Detailed kinetic analysis of oil shale pyrolysis TGA data

There are significant resources of oil shale in the western United States, which if exploited in an environmentally responsible manner would provide secure access to transportation fuels. Understanding the kinetics of kerogen decomposition to oil is critical to designing a viable process. A dataset of thermogravimetric analysis (TGA) of the Green River oil shale is provided and two distinct data analysis approaches—advanced isoconversional method and parameter fitting are used to analyze the data. Activation energy distributions with conversion calculated using the isoconversional method (along with uncertainties) ranged between 93 and 245 kJ/mol. Root mean square errors between the model and experimental data were the lowest for the isoconversional method, but the distributed reactivity models also produced reasonable results. When using parameter fitting approaches, a number of models produce similar results making model choice difficult. Advanced isoconversional method is better in this regard, but maybe applicable to a limited number of reaction pathways. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

油页岩热解的FG-DVC模型

为研究油页岩结构与热解反应性之间的关系,在TG-FTIR分析仪上对甘肃油页岩在不同升温速率条件下（5、20、50℃·min^-1）进行了热解实验研究,对CH₄、CO、CO₂、H₂O和页岩油进行了定量分析,并采用非线性最小二乘拟合方法求解各组分析出的动力学参数,同时采用基于燃料化学结构的FG-DVC模型对各组分的析出过程进行了模拟。结果表明：油页岩的脱挥发分过程主要发生在200～600℃之间;油页岩中有机质所含官能团以脂肪烃为主;由于各官能团活性不同,导致气态产物的析出有先后顺序;由非线性最小二乘拟合方法获得的各种产物析出的活化能E分布在188～239 kJ·mol^-1之间,而指前因子A在10⁹～10¹³ s^-1之间;各产物的FG-DVC模拟结果与实验数据较为相符,这说明用FG-DVC模型来描述甘肃油页岩的热解脱挥发分过程是比较合适的。     

DTA derived kinetics of Jordan oil shale

The thermal behaviour of Jordan oil shale has been studied in a DTA apparatus in an He atmosphere. The thermal curves for both untreated and decarbonated shale exhibited two distinct endothermic peaks related to the softening and evolution of organic matter. The first peak relates to molecular rearrangement of the kerogen where nonisothermal kinetics found that the activation energy (E_a) in the range 13.4–25.1 kJ mol^?1 for both untreated and decarbonated samples. For the second peak, E_a was obtained from first order kinetics and varied from 54.9 kJ mol^?1 for decarbonated shale to 79.6 kJ mol^?1 for untreated samples. The effect of particle size on the DT curves was studied and showed a drift from zero base line. Spent shale for reference material improved the profile of DTA curves and minimized drift as compared to use of α-alumina.     

Rapid pyrolysis of brown coal and oil shale

A brown coal, peat and oil shale were subjected to a rapid pyrolysis process and medium-heat-value gases together with tar were collected. The char residue was of high activity and suitable for gasification to create a two-stage gasification system. The coal-tar is used for manufacturing liquid fuels and chemicals.     

Study of pyrolysis kinetics of oil shale

The pyrolysis experiments on oil shale samples from Fushun, Maoming, Huangxian, China, and Colorado, USA, were carried out with the aid of thermogravimetric analyzer (TGA) at a constant heating rate of 5 °C/min. A kinetic model was developed which assumes several parallel first-order reactions with changed activation energies and frequency factors to describe the oil shale pyrolysis. The kinetic parameters of oil shale pyrolysis were determined on the basis of TGA data. The relationship between the kinetic parameters was further investigated and the correlation equations of x_∞-E and ln A-E were obtained. These equations show that the final fractional conversion of each parallel reaction, x_∞(j), can be expressed as an exponential function of the corresponding activation energy. The plot of ln A-E for different reactions becomes a straight line. These relationship equations can provide important information to understand the pyrolysis mechanism and to investigate the chemical structure of oil shale kerogen.     

