钙对神华褐煤水蒸气气化特性影响的实验研究
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摘要
褐煤是我国重要的煤炭资源。钙对褐煤在热解及气化过程的影响的研究在文献中受到很多关注,但目前为止,研究较多的是澳大利亚褐煤或印尼褐煤,对国产褐煤的相关研究较少。本论文针对国产神华褐煤进行钙对其水蒸气气化特性影响的研究。
论文采用国产神华6#褐煤为原料,利用化学沉淀的方法向酸洗后的褐煤中植入钙元素;在不同温度下对植入不同含量钙的煤样进行热解,并利用小型石英反应器和热重分析仪(TGA)对半焦进行水蒸气气化实验。热解实验结果表明,钙的植入对褐煤在热解过程中挥发份析出量产生显著影响。气化实验结果表明,与酸洗煤相比,钙的植入明显提高褐煤半焦在水蒸气中的气化速率。低温下气化以及气化的初始阶段,气化速率随钙含量提高显著提高;但在高温下气化以及气化程度较高的情况下,由于钙的烧结作用,随植入的钙含量的增加则半焦的气化速率下降。钙的植入量为2%时对褐煤半焦的气化速率的提高最明显,进一步提高钙含量,则进一步增加不明显。
采用XRD、SEM、BET等手段对热解半焦以及水蒸气气化后的半焦进行了表征。XRD分析表明,随着气化时间、气化温度及钙植入量的增加,气化半焦中钙更多以CaO的形式存在。通过SEM分析可以看出钙的氧化物以纳米颗粒的形式高度分散于活性半焦微孔表面或外表面,因而植入钙的褐煤半焦具有非常高的反应活性。通过BET实验结果表明,煤中植入钙后,气化半焦的比表面积增大,平均孔径尺寸减小,增加了半焦的反应活性,钙的植入量进一步增加,微孔体积增加,平均孔径过分减少,使得比表面积减少,不利于半焦的反应活性;气化温度升高,半焦的比表面积增加,同时对微孔体积和微孔面积的增加起抑制作用,有利气化反应的进行;气化时间较短时,半焦气化活性较高,随着气化时间的延长,半焦的活性反应下降。
The optimal using of lignite is a hot topic in the field of chemical engineering science. The effect of calcium on pyrolysis and gasification process of brown coal is very important and needs more attention. Most of the research lignite in this field has been done on Australian brown coal and Indonesian coals. More research on Chinese domestic low-rank coal seems to be very critical. In this thesis, steam gasification of Shenhua lignite and the effects of calcium on it are investigated.
Shenhua #6 lignite was used as raw material. The raw coal was washed using acid and then the calcium was impregnated into coal at different temperatures with different concentrations of calcium. Char supported calcium was prepared by pyrolysis of those coal samples. The reactivity of char in steam gasification was then investigated. Pyrolysis results showed that the content of calcium in the temperature range of 823-1100K did not have obvious effects on pyrolysis. Gasification results showed that gasification rate increased with the calcium content at low temperatures, but it was less influenced by calcium content which is more than 2% at high temperatures. The gasification rate increased with the calcium content at the beginning of gasification but decreased in the later period of gasification. Those results suggested that calcium could increase lignite char gasification rate, but the content of calcium in char did not play the key role in the gasification rate. The optimum experiment conditions for steam gasification are the 2% calcium content, gasification time for 30min, and gasification temperature of 1100K, respectively.
XRD, SEM, BET analysis were used to characterize the char property after pyrolysis and steam gasification. XRD results showed that there would be more content of CaO in char with the increasing of gasification time, the gasification temperature or the content of calcium, which made the calcium have more time to react with water vapor. SEM showed that calcium oxide in the form of nano-particles was highly dispersed on char porous surface, thus the lignite char impregnated with calcium performed a very high reactivity. BET showed that the char surface area after gasification increased with increasing calcium content, which decreased the average pore size but improved the reactivity of char. The micro-pore volume of char increased as the average pore size decreased, which resulted in the increased calcium content, the BET surface area reduction and the decreased reactivity of chars. The BET surface area of char increased with the increasing temperature and was beneficial to the gasification while inhibiting action on the growth of micro-pore volume and surface area. The reactivity of char is higher in a short gasification time while it decreased in a longer gasification time.
