Thermal analysis studies of oil shale residual carbon

Thermal analysis has been used to determine the impact of heating on the decomposition reaction of two Moroccan oil shales between ambient temperature and 500°C. During pyrolysis of raw oil shale, the residual organic matter (residual carbon) obtained for both shales depends on the heating rate (5 to 40°C min^-1). Three stages characterize the overall process: the concentration of carbonaceous residue decreases with increase of heating rate, become stable around 12°C min^-1 and continue to decrease at higher heating rates. Activation energies were determined using the Coats-Redfern method. Results show a change in the reaction mechanism at around 350°C. Below this temperature, the activation energy was 41.3 kJ mol^-1 for the decomposition of Timahdit, and 40.5 kJ mol^-1 for Tarfaya shale. Above this temperature the respective values are 64.3 and 61.3 kJ mol^-1. The reactivity of Timahdit and Tarfaya oil shale residual carbon prepared at 12°C min^-1 was subject to a dynamic air atmosphere to determine their thermal behaviour. Residual carbon obtained from Tarfaya oil shale is shown to be more reactive than that obtained from Timahdit oil shale. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study of the combustion mechanism of oil shale semicoke in a thermogravimetric analyzer

Oil shale semicoke, formed in retort furnaces, is a source of severe environmental pollution and is classified as a dangerous solid waste. For the industrial application of oil shale semicoke in combustion, this present work focused on the thermal analysis of its combustion characteristics. The pyrolysis and combustion experiments of semicoke were conducted in a Pyris thermogravimetric analyzer. From the comparison of pyrolysis curves with combustion curves, the ignition mechanism of semicoke samples prepared at different carbonization temperatures was deduced, and was found to be homogeneous for semicoke samples obtained at lower carbonization temperature, shifting to heterogeneous with an increase in the carbonization temperature. The effect of carbonization temperatures and heating rates on the combustion process was studied as well. At last, combustion kinetic parameters of semicoke were calculated with the binary linear regression method, showing that activation energy will increase with increasing the heating rate.     

Kinetic studies of oxidation of residual carbon from moroccan oil shale kerogens

Residual carbons from kerogen extracted from two Moroccan oil shales (from Timahdit and Tarfaya) were oxidized in air. The oxidations were studied by isothermal thermogravimetry. Several kinetic models for mechanisms of the reactions were tested to fit the experimental data. Oxidation of the residual carbon derived from Timahdit oil shale followed a two-third order reaction with an activation energy of 58.5 kJ mol^–1, whilst that from Tarfaya oil shale was a half order reaction with activation energy of 64.1 kJ mol^–1.     

Thermogravimetric investigation on combustion characteristics of oil shale and high sulphur coal mixture

Co-combustion experiments of mixture of Huadian oil shale and Heshan coal with high sulphur content have been conducted using a thermogravimetric analyzer. The effects of five different Ca/S mol ratios on the combustion characteristics of mixture fuel are analyzed using TG and DTG curves. The results show that the initial temperature of combustion of mixture fuel is decreased with an increase in the oil shale content of mixture fuel. The combustion characteristic of mixture fuel is superior to that of Heshan coal. Adding about 20 mass% Huadian oil shale into Heshan coal is feasible for desulfurization of mixture fuel during combustion.     

Kinetics of crude oil combustion

In this research, thermal characterization and kinetics of Karakus crude oil in the presence of limestone matrix is investigated. Thermogravimetry (TG/DTG) is used to characterize the crude oil in the temperature range of 20-900°C, at 10°C min ^-1 heating rate using air flow rate of 20 mL min ^-1. In combustion with air, three distinct reaction regions were identified known as low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO). Five different kinetic methods used to analyze the TG/DTG data to identify reaction parameters as activation energy and Arrhenius constant. On the other hand different f(α) models from literature were also applied to make comparison. It was observed that high temperature oxidation temperature (HTO) activation energy of Karakus crude oil is varied between 54.1 and 86.1 kJ mol ^-1, while low temperature oxidation temperature (LTO) is varied between 6.9 and 8.9 kJ mol ^-1.     

