Comparison of the reducing activity of coke powder and semi-coke and its application in the carbonization process of Ti-bearing blast furnace slag
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摘要: 在含钛高炉渣“高温碳化-低温氯化”提钛工艺中，高温碳化是关键且重要的工艺环节。高温碳化过程采用的碳质还原剂直接影响着该工序的成本和高炉渣中二氧化钛的碳化率，选取更加优质廉价的碳质还原剂是高温碳化工序提质降本的重要手段之一。研究选取兰炭和焦粉进行对比，通过研磨筛分获得不同粒径范围的碳质还原剂，并采用X-射线衍射仪、热重分析仪、比表面积分析仪等研究了兰炭和焦粉还原活性的差异，提出了与产线当前应用焦粉达到相同还原反应活性时兰炭对应的粒径控制范围，并进行了工业应用试验。结果表明，兰炭较焦粉石墨化度弱，在转化率0.3～0.8的范围内平均活化能低，粒径在0.150 mm以上比表面积大，导致兰炭反应活性高于焦粉。基于此提出了兰炭的粒径应在1～2 mm和0.150～1 mm的区间内进行协同控制，工业试验结果表明，按照此范围控制的兰炭应用于含钛高炉渣高温碳化过程，吨渣冶炼电耗和碳化率均与当前使用粒径分布的焦粉达到相同控制水平。Abstract: In the process of titanium extraction from Ti-bearing blast furnace slag by “high temperature carbonization and low temperature chlorination”, high temperature carbonization is very critical and important. The carbonaceous reducing agent used in the high temperature carbonization process directly affects the cost of the process and the carbonization rate of titanium dioxide in the blast furnace slag, so the selection of more high-quality and low-cost carbonaceous reducing agent is one of the important means to improve the quality and reduce the cost of high temperature carbonization process. In this study, semi-coke and coke powder with different particle size ranges were obtained by grinding and sieving as raw materials. By XRD, TGA, BET and other analytical methods, the difference of the reducing activity between semi-coke and coke powder was studied. The particle size of semi-coke corresponding to coke powder with the same reduction reaction activity was proposed, and the industrial application test was carried out. The results show that the graphitization degree of semi-coke is much lower than that of coke powder. In the range of conversion rate of 0.3~0.8, the average activation energy of semi-coke is lower than that of coke powder. When the particle size is more than 0.150 mm, the specific surface area of semi-coke is greater than that of coke powder, contributing to its higher reactivity than that of coke powder. Based on these, it is proposed that the particle size of semi-coke should be collaboratively controlled in the range of 1~2 mm and 0.150~1 mm. The industrial test results reveal that the power consumption per ton of slag and carbonization rate are the same as those of coke powder with particle size distribution currently used, when this above range-controlled semi-coke is applied to the high temperature carbonization process of Ti-bearing blast furnace slag.
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图 2 兰炭和焦粉在CO2气氛下的动力学曲线
（a）兰炭；（b）焦粉
Figure 2. Kinetic curves of semi-coke and coke powder in CO2 atmosphere
图 3 不同转化率下兰炭和焦粉的活化能
Figure 3. Activation energy of semi-coke and coke powder at different conversion ratio
图 4 兰炭和焦粉的BET表面积
(a) 兰炭；（b）焦粉
Figure 4. BET surface area plots of semi-coke and coke powder
表 1 高钛型高炉渣的典型化学成分
Table 1. Typical chemical composition of high-titanium blast furnace slag
% TiO2 Al2O3 MgO CaO SiO2 TFe V2O5 20.90～23.64 12.60～14.69 6.98～7.85 27.31～29.23 24.20～25.12 1.70～2.88 0.26～0.28 
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表 2 粒径筛分前焦粉和兰炭的主要成分
Table 2. The main components of coke powder and semi-coke
样品名称 成分/% 粒径分布/% 固定碳 灰分 挥发分 ＞2 mm 1～2 mm 0.15～1 mm 0.075～0.15 mm ＜0.075 mm 焦粉 85.44 13.17 1.19 3.47 4.69 31.51 22.47 37.86 兰炭 83.14 9.97 3.90 33.28 60.72 5.83 0.06 0.11
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表 3 兰炭和焦粉石墨化度计算结果