论文采用国产神华6#褐煤为原料,利用化学沉淀的方法向酸洗后的褐煤中植入钙元素;在不同温度下对植入不同含量钙的煤样进行热解,并利用小型石英反应器和热重分析仪(TGA)对半焦进行水蒸气气化实验。热解实验结果表明,钙的植入对褐煤在热解过程中挥发份析出量产生显著影响。气化实验结果表明,与酸洗煤相比,钙的植入明显提高褐煤半焦在水蒸气中的气化速率。低温下气化以及气化的初始阶段,气化速率随钙含量提高显著提高;但在高温下气化以及气化程度较高的情况下,由于钙的烧结作用,随植入的钙含量的增加则半焦的气化速率下降。钙的植入量为2%时对褐煤半焦的气化速率的提高最明显,进一步提高钙含量,则进一步增加不明显。
采用XRD、SEM、BET等手段对热解半焦以及水蒸气气化后的半焦进行了表征。XRD分析表明,随着气化时间、气化温度及钙植入量的增加,气化半焦中钙更多以CaO的形式存在。通过SEM分析可以看出钙的氧化物以纳米颗粒的形式高度分散于活性半焦微孔表面或外表面,因而植入钙的褐煤半焦具有非常高的反应活性。通过BET实验结果表明,煤中植入钙后,气化半焦的比表面积增大,平均孔径尺寸减小,增加了半焦的反应活性,钙的植入量进一步增加,微孔体积增加,平均孔径过分减少,使得比表面积减少,不利于半焦的反应活性;气化温度升高,半焦的比表面积增加,同时对微孔体积和微孔面积的增加起抑制作用,有利气化反应的进行;气化时间较短时,半焦气化活性较高,随着气化时间的延长,半焦的活性反应下降。
The optimal using of lignite is a hot topic in the field of chemical engineering science. The effect of calcium on pyrolysis and gasification process of brown coal is very important and needs more attention. Most of the research lignite in this field has been done on Australian brown coal and Indonesian coals. More research on Chinese domestic low-rank coal seems to be very critical. In this thesis, steam gasification of Shenhua lignite and the effects of calcium on it are investigated.
Shenhua #6 lignite was used as raw material. The raw coal was washed using acid and then the calcium was impregnated into coal at different temperatures with different concentrations of calcium. Char supported calcium was prepared by pyrolysis of those coal samples. The reactivity of char in steam gasification was then investigated. Pyrolysis results showed that the content of calcium in the temperature range of 823-1100K did not have obvious effects on pyrolysis. Gasification results showed that gasification rate increased with the calcium content at low temperatures, but it was less influenced by calcium content which is more than 2% at high temperatures. The gasification rate increased with the calcium content at the beginning of gasification but decreased in the later period of gasification. Those results suggested that calcium could increase lignite char gasification rate, but the content of calcium in char did not play the key role in the gasification rate. The optimum experiment conditions for steam gasification are the 2% calcium content, gasification time for 30min, and gasification temperature of 1100K, respectively.
XRD, SEM, BET analysis were used to characterize the char property after pyrolysis and steam gasification. XRD results showed that there would be more content of CaO in char with the increasing of gasification time, the gasification temperature or the content of calcium, which made the calcium have more time to react with water vapor. SEM showed that calcium oxide in the form of nano-particles was highly dispersed on char porous surface, thus the lignite char impregnated with calcium performed a very high reactivity. BET showed that the char surface area after gasification increased with increasing calcium content, which decreased the average pore size but improved the reactivity of char. The micro-pore volume of char increased as the average pore size decreased, which resulted in the increased calcium content, the BET surface area reduction and the decreased reactivity of chars. The BET surface area of char increased with the increasing temperature and was beneficial to the gasification while inhibiting action on the growth of micro-pore volume and surface area. The reactivity of char is higher in a short gasification time while it decreased in a longer gasification time.