Effects of acid treatments on Moroccan Tarfaya oil shale and pyrolysis of oil shale and their kerogen

In this study, the kerogen of oil shale from Moroccan Tarfaya deposits was isolated and the changes in the initial organic matter during the removal of the mineral matrix were examined. Chloroform extraction of the oil shale increases the intensity of the peaks in the X-ray diffractograms. Infrared spectra and X-ray diffractograms reveal the presence of mineral, calcite, quartz, kaolinite, and pyrite in the mineral matrix of the oil shale. Hydrochloric and hydrofluoric acids dissolution do not alter the organic matter. The nonisothermal weight loss measurements indicate that thermal decomposition of the isolated kerogen can be described by firstorder reaction. A single kinetic expression is valid over the temperature range of kerogen pyrolysis between 433K and 873K. Furthermore, the results indicate that the removal of mineral matter causes a decrease in the activation energies of the pyrolysis reactions of oil shale.     

油页岩飞灰对重金属离子的吸附动力学及热力学

采用批式振荡吸附法研究了燃油页岩电厂循环流化床锅炉飞灰对重金属离子Pb²+、Cu²+、Zn²+、Cd²+的吸附动力学及吸附热力学特性,并提出了吸附机理。结果表明,油页岩飞灰对Pb²+、Cu²+、Zn²+、Cd²+的吸附平衡数据符合Langmuir和Freundlich吸附等温方程,但Freundlich方程能够更好地描述吸附等温线。在油页岩飞灰对重金属离子吸附的初始阶段,拉格朗日准一级动力学方程、准二级动力学方程、Elovich方程、粒子内扩散模型均能很好地反映吸附模式,而整个吸附过程则遵循二级反应动力学方程,其吸附过程是液膜扩散和粒子内扩散共同作用的结果。油页岩飞灰对Pb²+、Cu²+、Zn²+、Cd²+的吸附是吸热反应。     

Non-Isothermal Pyrolysis and Kinetics of Oil Shales

In this research, non-isothermal pyrolysis behavior and kinetics of three oil shales were studied by thermal analysis methods. All the thermal effects were endothermic and no exothermic region was observed in DSC curves. When oil shales are heated in nitrogen atmosphere in TG/DTG, two different mechanisms causing loss of mass were observed. The region between ambient temperature and 500 K was distillation. The second mechanism was visbreaking and cracking and it was observed between the region 500 and 800 K. Kinetic parameters of all the samples are determined by Coats and Redfern method and the results are discussed with regard to their accuracy and the ease of interpretation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Supercritical fluid extraction of Moroccan (Timahdit) oil shale with water

Timahdit oil shale was subjected to supercritical water extraction. The results reveal significant difference in oil yields and composition when compared with those obtained from conventional pyrolysis. In addition, the effect of temperature and residence time on the supercritical water extraction of oil was investigated in a set of three experiments. The results revealed that the yield and the fraction of paraffins and aromatics increase while the percentage of asphaltenes decreases as the temperature is increased from 380 to 400°C. The residence time was found to affect the yield and the fraction of asphaltenes and polar compounds.     

ASTM Kinetics of Oil Shales

Thermal analysis is increasingly being used to obtain kinetic data relating to sample decomposition. In this research differential scanning calorimeter (DSC) was used to determine the combustion kinetics of three (Çan, Himmetoglu and Mengen) oil shale samples by ASTM and Roger &; Morris methods. On DSC curves two reaction regions were observed on oil shale sample studied except Çan oil shale. In DSC experiments higher heating rates resulted in higher reaction temperatures and higher heat of reactions. Distinguishing peaks shifted to higher temperatures with an increase in heating rate. Three different kinetic models (ASTM I-II and Rogers &; Morris) were used to determine the kinetic parameters of the oil shale samples studied. Activation energies were in the range of 131.8-185.3 kJ mol-1 for ASTM methods and 18.5-48.8 kJ mol-1 for Rogers &; Morris method.     

