Thermal degradation of shale oils: 1. Kinetics of vapour phase oil degradation

As vertical modified in-situ retorts (VMIS) have been scaled up and tested, the overall oil yield has declined and is generally lower than that observed in an above-ground process. This reduced oil yield could adversely affect the economics of VMIS retorting. Diminished yields are attributed to a combination of factors associated with scale-up such as in complete rubblization, wide particle size distributions (large blocks of shale), and poor flow distributions. Additionally, oil losses can occur by comparatively long exposure of the oil vapours to high temperatures, by exposure to successive condensation and revaporization of the oil as it travels down the retort, and finally by long time thermal exposure of the condensed oil retained in the bottom portion of large VMIS retorts. To study such vapour phase degradation of shale oil using oil produced from Occidental Petroleum's No. 6 VMIS retort, a tubular continuous flow reactor, with an on-line gas chromatograph for gas composition monitoring was used to study thermal degradation of shale oil under retorting conditions. Oil and a combination of gases including steam were metered into the preheater and then the vapours passed into a quartz tubular reactor where the temperature and residence time of the gaseous mixture were controlled. Complete mass balances were performed giving the weight fraction of oil converted to noncondensable hydrocarbon gases and coke. This experimental design is novel because high temperature thermal degradation of shale oil was studied for the first time under steady state flow conditions with carefully controlled residence time and temperature. A range of temperatures (425–625 °C) and residence times (2–10 s) were used in a series of factorial-designed experiments (3²) to accurately determine the effects of these variables. Results of the study showed that the addition of steam to the carrier gas did not reduce oil degradation losses but did react with the coke thereby changing the product gas composition and quantity. A first-order oil degradation rate expression was used to model the rate of oil loss. The calculated activation energy was 17.3 kcal mol^?1. Chemical analyses of the product liquids and gases confirmed previously reported findings that the oil loss indices (alkene/alkane, ethylene/ethane, naphthalene/(C₁₁ + C₁₂), and gas/coke) increase with increasing oil degradation.     

Pyrolysis kinetics for Green River oil shale from the saline zone

The nature of the organic and mineral reactions during the pyrolysis of Saline-zone Colorado oil shale containing large amounts of nahcolite and dawsonite has been determined. Results reported include a material-balanced Fischer assay and measurements of gas evolution rate of CH₄, C₂H_x, H₂, CO and CO₂, Stoichiometry and kinetics of the organic pyrolysis reactions are similar to oil shale from the Mahogany zone. X-ray diffraction and thermogravimetric analysis results are used to help determine the characteristics of the mineral reactions. Kinetic expressions are reported for dawsonite decomposition, and it is demonstrated that the temperature of dolomite decomposition is substantially lower than for Mahogany-zone shale because of the presence of the sodium minerals.     

Composition and kinetics of oil generation from non-isothermal oil shale retorting

Oil shale retorting has been carried out under non-isothermal conditions between 623 and 773 K and at different pressures(78 and 765 kPa). The shale oil is separated into five individual components: polar, weak polar, saturates, aromatics and olefin, using a comprehensive analytical procedure. The effects of retorting pressure and heating rate have been studied. The oil yield under high pressure (765 kPa) is ≈10% less than the oil yield under ambient pressure (78 kPa). Much of this reduced yield can be accounted for by the reduced amount of polar component formed at high pressure. Heating rates of 1.67 × 10^?2, 6.67 × 10^?2and 8.33 × 10^?2Ks^?1 have been used; a higher heating rate causes a delay in the appearance of the oil. A simplified kinetic scheme is proposed which includes the distribution of liquid products and pressure effects. The activation energies and frequency factors of generation reactions for total oil and individual components have been obtained.     