引文
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[2].赵虹,郭飞,杨建国.印尼褐煤的吸附特性及脱水研究[J].煤炭学报,2008,33(7):799-802.
[3].张殿奎.我国褐煤综合利用的发展现状及展望[J].神华科技,2010,8(1):51-56.
[4].白向飞.中国褐煤及低阶烟煤利用与提质技术开发[J].煤质技术,2010,6:9-11.
[5].冯孔方,胡汉,朱云.褐煤吸附钯的研究[J].稀有金属,2009,33(3):415-419.
[6].文兵.论述褐煤的化工技术及应用[J].工业技术,2010,22(155.
[7].刘卫兵等.褐煤超临界醇解影响因素的研究[J].武汉科技大学学报,2010,33(1):95-98.
[8].邹炎,李晓芸,孟辉.活性焦干法烟气污染控制技术与褐煤活性焦的开发[J].华电技术,2010,32(9):78-82.
[9].冯林永等.褐煤干馏试验研究[J].云南冶金,2007,36(6):29-32.
[10].陈雯等.云南褐煤非燃料应用——褐煤成型半焦制备研究[J].中国工程科学,2005,7(334-346),356.
[11].张旭辉等.中国褐煤在活性焦制备及应用方面的发展前景[J].煤质技术,2011,17(1):59-61.
[12].谢克昌.煤的结构与反应性. 2002,北京:科学出版社.
[13].廖洪强等.煤热解机理研究新进展[J].煤炭转化,1996,19(3):1-8.
[14].郭治,杜铭华,杜万斗.固体热载体褐煤热解过程的数学模型与模拟计算[J].神华科技,2010,8(2):69-72.
[15].Zhiheng Wu,Yasuo Ohtsuka.Key Factors for Formation of N2 from Low-Rank Coals during Fixed Bed Pyrolysis: Pyrolysis Conditions and Inherent Minerals[J].Energy & Fuels,1997,11:902-908.
[16].王子兵,康占肖,杨建山.褐煤干馏半焦挥发份残留率的研究[J].中国煤炭,2010,36(9):94-97,101.
[17].陈贵峰等.低煤阶煤热解煤气性质研究[J].洁净煤技术,1997,3(1):28-31.
[18].李海滨等.二次反应对煤热解产品组成的影响[J].化学工业与工程,1997,14(4):45-51,62.
[19].郭树才.褐煤新法干馏[J].煤化工,2000,3(6-8.
[20].宋振玲,杨奎奇,赵跃民.煤炭燃前脱硫技术研究进展[J].江苏煤炭,2003,4:43-44.
[21].周继红.脱硫(H2S)技术进展[J].河北建筑科技学院学报,2003,20(2):27-29.
[22].李丽娟,李彦旭,韩锋.改性半焦在废气治理中的应用研究[J].洁净煤技术,2007,13(2):90-93.
[23].张芸,兰新哲,宋永辉.活性半焦(兰炭)烟气脱硫的研究进展[J].洁净煤技术,2008,14(1):65-69.
[24].邢德山,阎维平.工业半焦水蒸气活化孔隙结构的变迁[J].中国电机工程学报,2008,28(2):14-19.
[25].王辅臣等.大型煤气化技术的研究与发展[J].化工进展,2009,28(2):173-180.
[26].Sebastlan Reyes,Klavs F Jensen.Modeling of Catalytic Char Gasification[J].Ind. Eng. Chem. Fundam,1984,23(2):223-229.
[27].K J Hiittinger,C Nattermann.Correlations between coal reactivity and inorganic matter content for pressure gasification with steam and carbon dioxide[J].Fuel,1994,73(10):1682-1684.
[28].鲍卫仁等.等离子体煤热解与气化工艺的研究进展[J].现代化工,2003,23(12):10-14.
[29].苑卫军,李建胜,李金海.CRCD煤气化技术与石灰生产的节能减排[J].冶金能源,2009,28(3):39-41.
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