TG-FTIR study of gaseous compounds evolved at thermooxidation of oil shale

The combined thermogravimetric (TG) Fourier transform infrared (FTIR) techniques were used for studying the gaseous compounds evolved at thermooxidation of oil shale samples from different deposits (Estonia, Jordan, Israel). In addition to H₂O and CO₂as the major species, the formation and emission of CO, SO₂, HCl and a number of organic species as methane, ethane, ethylene, methanol, formic acid, formaldehyde, chlorobenzene, etc. was determined. Differences in the absorbance of respective bands in FTIR spectra depending on the origin of oil shale and on the heating rate used were established. This revised version was published online in July 2006 with corrections to the Cover Date.     

FLASHCHAIN模型应用于汪清油页岩热解研究

采用~(13)C-NMR技术表征出汪清三个矿区油页岩的碳原子化学结构,并获得碳骨架结构的12个重要参数。利用热重和傅里叶红外联用技术(TG-FTIR)得出了在50℃/min升温速率和热解终温600℃下油页岩热解时轻质气体的生成规律。采用基于燃料化学结构的FLASHCHAIN模型对热解产物的析出进行了模拟,并与实验结果相比较。结果表明,FLASHCHAIN模型用来模拟汪清油页岩热解时,在520℃之前有较好的效果,当温度高于520℃时,由于二次热解反应及页岩中矿物质分解对热解过程的影响,导致模型的预测值与实验值存在一定的误差,且随着温度的升高两者之间的误差也随之加大。     

油页岩中几种微量元素在干馏过程的形态变迁

以桦甸油页岩为研究对象,采用逐级提取实验,考察了不同升温速率及干馏终温对其内部赋存的Cr、Co、Pb、Cu、V五种微量元素的形态变迁特性的影响。结果发现,各元素均在2.5℃/min和20℃/min升温速率下表现出了较大的迁移率,且干馏终温升高更有利于元素的迁移;低升温速率和高干馏终温更能促进元素大部分形态的迁移,但硫化物结合态的迁移在高升温速率和高干馏终温则更为有利;元素不同形态的迁移总会有一部分向有机物结合态转变。     

油页岩热解过程矿物质行为分析

采用XRD、SEM、灰成分测定等方法对桦甸两个矿区的油页岩样品以及制备的半焦样品矿物质组成进行了分析,确认其主要成分均为,石英、方解石和黏土矿物。而半焦中矿物组成反映了油页岩中矿物质在热解中的变化。研究表明,在热解过程中油页岩中矿物质变化细微,其中,石英、长石没有变化;方解石有微量分解,生成的固体产物CaO与黄铁矿分解的硫反应生成CaS矿物;黏土矿物质受热脱除羟基,放出大量水分,同时分解产生的无定形玻璃体氧化硅与其他金属形成低熔点的共融物,导致部分半焦样品颗粒表面出现熔融态囊状结构。     

龙口页岩油中含氧化合物的分析与鉴定

用酸碱分离和萃取色谱分离相结合的方法将龙口页岩油分离为酸性组分、碱性组分和五个中性组分(饱和烃、芳香烃、含氮化合物、含氧化合物1、含氧化合物2)。采用GC-MS和负离子ESI FT-ICR MS鉴定了龙口页岩油中酸性组分、中性组分4和中性组分5中含氧化合物的组成。GC-MS分析结果表明,龙口页岩油酸性组分含氧化合物主要包括苯酚类、茚满酚类、萘酚类、联苯酚类、芴酚类、菲酚类,以及C_5～16烷酸;龙口页岩油中性组分4和中性组分5中含氧化合物主要包括C_9～32脂肪酮和酯类化合物。FT-ICR MS分析结果表明,龙口页岩油中含氧化合物主要有O₁、O₂、O₃、N₁O₁、N₁O₂类化合物,其中,O₁和O₂类化合物种类较多。龙口页岩油重均相对分子质量集中在150～600 Da,说明龙口页岩油是由小分子化合物组成的。其表现出来的某些大分子化合物的性质,是由小分子化合物通过范德华力或氢键聚合在一起而形成的。龙口页岩油中O₁、O₂、O₃类化合物中DBE主要分布在1和4,说明龙口页岩油中O₁、O₂、O₃类化合物不饱和度和缩合度较低,因此,龙口页岩油是生物降解程度较低的油。     

