Combustion characteristics of different types of quasi-particles in iron ore sintering process
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摘要: 采用豎直管式爐研究了焦炭粒徑、黏附層、黏附比、焦粉比例對不同類型準顆粒質量轉化率和燃料氮轉化率的影響.結果表明, 對于S和S'型準顆粒, 質量轉化率均隨焦炭粒徑的增大而降低; 對于S'型準顆粒, 燃料氮轉化率隨著焦炭粒徑的增大而減小, 而對于存在黏附層的S型準顆粒, 內核焦炭粒徑越大, 燃料氮轉化率越大; 通過對比S和S'型準顆粒的燃燒情況, 發現黏附層的存在有利于提高準顆粒的質量轉化率和燃料氮轉化率; 對于C型準顆粒, 黏附比越大, 質量轉化率和燃料氮轉化率均越小; P型準顆粒的質量轉化率隨著焦粉比例的增加而減小, 燃料氮轉化率在焦粉比例為50%時達到最低值.Abstract: The iron ore sintering process is the main source of NOx emissions and accounts for about 48% of the total NOx emissions in the iron and steel industry. The generated NOx is mainly from fuel consumption, and it usually exists in the form of quasi-particle in iron ore sintering bed. Therefore, it is important to deeply understand the combustion characteristics and NOx formation mechanism of quasi-particles in iron ore sintering process. Based on this, the effects of coke breeze particle size, presence of an adhering layer of quasi-particles, adhering ratio of quasi-particle, and coke breeze content on the mass conversion rate of different types of quasiparticles and conversion rate of fuel-N to NOx were investigated in a vertical quartz tube reactor in detail. The results show that the mass conversion rate decreases with increasing coke breeze particle size for S'- and S-type quasi-particles; the conversion rate of fuel-N to NOx decreases with increasing coke breeze particle size for S'-type quasi-particle and exhibits the opposite trend for S-type quasi-particle, which is because of the presence of an adhering layer consisting of fine iron ore and limestone. Considering the combustion characteristics of S-and S'-type quasi-particles, the presence of an adhering layer of quasi-particles favors the increase of mass conversion rate and conversion rate of fuel-N to NOx. The mass conversion rate and conversion rate of fuel-N to NOx both decrease with increasing adhering ratio for C-type quasi-particles whose adhering layer consists of fine limestone and coke breeze. For P-type quasi-particles comprising coke breeze, fine limestone, and fine iron ore, the mass conversion rate decreases with increasing coke breeze content. The conversion rate of fuel-N to NOx is not linear and reaches the lowest value when coke breeze content is 50%.
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圖 1 不同類型準顆粒示意圖. (a) S'型; (b) S型; (c) C型; (d) P型
Figure 1. Schematic diagram of different types of quasi-particles: (a) S'-type; (b) S-type; (c) C-type; (d) P-type
圖 2 不同類型的準顆粒. (a) S型; (b) P型; (c) C型; (d) S'型
Figure 2. Different types of quasi-particles: (a) S-type; (b) P-type; (c) C-type; (d) S'-type
圖 3 準顆粒燃燒試驗臺
Figure 3. Schematic diagram of the experimental rig for quasi-particle combustion
圖 4 體積分數變化曲線(P型, 入口氣體體積分數O2/N2為21%/79%, 爐膛溫度T=1000℃)
Figure 4. Volume fraction changes of flue gas components during P-type quasi-particle combustion at 1000℃and atmospheric O2to N2volume ratio of 21∶79
圖 5 粒徑變化對S'型準顆粒燃燒的影響. (a) 對質量轉化率的影響; (b) 對反應指數的影響; (c) 對燃料氮轉化率的影響
Figure 5. Effect of different coke sizes on the combustion characteristics of S'-type quasi-particles: (a) mass conversion rate; (b) reactivity index; (c) conversion rate of fuel-N to NOx
圖 6 內核粒徑對S型準顆粒燃燒的影響. (a) 對質量轉化率的影響; (b) 對反應指數的影響; (c) 對燃料氮轉化率的影響
Figure 6. Effect of different nuclei coke sizes on the combustion characteristics of S-type quasi-particles: (a) mass conversion rate; (b) reactivity in-dex; (c) conversion rate of fuel-N to NOx
圖 7 黏附層對準顆粒燃燒的影響. (a) 對質量轉化率的影響; (b) 對反應指數的影響; (c) 對燃料氮轉化率的影響
Figure 7. Effect of adhering layer on the combustion characteristics of quasi-particles: (a) mass conversion rate; (b) reactivity index; (c) conversion rate of fuel-N to NOx
圖 8 不同黏附比對C型準顆粒燃燒的影響. (a) 對質量轉化率的影響; (b) 對反應指數的影響; (c) 對燃料氮轉化的影響
Figure 8. Effect of different adhering ratios on the combustion characteristics of C-type quasi-particles: (a) mass conversion rate; (b) reactivity index; (c) conversion rate of fuel-N to NOx
圖 9 不同焦粉比例對P型準顆粒燃燒的影響. (a) 對質量轉化率的影響; (b) 對反應指數的影響; (c) 對燃料氮轉化率的影響
Figure 9. Effect of different coke breeze contents on the combustion characteristics of P-type quasi-particles: (a) mass conversion rate; (b) reactivity index; (c) conversion rate of fuel-N to NOx
表 1 不同類型準顆粒的組成和質量比
Table 1. Composition and mass ratio of different types of quasi-particles
類型 內核 黏附層 焦粉比例*/% 黏附比**/% 組分 粒徑/mm 組分 粒徑/mm S 焦炭 1.0~1.4;1.4~2.0;2.0~2.8 石灰石; 鐵礦石 -0.25 75 33.3 P — — 焦炭; 石灰石; 鐵礦石 -0.25 10，30，50，70，100 — C 鐵礦石 2.0~2.8 焦炭; 石灰石 -0.25 5，7.14，12.5 11.1，16.7，33.3 S' 焦炭 1.0~1.4，1.4~2.0，2.0~2.8 — — 100 0 
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表 2 原料化學組分(質量分數)
Table 2. Chemical composition of raw materials ?
% 原料 Fe FeO Al2O3 SiO2 MgO CaO LOI1000* 鐵礦石 62.39 0.35 2.23 4.28 0.13 0.15 3.51 石灰石 0.36 0.10 0.98 2.23 0.48 53.40 42.00 焦炭 1.07 0 4.32 6.11 0.04 0.62 86.85 注: *表示樣品在1000 ℃下的燒失量.
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表 3 不同粒徑焦炭中氮元素質量分數
Table 3. Analysis of nitrogen content in coke of different particles sizes ?
% 1.0 ~ 1.4 mm 1.4 ~ 2.0 mm 2.0 ~ 2.8 mm -0.25 mm 0.92 0.95 0.92 0.86
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