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     

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.     

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     

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。     

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.     

Phase behaviour modelling of Athabasca bitumen for in situ combustion applications

Phase behaviour modelling of reservoir fluid is a fundamental step for reservoir simulation. Furthermore, as the complexity of the recovery process increases, the fluid model plays a more important role in the reliability of the simulation outputs. Although the in situ combustion enhanced oil recovery method (ISC) is one of the most complex recovery techniques available in the petroleum engineering literature, for most of the simulation jobs related to this elaborate process only simple and rudimentary fluid characterization layouts are considered. In this work, the principal fluid properties of Athabasca bitumen with regard to the ISC process are recognized, extracted from the literature, validated for consistency, and used for the development of an inclusive and accurate fluid model. Then the fluid model is fully developed while considering the ISC reaction kinetics so that the model has both accuracy, indispensable for phase behaviour modelling, and consistency, essential for the reactions definitions.     

Kinetics of reactions involved in pyrolysis of cellulose I. The three reaction model

Kinetics of reactions involved in pyrolysis of cellulose has been modeled in terms of a three reaction model. In this model it is assumed that cellulose decomposes to tars, chars and gaseous products via three competitive first-order reactions. Arrhenius parameters have been obtained to describe the rate constants of these reactions. The three reaction model predicts the weight loss data reasonably well. Product yields of tars, chars and gases predicted by the three reaction model are compared over the temperature range 250 to 360°C. In this communication a technique for analyzing experimental data of a solid state reaction is presented.     

Simulation analysis of biomass pyrolysis based on the improved chemical percolation devolatilization model with chain reaction dynamics

The complex composition and molecular structure of biomass lead to more complex and diversified chemical reactions in the pyrolysis. According to the structural characteristics of the reactants, this article simplifies the pyrolysis process and extends the research focus from the micro-molecular elementary reactions to the macro reaction kinetics. The wheat straw is chosen as the investigated biomass, and the promoted chemical percolation devolatilization with modified pseudo-grid and chain reaction kinetics pyrolysis models were constructed for predicting the pyrolysis characteristics. Under the condition of slow pyrolysis, by calculating the average difference between the collected calculated values and the corresponding experimental values, the prediction errors of bio-char, bio-oil, and gas production are in a reasonable range of <10%. Moreover, the reliability of the model is verified by comparing with the experimental thermogravimetric curve, which shows that the model could well predict the mass loss, product distribution, and component characteristics, and provides a reasonable prediction for the pyrolysis of biomass. However, the simplifications and assumptions about the model also lead to some deviations of the predicted values, which should be considered and improved in future research.     

A unified polymer reaction engineering methodology for catalytic olefin polymerization: From reaction conditions and catalyst reaction performance to molecular and rheological properties for forward,reverse engineering and deconvolution applications

This work presents a unified polymer reaction engineering methodology for the catalytic olefin polymerization process. The proposed modelling approach offers a modelling pathway from the polymerization recipe to production rate and polymer microstructure, and finally to rheological properties. Furthermore, this work introduces for the first time the constraint of the actual reaction performance of the polymerization catalyst in the inverse rheology and microstructural deconvolution problem, limiting the solution only to the most realistic potential molecular weight distributions (MWDs) that a specific catalyst can produce. This approach can be applied for both single- and multi-site catalysts, providing not a potential MWD but the unique one that the selected catalyst can offer under given polymerization conditions. Depending on the available catalyst reaction performance insight, the constraint can vary and include from the number of active sites in use to the exact kinetic parameters of each site type. The potential of the proposed methodology is highlighted within a series of indicative examples, including forward, reverse engineering and deconvolution applications.     

CaSO4与CaS在N2气氛下反应动力学

利用热重分析仪研究了不同摩尔比下的硫酸钙和硫化钙混合物在N₂气氛下的反应特性，探讨了其化学反应动力学及反应机理.CaSO₄和CaS的固-固反应是CaS氧化生成CaO反应的速率控制反应.当CaSO₄过量时，CaSO₄与CaS的反应分两个阶段.在890～1120 ℃温度范围内CaSO₄与CaS发生固-固反应.在1160～1330 ℃温度范围内，剩余的CaSO₄发生自身分解.当CaSO₄与CaS的摩尔比为3∶1时，反应的活化能最大.CaSO₄和CaS的反应机理可以采用液态共熔体模型来解释.     

甲醇蒸汽重整制氢反应动力学研究进展

甲醇蒸汽重整制氢技术对于解决汽车、船舶等交通工具上燃料电池的氢源问题具有重要意义,近年来已成为碳氢燃料重整制氢的研究热点。本文首先综述了甲醇蒸汽重整制氢的5种反应机理,该方面的研究仍处于定性和推理阶段,尚未达成统一的结论。然后分析了甲醇蒸汽重整反应动力学的研究进展,发现大多研究是基于Cu系催化剂提出,反应温度集中在160～350℃,反应压力多为1atm,研究表明反应物水醇比最优值为1.3～1.4。最后,整理了研究中所提出的动力学模型,指出相较于单速率和三速率模型,双速率模型可反映产物中CO的含量及其对反应速率的影响,且模型相对简单,动力学方程的求解过程也相对容易,但其适用性还有待进一步验证。本文可为甲醇蒸汽重整制氢系统的设计与优化提供理论依据。     

