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.     

Investigation on pyrolysis of Moroccan oil shale/plastic mixtures by thermogravimetric analysis

Thermal degradation processes for a series of mixtures of oil shale/plastic were investigated using thermogravimetric analysis (TGA) at four heating rates of 2, 10, 20 and 50 K min^− 1 from ambient temperature to 1273 K. High density polyethylene (HDPE), low density polyethylene (LDPE) and polypropylene (PP) were selected as plastic samples. Based on the results obtained, three thermal stages were identified during the thermal degradation. The first is attributed to the drying of absorbed water; the second was dominated by the overlapping of organic matter and plastic pyrolysis, while the third was linked to the mineral matter pyrolysis, which occurred at much higher temperatures. Discrepancies between the experimental and calculated TG/DTG profiles were considered as a measurement of the extent of interactions occurring on co-pyrolysis. The maximum degradation temperatures of each component in the mixture were higher than those of the individual components; thus an increase in thermal stability was expected. In addition, a kinetic analysis was performed to fit thermogravimetric data. A reasonable fit to the experimental data was obtained for all materials and their mixtures.     

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.     

Characteristics of oil shale pyrolysis in a two-stage fluidized bed

Rapid pyrolysis of oil shale coupled with in-situ upgrading of pyrolysis volatiles over oil shale char was studied in a laboratory two-stage fluidized bed(TSFB) to clarify the shale oil yield and quality and their variations with operating conditions. Rapid pyrolysis of oil shale in fluidized bed(FB) obtained shale oil yield higher than the Fischer Assay oil yield at temperatures of 500-600 ℃. The highest yield was 12.7 wt% at 500 ℃ and was about1.3 times of the Fischer Assay oil yield. The heavy fraction(boiling point 350 ℃) in shale oil at all temperatures from rapid pyrolysis was above 50%. Adding an upper FB of secondary cracking over oil shale char caused the loss of shale oil but improved its quality. Heavy fraction yield decreased significantly and almost disappeared at temperatures above 550 ℃, while the corresponding light fraction(boiling point 350 ℃) yield dramatically increased. In terms of achieving high light fraction yield, the optimal pyrolysis and also secondary cracking temperatures in TSFB were 600 ℃, at which the shale oil yield decreased by 17.74% but its light fraction yield of 7.07 wt% increased by 86.11% in comparison with FB pyrolysis. The light fraction yield was higher than that of Fischer Assay at all cases in TSFB. Thus, a rapid pyrolysis of oil shale combined with volatile upgrading was important for producing high-quality shale oil with high yield as well.     

Study of the pyrolysis of Maoming oil shale lumps

Pyrolysis experiments on Maoming oil shale lumps (10–60 mm in diameter) were carried out with the aid of large-particle thermogravimetric analysis apparatus at constant heating rates of 1, 2 and 5 °C min⁻¹. A pyrolysis kinetic model was developed which took into account both the pyrolysis reaction and intraparticle heat transfer. Oil shale pyrolysis kinetic parameters were then determined on the basis of experimental data concerning weight loss, shale oil production, gas evolution and intraparticle temperature distribution versus time, by using the developed model. Furthermore, the effects of variables (e.g. temperature, lump size, heating rate) on oil shale pyrolysis were assessed during experimentation. It is found that model predictions agree reasonably well with experimental data.     

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。     

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%。     

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。     

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.     

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     

油页岩低温热解过程中轻质气体的析出特性

为研究油页岩低温热解过程中轻质气体的析出特性,在热重-红外-质谱三联机上对国内有代表性的4个地区(FS、HD、MM和NM)油页岩以20℃·min^-1的升温速率进行了热解实验研究,考察了H₂、H₂O、CO、CO₂、CH₄和C_nH_m 6种轻质气体的析出速率和累积产量随温度变化的规律。实验结果表明:油页岩轻质气体析出的温度范围在180～540℃;H₂、CH₄和C_nH_m的析出速率曲线大致相似,呈高斯分布,CO和CO₂的析出速率则是先缓慢增加随后快速增加,达到最大值后又快速下降,直到析出结束,H₂O的析出速率相对比较复杂,油页岩的内水、矿物质的结晶水和热解水在3个阶段析出,析出速率都是先增大,达到最大值而后减小。     

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。     

Kinetics of pyrolysis and combustion of oil shale sample from thermogravimetric data

Thermogravimetric (TG) data of oil shale obtained at MI (Waste to Energy laboratory) were studied to evaluate the kinetic parameters for El-Lujjun oil shale samples. Different heating rates were employed simulating pyrolysis reaction using Nitrogen as purging gas up to ∼800 °C. The extent of char combustion was found out by relating TG data for pyrolysis and combustion with the ultimate analysis. Due to distinct behavior of oil shale during pyrolysis, TG curves were divided into three separate events: moisture release; devolatization; and evolution of fixed carbon/char, where for each event, kinetic parameters, based on Arrhenius theory, were calculated. Three methods were used and compared: integral method; direct Arrhenius plot method; and temperature integral approximation method. Results showed that integral method is closer to the experiment, while no relationship was observed between activation energy and the heating rate.     

