}{c}0.051115629\\ 0.057045279\end{array}\end{array}\end{array}\end{array}\end{array}\right]$$

(A.6)