Reactivity of oil shale ashes in the binding of SO<Subscript>2</Subscript>

The extensive use of fossil fuels in energy production causes serious pollution of atmosphere with SO₂, CO₂, NO_x, etc. In Estonia the electricity production is based mainly on the pulverized firing (PF) of low-grade local fuel – Estonian oil shale (EOS) which is characterized by a low calorific value (~9 MJ kg^–1) and a high content of mineral matter (65–70%) from which approximately 50% are carbonates. Since 2004, also two boilers based on circulating fluidized bed combustion (CFBC) of EOS are in exploitation. The present study is focused on the comparative investigation of the efficiency of different ashes collected from different technological points of CFB and PF boilers as sorbents for SO₂. The influence of experimental temperature on the SO₂-binding characteristics of ashes as well as the possibilities of activation of ashes (grinding, hydration) were investigated. It was shown that the SO₂-binding capacity of initial ashes at 700°C and p(SO₂)=190 mm Hg was for CFBC ashes 24–30 mg and for PF ashes 10–23 mg SO₂ per 100 mg sample, the best binding capacities belonging to economizer ash (ECOA) and electrostatic precipitator ash from the 1st field (PESPA1f), respectively. However, during initial stage of binding the best results were obtained with air pre-heater ash (PHAA) and ESPA1f (both CFBC ashes). Grinding improved the SO₂-binding ability, being the most effective in the case of bottom ash (BA) from CFBC and cyclone ash (PCA) from PF – increase in binding capacity 2 and 2.3 times, respectively. As compared to initial CFBC ashes, the binding characteristics of PF ashes remained lower even after grinding. Hydration and previous calcination improved the binding characteristics only of PF ashes. Hereby, the SO₂-binding ability of CFBC ashes is better than of PF ashes and they are more promising sorbents for acidic gases, for example, for sulphur dioxide.     

桦甸油页岩中稀土元素赋存状态研究

以吉林省桦甸油页岩为研究对象,采用电感耦合等离子质谱( ICP-MS)和化学逐级提取方法相结合,对油页岩中稀土元素的分布特征以及油页岩中稀土元素的赋存状态进行研究.结果表明,相对于中国煤,桦甸油页岩表现为轻稀土元素富集程度高于重稀土元素.油页岩中稀土元素与陆源碎屑岩关系密切,且陆源物质的供应相对比较稳定.轻重稀土间分馏...     

柳树河油页岩微波干燥及其对热解特性的影响

在对家用微波炉改造基础上搭建了微波干燥实验台,研究了柳树河油页岩微波干燥特性及对热解特性的影响。结果表明,微波干燥所需的时间为传统干燥所需时间的20%;微波干燥速率要明显大于传统干燥速率;Page模型适用于描写柳树河油页岩微波干燥过程。微波干燥的油页岩同热风干燥后及原样油页岩的热解活化能随转化率的变化曲线基本一致,整体呈先上升后下降的趋势,在转化率为0.7时达到最大值;热解活化能在80~200 kJ/mol变动;微波干燥油页岩热解反应有机质分解段的活化能增加。     

Oil shale kinetics by differential methods

In this research, pyrolysis and combustion behavior of three different oil shale samples from Turkey were characterized using thermal analysis techniques (TG/DTG). In pyrolysis experiments, two different mechanisms causing mass loss were observed as distillation and cracking. In combustion experiments, two distinct exothermic peaks were identified known low and high temperature oxidation. On the other hand, determination of activation energies are required for the estimation of oil extraction conditions from the oil shales. Differential methods are used to determine the activation energies of the samples where various f(α) models are applied from the literature. It was observed that the activation energies of the all oil shale samples are varied between 13.1–215.4 kJ mol⁻¹ in pyrolysis and 13.1–408.4 kJ mol⁻¹ in combustion experiments which are consistent with other kinetic results.