Structure evolution characteristics of Inner Mongolia coal char during CO2 gasification
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摘要: 基于滴管炉制备内蒙褐煤快速热解焦，借助高频炉开展快速热解焦与CO2的气化实验，考察了煤焦气化过程的结构演变特性。结果表明，随着反应的进行，气化半焦的石墨化程度不断增加，但未达到天然石墨的有序化程度；比表面积先增大后减小，而平均孔径总体呈相反的变化趋势；气化半焦的粒径在反应前期逐渐减小，当转化率大于74%，半焦粒径逐渐增大，归因于气化后期部分颗粒的黏结。Abstract: The rapid pyrolysis chars of an Inner Mongolia (Neimeng) lignite were prepared in a drop tube furnace, and the coal char gasification experiments with CO2 were conducted using a high-frequency induction furnace. The characteristics of char structure evolution during gasification were studied. Results show that as the reaction proceeds, the graphitization degree of gasified chars increases, but it is far less than the degree of natural graphite. The specific surface area firstly increases and then decreases with char conversion, while the average pore size has an opposite trend overall. The particle size of gasified chars gradually increases with conversion in the early stage, and the particle size of gasified chars increases when the conversion exceeds 74%, which could be ascribed to the cohesion of some particles in the later stage of gasification.
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Key words:
- rapid pyrolysis /
- coal char /
- CO2 gasification /
- structure evolution
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图 1 滴管炉实验装置流程示意图
Figure 1 Schematic diagram of drop tube furnace setup
1: corundum tube; 2: heater; 3: insulation; 4: feed nozzle; 5: N2 inlet; 6: hopper; 7: screw feeder; 8: air lock; 9: hopper weigher; 10, 13: cooling water; 11: weighing controller; 12: temperature controller; 14: pressure gage; 15: char collector; 16: filter; 17: cooler; 18: dry box; 19: gas flowmeter
图 2 高频炉实验装置流程示意图
Figure 2 Schematic diagram of high-frequency induction furnace setup
1: quartz tube; 2: feed tube; 3, 5: flowmeter; 4: N2 inlet; 6: CO2 inlet; 7: power controller; 8: molybdenum tube; 9: induction coil; 10: high-frequency current generator; 11: corundum tube; 12: emulsion pipe; 13: settling chamber; 14: gas washing bottle
图 3 进样示意图
Figure 3 Schematic diagram of sample feeding
1: feed tube; 2: quartz tube head; 3, 5: emulsion pipe; 4: spring water stopper; 6: dropper; 7: rubber drop head
图 4 内蒙煤焦及其气化半焦的XRD谱图
Figure 4 XRD spectra of NM char and gasified chars
a: x=0; b: x=28%; c: x=52%; d: x=62%; e: x=74%; f: x=79%; g: x=86%; h: x=89%
图 5 内蒙煤焦与气化半焦的微晶结构参数随转化率的变化
Figure 5 Variation of crystallite parameters of NM char and gasified chars with conversion
图 7 内蒙煤焦及其气化半焦的比表面积 (ABET) 和平均孔径 (dave) 随转化率的变化
Figure 7 Variation of surface areas (ABET) and average pore sizes (dave) of NM char and gasified chars with conversion
图 8 内蒙煤焦与气化半焦的的孔径分布
Figure 8 Pore size distribution curves of NM char and gasified chars
图 9 气化半焦的粒径随转化率的变化
Figure 9 Variation of particle size of NM gasified char with conversion
图 10 转化率为86%的气化半焦及其黏结块的SEM照片
Figure 10 NM gasified chars (a) at 86% conversion and SEM image of the agglomerates (b)
表 1 煤样的工业分析和元素分析以及煤灰熔融特征温度
Table 1 Proximate and ultimate analysis and ash fusion temperatures of coal sample
Sample Proximate analysis wd/% Ultimate analysis wd/% Ash fusion temperature t/℃ V FC A C H N S O DT ST HT FT NM 42.09 43.60 14.31 61.18 2.35 1.21 0.64 20.31 1119 1169 1200 1218 note: d: dry basis; V: volatile matter; FC: fixed carbon; DT: deformation temperature; ST: softening temperature; HT: hemispherical temperature; FT: flow temperature 
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表 2 内蒙煤焦及其气化半焦的灰含量和转化率
Table 2 Ash contents and conversions of NM char and gasified chars
Sample Ad/% Conversion x/% NM-1200 51.75 NM-1230(g)-1 59.90 28 NM-1230(g)-2 69.28 52 NM-1230(g)-3 73.69 62 NM-1230(g)-4 80.28 74 NM-1230(g)-5 83.84 79 NM-1230(g)-6 88.15 86 NM-1230(g)-7 90.37 89 note:Ad: ash on dry basis; NM-1200: NM char obtained at 1200℃; NM-1230(g)-1: NM char gasified at 1230℃ for one time
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