Analysis of active microstructure during steam gasification of Shengli char catalyzed by calcium component
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摘要: 针对胜利褐煤焦水蒸气气化反应过程中钙组分的催化作用，在脱除矿物质胜利褐煤煤样SL+中添加CaO在1 100℃热解得到添钙煤焦样品Ca-J，Ca-J经盐酸处理脱除其游离钙组分，得到添钙焦酸洗煤样Ca-J+，采用BET、SEM-EDS、XRD、FT-IR及XPS等技术对所制备煤样进行表征，并在微型固定床反应装置上进行水蒸气气化反应性测试，对煤样微结构特性进行研究，提出了钙催化水蒸气气化反应中的活性微结构模型。结果表明，水蒸气气化反应中，添钙焦样酸洗前后的Ca-J和Ca-J+碳转化率及反应活性指数基本相同，但比酸洗煤焦样SL+-J高出许多。样品XPS的Ca 2p谱图分峰说明，Ca-J+中存在Ca（CH3COO）2与Ca-OOR两种化学形态的钙。化学分析及SEM-EDS表征均表明，Ca-J+中钙含量比Ca-J减少了97%以上；XRD表明，Ca-J中游离存在的CaS、CaO经酸洗被脱除；FT-IR表明，Ca-J及Ca-J+中含有C=O、C-O等特征吸收峰。综合上述结果，可推测“R-O-Ca-O-R'”（R及R'可为脂肪族或芳香族结构体）是钙组分催化胜利褐煤焦水蒸气气化的活性微结构。Abstract: The catalytic effect of calcium component on steam gasification of Shengli lignite char was studied. Demineralized coal samples were loaded with calcium oxide and pyrolyzed at 1 100℃ (Ca-J). Ca-J+ was prepared from Ca-J treated by hydrochloric acid. The char samples were characterized by BET, SEM-EDS, XRD, FT-IR and XPS. The steam gasification of the char samples was performed in a micro fixed bed reactor. The possible catalytic active micro structure was discussed and proposed. The results show that carbon conversion and reactivity index of Ca-J and Ca-J+ samples during steam gasification were substantially similar, but much higher than those of demineralized char samples (SL+-J). Ca (CH3COO)2 and Ca-OOR, two calcium species are present in Ca-J+ sample determined by XPS. Chemical analysis and SEM-EDS prove that calcium content of Ca-J+ decreases by more than 97% than that of Ca-J sample. XRD analysis indicates free inorganic mineral (CaS, CaO) is removed by hydrochloric acid. FT-IR spectra show C=O, C-O peaks present in Ca-J and Ca-J+ samples. So it is postulated that "R-O-Ca-O-R'" (R and R' are aliphatic and aromatic structures, respectively) is the catalyst active microstructure during char steam gasification.
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图 1 煤焦碳转化率随温度的变化
Figure 1 Carbon conversion versus reaction temperature for steam gasification of char samples
图 3 煤焦样品的SEM-EDS照片
Figure 3 SEM-EDS pictures of char samples
(a1)-(a4): Ca-J; (b1)-(b4): Ca-J+; (a1), (a3), (b1), (b3): SEM; (a2), (b2): Ca; (a4), (b4): EDS
图 5 煤焦样品、CaO及Ca (CH3COO)2的FT-IR谱图
Figure 5 FT-IR spectra of char samples, CaO and Ca (CH3COO)2
表 1 试验煤样及所对应灰分中主要金属元素的含量
Table 1 Metal ion percentage in coal samples and ashes
Sample Coal based/ash based w/% Al Na Ca Si Fe K Mn SL 2.40/35.50 0.58/8.59 0.41/6.08 3.11/46.09 0.11/1.69 0.08/1.18 0.06/0.88 SL+ 0.90/32.94 0.00/0.16 0.01/0.19 2.89/64.58 0.03/0.92 0.03/1.18 0.00/0.03 
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表 2 煤焦样品的工业分析和元素分析
Table 2 Proximate and ultimate analyses of chars samples
Sample Proximate analysis wd/% Ultimate analysis wdaf/% A V FC C H N St+O* SL+-J 6.33 2.84 90.83 94.48 0.30 1.16 4.06 Ca-J 18.42 3.34 78.23 93.97 0.42 1.36 4.25 Ca-J+ 8.13 5.45 86.42 94.42 0.59 1.14 3.85 *: by difference
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表 3 煤焦样品孔结构参数
Table 3 Porosity characteristics of char samples
Sample Surface area A/(m2·g-1) Pore volume v/ (cm3·g-1) Average pore diameter d /nm SL+-J 6.88 3.53×10-3 2.26 Ca-J 39.55 66.72×10-3 7.09 Ca-J+ 19.99 27.21×10-3 5.43
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表 4 煤焦样品EDS元素含量
Table 4 Element percentage in char samples of the EDS
Sample Element watomic/% C O Al Si S Cl Ca Ca-J 85.01 7.35 1.37 0.72 1.18 0.35 4.89 Ca-J+ 78.58 18.80 - 1.39 0.58 0.51 0.14
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