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。     

Effects of prewash on the pyrolysis kinetics of cut tobacco

ABSTRACT

Smoking is a big public health issue because of the harmful substances generated. To diminish the risk of smoking, cut tobacco was washed with pure water, aqueous solution of sodium carbonate, or citric acid to remove the precursors of harmful substances in this work. The composition and pyrolysis kinetics of washed cut tobacco were determined to interpret the reduction in harmful substances generated during fast pyrolysis process. Sugar and alkaloid in cut tobacco were removed partly during prewash process. Thermogravimetric analysis demonstrated that cut tobacco washed with aqueous solution of citric acid was pyrolyzed at higher temperature, while the one washed with the solution of sodium carbonate was pyrolyzed at lower temperature. The changes in composition and pyrolysis kinetics resulted in significant reduction in benzo[a]pyrene, phenol, and nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone generated during pyrolysis, demonstrating that wash of cut tobacco with suitable chemicals is a promising approach to reduce the harmful substances generated during smoking.     

钴离子对阳离子交换树脂氧化裂解反应的催化作用

氧化裂解能有效增大放射性废阳离子交换树脂的减容比,但是较高的裂解温度易导致核素挥发。为了降低裂解温度,以硝酸钴和阳离子交换树脂为原料,制备了不同钴含量的含钴树脂,在热重分析仪上考察了钴含量对树脂裂解反应的影响。采用离子交换的方法掺入10~40 g/L的钴离子,可以使树脂共聚物基体裂解峰的峰值温度降低232~263℃,而对减容比的影响较小。通过对残渣的XRD、FT-IR、XPS及元素分析,发现由钴离子转化形成的氧化钴对共聚物基体的裂解具有催化作用,促进了硫键（—S—）的断裂,使裂解温度降低。     

垃圾裂解动力学研究现状

本文中介绍了垃圾裂解动力学的研究现状,并较为详细的介绍了垃圾热裂解和微波裂解动力学的发展状况。比较了两者各自的特点。     

含氰基聚酰亚胺薄膜的制备及其热分解动力学

以4-[3,5-双(4-氨基苯氧基)苯氧基]邻苯二甲腈和3,3′,4,4′-联苯四甲酸二酐为原料,经聚酰胺酸热酰亚胺化制备含氰基的聚酰亚胺(CN-BP-PI)薄膜。采用傅里叶变换红外光谱、热重分析、差示扫描量热法对CN-BP-PI薄膜进行了分析。采用动态热重法研究了CN-BP-PI的分解动力学,用积分法结合常见固相热分解反应动力学函数来判断热分解的动力学函数。由Ozawa,KAS,Kissinger,Achar,Coats-Redfern,MacCallum-Tanner,van Krevelen方程求热分解反应的动力学参数。转化率为0.2~0.8时所得CN-BP-PI在氮气中热分解反应的表观活化能为119.68~215.61 kJ/mol,平均活化能为136.35 kJ/mol,指前因子平均值为8.52×107 s-1。     

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.     

低阶煤热解条件对高炉喷吹半焦燃烧性能及动力学特性的影响

采用热重分析法研究了不同热解条件下半焦的燃烧性能和动力学特征,利用Ozawa法求取动力学参数。结果表明,热解温度越低、保温时间越短时,半焦的燃烧性能越好;热解升温速率对半焦燃烧过程的反应程度影响不大;粒度越大,燃烧性能差异性越明显。热解温度对半焦燃烧性能影响较大,550℃是本研究中制备高燃烧反应性半焦的适宜热解温度。两种不同粒度原煤制得的半焦均随转化率增大,活化能减小。1~3 mm原煤在热解温度为550℃时所得半焦在燃烧过程中符合反应级数模型,化学反应为限制性环节,反应最概然机理函数为f(α)=(1–α)2。     

废旧电路板真空热解

采用热重分析仪和固定床热解反应器对废旧电路板进行了低真空条件下的热分解实验.研究了混合废旧电路板在真空下的降解特性、热解动力学以及热解条件对热解产品产率的影响,并讨论了真空和氮气条件下电路板热解的差异.实验结果表明真空降低了电路板热解的表观活化能,提高了热解产物的挥发性,减少了二次裂解反应,因而真空有利于提高液体产品的产率,降低气体和固体产品的产率.废旧电路板的真空热解液体产品主要由酚、烷基酚、双酚A、水以及各种溴酚构成,液体中总溴高达13.47％,其中一半左右以有机溴的形式存在,因此液体产品适合用于分离提取化工原料而不宜用于作燃料.     

