生物质热解特性和动力学研究

利用热重分析对在氮气气氛下不同升温速率的马尾松生物质原料热失重行为进行了研究。由失重和失重速率曲线分析可知,生物质热解过程分为三个阶段。根据热重实验数据建立动力学热解模型,运用Popescu法从22种动力学机理函数中寻求裂解的最概然机理函数并计算裂解的动力学参数。结果表明,Zhuralev,Lesokin和Tempelmen(Z-L-T)方程为最概然机理函数。     

生物质催化热解特性和动力学研究

利用热分析技术对氮气气氛下不同升温速率下马尾松生物质试样的热解过程和以Na2CO3为催化剂的催化热解过程进行了研究。结果表明,Na2CO3催化剂可使生物质的主要热解区向低温区移动,而最大失重速率减少。根据热重实验数据,运用Popescu法对马尾松热解和催化热解动力学进行了研究。结果表明,Z-L-T方程为热解和催化热解的最概然机理函数,并计算出其相应的热解动力学参数。     

秸秆类生物质低温热解及混合气化的研究

生物质能源是一种重要的可再生能源,利用生物质和煤混合气化技术可以减少CO2的排放。研究了低温热解预处理对秸秆类生物质产物和气体浓度分布的影响,结果表明：经低温热解预处理后制得的生物焦的量和气体的浓度分布不仅与热解温度有关,而且与生物质种类的组成有很大的关系,考察了生物质焦和煤炭混合气化的热重试验,对混合气化反应性进行了有益的探索。     

板栗壳的热解特性研究

采用热重分析仪和三种动力学计算方法研究了板栗壳的热解过程,可分为失水干燥、主热解和炭化三个阶段。含量较高挥发分(68.42%)造成主热解区间质量损失最多,主要是木质素、纤维素和半纤维素三种生物质组分的分解,其含量和特性使热解过程产生不同趋势。提高升温速率产生的热滞后现象使热解不够充分,导致主热解阶段活化能和频率因子增大。     

生物质与油页岩混合热解特性研究

为了充分利用油页岩和生物质,以生物质和油页岩按照不同质量比的混合试样作为研究对象,采用TG-DSC联用技术进行了热重实验,分析了热解过程特性曲线并计算热解特性参数,采用差减微分法计算了热解动力学参数。结果表明:混合试样DTG曲线分别在低温段及高温段出现2个峰,前者主要是生物质的纤维素及半纤维素挥发分的热解析出,后者主要为油页岩热解析出挥发分;随混合试样中油页岩含量逐渐增多,热解后期逐渐出现因油页岩无机盐热分解吸热过多而出现DSC曲线吸热峰;混合试样低温段挥发分析出量及挥发分综合释放特性指数均大于高温段的值;生物质含量最高的混合试样(生物质与油页岩的质量比为4∶1)的挥发分初始析出温度最低,其挥发分最大释放速度的峰值及挥发分综合释放特性指数均最大;生物质含量较多的混合试样低温段活化能大于高温段活化能的值,油页岩含量较多的混合试样低温段活化能低于高温段的值。     

生物质热解动力学模型的研究

在氮气气氛和不同的加热速率下对杉木原料进行了热重分析.由失重和失重速率曲线分析可知,生物质热解过程分为三个阶段.采用非线性最小平方算法,按三组分独立平行一级反应热解动力学模型,模拟计算的曲线与实验结果吻合较好,求解的动力学参数与文献报道值吻合较好,且随着升温速率的加快,纤维素和木质素热解的活化能有增加的趋势,而半纤维素活化能有下降的趋势.     

松木屑生物质热解特性研究

以氮气为载气,采用热重分析仪对松木屑进行热解实验,考察了载气流速、升温速率等对松木屑热解过程的影响,求解了热解表观动力学参数。研究表明,松木屑的热解过程分三个阶段,主要热解温度为200～450℃,600℃后热解反应基本完成;载气流速对热解反应影响较小,升温速率对热解反应影响较大;松木屑热解表观活化能在40～70 kJ/mol范围内。     

几种纤维素类生物质的热重分析研究

采用热重分析法(TGA)对几种纤维素类生物质(稻壳、豆杆、豆壳、稻杆)的热解过程及其动力学进行了研究.实验是在氮气气氛下,分别以10,20,30,40,50℃/min等加热速率和40～60,60～80,80～100,100目等粒径进行的.实验结果表明:几种纤维素类生物质的非等温热解只有1个剧烈失重阶段.随升温速率的提高...     

