基于热重法的准东煤等转化率热解动力学模型

准东煤热解脱挥发分特性对其热加工利用过程具有重要影响,建立准东煤热解通用动力学模型对预测挥发分产率及反应性能具有重要意义。采用热重测量了不同升温速率条件下的准东煤脱挥发分失重特性,使用Friedman、Flynn-Wall-Ozawa（FWO）和Kissinger-Akahira-Sunose（KAS）3种等转化率模型来处理热重实验数据,仔细分析了不同模型参数的获得方法及不同模型中活化能及指前因子的差异。研究结果表明,准东煤活化能分布函数呈现单峰分布;相比其他模型,FWO模型能够较好地描述准东煤的热解过程。     

基于热重法的准东煤等转化率热解动力学模型

准东煤热解脱挥发分特性对其热加工利用过程具有重要影响,建立准东煤热解通用动力学模型对预测挥发分产率及反应性能具有重要意义。采用热重测量了不同升温速率条件下的准东煤脱挥发分失重特性,使用Friedman、Flynn-Wall-Ozawa(FWO)和Kissinger-Akahira-Sunose(KAS)3种等转化率模型来处理热重实验数据,仔细分析了不同模型参数的获得方法及不同模型中活化能及指前因子的差异。研究结果表明,准东煤活化能分布函数呈现单峰分布;相比其他模型,FWO模型能够较好地描述准东煤的热解过程。     

热重法研究介休煤的热解与燃烧特性

采用热重(TG)分析仪对介休水峪煤样的热解及燃烧特性进行了研究,并考察了升温速率对煤的热解与燃烧特性的影响,得出了不同升温速率下的燃烧特性参数,如着火温度、燃烧最大速率、燃尽温度、燃烧特性指数等,并计算了不同升温速率下的反应动力学参数。经研究发现:煤在热解与燃烧区间的某一温度范围内能较好地满足一级反应方程,且线性相关系数都在0.98以上。由一级反应动力学模型得出的活化能与指前因子等数据能较好地验证煤的TG/DTG曲线所得出的一些结论。     

动力学参数的补偿效应及改进的求解方法

阐述了目前被许多研究者所运用的模型匹配方法求解动力学参数的不足之处,并从动力学补偿效应的角度来说明一组实验数据可以与多个模型匹配的情况。然后应用 Friedman 法求出了黄桷树叶在4个不同升温速率条件下,黄桷树叶热解的活化能与转化率之间的关系,判断出整个反应过程不遵循单一的动力学反应机制。根据活化能在各个阶段受转化率的影响将黄桷树叶的热解过程划分为两个阶段,然后分别求出了两个阶段的活化能,以它们作为参考活化能,运用 Freeman-Carroll 法求出了反应级数和指前因子。     

热分析在煤燃烧和热解及气化动力学研究中的应用

论述了煤的燃烧、热解、气化反应动力学的常用的单一升温速率法、多重扫描速率法、动力学补偿效应以及分布活化能动力学模型等热分析研究方法，分析了现用热分析动力学方法的局限性；并对反应控制热分析、微热分析技术、微波热分析以及热分析技术与其他分析技术的联用，热分析技术间的联用等热分析新技术在煤的燃烧、热解、气化反应动力学研究上的应用进行了展望．     

煤热解动力学分布活化能模型适用性分析

以三种不同升温速率下准东原煤样品的热解失重数据为研究对象,应用分布活化能模型(DAEM)法进行动力学计算,分析了此种方法在煤热解整体动力学研究中的适用性.结果表明,由于升温速率对热解过程的影响以及反应机理的转变,DAEM法对煤热解二次脱气阶段失重数据的适用性较差;失水脱气及二次脱气阶段失重的取舍对各转化率所对应的活化能值具有不同的影响,而对活化能分布函数则影响不大;在几乎整个热解过程中,频率因子和活化能之间均呈现明显的动力学补偿效应,且其具体表现形式仅取决于煤种,而与所选取的温度计算范围关系不大.     

阻燃HIPS塑料热解动力学模型

采用热重法进行了含阻燃添加剂的高抗冲聚苯乙烯塑料(flame retarded high impact polystyrene,Br-Sb-HIPS)在不同升温速率下的热解实验,建立了包含3个连续反应的阻燃HIPS热解动力学模型。通过Flynn-Wall-Ozawa法得到阻燃HIPS热解过程的活化能为103~307 kJ·mol-1,利用多元非线性无约束最优化方法求得模型参数。研究表明,Br-Sb-HIPS 3个反应的活化能和指前因子分别为191.632、213.263、238.331 kJ·mol-1和11.641、12.772、11.666 min-1。动力学模型能够很好地预测阻燃HIPS热解过程。     