中国油页岩开发利用现状及发展前景

简单介绍了油页岩的用途及中国油页岩开发利用的历史,总结了油页岩的干馏工艺技术和开发利用现状,展望了油页岩的发展前景。     

Thermogravimetry and decomposition kinetics of British Kimmeridge Clay oil shale

The characteristics of volatile matter evolution and the kinetics of thermal decomposition of British Kimmeridge Clay oil shale have been examined by thermogravimetry. TG has provided an alternative to the Fischer assay for shale grade estimation. The following relation has been derived relating TG % volatiles yield to the shale gravimetric oil yield: oil yield (g kg^?1) = (TG volatiles, % × 5.82) ? 28.1 ± 14.5 g kg^?1. A relationship has also been established for volumetric oil yield estimation: oil yield (cm³ kg^?1) = (TG volatiles, % × 4.97) – 5.43. TG is considered to give a satisfactory estimation of shale oil yield except in certain circumstances. It is found to be less reliable for low yield shales producing <≈40 cm³ kg^?1 of oil (≈10 gal ton^?1) where oil content of the TG volatiles is low: volumetric yield estimation accuracy is affected by variations in shale oil specific gravity. First order rate constants, k = 4.82 × 10^?5s^?1 (346.3 cm³ kg^?1shale) and k = 6.78 × 10^?5s^?1 (44.6cm³ kg^?1shale) have been obtained for the devolatilization of two Kimmeridge oil shales at 280 °C using isothermal TG. Using published pre-exponential frequency factors, an activation energy of ≈57.9 kJ mol^?1 is calculated for the decomposition. Preliminary kinetic studies using temperature programmed TG suggest at least a two stage process in the thermal decomposition, with two maxima in the volatiles evolution rate at ≈450 and 325 °C being obtained for some samples. Use of published pre-exponential frequency factors gives activation energies of ≈212 and 43 kJ mol^?1 for these two stages in the decomposition.     

甘肃油页岩红外光谱分析及热解特性

基于热重分析仪（TG）、傅里叶变换红外光谱分析仪（FTIR）和质谱分析仪（MS）三机联用对甘肃油页岩进行光谱和热解实验。通过分析光谱谱图,得到了样品中的化学成分和化学结构的相关信息。结果表明,其化学结构的特征在于相对较高量的脂肪族基团。在TG/FTIR/MS三联机上研究了甘肃油页岩的热解特性,实验结果表明：整个热解过程主要有两个阶段,即低温段和高温段。大部分的热解行为发生在低温段（400～600℃）,此阶段里油页岩的失重量占总失重量的70%,可挥发物质迅速热解,热解产生的气体有H2、H2O、CO2、CH4、CO、轻质烃等。而在高温段（600～850℃）的热解气体产率很小,失重量只占总重量的2.167%。这个阶段主要是含碳酸盐的矿物质分解而产生一定量的气体。本文主要研究两个热解阶段产生的气体。对产生气体的种类、时间和产生机理进行了研究,并得出热解的化学反应动力学参数。     

Kinetics of oil generation from Colorado oil shale

Isothermal and nonisothermal methods have been used to investigate the kinetics of oil generation during decomposition of 91.7 ml/kg (22 U.S. gal/short ton) Colorado oil shale. The result from the nonisothermal method gives an apparent activation energy of 219.4 kJ/mol and a frequency factor of 2.81 × 10¹³s^?1. Furthermore, the process is found to be first-order to within experimental error. These results compare favourably with isothermal data reported here and in the literature. The results show the reliability and convenience of nonisothermal kinetic experiments in studying oil-shale decomposition reactions. The principal advantages are short-term experiments and the lack of initial heat-up periods. Moreover, nonisothermal experiments more accurately simulate actual conditions of above-ground and in situ oil-shale retorting. These kinetics are ‘effective’ values and can only properly be used to describe the macroscopic oil-production process rather than the complex microchemistry.     

