Oxidation reaction kinetics of Athabasca bitumen

The oxidation reaction kinetics of bitumen from Athabasca oil sands have been investigated in a flow-through fixed bed reactor using gas mixtures of various compositions. The system was modelled as an isothermal integral plug-flow reactor. The oxidation of bitumen was found to be first order with respect to oxygen concentration. Two models were examined to describe the kinetics of bitumen oxidation. In the first, the Athabasca bitumen is considered to be a single reactant and the oxidation reaction a single irreversible reaction. The activation energy for the overall reaction was found to be 80 kJ mol^?1. This model is limited to calculating the overall conversion of oxygen. Because the fraction of oxygen reacting to form carbon monoxide and carbon dioxide increases with temperature, a more sophisticated model was proposed to take this into account. The second model assumes that the bitumen is a single reactant and that the oxidation of bitumen may be described by two simultaneous, parallel reactions, one producing oxygenated hydrocarbons and water, the other producing CO and CO₂. The activation energy for the first reaction was found to be 67 kJ mol^?1, and for the second, 145 kJ mol^?1. This more sophisticated model explains the result that at higher temperatures more oxygen is consumed in the oxidation of carbon, because this reaction has a higher activation energy than the reaction leading to the production of oxygenated hydrocarbons and water. This model can also predict the composition of the product gases at various reaction conditions.     

Kinetics of the thermo-oxidative and thermal cracking reactions of Athabasca bitumen

The thermo-oxidative and thermal cracking reactions of Athabasca bitumen were examined qualitatively and quantitatively using differential thermal analysis (DTA). Reaction kinetics of low temperature oxidation (LTO) and high temperature cracking (HTC) were determined. The rate of the LTO reaction was found to be first order with respect to oxygen concentration. The activation energy and the Arrhenius pre-exponential factor were 64 MJ kg^?1 mol^?1 and 10^5.4 s^?1, respectively. The effects of atmosphere, pressure, heating rate and support material on the thermal reactions of bitumen were studied. In general, it was found that partial pressures of oxygen > 10% O₂ favoured exothermic oxidation reactions. High pressure increased the rates of LTO and HTC as well as the exothermicity of these reactions. A major contribution of this study to thermal in-situ processes is that heating rate can be used effectively to control the extent of low temperature oxidation and hence fuel availability during in-situ combustion. Low linear heating rates (2.8 °C min^?1) favoured low temperature oxidative addition and fission reactions. The reaction products readily formed coke and combusted upon heating. High linear heating rates (24.5 °C min ^?1) led to rapid oxidation reactions in the high temperature zone; the high temperature and the energy released during oxidation appeared to promote combustion. Finally, when sand was used as the support material there appeared to be a catalytic effect in both LTO and HTC reactions.     

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。     

PVC木塑复合材料热解动力学

将木粉按一定比例添加到PVC中得到复合材料,通过热重分析研究复合材料在空气、N2气氛下不同升温速率时的热解行为。通过Doyle和Tang method法计算了木塑材料的降解活化能。利用活化能分布函数,分析了复合材料在热解、燃烧过程中不同阶段的反应活性变化规律。研究表明,热解过程可分为3个阶段,230～360℃为第一失重阶段,360～430℃为稳定阶段,430～580℃为第二失重阶段。升温速率及反应气氛对热解过程有显著影响。由分布活化能模型计算表明,其热解动力学为一级反应,两个失重阶段的活化能分别为220kJ·mol-1和139kJ·mol-1,反应活性随失重率的增加而减少。     

A new reaction model for aquathermolysis of Athabasca bitumen

Aquathermolysis of bitumen occurs when it is thermally cracked in the presence of water. Current in situ technologies for bitumen production, such as Cyclic Steam Stimulation and Steam‐Assisted Gravity Drainage, inject high pressure, high temperature steam in the reservoir to heat the bitumen which in turn lowers its viscosity enabling flow to a production well. Thus, the major physical effect of steam is the heating of bitumen which mobilises it. Beyond physical interactions, chemical effects also result: steam heating produces acid gases, such as carbon oxides, sulphur dioxide and hydrogen sulphide along with small amounts of hydrogen and methane. For steam‐based in situ bitumen recovery processes, nearly all analyses, including simple drainage theories and thermal reservoir simulations, focus solely on the physical processes: heat transfer, fluid flow and thermodynamic equilibrium. However, steam chambers are also underground reactors: bitumen aquathermolysis occurs due to high temperatures and water saturation. Here, we describe a new in situ aquathermolysis reaction scheme for Athabasca bitumen to predict hydrogen, methane, carbon oxides, hydrogen sulphide and other heavy molecular weight hydrocarbons. Reaction parameters were fitted against one experimental data set and validated against other independent experimental data sets, both from the literature. Our results indicate that, to more accurately predict gas compositions and rates, the effects of aquathermolysis should be taken into account in reservoir modelling. © 2012 Canadian Society for Chemical Engineering     