用热分析技术研究煤的热解特性

用热分析技术研究了自洗蒙古煤和乌煤在氮气中的热解特性,探讨了升温速率和煤样粒径对热解过程的影响,根据煤热解产物释放特性指数r的大小来确定两种煤的热解性能。结果表明:同一升温速率下,自洗蒙古煤的热解特性要好于乌煤;同一种煤,升温速率越高,r值越大,热解特性越好。应用不同升温速率下的热解曲线计算出两种煤热解过程的动力学参数。用等转化率法求得热解过程的活化能;用主曲线法确定失重过程的最可几机理函数。     

阻燃HIPS塑料热解动力学模型

采用热重法进行了含阻燃添加剂的高抗冲聚苯乙烯塑料（flame retarded high impact polystyrene,Br-Sb-HIPS）在不同升温速率下的热解实验,建立了包含3个连续反应的阻燃HIPS热解动力学模型。通过Flynn-Wall-Ozawa法得到阻燃HIPS热解过程的活化能为103～307 kJ·mol^-1,利用多元非线性无约束最优化方法求得模型参数。研究表明,Br-Sb-HIPS 3个反应的活化能和指前因子分别为191.632、213.263、238.331 kJ·mol^-1和11.641、12.772、11.666 min^-1。动力学模型能够很好地预测阻燃HIPS热解过程。     

还原性气氛下煤中硫热解迁移规律 (Ⅱ)氢气气氛与煤半焦中有机硫反应的动力学研究

在常压固定床反应器上考察了氢气分压对煤热解残焦中硫释出的影响,并通过差减微分法求取了反应的宏观动力学参数.研究结果表明:不同的氢气分压对反应具有一定的影响.氢气分压在0.02 MPa～0.1 MPa范围内,较高的氢气分压条件下,煤焦中有机硫与氢气的反应速率较快.通过动力学计算得出:不同的氢气分压下对应的反应级数、活化能和指前因子均不相同.实验结果表明,氢气与热解残焦中硫的作用是一个复杂的过程,反应过程可能受气体扩散控制.     

Chemical looping gasification of maceral from low-rank coal:Products distribution and kinetic analysis on vitrinite

The product distribution and kinetic analysis of low-rank coal vitrinite were investigated during the chemical looping gasification (CLG) process.The acid washing method was used to treat low-rank coal,and the density gradient centrifugation method was adopted to obtain the coal macerals.By combining thermogravimetric analysis and online mass spectrometry,the influence of the heating rate and oxygen carrier (Fe2O3) blending ratio on product distribution was discussed.The macroscopic kinetic parameters were solved by the Kissinger-Akahira-Sunose (KAS) method,and the main gaseous product formation kinetic parameters were solved by the iso-conversion method.The results of vitrinite during slow heating chemical looping gasification showed that the main weight loss interval was 400-600 ℃,and the solid yield of sample vitrinite-Fe-10 at different heating rates was 64.30％-69.67％.When β =20 ℃·min-1,the maximum decomposition rate of vitrinite-Fe-10 was-0.312％·min-1.The addition of Fe2O3 reduced the maximum decomposition rate,but by comparing the chemical looping conversion characteristic index,it could be inferred that the chemical looping gasification of vitrinite might produce volatile sub-stances higher than the pyrolysis process of vitrinite alone.The average activation energy of the reaction was significantly reduced during chemical looping gasification of vitrinite,which was lower than the average activation energy of 448.69 kJ·mol-1 during the pyrolysis process of vitrinite alone.The gaseous products were mainly CO and CO2.When the heating rate was 10 ℃·min-1,the highest activation energy for CH4 formation was 21.353 kJ·mol-1,and the lowest activation energy for CO formation was 9.7333 kJ·mol-1.This study provides basic data for exploring coal chemical looping gasification mecha-nism and reactor design by studying the chemical looping gasification process of coal macerals.     

非等温热重分析长焰煤热解过程与动力学特征

为提高煤热解过程中焦油的产率,用非等温热重分析方法研究了不同粒径、热解终温和升温速率条件下长焰煤的热解过程和机理,分析了20和100℃/min升温速率下长焰煤热解过程特征,并求解了热解动力学参数。结果表明,煤颗粒在2.8mm以下时,粒径对热解过程影响较小;热解终温越高,热解最终固体产物中挥发分产率越低;升温速率越快,挥发分的析出速率越快。在同一升温速率下,不同热解温度段得到的活化能呈现两头大中间小的特征,且指前因子随活化能的增大而增大。     

窑街油页岩热解动力学研究

利用差热分析仪对窑街油页岩进行不同恒速升温速率的热解实验,考察升温速率对热解的影响,随着升温速率加快,失重曲线和最大热解速率向高温区。建立Friedman动力学模型对热解数据进行了数学处理,得到了活化能的变化范围为120～190kJ·mol^-1,而且活化能E与频率因子A的对数呈良好的线性关系,对认识油页岩干酪根的热解机理和化学结构提供重要信息。     