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。     

油页岩微波热解气态产物析出特性

利用微波化学试验装置研究了油页岩微波热解过程中挥发分析出特性, 考察了微波功率、热解温度、不同热解温度阶段和催化剂对气体组成的影响。结果表明:微波加热能够提高油页岩热解气中H₂、CO和C₂H₄的析出, 降低CO₂的析出;50%(1600W)微波功率时烃类的析出量最大;在150~350℃的低温阶段热解气的析出量大, 主要由吸附气体的释放, 不稳定支链和基团的分解产生;温度升高, 气态产物的析出主要由脱氢、芳构化、缩聚和自由基反应产生。催化剂促进了气体的析出, 但不同类型催化剂对油页岩热解气组成的影响不同, 分子筛的吸附作用促进二次分解和缩聚反应;黏土类催化剂在质子酸作用下促进有机质催化裂解加氢反应, 加快断链和基团的稳定;金属类催化剂是强吸波性介质, 能够提高升温速率, 促进热解反应, 其次促进氢自由基的产生和转移。     

金属氧化物对油页岩热解产物收率及组成分布的影响

通过固定床反应器,对4种金属氧化物（Al₂O₃、MgO、CaO、Fe₂O₃）对油页岩热解所得油、气产率及成分的影响进行了研究。结果显示,碱性CaO对油、水、气、焦产率分布影响较为突出,可提高页岩油与半焦产率,并降低热解气产率;而酸性较强的Al₂O₃可同时提高页岩油、热解气和热解水的产率,有利于促进挥发分的析出;比较而言,MgO和Fe₂O₃的作用相对较弱。4种金属氧化物均可提高热解气中H₂、CH₄和C₂的产率;CaO作用下CO₂含量降低,而其他金属氧化物对CO₂的产生有不同程度的促进作用;Fe₂O₃可促进H₂产生;Al₂O₃作用下CH₄含量有所增加。4种金属氧化物均可促进页岩油中芳香烃的产生,并且CaO和MgO两种碱土金属氧化物作用下,短链（C₆~C₁₂）烷烃和烯烃含量均增加,而掺混Al₂O₃时页岩油中仅短链（C₆~C₁₂）烷烃含量增加。对此机理进行推测认为,碱性CaO和MgO首先与以脂肪酸形式存在的有机质进行酸碱反应,得到脱羧活性更高的羧酸盐,后者脱羧所得中间产物具有生成烷烃或烯烃两条可能路径,同时得到碳酸盐;而在具有Lewis酸特征的Al₂O₃作用下,脱羧产物为CO₂,并同时得到饱和烃产物。     

页岩灰和FCC催化剂调控油页岩热解产物二次反应特性

采用两段反应器对油页岩热解初级挥发分进行二次催化反应特性研究,考察了第2段反应器内不同的催化载体、反应气氛与停留时间对油气收率及品质的影响。结果表明,在考察的停留时间范围内页岩灰具有相对适中的催化活性来调控热解挥发分产物的二次反应,水蒸气气氛能够进一步提高热解油收率约5%,并能够在一定程度上抑制裂解气体中C₂~C₃组分的生成。页岩灰作为催化载体能够转化热解油中VGO（馏程>350℃）等重质组分,随停留时间增加油品馏程向轻组分转移。油品组分GC-MS结果表明,较短停留时间内（<3 s）,水蒸气添加能够有效抑制热解油中脂肪烃类的过度裂解,与氮气相比提高汽柴油馏分含量20%以上。过长的停留时间（3~5 s）会造成VGO等馏分缩聚生成焦炭,从而大幅降低热解油收率。     

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。     

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.     

煤与油页岩热预处理特性及对热解的影响

对比研究了神木煤和桦甸油页岩在150~400℃热预处理时的孔隙变化和挥发分析出规律以及热预处理对后续慢速升温热解反应产物的影响。结果表明,热预处理显著增加了油页岩的孔隙结构,其比表面积提高4倍、孔体积提高5倍以上,而神木煤的孔隙结构则减少了,特别是孔径大于1 nm的孔体积减少了近60%、比表面积减少了近80%,而其1 nm以下的孔则相对稳定,孔体积和比表面积分别只减少了10%左右。低于400℃时热预处理过程中除脱去吸附水外,其他挥发分也有一定析出,并以CO₂为主,另有少量CO,但挥发分总失重量不超过5%。固定床慢速升温热解研究表明,经热预处理后,油页岩的油产率最高提高了22.7%,而水和气的产率则相应降低,气体中CH₄增加而H₂降低。热预处理对煤的热解油产率影响不明显,但热解水产率降低而热解气产率增加且其中CH₄增多而H₂降少。