油页岩热解技术研究进展

针对油页岩热解反应过程复杂,产油率低的问题,进行了油页岩的热解机理和反应过程介绍,探讨了材料特性、炉型种类、催化剂类型、热解温度、加热速率和停留时间对热解转化率的影响及其变化规律。研究发现材料特性影响页岩油产率和品质,粒径尺寸适宜范围在1. 2³ mm;固体干馏炉比气体干馏炉好,其油页岩利用率和油收率最高可达100%;催化剂由于其独特的性质和结构特点能够加速油页岩的热解,增大油页岩热解转化率,提高页岩油产率;此外,热解温度在5203 mm;固体干馏炉比气体干馏炉好,其油页岩利用率和油收率最高可达100%;催化剂由于其独特的性质和结构特点能够加速油页岩的热解,增大油页岩热解转化率,提高页岩油产率;此外,热解温度在520⁵50℃、加热速率在12550℃、加热速率在12¹5℃/min和停留时间在2015℃/min和停留时间在20⁴0 min范围内能够提高页岩油产率,改善页岩油的品质。指出了油页岩热解技术发展趋势,以期为我国非常规、战略接替能源的开发利用提供一定的参考。     

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。     

Kinetics of tetralin extraction of Jordan oil shale

Isothermal kinetic data are obtained for the dissolution of Jordan oil shale in a hydrogen-donating solvent (1,2,3,4-tetrahydronaphthalene) in the temperature range 229–315 °C for untreated (as received mf) shale and 230–360 °C for the decarbonated shales. Preheating time was not accounted for in the treatment. For the untreated shale, the first-order plots have two distinct slopes at the lower temperature. For the higher temperatures, the plots fitted a single first-order expression. The activation energies were 42.6 and 85.6 kJ mol^?1 respectively. The data for the decarbonated shale fit a first-order expression with one low activation energy (E_a = 37.6 kJ mol^?1), suggesting a physical control of the dissolution process. Particle size variation showed a maximum yield at 200 mesh and smaller, although tests using large particles were hampered by settling. Solvent to shale ratios variation showed an optimum at about 180 g shale to 550 ml solvent. No effects of pressure of N₂ and H₂ upon the shale slurry yield were found. A reaction mechanism explaining the kinetic data is postulated.     

大庆油页岩及干馏产物的利用途径分析

大庆油页岩的舍油率大部分都在10%以上,具有很好的经济开发价值.对大庆油页岩及其干馏产物性质的实验研究表明,油页岩的机械强度较低,应选择粉末、颗粒干馏炉进行加工处理;页岩油主要由柴油馏分和重油馏分组成,分别可加工成成品油和直接用作燃料油;热解干馏气热值约为17MJ/m3,可以在除作自身干馏所需的热量燃料外,用作城市煤气或工业锅炉的燃料;半焦着火点低,热值约为23 MJ/kg,可作为清洁燃料用于发电或民用;页岩灰的主要组分是氧化钙争氧化硅,可用于生产建筑材料.     

Chemical transformations during pyrolysis of Rundle oil shale

Rundle shale (Queensland, Australia) was pyrolysed at 12.5 K min⁻¹ to 350–500 °C for 10–240 min. The structures of the liquid products and pyrolysis residues were investigated by a number of n.m.r. spectroscopic techniques including cross-polarization and dipolar dephasing. N.m.r. provided a simple method for detecting nitrile carbon and measuring terminal and internal olefinic hydrogen in shale oil. It was found that the ratio of terminal olefinic hydrogen to internal olefinic hydrogen in shale oil increases by a factor of three over the range 350–500 °C. Moreover, the results suggest that aromatic rings in Rundle shale residues are not highly substituted and hence that aromatic ring condensation reactions are not important during pyrolysis. From elemental, yield and n.m.r. data, the conversion of aliphatic carbon to aromatic carbon during pyrolysis was found to be as high as 25% at 500 °C.     