石油热解过程中自由基调控反应机理的构建与应用

石油热解是生产高品质气液燃料和化学品的重要步骤,不仅涉及非催化过程,也涉及催化过程。石油热解过程反应机理不仅为解析不同类型的热解反应过程、构建反应动力学模型以及定向调控和强化,而且对于工艺条件优化、反应调控和强化、催化剂开发和优化以及反应装备技术开发和强化等均能指明方向和提供依据,但现有热裂解自由基链式反应机理和催化裂化正碳离子反应机理均存在实验现象尚未能合理解释。本文提出了石油热解过程的化学反应主体均由受热离解的自由基主导的观点,创建了石油热解过程自由基调控反应机理,不同热解工艺区别主要在于二次自由基调控,自由基复合产物以及稳定产物形成了特定热解过程的产物分布。按照初始自由基产生、二次自由基调控和自由基复合3个阶段的反应机理,合理解析石油催化裂化过程各种应用现象,有效指导了劣质重油快速催化热解-气化耦合技术和原油直接分级气相毫秒催化裂解制化学品技术的开发,证实了石油热解过程自由基调控反应机理的普适性,为工艺条件优化、反应调控和强化、催化剂优化提升和反应装备技术强化等均能指明方向和提供依据。     

集液硫脱气于一体的硫磺收集系统新标准（RSC-D）^TM

从安全及改善粉碎和成型的角度考虑,通常推荐脱气后液硫中的总H2S质量分数小于0．001％。介绍了6种能够满足该指标要求的主要工业脱气技术。所有脱气技术都采用搅动与气提相结合,有些还采用了液体或固体床催化剂和／或冷却技术。重点介绍了Worley Parsons开发的集液硫脱气于一体的硫磺收集新系统（RSC—D）^TM。该系统采用液体喷射泵代替重力自流收集硫磺,因此所有设备都可布置在地面,而且液硫池可远离硫回收装置。新发明消除了重力自流的约束及堵塞问题,改善了硫收集系统的可靠性和操作性。     

A mechanistic model for the water‐gas shift reaction over noble metal substituted ceria

The water‐gas shift (WGS) reaction was carried out in the presence of Pd and Pt substituted nanocrystalline ceria catalysts synthesized by solution combustion technique. The catalysts were characterized by powder XRD and XPS. The noble metals were found to be present in ionic form substituted for the cerium atoms. The catalysts showed high activity for the WGS reaction with high conversions below 250°C. The products of reaction were only carbon dioxide and hydrogen, and no hydrocarbons were observed even in trace quantities. The reactions were carried out with different amounts of noble metal ion substitution and 2% Pt substituted ceria was found to be the best catalyst. The various possible mechanisms for the reaction were proposed and tested for their consistency with experimental data. The dual site mechanism best described the kinetics of the reaction and the corresponding rate parameters were obtained. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

碳酸钙分解动力学TGA实验数据的新诠释

对热学分析(TGA)实验测得的CaCO3分解反应动力学数据的解释曾一直采用了气固反应缩核模型的假设，这一简化处理方法导致了难以对实验中反应过程和输运现象间的关系作出定量描述，所获的动力学数据均具表观性质。作者基于气固反应结构模型观点提出了描述CaCO3分解反应等TGA实验的数学模型及相关数值模拟程序，并对文献记载的一组CaCO3分解动力学TGA实验数据作了新诠释。     

硫化氢间接电解制氢中试阴极动力学

从硫化氢间接电解制氢中试的阴极过程出发,对传质过程与电化学反应过程分别进行了考察,并通过理论模型将两者结合起来,根据中试的实际情况,建立了阴极析氢过程宏观动力学模型.该模型在实验测量的范围内,得到了较好的验证;通过理论推导和实验验证,确立了硫化氢间接电解制氢中试阴极反应的主要影响因素为氢离子浓度、槽压和电解液温度,其中槽压的影响最大.本模型为后续的中试和工业生产提高析氢速度提供了一定的理论依据.     

加氢裂化反应动力学建模研究进展

加氢裂化是炼油与石化行业的关键技术,借助反应动力学建模以及软件模拟技术来深入认识加氢裂化反应机理并指导生产,优化装置操作条件,可以给企业带来显著的经济效益.本文主要对利用集总法来模拟加氢裂化反应过程动力学的相关研究进行了综述,包括基于生产方案划分的集总、离散集总以及连续集总建立的反应动力学模型[微软用户1],重点介绍了这三类集总模型的建模思路及发展现状,对不同模型的优缺点和反应网络进行了详细的对比分析,其中连续集总模型能够充分考虑混合物性质、反应途径以及切割方案变化的影响,进而实现对加氢裂化这一复杂体系反应器的模拟,准确预测其产品分布和产品性质.同时,本文还指出未来加氢裂化反应动力学建模深入研究的方向,将集总法建模和分子法建模有效结合,开发出一个全面的混合动力学模型,将是未来加氢裂化反应器模拟中一项很有意义并且具有挑战的工作.     

催化裂化汽油二次反应过程中反应热的变化

根据热力学理论,通过产物和反应物的生成焓计算了催化裂化汽油在降烯烃改质以及催化裂解过程中的反应热,并根据不同反应过程的实验结果考察了反应温度、停留时间和剂油比对反应热的影响。计算结果表明,催化裂化汽油降烯烃改质和催化裂解过程都是吸热反应体系,降烯烃改质过程的反应热为80～150 kJ·kg^-1,催化裂解过程的反应热为370～620 kJ·kg^-1;反应条件对反应热的影响通过改变反应物的转化率和产物分布实现。在实验条件范围内,随着反应温度的升高、剂油比的增大和停留时间的延长,反应热逐渐增大;当剂油比增大到一定程度时,反应热随剂油比的增加趋势变缓。