煤焦油馏分微波萃取神府煤热解液体产物的研究

为提高煤在萃取过程中的转化率,考察微波辅助萃取煤的工业化可行性。在微波辅助下,以神府低温煤焦油馏分为溶剂,在最优操作条件下萃取神府煤,将萃取混合液在510℃条件下热解,分析了热解液体产物的性质及组成,得到了加工方案。结果表明:液体产物主要由酚类化合物、芳烃化合物及烷烃组成,酚类含量较高,其在萃取热解液体产物中的比例均达到50%以上,主要由苯酚、C1～C4苯酚组成,大于C4苯酚的含量很小,其中由苯酚、C1-苯酚、C2-苯酚组成的低级酚含量占总酚含量的70%以上,因此对液体产物进行加工时,需要将低级酚类化合物从液体产物中先分离出来。     

Revealing low temperature microwave‐assisted pyrolysis kinetic behaviors and dielectric properties of biomass components

The kinetic characteristics of microwave‐assisted pyrolysis (MAP) of biomass components were investigated in a self‐designed microwave thermogravimetric analysis using the KAS model and the master plot method. Compared with conventional pyrolysis, the initial decomposition temperatures of biomass components were reduced by 50–100°C and the fastest weight loss regions were shifted to lower temperatures. The average apparent activation energies of cellulose, hemicellulose, and lignin were 47.82, 44.81, and 51.54 kJ/mol, respectively. Analysis with master plot method suggested the MAP of cellulose followed the 2‐D diffusion reaction model, while hemicellulose and lignin could be interpreted by third order‐based and 3‐D diffusion model. The change of dielectric properties was consistent with the weight loss behaviors of biomass components during the pyrolysis process. The increase of dielectric properties with temperature can lead to a thermal gradient and “hot spots” within biomass, which accelerated the pyrolysis process at low temperatures and reduced the apparent activation energy. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2124–2134, 2018     

桦甸油页岩的微波干馏特性

在自行设计的微波干馏装置上研究了桦甸油页岩、半焦及其混合物在微波场中的升温特性。发现油页岩本身是一种微波弱吸收物质,纯油页岩在微波场中升温能力较差;油页岩热解产物半焦在微波场中升温很快,可以作为油页岩微波干馏的微波吸收剂,将油页岩和半焦的混合物放入微波场中能达到良好的热解效果。实验研究了半焦和油页岩的混合比、微波功率、粒径等因素对微波干馏效果的影响,结果发现,随着半焦比例加大,产油率增加,半焦产率降低;在相同时间内,微波功率越大,产油率和气体损失产率越大,半焦产率降低;油页岩粒径对微波热解影响较小,但当粒径小于0.2mm时实验中出现了较严重的夹带现象。     

Effects of liquid accelerant on the pyrolysis behaviors and kinetics of PMMA,a noncharring polymer

Thermal decomposition of solid combustibles infiltrated with combustible liquids (liquid accelerants) is one typical fire behavior in arsons. In the present study, thermogravimetric and kinetic analyses are used to investigate the pyrolysis of one typical noncharring polymer namely polymethyl methacrylate (PMMA) infiltrated with different contents of one representative liquid accelerant namely kerosene. Results indicate that the thermal decomposition process of pure PMMA and PMMA infiltrated with kerosene show a one-stage and a three-stage process, respectively. Furthermore, the first and third stages for PMMA infiltrated with kerosene can be both regarded as one-step reaction. With the increase of kerosene content, the conversion rate ranges of the first and third stages for PMMA infiltrated with kerosene are shortened. The peak and average reaction rates of the first and second stages increase, while the peak and average reaction rates of the third stage decrease. The maximum and average reaction rates for the entire decomposition process also decrease. The average activation energy values for the whole and one certain stage both increase. Moreover, the calculated kinetic parameters can be used to accurately predict the thermal decomposition behavior of PMMA infiltrated with kerosene.     

