Bio-oil production from Onopordum acanthium L. by slow pyrolysis

In this study, the usability of the plant thistle, Onopordum acanthium L., belonging to the family Asteraceae (Compositae), in liquid fuel production has been investigated. The experiments were performed in a fixed-bed Heinze pyrolysis reactor to investigate the effects of heating rate, pyrolysis temperature and sepiolite percentage on the pyrolysis product yields and chemical compositions. Experiments were carried out in a static atmosphere with a heating rate of 7 °C/min and 40 °C/min, pyrolysis temperature of 350, 400, 500, 550 and 700 °C and particle size of 0.6 < D_p < 0.85 mm. Catalyst experiments were conducted in a static atmosphere with a heating rate of 40 °C/min, pyrolysis temperature of 550 °C and particle size of 0.6 < D_p < 0.85 mm. Bio-oil yield increased from 18.5% to 27.3% with the presence of 10% of sepiolite catalyst at pyrolysis temperature of 550 °C, with a heating rate of 40 °C/min, and particle size of 0.6 < D_p < 0.85 mm. It means that the yield of bio-oil was increased at around 48.0% after the catalyst added. Chromatographic and spectroscopic studies on the bio-oil showed that the oil obtained from O. acanthium L. could be used as a renewable fuels and chemical feedstock.     

The relation between dioxin concentration from exhaust gas of diesel engine and chlorine content

In this paper, an experiment has been used to study the effect of pyrolysis stage (from injection to combustion) to dioxin exhaust from diesel engine. The characteristics of diesel fuel pyrolysis have been applied in order to calculate the mean molecular weight in varied temperatures and measure the concentration of inorganic chlorine (HCl). On the other hand, measuring the chlorine content of these particles after diesel pyrolysis enables researchers to find out the pyrolysis temperature that has the lowest possibility to produce dioxin. Additionally, the post-pyrolysis carbon particle diameter has been observed through electronic microscope so as to evaluate the combustion condition of the combustion stage. Result from this study would be helpful for researchers to understand the probability of dioxin formation.     

Pyrolysis of chromated copper arsenate (CCA) treated wood waste at elevated pressure: Influence of particle size, heating rate, residence time, temperature and pressure

Lab-scale pyrolysis experiments with weathered CCA treated wood chips have been performed and the influence of particle size, residence time (10-40 min), heating rate (5-20 °C/min), temperature (330-430 °C) and pressure (0 bar, 5 bar) has been investigated. Few data, covering the pyrolysis of weathered wood was found in the literature and the literature data on pyrolysis experiments with a controlled CCA wood input, showed that results were often highly affected by experimental uncertainty. In order to reduce the uncertainty on the results, a thorough characterization of the wood input has been performed and a ratio method has been proposed which allows to study the effect of particle size on arsenic and chromium volatilization. Larger wood particles show a higher arsenic and chromium retention during pyrolysis which is attributed to the higher mass transfer resistance in these particles. Residence time has a limited effect on arsenic retentions. Increasing heating rate results in a limited increase in arsenic retentions and a more profound increase in chromium retentions. The latter is attributed to a lower average particle temperature during heating caused by the thermal lag in larger particles. Elevated pressure results in a significant increase of arsenic retentions, which is probably due to higher mass transfer resistance. Increasing temperature results in a slight decrease in arsenic retentions till 390 °C, with a sharp decrease at higher temperatures. Chromium retentions are less affected by increasing temperature, especially at higher temperatures. To conclude, a mechanism is proposed for the volatilization of chromium and arsenic during low temperature pyrolysis of CCA wood. Mass transfer resistance and the formation of As₄O₆ are crucial for the control of arsenic volatilization, while heat transfer resistance and thermal lag are more important for the control of chromium volatilization.     

