Particle size classification and CO2 gasification of the char fines from fluidized bed gasification of Shenhua coal
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摘要: 按粒径将神华煤流化床气化带出细粉(简称细粉) 依次筛分为七个组分。采用工业分析仪、元素分析仪、热重分析仪、X射线粉末衍射仪、物理吸附仪等对各组分细粉的基本物化特性、CO2恒温和程序升温气化行为进行了考察。在此基础上, 对气化活性差异及其原因进行初步探索。结果表明, 细粉经历部分气化后, 由于挥发分的析出, 细粉的固定碳含量较原煤高, 但较相应半焦低。细粉的粒径分布范围较宽, 呈近似"M"形分布。随细粉粒径减小, 灰分含量增大, 而含碳量减少。CO2恒温气化与程序升温气化获得的气化反应活性顺序一致:均随细粉粒径的减小先逐渐降低而后又逐渐升高。不同细粉气化反应活性的差异与其自身的石墨化程度及灰分含量有关, 而在研究实验条件下与孔径结构关系不大。Abstract: The char fines from fluidized bed gasification (fines for short) are classified into 7 components based on particle size. The basic physicochemical properties, the constant and programmed increasing temperature CO2 gasification behaviors were investigated by coal quality analyzer, elemental analyzer, X-ray powder diffractometer, gas sorption analyzer and thermogravimetric analyzer. The difference of gasification reactivity and its reasons were discussed. The results show that after partial gasification, fixed carbon of the fines is higher than that of its parent coal but lower than the corresponding coal char because of the escape of volatiles. The particle size distribution of fines is very wide and multimodal distribution with the shape of "M". In addition, the ash content of fines approximately increases with decreasing particle size. However, the carbon content decreases with decreasing particle size. Both the constant and programmed increasing temperature CO2 gasification show the same result. The gasification reactivity firstly decreases and then gradually increases with decreasing particle size. Furthermore, the carbon crystalline structure and ash content are contributed to the difference in gasification reactivity of fines, and the different reactivity is not related to the pore structure in this experimental condition.
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图 1 常压快速热解固定床示意图
Figure 1 Scheme of atmospheric pyrolysis fixed bed reactor
1: cylinder; 2: flange; 3: stainless rod; 4: reactor; 5: furnace; 6: crucible; 7: thermocouple; 8: temperature controller
图 3 不同种类细粉在950 ℃下的碳转化率
Figure 3 Carbon conversion of different fines at 950 ℃
■: F(d > 2); ○: F(0.9-2); ▲: F(0.5-0.9); ▽: F(0.098-0.5); ◇: F(0.038 5-0.098); ◁: F(0.001-0.038 5); ▶: F(d < 0.001)
图 4 30 ℃/min升温速率下两种神华细粉的气化反应速率
Figure 4 Gasification curves of Shenhua fines at a heating rate of 30 ℃/min (a): gasification curves; (b): the partial enlarged drawing of gasification curves
■: F(d > 2); ○: F(0.9-2); ▲: F(0.5-0.9); ▽: F(0.098-0.5); ◇: F(0.038 5-0.098); ◁: F(0.001-0.038 5); ▶: F(d < 0.001)
图 5 30 ℃/min升温速率下tpeak与各粒径细粉对应关系
Figure 5 Correlation between tpeak of the fines at a heating rate of 30 ℃/min and the different particle size fines
图 7 灰分含量与反应性指数的对应关系
Figure 7 Correlations between ash content and gasification reactivity
图 8 未脱灰与脱灰细粉在950 ℃下的碳转化率
Figure 8 Carbon conversions of three un-demineralized and demineralized coal fines at 950 ℃
■: F(d>2); ▲: F(0.5-0.9); ▶: F(d < 0.001); □: DF(d>2); △: DF(0.5-0.9); ▷: DF(d < 0.001)