Non-isothermal programmed pyrolysis studies of oil sand bitumens and bitumen fractions: 1. Athabasca asphaltene

Characteristic pyrolysis thermograms for 12 gases have been obtained for Athabasca asphaltene, using a combination of non-isothermal, programmed pyrolysis (ambient to 1200 K at 3 K min^?1) and gas chromatography. Such thermograms provide information for the characterization of asphaltenes in the form of gas yields, specific rates and Arrhenius kinetic parameters. All thermograms comprised more than one peak. These peaks lie in distinct temperature zones and are associated with primary and secondary cracking and coking reactions. Useful insights into the structure of Athabasca asphaltene and, indirectly, the composition of its pyrolytic cokes have been obtained. The present results provide a body of useful reference material which may be useful for monitoring processes, which may chemically modify the asphaltene fraction of bitumens and heavy oils, and for comparative studies of asphaltenes from a variety of sources.     

Cracking of vacuum residue from Athabasca bitumen in a thin film

A novel apparatus for cracking experiments based on very rapid induction heating is described. Oil and catalyst is deposited in a thin film on a metal strip made from a Curie-point alloy and heated rapidly by induction in an induction furnace. The setup offers several advantages, such as rapid heating and quenching, precise control of reaction times and temperatures, and minimization of heat and mass transfer effects. The apparatus is used in a study of the catalytic activity of calcium-modified chabazite for heavy oil cracking. The catalyst was also tested in a conventional setup in cracking of hexadecane to verify its catalytic activity. A clear catalytic effect can be seen for the hexadecane cracking, but the effect is absent for thin film cracking of the vacuum residue.     

加拿大油砂沥青部分改质技术综述

介绍了加拿大油砂资源情况、主要性质、改质技术现状和原油外输能力,重点调研了有工业应用潜力的部分改质技术,包括工艺技术现状、核心流程、技术特点和存在问题等。从部分改质产品性质、改质深度、改质过程的碳排放强度、是否存在副产品等多种维度,分析油砂沥青部分改质技术的未来发展趋势。其中对油砂沥青进行缓和热裂解,或缓和热裂解结合沥青质脱除技术是油砂沥青部分改质的技术核心;目标是在满足加拿大管道要求的前提下,尽可能减少稀释剂用量、保证部分改质产品的稳定性,降低改质工艺过程的碳排放强度。     

Study of the kinetics of sewage sludge pyrolysis using DSC and TGA

Thermogravimetry and differential scanning calorimetry were used to examine, in nitrogen, four sewage sludges at modest heating rates. A mechanism consisting of two independent reactions was derived for an undigested sludge. The parameters are: n₁ = 10, E₁ = 130 kJ mol^?1, A₁ = 1 × 10¹⁸s^?1, n₂ = 15, E₂ = 250 kJ mol^?1, A₂ = 1 × 10²⁵s^?1, with initial weight fractions of W₁ = 0.20, W₂ = 0.43, the remainder being non-reactive ash. Analysis was performed by comparing Friedman multiple-heating-rate analyses of experimental and model curves in an iterative manner. DSC experiments provide an understanding of the pyrolytic reaction mechanism and heat transfer in the thermogravimetric analyser. DSC analysis of sewage sludge was sensitive to decomposition reactions of small quantities of organic salts in the sludge. Sewage sludge could be a profitable pyrolysis feedstock if mixed with municipal solid waste.     

A new kinetic model for pyrolysis of Athabasca bitumen

Pyrolysis of bitumen is a key contributor to gas production in in situ combustion and in situ gasification recovery processes, yet a detailed reaction scheme, that includes a breakdown of products into the most abundant gas components, that is simple enough to be used in detailed thermal‐reactive simulation models, does not exist. Here, we present a novel reaction scheme for pyrolysis of Athabasca bitumen that was developed and calibrated against four experimental data sets (65 data points) over a temperature range from 130 to 422°C. The new model was then verified by comparing its thermogravimetric behaviour against published literature. © 2012 Canadian Society for Chemical Engineering     

三种木材的裂解动力学研究

在氮气氛和不同的加热速率下对三种木材(马尾松、棉杆和杉木)进行了热重分析.同时研究了碳酸钠对这三种木材热解的催化效应.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 and Tempelmen(Z-L-T)方程为最概然机理函数.根据Z-L-T方程计算的动力学参数表明,在裂解的低转化率范围,碳酸钠可以降低表观裂解活化能,而在裂解的高转化率范围,碳酸钠可以增加表观裂解活化能.根据木材的结构成分对碳酸钠的催化行为进行了分析.     

