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。     

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.     

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.     

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.     

Effect of demineralization and heating rate on the pyrolysis kinetics of Jordanian oil shales

The effect of mineral matter content on the activation energy of oil shale pyrolysis has been studied. Kerogen was isolated from raw oil shale by sequential HCl and HCl/HF digestion. Oil shale and kerogen samples were pyrolyzed in a Thermogravimetric Analyzer at different heating rates (1, 3, 5, 10, 30, and 50 °C/min) up to a temperature of 1000 °C. Total mass loss of all oil shale samples remained almost constant irrespective of the heating rate employed, whereas it decreased with the increase of heating rate for kerogen (74.5 to 71.4%). From the pyrolysis profile activation energy (Ea) was found to vary between 70 and 83 kJ/mol for oil shale, while 82-112 kJ/mol has been determined for isolated kerogen. An increase of both Ea and pre-exponential factor was observed with an increasing heating rate. It is concluded that the mineral matter in oil shale enhances catalytic cracking as is evident from the reduced Ea values of oil shale compared with those for kerogen.     

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.     

Changes in the cross-link density of Goynuk oil shale (Turkey) on pyrolysis

The effect of temperature and heating rate on the cross-link density of char samples obtained by pyrolysing Goynuk oil shale was investigated using the volumetric solvent swelling technique. The cross-link density decreases slightly with increasing pyrolysis temperature. The heating rate and thus the pyrolysis time had at most a small effect on the cross-link density. Char-solvent interactions do not follow regular solution theory. The demineralized kerogen swells more than does the native kerogen (16% ash).     

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.     

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.     

Effect of demineralization of El-lajjun Jordanian oil shale on oil yield

The effect of demineralization on oil yield and mineral composition of Jordanian oil shale was investigated. A standard digestion procedure using a range of inorganic and organic acids including HCl, HNO₃, HF, and CH₃COOH was used to enhance the oil recovery of oil shale samples collected from the El-lajjun area. The total yield of the digested samples, as determined by Fischer Assay, has shown a maximum value (two folds the untreated sample) obtained when using CH₃COOH. The kaolin in the treated oil shale with a high concentration of CH₃COOH is believed to have transformed to illite as found in the XRD analysis. The treatment of oil shale using HCl has shown an increased ratio of oil to gas as a result of the digestion of calcite in the oil shale. At higher concentrations of HNO₃, the acid is believed to react with the kerogen in the oil shale resulting in high levels of low molecular weight compounds. Therefore, the amount of non-condensable gases produced by Fischer assay after treatment with a high concentration of HNO₃ is relatively high. HF is believed to drive off water from the oil shale by dissolving the clay minerals leading to increased oil to gas ratio.     

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。     

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。     

Utilization of Estonian oil shale semicoke

In thermal processing of oil shale in vertical retorts huge quantities of a solid waste — semicoke are formed. It has been shown that circulating fluidized bed combustion of semicoke could be a promising technology allowing utilization of its high residual energy potential. The main parameters of combustion process and the additional heat produced were calculated and verified by combustion tests in a fluidized bed device with a thermal capacity of 50 kW_th. The experiments indicated that semicoke with low moisture content can be burnt directly in fluidized bed. For the combustion of semicoke with higher moisture content (over 10%) about 10% of oil shale must be added. In addition, possibilities for utilizing residual carbon present in semicoke by obtaining carbon-rich materials with further production, for example, activated carbon were discussed. A series of experiments accompanied by SEM and EDAX analysis was carried out in order to elucidate the distribution of carbon and mineral part in semicoke and to find possibilities for their separation and subsequent enrichment. Different separation methods — selective grinding and subsequent screening, pneumatic separation and triboelectroseparation method were analyzed. It was shown that due to close integration of mineral and organic part in semicoke, the separation of carbon-rich ingredients by these methods was not enough effective to obtain enriched products suitable for the production of activated carbon.     

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     

Mechanisms and kinetics of homogeneous secondary reactions of tar from continuous pyrolysis of wood chips

The change of mass and composition of biomass tar due to homogeneous secondary reactions was experimentally studied by means of a lab reactor system that allows the spatially separated production and conversion of biomass tar. A tarry pyrolysis gas was continuously produced by pyrolysis of wood chips (fir and spruce, 10-40 mm diameter) under fixed-bed biomass gasification conditions. Homogeneous secondary tar reactions without the external supply of oxidising agents were studied in a tubular flow reactor operated at temperatures from 500 to 1000 °C and with space times below 0.2 s. Extensive chemical analysis of wet chemical tar samples provided quantitative data about the mass and composition of biomass tar during homogeneous conversion. These data were used to study the kinetics of the conversion of gravimetric tar and the formation of PAH compounds, like naphthalene.It is shown that, under the reaction conditions chosen for the experiments, homogeneous secondary tar reactions become important at temperatures higher than 650 °C, which is indicated by the increasing concentrations of the gases CO, CH₄, and H₂ in the pyrolysis gas. The gravimetric tar yield decreases with increasing reactor temperatures during homogeneous tar conversion. The highest conversion reached in the experiments was 88% at a reference temperature of 990 °C and isothermal space time of 0.12 s. Hydrogen is a good indicator for reactions that convert the primary tar into aromatics, especially PAH. Soot appears to be a major product from homogeneous secondary tar reactions.     

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。     

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.     

Extracting hydrocarbons from Huadian oil shale by sub-critical water

The possibility of extracting hydrocarbons from Huadian oil shale by sub-critical water was found in a stainless steel vessel. The effects of temperature and pressure on the extraction of hydrocarbons were studied. After extraction experiments, the residual solid, liquid and gas phase samples were collected and characterized, respectively. The extract yield could reach 7 wt.% (ad) when the extraction of oil shale was conducted at 260 °C for 2.5 h with the pressure of 15 MPa. The results of thermogravimetry (TG) showed that the weight loss of residual solid samples was much smaller than that of the original oil shale. It indicated that kerogen components had been decomposed partly by treatment with sub-critical water. Gas chromatography-mass spectrometry (GC-MS) analysis showed that there were more than 300 recognizable peaks in the extracting solution following processing at 330 °C and 18 MPa. Large amounts of high molecular weight hydrocarbons were gradually decompounded by the increase in types and levels of low molecular weight hydrocarbons, and polycyclic and heterocyclic compounds with the rising of pressure and temperature. These indicated that sub-critical water is capable of cracking kerogen into smaller hydrocarbon compounds at relatively low temperatures.     

Synthesis of Na-A and -X zeolites from oil shale ash

The solid by-product of oil shale processing (PETROBRAS-Brazil) was used as a raw material to synthesize Na-A and -X zeolites. Two preparation methods using the same starting material composition were carried out. In Method (1), alkaline fusion was used to prepare a glass, which was then hydrated by refluxing. The largest amount of crystallinity was reached with 2 h 30 min of refluxing. In Method (2), alkaline fusion was followed by hydrothermal treatment. The most crystalline sample was obtained after 12 h of heat treatment, and after 96 h hydroxysodalite zeolite was formed. In both procedures, the synthesis products were mainly composed of Na-X zeolite, whose content was influenced by the crystallization time, and of Na-A zeolite, with a practically constant content.