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。     

油页岩半焦燃烧动力学研究

燃烧动力学是研究油页岩半焦颗粒燃烧特性的基础。利用热重分析仪对油页岩半焦进行了恒温燃烧实验研究,在排除外扩散影响的基础上,分析了燃烧温度、氧气浓度对油页岩半焦燃烧过程的影响。在实验范围内,氧气浓度和燃烧温度均能对油页岩半焦燃烧速率产生重要影响,更高的氧气浓度和燃烧温度可以加快油页岩半焦燃烧速率。结合实验结果,建立了考虑氧气浓度影响的油页岩半焦燃烧动力学模型,发现油页岩半焦燃烧速率与氧气浓度的0.97次方呈线性关系。模型计算结果与实验结果符合较好,为进一步研究油页岩半焦大颗粒燃烧特性提供了燃烧动力学基础。     

油页岩过热蒸汽的干燥动力学

以油页岩颗粒作为干燥物料,以过热蒸汽和热空气分别作为干燥介质,进行了油页岩干燥实验的研究。当颗粒粒径减小时,油页岩干燥速率越大;过热蒸汽和热空气温度增大时,干燥速率也越大。对比相同条件下过热蒸汽和热空气干燥油页岩的平均干燥速率,发现当干燥介质温度超过逆转点温度时,过热蒸汽条件下的平均干燥速率大于热空气下的数值。实验得出粒径分别为9,7,5 mm的油页岩颗粒逆转点温度值分别是154,179,177℃;逆转点温度值是个变量,随颗粒粒径大小变化而变化。颗粒粒径越大时逆转点温度值越小,粒径较小时逆转点变化不大。采用薄层干燥模型对油页岩的干燥数据进行动力学模拟,可得修正Page模型(Ⅱ)干基水分比w模拟值与实验值的最大绝对偏差是12%,综合比较发现修正Page模型(Ⅱ)能较好地描述油页岩在过热蒸汽条件下的干燥过程。     

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     

中国油页岩成矿特征分析

中国油页岩资源丰富,陆相、湖泊海相以及海陆交互相都有油页岩沉积,而陆相沉积最为普遍。油页岩资源丰富的盆地主要有松辽、鄂尔多斯、准噶尔3个盆地,共占全国油页岩资源储量的76．8％以上,主要赋存于新生代地层中。油页岩产出状态多样,以薄层状为主,多为褐黑色,有机质类型属于Ⅰ-Ⅱ型干酪根。含油率大于5％的页岩油资源占67．64％,表明中国油页岩品质中等偏好。     

蒙脱石对油页岩干酪根热解特性的影响

选取中国桦甸、抚顺、窑街3个地区油页岩,酸洗得到各干酪根样品。应用TG-FTIR技术对不同升温速率下各干酪根与蒙脱石共热解行为进行了研究,并利用Coats-Redfem积分法对升温速率为10℃/min下的干酪根掺混样品进行热解反应动力学分析,获得了蒙脱石对干酪根热解产物析出规律的影响及热解过程的活化能(E)和指前因子(A).结果表明,随着蒙脱石掺混比例增大,桦甸和抚顺干酪根热解失重率先升高后降低;在热解过程中,440℃前干酪根与蒙脱石掺混样品的热解失重率较干酪根单独热解低,而440℃后其热解失重率较干酪根热解有所提高;蒙脱石掺混比例增大使得各干酪根热解产物中CH₃/CH₂值有所增加;有蒙脱石掺混的干酪根热解活化能相比干酪根热解活化能有所降低。表明蒙脱石对油页岩干酪根热解具有物理吸附和裂解催化两种作用,且随着热解过程的加深和蒙脱石配比的改变而不同。最后,对升温速率为10℃/min的样品进行了热解反应动力学分析,进一步探讨了蒙脱石对干酪根的热解影响机理。     