钢丝对废橡胶微波裂解过程的影响分析

研究钢丝对废橡胶微波裂解过程的影响并进行有限元仿真和试验探究。仿真结果表明,含钢丝的废橡胶在钢丝附近场强明显增强,热点增多且分布均匀。裂解试验结果表明,废橡胶中存在适量钢丝会促进废橡胶的裂解,使裂解升温更快,出油比例更高。由此认为,废轮胎整胎微波裂解更有利于提高裂解效率、促进节能环保和改善裂解产物品质。     

Modelling of the pyrolysis of biomass particles. Studies on kinetics,thermal and heat transfer effects

The present work provides a rationally-based model to describe the pyrolysis of a single solid particle of biomass. As the phenomena governing the pyrolysis of a biomass particle are both chemical (primary and secondary reactions) and physical (mainly heat transfer phenomena), the presented model couples heat transport with chemical kinetics. The thermal properties included in the model are considered to be linear functions of temperature and conversion, and have been estimated from literature data or by fitting the model with experimental data. The heat of reaction has been found to be represented by two values: one endothermic, which prevails at low conversions and the other exothermic, which prevails at high conversions. Pyrolysis phenomena have been simulated by a scheme consisting of two parallel reactions and a third reaction for the secondary interactions between charcoal and volatiles. The model predictions are in agreement with experimental data regarding temperature and mass-loss histories of biomass particles over a wide range of pyrolysis conditions.     

Value-added products from waste: Slow pyrolysis of used polyethylene-lined paper coffee cup waste

The objectives of this study were to examine how to recycle cup waste efficiently and effectively and to determine if cup waste can be converted into liquid, solid, and gas value-added products by slow pyrolysis. The characteristics and potential utilizations of the pyrolysis products were investigated. The study included the effects of temperature, heating rate, and different feedstocks. The yield of pyrolysis oil derived from cup waste increased from 42% at 400°C to 47% at 600°C, while the yield of char decreased from 26% at 400°C to approximately 20% at 600°C. Acetic acid and levoglucosan were identified as the main components of the pyrolysis oil. The char obtained at 500°C was physically activated at 900°C for 3 h with CO₂. The adsorption capacity of the activated char was investigated with model compounds, such as methyl orange, methylene blue, ibuprofen, and acetaminophen. The results showed that the adsorption capacity of the activated char was similar to that of commercial activated carbon produced from peat. The higher heating value of the produced gas stream calculated at 400°C was 19.59 MJ/Nm³. Also, conventional slow pyrolysis (CSP) and microwave-assisted pyrolysis (MAP) technologies were compared to determine the differences in terms of products yields, composition and characteristics of the pyrolysis oil, and their potential applications. The CSP yields higher liquid products than MAP. Also, the pyrolysis oil obtained from the CSP had significantly more levoglucosan and acetic acid compared to that of the MAP.     

Kinetic studies of the pyrolysis of sewage sludge by tga and comparison with fluidized beds

The pyrolysis of sewage sludge was examined by thermogravimetric analysis using different heating rates, particle sizes and final temperatures. A semi-empirical model was developed with four global consecutive/competitive reactions to volatile and solid products including also a heat balance. This model was extrapolated to isothermal reactor conditions and compared to experimental data on fluidized bed pyrolysis. Depending on the particle size and reactor temperature, about 90% of the maximum conversion in a fluidized bed takes place under external heat transfer control, the rest under kinetic control. Incomplete conversion occurs at short particle residence times, which were calculated approximately by the model.     

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。