美国绿河油页岩中沥青热解特征及动力学

沥青是油页岩中的重要有机质,也是油页岩中油母质热解产油和气过程的重要中间产物,对其热解研究有利于加深油页岩/油母质热解理解。通过索氏萃取提取出了绿河油页岩中的沥青,并对其进行了不同升温速率下热解实验。基于热重（TGA）数据,使用Friedman法计算了沥青热解的活化能,并通过活化能分布特征,推测沥青热解可能包含三个过程。接着,使用双高斯函数对含有交叠峰的DTG曲线进行反褶积处理,分解成三个峰,依次对应每一个过程。使用最小二乘法获得了这三个过程的活化能、指前因子和反应模型通式,并将获得的通式与四类固态物质热解模型中的11种理想模型进行对比,辨识出上述三个过程均遵循n级反应模型。     

Application of chemometrics to study the kinetics of coal pyrolysis: A novel approach

In present investigation, chemometric tools, principal component analysis (PCA) and Hierarchical clustering analysis (HCA) are used to get the linkage between the coal properties and kinetics of pyrolysis. Thermo gravimetric analysis (TGA) of 10 perhydrous Indian coals was done. Devolatilization of these coals showed five independent reactions. Kinetic parameters were calculated for individual reaction. Activation energy and weight loss of each reaction has been analyzed as a function of coal properties (moisture, volatile matter, ash, fixed carbon, carbon, hydrogen, nitrogen and sulfur). By applying chemometric, was extracted information about the linkage between activation energies of each reaction and coal properties. The mathematical treatment of data has provided conclusions on properties of coal and kinetic parameters.     

Pyrolysis kinetics of Athabasca bitumen using a TGA under the influence of reservoir sand

Pyrolysis kinetics of thermal decomposition of bitumen was investigated by thermogravimetric analysis (TGA). TGA experiments were conducted at multiple heating rates of 5, 10, 20°C min^–1 up to 800°C to obtain the pyrolysis characteristics of bitumen. Weight loss curve from TGA shows that two different stages occurred during bitumen pyrolysis. Differential method has been used for determining the kinetic parameters and the best fit for the order of reaction was found based on the R² values. Kinetics results confirm the presence of two different stages in bitumen pyrolysis with varying kinetic parameters. The average activation energy for the first and second stage was 29 and 60 kJ mol^?1 and the average order of the reaction was 1.5 and 0.25, respectively. Experiments have been conducted with different reservoir sand. The effect of different source of sand reveals no effect on the pyrolysis behaviour of bitumen. A considerable difference was found with the pyrolysis of bitumen–sand mixtures and bitumen alone based on coke yield and activation energy. © 2011 Canadian Society for Chemical Engineering     

微型流化床与热重测定煤焦非等温气化反应动力学对比

利用微型流化床反应分析仪(MFBRA)和热重分析仪(TGA)比较煤焦与CO₂的非等温气化反应特性,并利用单一升温速率法和组合升温速率法计算反应动力学数据。结果表明:升温速率对半焦非等温气化过程有重要影响,随着升温速率的增大,起始反应温度和最大反应速率对应的气化温度增加,同一气化温度下的碳转化率降低,而且利用单一升温速率法求取气化反应的活化能逐渐减小。与TGA相比,同一升温速率下,MFBRA中半焦气化反应的起始反应温度和最大反应速率对应的反应温度明显较小,而且升温速率越大差异越显著。无论是单一升温速率法(升温速率≥5℃·min^-1)还是组合升温速率法,TGA测得的动力学数据均明显小于MFBRA测得的动力学数据。高升温速率下(升温速率≥5℃·min^-1)半焦在TGA和MFBRA中非等温气化行为和动力学数据的差异很可能与MFBRA内较好的热量传递和受扩散的抑制作用较小有关。     

Study of sawdust pyrolysis and its devolatilisation kinetics

Pyrolysis of sawdust was studied using a thermogravimetric analyser (TGA) to understand the devolatilisation process and to obtain its global kinetic parameters. The influences of particle size, initial weight of the sample and heating rate on the devolatilisation of sawdust particles have been studied. Results from proximate analysis show that smaller particle size has more ash content compared to larger particle size. The TG and derivative TG curve for variation in particle size and initial weight of the sample showed significant difference in the third stage of the pyrolysis. In addition, the pyrolysis of sawdust differed significantly for variation in heating rate. As the heating rates increased, the char yield also increased. The devolatilisation kinetics was studied considering different stages of pyrolysis. The kinetic parameters for thermal devolatilisation of the sawdust were determined through a nonlinear optimisation method of two independent parallel nth‐order reaction models. The kinetic parameters such as activation energy, frequency factor and order of the reaction for the two stages considered in the model were: E₂ = 79.53 (kJ/mol), E₃ = 60.71 (kJ/mol); k₀₂ = 1.90 × 10⁶ (1/min), k₀₃ = 1.01 × 10³ (1/min); n₂ = 0.91, n₃ = 1.78, respectively. The results show good agreement between the proposed model and the experimental data of the sawdust pyrolysis.