影响油页岩热分解的因素

介绍了抚顺式干馏炉的工作原理;论述了油页岩的含水量、热稳定性、粘结性、结焦性、粒度组成等性质及干馏加热的温度、速度和时间等不同受热条件对其热分解的影响;总结出干馏炉内油页岩受热条件的控制须根据页岩的各种实际物理性质进行操作。     

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。     

Current trends in the pyrolysis of oil shale: A review

The review surveys recent publications on the pyrolysis of oil shale. The effect of process parameters on the composition and properties of the resulting products and problems related to the further thermal processing of shale oils are considered.     

Seven-lump kinetic model for catalytic pyrolysis of heavy oil

A 7-lump kinetic model is proposed to describe the catalytic pyrolysis of heavy oil. The kinetic model contains 15 kinetic constants and one for catalyst deactivation. The experimental data were obtained in a confined fluidized bed reactor. The kinetic constants were estimated by a special program compiled based on the Marquardt’s algorithm. The apparent activation energies were calculated according to the Arrhenius equation. This model fits the experimental data well. The prediction shows that catalytic pyrolysis of Chinese Daqing atmospheric residue should be conducted at low space velocity to produce much ethene and at space velocity around 15 h⁻¹ to produce much propene and butene.     

A comparison of the dissolution of model compounds and the kerogen of Green River oil shale by oxidation with perchloric acid — A model for the kerogen of Green River oil shale

A stepwise degradation of a kerogen concentrate of Green River oil shale was effected by oxidation with perchloric acid of varying boiling point and concentration. Dissolution of the kerogen concentrate occurred between 160 and 170°C. Several model compounds were also oxidized with perchloric acid. The model compounds were polyethylene, graphite, nylon, and polyethylene oxide. The results indicated that the kerogen was similar to polyethylene oxide. The results of this study and previous work were used to present a model for the structure of the kerogen of Green River oil shale.     

Tetralin extraction of Jordan oil shale with ultrasonic irradiation

The kinetics of dissolution of decarbonated Jordan oil shale in tetralin, in the presence of ultrasonic irradiation at relatively low temperatures, has been evaluated. The solvolysis was found to fit a first-order integrated equation between 28 and 95 °C, and a second-order equation for the temperatures 121 and 132 °C. Negligible reverse reactions were detected when shale residue was exposed to the solution for long periods of time. A slurry of 1:1 ratio by weight of shale to solvent was found to be best for maximum yield of extract (oil). The rate processes were concluded to be determined by diffusion-controlled kinetics, with an apparent energy of activation of 7.15 kcal/mol¹, and apparent enthalpy and entropy according to the Eyring equation of 5.2 kcal/mol and ?58 e.u. ² respectively.     

油页岩热解过程中微量元素迁移及其作用规律

利用电感耦合等离子质谱仪（ICP-MS）测定油页岩样品和不同终温下热解半焦中13种金属微量元素的含量,分析这些元素在样品中的含量分布特征及其迁移规律。结果显示：龙口油页岩中富集Ba、Cd,巴里坤油页岩中富集Ba、Cd、Li、V、Sb,且样品中多数微量元素在500℃时挥发性最强。将不同形态的微量元素负载于干酪根上并进行热重分析,根据热重结果计算其动力学,再通过裂解气质联用实验（PY-GC/MS）测定干酪根和浸渍硝酸镍的干酪根热解时烷烃类产物的相对含量,研究微量元素对干酪根热解生烃转化率、热解速率以及产物分布的影响。结果表明：微量元素的盐类可以催化干酪根热解生烃,增大其热解转化率和热解速率,提高轻组分烷烃产率,降低重组分烷烃产率。     

微波功率对油页岩热解的影响

对甘肃油页岩进行了微波热解实验研究,考察了油页岩在微波场中的升温特性及功率对页岩油、半焦、干馏气产率和组成的影响。结果表明：在微波场中油页岩干馏终温可达800℃以上;不同功率下干馏气组成不同,在480 W时干馏气中有效组分（H2＋CH4＋CO）达55%以上;随着功率的增大,半焦产率逐渐减小;页岩油产率随功率先增加后减小,在480 W时达到最大值13.5%;而干馏气产率随功率逐渐增大,在480 W时可达10%。