Effect of Ca/Fe additives on solution loss reactions of cokes in H2O+CO2 atmosphere
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摘要: 為了探究富氫高爐內Ca/Fe基高反應性焦炭的溶損反應特性，以CO2（N2）載帶不同摩爾比例H2O蒸氣（0～30%）進行焦炭溶損實驗，通過分析尾氣中CO和H2的含量，研究Ca/Fe添加劑對焦炭在H2O+CO2混合氣氛下碳溶反應和水煤氣反應的影響。研究表明，焦炭在H2O+CO2和H2O+N2兩種氣氛下的焦炭反應性隨H2O蒸氣載帶率增加呈線性關系，焦炭在H2O+CO2氣氛中溶損反應的擬合斜率k值明顯小于在H2O+N2氣氛中的k值，H2O+CO2混合氣氛中H2O和CO2與焦炭反應存在競爭關系。而且基礎焦炭（BC）反應性的實驗與理論的差值明顯小于Ca/Fe基焦炭（BC+Ca、BC+Fe）的差值，表明Ca/Fe添加劑影響了CO2和H2O與焦炭共同反應時的競爭關系。基于兩種氣氛下速率常數的差異提煉了兩個抑制因子
$\alpha_{{\rm{CO}}_2/{\rm{H}}_2{\rm{O}}} $ 和$\alpha_{{\rm{H}}_2{\rm{O}}/{\rm{CO}}_2} $ ，$\alpha_{{\rm{CO}}_2/{\rm{H}}_2{\rm{O}}} $ 定量表征CO2對C+H2O反應的抑制程度，$ \alpha_{{\rm{CO}}_2/{\rm{H}}_2{\rm{O}}}$ 定量表征H2O對C+CO2反應的抑制程度，BC、BC+Fe、BC+Ca三種焦炭的$\alpha_{{\rm{CO}}_2/{\rm{H}}_2{\rm{O}}} $ 分別為0.260、0.251、0.170，而$\alpha_{{\rm{H}}_2{\rm{O}}/{\rm{CO}}_2} $ 分別為0.121、0.217、0.263，Ca/Fe添加劑降低了$\alpha_{{\rm{CO}}_2/{\rm{H}}_2{\rm{O}}} $ 而提高了$\alpha_{{\rm{H}}_2{\rm{O}}/{\rm{CO}}_2} $ ，說明Ca/Fe添加劑能夠減小CO2對C+H2O反應的抑制程度，顯著增強C+H2O反應的活性。Ca/Fe基焦炭中催化活性物質為鐵酸鈣和硅鋁酸鈣，Ca/Fe元素在焦炭中賦存形式的不同導致了Ca/Fe添加劑對焦炭溶損反應催化效果的差異性。Abstract: To examine the solution loss reaction properties of cokes with Ca/Fe additives in a hydrogen-rich blast furnace, the solution loss reactions of cokes were performed using a CO2 (N2) carrier gas with various percentages (0–30%) of H2O vapor, and the effect of Ca/Fe additives on the Boudouard reaction (C + CO2 = 2CO) and water–gas reaction (C + H2O = CO + H2) of cokes in a H2O + CO2 atmosphere was studied by examining the content of CO and H2 in the off-gas. The results demonstrate that the coke reactivity has a positive linear relationship with the percentages of H2O vapor in H2O + CO2 and H2O + N2 atmospheres, and the fitting slope k could be used to characterize the rate constant for the solution loss reaction of cokes in H2O + CO2 and H2O + N2 atmospheres. The k value for the solution loss reaction of the coke in the H2O + CO2 atmosphere is smaller than that of the coke in the H2O + N2 atmosphere, which shows that there is a competition between the reactions of H2O and CO2 with cokes in the H2O + CO2 atmosphere. Furthermore, the experimental reactivities of coke are smaller than their theoretical reactivities in the H2O + CO2 atmosphere, and the difference between the experimental and theoretical reactivities of the basic coke (BC) is less than those of the cokes with Ca/Fe additives (BC + Ca, BC + Fe), which shows that the Ca/Fe additives affect the competitive relationship of the reactions of CO2 and H2O with coke. Two inhibition factors,$\alpha_{{\rm{CO}}_2/{\rm{H}}_2{\rm{O}}} $ and$\alpha_{{\rm{H}}_2{\rm{O}}/{\rm{CO}}_2} $ , are proposed to measure the degree of inhibition based on the difference in the k value for the cokes in H2O + CO2 and H2O + N2 atmospheres. The inhibition factor$\alpha_{{\rm{CO}}_2/{\rm{H}}_2{\rm{O}}} $ could quantitatively characterize the inhibition degree of CO2 on C + H2O reaction in the H2O + CO2 atmosphere, and the inhibition factor$\alpha_{{\rm{H}}_2{\rm{O}}/{\rm{CO}}_2} $ could quantitatively characterize the inhibition degree of H2O on the C + CO2 reaction in the H2O + CO2 atmosphere. The$\alpha_{{\rm{CO}}_2/{\rm{H}}_2{\rm{O}}} $ factors of BC, BC + Fe, and BC + Ca cokes are 0.260, 0.251, and 0.170, respectively, and the$\alpha_{{\rm{H}}_2{\rm{O}}/{\rm{CO}}_2} $ factors of BC, BC + Fe, and BC + Ca are 0.121, 0.217, and 0.263, respectively. The Ca/Fe additives in cokes reduce the$\alpha_{{\rm{CO}}_2/{\rm{H}}_2{\rm{O}}} $ factor and increase the$\alpha_{{\rm{H}}_2{\rm{O}}/{\rm{CO}}_2} $ factor, showing that Ca/Fe additives can attenuate the inhibition degree of CO2 on the C + H2O reaction and improve the activity of the C + H2O reaction, and the Ca additive has a greater impact on the competitive relationship between the reactions of CO2 and H2O with coke than the Fe additive. The catalytically active substances in Ca/Fe additives in cokes could be CaFe2O4 and Ca2Al2SiO7, and the difference in the existing states of Ca/Fe elements in cokes causes the difference in the catalytic effect of Ca/Fe additives on the solution loss reactions of cokes.-
Key words:
- coke /
- Ca/Fe additives /
- solution loss reaction /
- H2O + CO2 atmosphere /
- catalysis /
- inhibition factor
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圖 2 焦炭的反應性（PRI）與水蒸氣載帶率的關系. (a) BC (b) BC+Fe; (c) BC+Ca
Figure 2. Relationship of coke reactivity (PRI) with the percentages of steam in carrier gas: (a) BC; (b) BC + Fe; (c) BC + Ca
圖 3 H2O+CO2混合氣氛下焦炭溶損反應尾氣中CO/H2含量曲線. (a) BC; (b) BC+Fe; (c) BC+Ca
Figure 3. CO/H2 content curves in the off-gas for coke solution loss reactions in the H2O + CO2 atmosphere: (a) BC; (b) BC + Fe; (c) BC + Ca
圖 4 C+H2O反應的焦炭反應性與水蒸氣載帶率的關系. (a) BC; (b) BC+Fe; (c) BC+Ca
Figure 4. Relationship of PRI in the C + H2O reaction with the percentages of steam in carrier gas: (a) BC; (b) BC + Fe; (c) BC + Ca
圖 5 C+ CO2反應的焦炭反應性與水蒸氣載帶率的關系. (a) BC; (b) BC+Fe; (c) BC+Ca
Figure 5. Relationship of PRI in the C + CO2 reaction with the percentages of steam in carrier gas: (a) BC; (b) BC + Fe; (c) BC + Ca
圖 6 焦炭SEM-EDS能譜圖. (a) BC; (b)BC+Fe; (c)BC+Ca
Figure 6. SEM-EDS morphologies of cokes: (a) BC; (b) BC + Fe; (c) BC + Ca
圖 7 焦炭溶盡碳素后灰渣的XRD圖譜. (a) BC; (b) BC+Fe; (c) BC+Ca
Figure 7. XRD patterns of ashes derived from cokes reacted with CO2: (a) BC; (b) BC + Fe; (c) BC + Ca
表 1 配合煤樣性質指標
Table 1. Main characteristics of the blending coals
Mad/% Ad/% Vad/% St,d/% G/% Y/mm b/% Rmax/% A/I 0.94 9.93 21.50 1.05 86.3 15.5 12 1.39 2.25 
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表 2 焦炭的工業分析和熱性質
Table 2. Proximate analysis and thermal properties of cokes
Coke Mad/% Aad/% Vad/% St,ad/% CRI/% CSR/% BC 0.07 12.3 0.9 1.0 22.24 63.39 BC + Fe 0.10 13.2 0.7 0.7 28.52 53.23 BC + Ca 0.09 13.4 1.2 0.8 39.26 36.94
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表 3 H2O+CO2混合氣氛中焦炭反應性的實驗值與理論值
Table 3. Experimental and theoretical values of coke reactivity in the H2O + CO2 atmosphere
Coke $x_{{\rm{H}}_2{\rm{O}}} /\% $ PRIexp/% PRIcal/% BC 0 17.24 17.24 10 18.90 24.19 20 20.80 28.44 30 22.44 32.34 BC + Fe 0 26.44 26.44 10 27.65 33.64 20 30.33 40.48 30 31.70 45.04 BC + Ca 0 34.85 34.85 10 37.40 43.45 20 38.50 47.40 30 41.07 53.61
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中文字幕在线观看表 4 H2O與CO2與焦炭反應的相互抑制因子
Table 4. Inhibition factors of the reactions of H2O and CO2 with cokes
Coke k1′ k1 $\alpha_{{\rm{CO}}_2/{\rm{H}}_2{\rm{O}}} $ k2′ k2 $\alpha_{{\rm{H}}_2{\rm{O}}/{\rm{CO}}_2} $ BC 0.548 0.288 0.260 0 ?0.121 0.121 BC + Fe 0.651 0.400 0.251 0 ?0.217 0.217 BC + Ca 0.636 0.466 0.170 0 ?0.263 0.263
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