Table 3. Graphitization degree of coke powder and semi-coke
样品名称 2θ/(°) d002/nm g 兰炭 26.058 0.3417 0.2706 焦粉 26.342 0.3381 0.6915
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表 4 兰炭在CO2气氛下的动力学求解结果
Table 4. Kinetic calculation results of semi-coke in CO2 atmosphere
转化率α 斜率k 截距b 活化能Ea/
(kJ·mol−1)指前因子A 相关系数R 0.3 −20.710 2.815 172.1829 188.341450 0.9195 0.4 −19.120 0.883 158.9637 25.185660 0.9445 0.5 −17.618 −0.780 146.4761 4.397609 0.9545 0.6 −17.151 −1.478 142.5934 2.129945 0.9692 0.7 −16.664 −2.146 138.5445 1.061084 0.9745 0.8 −16.318 −2.691 135.6679 0.602847 0.9799 平均 149.07
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表 5 焦粉和CO2还原反应的动力学求解结果
Table 5. Kinetic solution results of coke powder in CO2 atmosphere
转化率α 斜率k 截距b 活化能Ea/
(kJ·mol−1)指前因子A 相关系数R 0.3 −10.134 −8.063 84.2541 0.001738 0.9195 0.4 −20.335 −0.801 169.0652 4.972801 0.9442 0.5 −34.393 9.025 285.9434 155685.45 0.9545 0.6 −55.791 23.809 463.8464 6.65×1011 0.9598 0.7 −91.952 48.591 764.4889 6.35×1022 0.9633 0.8 −162.740 96.828 1353.0204 9.99×1043 0.9729 平均 520.10
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表 6 兰炭的BET表面积求解结果
Table 6. BET surface area calculation results of semi-coke
粒径区间
/mm斜率k 截距b 单层饱和气体吸附量Qm/(cm3·g−1) 比表面积SBET/(m2·g−1) 相关系数R ≥2.000 0.501750 − 0.003670 2.0077 8.7440 0.9986 1～2 0.503270 − 0.006758 2.0141 8.7716 0.9978 0.150～1 0.410177 − 0.001802 2.4487 10.6647 0.9991 0.075～0.150 0.379030 − 0.003601 2.6636 11.6006 0.9986 ＜0.075 0.252099 − 0.001549 3.9912 17.3825 0.9989
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表 7 焦粉的BET表面积求解结果
Table 7. BET surface area calculation results of coke powder
粒径区间
/mm斜率k 截距b 单层饱和气体吸附量Qm/(cm3·g−1) 比表面积SBET/(m2·g−1) 相关系数R ≥2 0.756079 − 0.013836 1.3473 5.8676 0.9965 1～2 0.672806 − 0.011914 1.5131 6.5899 0.9969 0.150～1 0.510554 − 0.007256 1.9869 8.6533 0.9974 0.075～0.150 0.308090 − 0.003710 3.2854 14.3084 0.9982 ＜0.075 0.217021 − 0.002348 4.6582 20.2876 0.9982
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表 8 兰炭和焦粉的失重率与最大失重速率
Table 8. Weight loss and maximum weight loss rate of coke powder and semi-coke
粒径区
间/mm焦粉 兰炭 失重率/% 失重速
率/(%·s−1)失重率/% 失重速率-
Ⅰ/(%·s−1)失重速率-
Ⅱ/(%·s−1)≥2 44.68 0.039 46.27 0.041 1～2 48.80 0.036 66.43 0.051 0.027 0.150～1 57.63 0.044 89.31 0.100 0.018 0.075～0.150 74.83 0.064 87.63 0.080 0.044 ＜0.075 79.11 0.076 84.32 0.066 0.039
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表 9 兰炭和焦粉在含钛高炉渣高温碳化过程的应用
Table 9. Application of semi-coke and coke powder in high temperature carbonization of Ti-bearing high furnace slag
编号 吨渣电耗/(kWh·t−1) 碳化率/% 焦粉 原兰炭 研磨筛分
后兰炭焦粉 原兰炭 研磨筛分
后兰炭1 845.82 886.69 814.75 87.12 85.82 87.39 2 826.81 904.77 852.49 86.30 85.69 86.23 3 860.55 874.45 843.06 86.54 85.13 87.66 4 869.25 855.05 845.70 87.35 84.82 86.47 5 834.28 836.47 840.28 87.64 85.78 88.04 6 842.20 837.67 832.87 86.92 85.96 87.92 7 850.25 861.88 840.44 88.10 86.13 87.88 8 832.87 874.12 842.20 87.67 85.74 87.67 9 835.38 840.34 834.92 86.38 86.25 87.89 10 836.53 861.56 835.25 86.60 86.86 86.71 11 841.90 864.89 821.53 87.42 86.14 87.21 12 828.90 857.01 835.38 88.13 85.98 86.62 13 848.62 854.29 834.28 87.42 84.77 86.89 14 814.44 871.92 865.65 87.63 86.92 87.40 15 847.88 918.49 852.63 86.88 85.84 87.09 标准差 13.20 22.45 11.97 0.57 0.59 0.56 均值 841.04 866.64 839.43 87.21 85.86 87.27 极差 54.81 82.02 50.90 1.83 2.15 1.81 备注：吨渣电耗为每批次加入高炉渣开始至碳化终点消耗的总电耗除以每批次加入的高炉渣量；碳化率为高炉渣中TiO2转变为TiC的比例。
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