汪清油页岩燃烧反应动力学研究

采用Pyris-1TGA热重分析仪测定汪清油页岩不同升温速率(20,50,80,100℃/min)下的一组燃烧TG曲线,根据Popescu提出的一种新的多重扫描法,将不同机理函数式进行线性回归。结果表明,该油页岩燃烧反应符合三维扩散机理,从而确定了该油页岩机理函数的积分式与微分式,获得了活化能与频率因子的值。取转化率为0.1,0.2,…,0.9,将冉全印-叶素温度积分近似式与所求机理函数结合,利用迭代法求出转化率-温度的理论值。结果发现,理论TG曲线与实验曲线吻合较好,表明了所求得的油页岩燃烧机理函数的合理性。     

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。     

油页岩半焦燃烧反应活性分析

采用美国Perk in E lm er公司生产的Pyris1 TGA热重分析仪,对桦甸油页岩半焦进行燃烧特性试验研究,得到3种不同升温速率下的油页岩半焦燃烧特性曲线,并使用平均质量反应性指数和燃烧稳定性指数对半焦反应性加以评价。油页岩半焦燃烧分燃烧快速段、过渡段和燃烧慢速段3个阶段进行。随着升温速率的提高,在燃烧快速段,表观活化能为133.901 3—100.204 2 kJ/mol;在燃烧慢速段,表观活化能为146.317 1—211.409 3 kJ/mol。利用Coats-Redfern法确定了燃烧快速段反应级数为3,而燃烧慢速段则为5.5,从而得到油页岩半焦燃烧化学反应的动力学参数,为油页岩半焦的有效开发与经济利用提供了理论依据。     

程序升温下页岩油泥热解机理

采用热重分析仪,进行了桦甸和汪清页岩油泥在不同升温速率（5 ℃/min,10 ℃/min,20 ℃/min,40 ℃/min）下热失重实验,并通过瓦斯气析出情况研究页岩油泥热解机理。结果表明,页岩油泥热解分为3个阶段：第一阶段（20～180 ℃）为水分和轻质组分析出;第二阶段（180～360 ℃）重质组分稳定析出,是动力学研究的重点;第三阶段（360～600 ℃）为半焦炭化及矿物质失重过程。研究发现,催化剂K2CO3能有效降低油泥热解温度及其残渣率,而Al2O3对油泥热解催化不明显甚至起抑制作用。在页岩油泥热解过程中,生成的有机大分子侧链发生C—C键断链,生成小分子的烷烃和不饱和烃,在低压高温条件下,其断链位置倾向于碳链端部,使得小分子烃含量较多。     

油页岩地下转化工艺技术

当前对油页岩的利用存在成本高和对环境污染大的问题。Shell公司研发的油页岩地下转化工艺技术,通过现场试验具有成本低、对环境污染小和效率高的特点,具有极大的商业推广价值。     

油页岩热解特性及其甲烷释放规律研究

为研究油页岩热解特性及热解过程中甲烷的释放规律,采用热重-傅里叶变换红外光谱（TG-FTIR）对龙口（LK）、内蒙（NM）、汪清（WQ）三个地区的典型油页岩进行热解实验,并结合固相红外（FTIR）对油页岩的官能团结构进行分析。研究结果表明,油页岩热解过程可分为四个阶段,热解反应及挥发分释放主要发生在第二阶段（400～600℃）。甲烷的析出与油页岩结构中的脂肪烃（光谱范围3000～2800 cm^-1）密切相关,脂肪烃含量越多,热解过程中释放的甲烷越多。通过对甲烷析出曲线分峰拟合及结合动力学分析,得出甲烷的生成是由一个脱吸附过程和四个化学反应共同作用的结果。     

Kinetics of decomposition of CaCo3 in an Australian oil shale

The kinetics of decomposition of calcium carbonate in an Australian (Julia Creek) oil shale were measured because the extent of the carbonate decomposition affects the energy balance for combustors burning either raw or spent shale. The apparent activation energy was similar to that previously reported for the decomposition of calcium carbonate in Colorado oil shale but the Julia Creek shale had rate constants which were smaller than those reported for the Colorado shale.