长白松热解特性及热解动力学研究

为获取长白松的热解特性,预防森林火灾发生,以长白松的树枝、球果、树皮和松针作为研究对象进行热解过程分析,并采用Coats-Redfern法进行热解动力学分析,以球果为研究对象探究各种因素对长白松热解的影响。实验结果表明：4种材料的热解过程均可分为4个阶段,其中主要失重阶段的质量损失率为60%左右。升温速率越大,热解越不充分,并且存在热滞后现象,25℃/min时质量损失率最小(80.34%);粒径大小对TG、DTG曲线影响较小,粒径越小,内外部受热更均匀,因此0.20 mm粒径的材料质量损失率最大(91.18%);氮气气氛下主要失重阶段有一个失重峰,而在高纯空气气氛下有两个失重峰,且长白松球果在高纯空气中热解时间更长,热解更充分,促进作用更强,质量损失率为98.14%。热解动力学分析结果显示：4种材料的最佳机理函数为“三维扩散”,活化能最大的是树枝(157.04 kJ/mol),最小的是松针(98.19 kJ/mol),球果的活化能为148.08 kJ/mol,树皮的活化能为115.04 kJ/mol,因此,要格外注意对松针和树皮的防火工作。     

芦苇秆热解特性及动力学分析

为了充分利用芦苇秆生物质能源,以不同升温速率对芦苇秆进行热重实验,分别运用Coats-Redfern（CR）法、Flynn-Wall-Ozawa（FWO）法、Kissinger-Akahira-Sunose（KAS）法计算芦苇秆热解动力学参数,并利用主函数图法确定反应机理和动力学。结果表明：芦苇秆热解可分为4个阶段,其中190~400℃为主要热解阶段。在此阶段,将3种方法计算所得转化率（α）与实验数据进行对比,发现当温度大于250℃时,Coats-Redfern法计算值与实验数据偏差较大,而Flynn-Wall-Ozawa法与Kissinger-Akahira-Sunose法在整个阶段内吻合度较高。由主函数图法可知芦苇秆热解最佳反应机理为随机成核,反应级数为2。对比残差平方和发现,Kissinger-Akahira-Sunose法相比于Flynn-Wall-Ozawa法更适合计算芦苇秆热解动力学参数,计算的表观活化能随转化率的增大呈先增大后减小的趋势,并在转化率为50%时达到最大值286.9 kJ/mol。     

椰壳、椰壳渣与脱灰椰壳渣热解及热解动力学

用热重技术分析了椰壳类活性炭原料的热解过程,采用Coats-Redfern积分法求解了热解反应动力学模型。椰壳渣及脱灰椰壳渣热解失重过程主要集中在280~370℃之间,在热失重速率曲线上呈单峰,而椰壳热解失重主要集中在230~300℃和300~350℃两个温度范围,在热失重速率曲线上呈双峰。在低温段三者热解反应表观活化能差别较大,高温段差别较小,且最大反应速率均出现高温段。     

生物质热解催化剂失活的研究进展

生物质催化热解是实现生物质能源高效、高值化利用的有效手段。综述生物质催化热解过程中催化剂失活的过程及原因,从生物质热解催化剂的积炭失活、原料杂质的影响、催化剂的水热失活和负载型催化剂金属颗粒的烧结等进行阐述。对生物质热解催化剂的研究重点与方向进行展望。     