基于热重-红外联用技术分析油酸的热解特性及动力学分析

利用热重红外联动技术（TG-DTG-FTIR）研究了橡胶籽油中的单不饱和游离脂肪酸油酸组分在不同升温速率（5℃/min、10℃/min、20℃/min、30℃/min）下的热解特性。然后,用多元线性回归法对油酸非等温热解所得到的特性参数进行研究并计算,求得不同升温速率下对应的反应级数、活化能和指前因子,并对不同升温速率下油酸热解反应活化能和指数前因子作线性拟合。结果表明：油酸热解过程主要可分为0～268℃和268～300℃两个阶段,由红外谱图特征峰的分析可知,不同升温速率下,在油酸热解的阶段内均出现了水蒸气、CH₄、CO₂和CO这4种主要气体挥发分。随着升温速率的增大,油酸热解的最大失重速率随之增大,热解区间也向着高温段移动,同时计算在升温速率从5～30℃/min的过程中,反应级数n=1时,热解反应活化能由105.57kJ/mol降低至93.99kJ/mol,指数前因子由6.99×10⁶降低至6.7×10⁵;n≠1时,热解反应活化能由102.45kJ/mol降低至93.38kJ/mol,指数前因子由3.13×10⁶降低至2.97×10⁴,反应活化能和指数前因子随升温速率的增大出现明显减小。通过对不同升温速率下油酸热解反应的活化能和指数前因子进行线性拟合后发现,两者间具有较好的补偿效应。     

氮气气氛下城市污水厂污泥热解特性

为了解城市污水厂污泥在氮气气氛下进行热解的特性,利用热重分析结合傅立叶红外光谱等方法对长沙某污水厂干燥污泥进行了研究。实验结果表明,在15℃/min和30℃/min的升温速率下,干燥污泥存在3个阶段的失重过程,结合FITR谱线可知,每一阶段的失重都有CO2和水析出。同时对实验数据进行了处理,采用微分法确定了热解反应的机理方程,并求出反应动力学参数活化能E和频率因子A。     

干燥前后花生壳的热解特性研究

用热重分析法对干燥前后花生壳的热解特性进行了研究。分析了干燥前后花生壳样品在升温速率为 25℃/min 下的热解特性,得到热重曲线(TG)、微商热重曲线(DTG)和差热曲线(DTA)。发现样品的失重过程由干燥阶段、预炭化阶段、炭化阶段、煅烧阶段4个阶段组成,并对所得曲线进行了详细分析。对比干燥前后花生壳的曲线差异,发现干燥后的花生壳TG/DTG曲线整体左移,热解温度降低。最后对花生壳的热解过程进行了动力学研究。为花生壳的合理利用提供了一定的理论基础。     

Viscous characteristics of a Utah tar sand bitumen

The viscous behaviour of an extracted tar sand bitumen has been experimentally examined and the results summarized in this Paper. The material studied was from the Asphalt Ridge, Utah area. The viscosity of the bitumen has been determined as a function of temperature (293–422 K), toluene (solvent) content (0–10%), composition (0–14.6% asphaltenes), oxidation and shear history. In all cases studied, the Arrhenius plots were significantly non-linear at temperatures s> 373 K, with viscous behaviour becoming less sensitive to toluene content with increasing temperature. Low temperature behaviour was strongly dependent on toluene content. The presence of asphaltenes in the bitumen was shown to be a strong viscosity enhancer. Oxidation and shear history were also shown to measurably increase the bitumen viscosity.     

Effect of low-temperature oxidation on the composition of Athabasca bitumen

The effect of low temperature oxidation on the composition of Athabasca bitumen was examined. Oxidation temperatures in the range 125–135 °C and extents of oxidation up to 100mg $\text{O}{}_2\text{g}$ bitumen were investigated. The aromatics concentration was observed to decline steadily and the concentration of asphaltenes to increase, during oxidation. The saturates were unaffected by low-temperature oxidation. The resins concentration displayed a strange behaviour, first dropping and then increasing to a maximum and again dropping as oxidation proceeded.     

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。