图 9 三类未脱灰细粉和相应的脱灰细粉的XRD谱图
Figure 9 XRD spectra of three un-demineralized and the corresponding demineralized coal fines
(a): three un-demineralized fines; (b): the corresponding demineralized coal fines
图 10 细粉DF(d > 2)002峰的Gaussian拟合曲线
Figure 10 Fitting curves for the 002 peak of coal fine DF(d > 2)
图 11 比表面积和反应性指数的关系
Figure 11 Correlation between the surface area and gasification reactivity
表 1 样品的工业分析和元素分析
Table 1 Proximate and ultimate analyses of samples
Sample Proximate analysis wad/% Ultimate analysis wad/% V M A FC C H O* N S SH Coal 28.93 2.49 16.84 51.74 56.30 - - - 0.33 F(d > 2) 2.20 0.91 12.16 84.73 77.50 0.62 8.16 0.60 0.05 F(0.9-2) 2.29 0.77 10.85 86.10 78.05 - - - 0.04 F(0.5-0.9) 1.77 0.65 11.37 86.21 76.15 0.20 11.08 0.52 0.03 F(0.098-0.5) 2.06 0.60 11.45 85.89 75.45 - - - 0.04 F(0.0385-0.098) 3.12 0.63 18.98 77.27 71.45 - - - 0.07 F(0.001-0.0385) 2.48 0.60 17.66 79.26 70.90 - - - 0.06 F(d < 0.001) 3.47 0.63 25.28 70.62 67.00 0.33 6.22 0.50 0.04 FSH 3.00 0.87 17.97 78.16 69.15 - - - 0.02 CSH 1.19 0.59 10.87 87.35 75.40 - - - 0.15 O*: by difference；-：not detected 
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表 2 三类细粉的灰成分分析
Table 2 Ash composition analysis of the three fines
Sample Content w / % SiO2 Al2O3 Fe2O3 CaO MgO TiO2 K2O Na2O SO3 P2O5 F(d > 2) 5.83 1.83 1.03 1.05 0.14 0.08 0.031 0.062 0.22 0.030 F(0.5-0.9) 6.02 2.04 1.09 1.39 0.17 0.075 0.065 0.089 0.15 0.041 F(d < 0.001) 8.91 3.25 1.46 4.24 0.28 0.14 0.12 0.18 0.25 0.06
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表 3 各类细粉在950 ℃温度下的反应性指数RS值
Table 3 Reactivity indexes of different fines at 950 ℃
Sample F(d > 2) F(0.9-2) F(0.5-0.9) F(0.098-0.5) F(0.038 5-0.098) F(0.001-0.098) F(d < 0.001) Rs/min-1 0.025 7 0.021 9 0.020 9 0.023 5 0.027 5 0.032 8 0.041 4
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表 4 30 ℃/min升温速率下细粉的特征气化温度
Table 4 Initial, peak and final temperature of the fines and the corresponding char at 30 ℃/min
Sample Temperature t/℃ tinitial tpeak tfinal F(d > 2) 857 1 091 1 191 F(0.9-2) 855 1 100 1 192 F(0.5-0.9) 861 1 102 1 207 F(0.098-0.5) 856 1 098 1 207 F(0.0385-0.098) 839 1 085 1 221 F(0.001-0.0385) 838 1 083 1 194 F(d < 0.001) 785 1 074 1 178
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表 5 三类脱灰后细粉的晶体结构参数
Table 5 Crystal structure parameters of three demineralized coal fines
Sample d002, P /nm Lc, P /nm d002, G /nm Lc, G /nm Xp XG d002, a /nm Lc, a /nm DF(d > 2) 43.90 172.00 35.80 156.80 0.15 0.85 37.10 159.10 DF(0.5-0.9) 44.40 182.60 35.90 158.50 0.14 0.86 37.10 162.00 DF(d < 0.001) 44.50 158.70 35.90 155.00 0.15 0.85 37.30 155.30
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表 6 三类细粉的孔结构
Table 6 Pore structure analysis of the three fines
Sample area BET surface area A/(m2·g-1) Micropore area A/(m2·g-1) Total pore volume v/(cm3·g-1) Micropore volume v/(cm3·g-1) F(d > 2) 224 145 0.145 6 0.058 4 F(0.5-0.9) 269 153 0.213 5 0.062 1 F(d < 0.001) 221 109 0.193 1 0.044 5
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