Heat transfer and kinetics in the pyrolysis of shrinking biomass particle

The impact of shrinkage on pyrolysis of biomass particles is studied employing a kinetic model coupled with heat transfer model using a practically significant kinetic scheme consisting of physically measurable parameters. The numerical model is used to examine the impact of shrinkage on particle size, pyrolysis time, product yields, specific heat capacity and Biot number considering cylindrical geometry. Finite difference pure implicit scheme utilizing tri-diagonal matrix algorithm (TDMA) is employed for solving heat transfer model equation. Runge-Kutta fourth-order method is used for chemical kinetics model equations. Simulations are carried out for radius ranging from 0.0000125 to , temperature ranging from 303 to and shrinkage factors ranging from 0.0 to 1.0. The results obtained using the model used in the present study are in excellent agreement with many experimental studies, much better than the agreement with the earlier models reported in the literature. Shrinkage affects both the pyrolysis time and the product yield in thermally thick regime. However, it is found that shrinkage has negligible affect on pyrolysis in the thermally thin regime. The impact of shrinkage reflects on pyrolysis in several ways. It includes reduction of the residence time of gases within the particle, cooling of the char layer due to higher mass flux rates of pyrolysis products and thinning the pyrolysis reaction region.     

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.     

生物质热解油雾化技术研究进展

生物质热解油是一种绿色低碳、可用于雾化燃烧的液体燃料,但在实际应用中存在运动粘度高、雾化燃烧不充分、现有燃油喷头及燃烧器不适用等问题。综述了热解油雾化技术最新研究进展,详细介绍了生物质热解油的组成成分和理化性质,系统分析了液相介质、雾化方式、雾化条件等对热解油雾化的影响以及内在规律。通过国内外雾化技术归纳总结,梳理了热解油雾化评价指标和较为先进的检测方法,以期为热解油高效清洁利用提供技术参考。     

TG study on pyrolysis of biomass and its three components under syngas

Pyrolysis of sawdust and its three components (cellulose, hemicellulose and lignin) were performed in a thermogravimetric analyzer (TGA92) under syngas and hydrogen. The effect of different heating rates (5, 10, 15 and 20 °C/min) on the pyrolysis of these samples were examined. The pyrolysis tests of the synthesized samples (a mixture of the three components with different ratios) were also done under syngas. The distributed activation energy model (DAEM) was used to study the pyrolysis kinetics. It is found that syngas could replace hydrogen in hydropyrolysis process of biomass. Among the three components, hemicellulose would be the easiest one to be pyrolyzed and then would be cellulose, while lignin would be the most difficult one. Heating rate could not only affect the temperature at which the highest weight loss rate reached, but also affect the maximum value of weight loss rate. Both lignin and hemicellulose used in the experiments could affect the pyrolysis characteristic of cellulose while they could not affect each other obviously in the pyrolysis process. Values of k₀ (frequency factor) change very greatly with different E (activation energy) values. The E values of sawdust range from 161.9 to 202.3 kJ/mol, which is within the range of activation energy values for cellulose, hemicellulose and lignin.     

生物质热解催化剂积炭问题的研究进展

生物质催化热解获得生物油等高质产品是最有前途替代传统化石能源的方法之一,但在热解过程中存在着严重的催化剂失活问题,其中积炭是导致催化剂失活的最主要因素。本文对近年来生物质催化热解领域的催化剂积炭问题进行综述,重点介绍催化剂积炭失活原因及表征方法、积炭的影响因素分析（催化剂结构、催化剂酸性与反应温度）、抑制催化剂积炭的方法 （催化剂改性、高压反应条件等）以及积炭催化剂再生方法 （氧化灼烧再生、臭氧低温再生、非热等离子体再生等）,并介绍了近年来新兴的微波催化热解技术对催化剂积炭的抑制和消除作用,然后针对该领域目前所面临的困难和发展方向进行展望,以期为生物质催化热解过程中催化剂积炭问题研究提供理论基础。     

生物质的微波热解技术研究进展

生物能源化转化技术是当今能源领域的热点之一,生物质微波热裂解技术被广泛认为是该领域中具有超强的发展前景技术。从生物质微波热解制油、生物质微波热解制取生物炭、生物质微波热解制取合成气以及生物质微波热解多联产技术等几个方向总结了国内外生物质微波热解技术的研究现状和趋势,最后提出了生物质微波热解技术的几点建议。