松木粉加压热解气化动力学特性
Kinetics characteristics of pressurized pyrolysis and gasification of pine powder
查看参考文献23篇
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文摘
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为了研究松木粉的加压气化特性,在加压热天平上分别进行了N_2、CO_2+N_2气氛下松木粉加压热解/气化试验,使用Malek法推断最概然机理,研究了反应压力与对热解/气化特性和动力学参数的影响。结果表明:压力对松木粉热解/气化过程有显著影响。N_2气氛下,压力的增大抑制了挥发分的析出,最大失质量由73.8%减小至71.4%;Malek法推断出二级反应级数和随机成核分别为加压热解第1、第2段最概然机理;热解第一段活化能由压力为0时41.15 kJ/mol增大至0.9 MPa时的52.41 kJ/mol。在CO_2+N_2气氛下,热解阶段压力的增大抑制挥发分的析出;半焦气化阶段,压力的增大促进气化反应的进行,使失质量速率峰值由0.101%/K增大至0.162%/K,且出现温度降低;二维扩散(圆柱形对称)为加压气化最概然机理;随着压力的提高,在碳转化率较高时,半焦CO_2气化速率逐渐提高。该文结果可为生物质的高效、清洁利用提供参考依据。 |
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其他语种文摘
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Gasification is one of the most important biomass energy utilization techniques, which is clean and efficient. The pressurized biomass gasification has the advantages of large capacity, high efficiency and low cost compared with the atmospheric gasification of biomass. Meanwhile, thermogravimetric analyzer is a widely used for studying biomass gasification. The researches on atmospheric gasification in thermogravimetric analyzer have been widely reported, but there are a few papers about the pressurized gasification. In this work, the processes of pressurized pyrolysis and CO_2 gasification of pine powder were performed in a pressurized thermogravimetric analyzer, which pressures were set as 0, 0.3, 0.6 and 0.9 MPa. The pressure of thermogravimetric analyzer was controlled by a pressure electromagnetic valve which could be operated by computer. Air was removed firstly by a vacuum air pump in order to avoid the influence of the air, and then N_2 and CO_2 were pumped in. When the pressure in the thermogravimetric analyzer reached the setting pressure, the temperature was increased to 1400℃ at the heating rate of 10℃/min. The Malek method was used for inferring the most probable mechanisms of pressurized pyrolysis and gasification, and the effects of pressure on pyrolysis and gasification process as well as their kinetics characteristics were investigated. The results showed that pressure had a significant effect on pyrolysis/gasification of pine powder. The release of volatile matter was inhibited and the maximum weight loss decreased from 73.80% at 0 MPa to 71.40% at 0.9 MPa with the increase of pressure under the N_2 atmosphere. According to the results of Malek method, the pressurized pyrolysis was divided into two stages, and the secondary reaction mechanism and the random successive nucleation growth were proved to be the most probable mechanisms for the first and the second stage of pressurized pyrolysis, respectively. The activation energy in the first stage of pressurized pyrolysis increased from 41.15 kJ/mol at 0 MPa to 52.41 kJ/mol at 0.9 MPa. Under CO_2 atmosphere, the high pressure inhibited the release of volatile matter in pyrolysis stage which also happened under N_2 atmosphere but promoted the char gasification in the gasification stage. The maximum weight loss rate increased from 0.101%/min to 0.162%/min and their corresponding temperatures decreased during the process of char gasification. Furthermore, the two-dimensional diffusion (cylindrical symmetry) was proved to be the most probable mechanism for pressurized CO_2 gasification. The activation energy of char gasification increased from 201.94 kJ/mol at 0 MPa to 230.73 kJ/mol at 0.9 MPa. Meanwhile, the frequency factor rose from 4.55E+06 to 7.04E+07 min~(-1). Additionally, when the value of carbon conversion was in the range of 0.6-0.95, the reaction rate of CO_2 gasification gradually increased with the increase of pressure, and the finish temperature of the char reaction shown a downward trend. The results provide a theoretical basis for the efficient and clean utilization of biomass. |
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来源
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农业工程学报
,2016,32(2):205-211 【核心库】
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DOI
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10.11975/j.issn.1002-6819.2016.02.030
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关键词
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生物质
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动力学
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气化
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加压
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热重分析
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地址
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中国科学院广州能源研究所, 中国科学院可再生能源重点实验室, 广州, 510640
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语种
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中文 |
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文献类型
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研究性论文 |
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ISSN
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1002-6819 |
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学科
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能源与动力工程 |
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基金
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广东省科技计划项目
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文献收藏号
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CSCD:5616412
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