基于不同燃料PAH特性改进的适用于多组分燃料的碳烟模型

将多环芳烃(PAH)骨架模型与甲苯参比燃料(TRF)氧化模型耦合,构建了一个新的TRF-PAH骨架模型.以新的TRF-PAH骨架模型作为燃料燃烧的气相化学反应模型,基于不同分子结构的燃料氧化过程中生成PAHs和碳烟的路径也不同的研究结论,本文进一步优化了以PAHs为碳烟前驱生成物的碳烟半经验模型.通过甲苯在流动反应器、搅拌反应器和激波管中的氧化/裂解实验验证发现,新的TRF-PAH骨架模型可以相对准确地预测小分子PAHs和重要中间组分的浓度.通过对比烷烃和芳香烃氧化过程中生成苯的计算值可以发现,燃料的分子结构对PAHs的生成路径影响很大.另外,改进后的碳烟模型利用甲苯、正庚烷/甲苯及异辛烷/甲苯混合物为燃料的激波管中裂解和氧化实验验证,结果表明在较宽的工况内碳烟模拟值与实验值吻合较好.最后,将新的碳烟模型应用于KIVA程序,模拟以TRF20为燃料的柴油机碳烟排放,结果表明TRF-PAH骨架模型和碳烟模型能重现缸内燃烧和排放的特性.     

Soot formation in the pyrolysis of benzene,methylbenzene, and ethylbenzene in shock waves

Soot formation in the pyrolysis of benzene, methylbenzene, and ethylbenzene and in the oxidative pyrolysis of benzene in shock waves has been investigated using an absorption-emission technique. Even in the presence of small amounts of oxygen, soot formation in the pyrolysis of these hydrocarbons is accompanied by a decrease in the temperature of the reacting mixture. The soot yield has been measured as a function of temperature over wide initial reactant concentration ranges. A new, larger value was obtained for the coefficient of light absorption by soot particles at a wavelength of 632.8 nm. A revised, substantially modified kinetic model is suggested for soot formation. This model has been verified against experimental data available from the literature on the time profiles of the concentrations of some key components at the early stages of pyrolysis and oxidation of various hydrocarbons in a wide range of process conditions. The model reproduces fairly well the time dependences of the soot yield and soot particle temperature measured in this study for benzene, methylbenzene, and ethylbenzene pyrolysis.     

Investigation of physicochemical properties of biooils produced from yellow poplar wood (Liriodendron tulipifera) at various temperatures and residence times

Fast pyrolysis of yellow poplar wood (Liriodendron tulipifera) was performed under different temperature ranges and residence times in a fluidized bed reactor to maximize the yield of biooil. In this study, the pyrolysis temperature ranged from 400 °C to 550 °C, and the residence time of pyrolysis products was controlled between 1.2 and 7.7 s by inert nitrogen gas flow. The results revealed that the distribution of thermal degradation products (biooil, biochar, and gas) from the woody biomass was heavily influenced by pyrolysis temperature, as well as residence time. The highest yield of biooil was approximately 68.5 wt% (wet basis), with pyrolysis conditions of 500 °C and 1.9 s of residence time. Water content of the biooils produced at different temperatures was 25-30 wt%, and their higher heating values were estimated to be between 15 MJ/kg and 17 MJ/kg. Using GC/MS analysis, 30 chemical components were identified from the biooil, which were classified into 5 main groups: organic acids, aldehydes, ketones, alcohols, and phenols. In addition, biochar was produced as a co-product of fast pyrolysis of woody biomass, approximately 10 wt%, at temperatures between 450 °C and 550 °C. The physicochemical features of the biochar, including elemental analysis, higher heating values, and morphological properties by SEM, were also determined.     

掺混含氧燃料的柴油替代物部分预混火焰中多环芳香烃的荧光光谱和碳烟浓度

为研究不同含氧燃料与柴油掺混后碳烟降低机理, 本文在自行设计的燃烧器上构建部分预混层流火焰, 采用甲苯和正庚烷混合物(T20, 20%(体积分数)甲苯、80%正庚烷)作为柴油替代物,并分别添加甲醇、乙醇、正丁醇、丁酸甲酯和2,5-二甲基呋喃(DMF), 且保证混合燃料的含氧量均为4%. 进而应用激光诱导荧光法和激光诱导炽光法分别测量不同混合燃料的火焰中多环芳香烃(PAHs)的荧光光谱和碳烟浓度. 结果表明: 通过PAHs的荧光光谱可测量不同燃料火焰中PAHs的生成和增长历程. 四环芳香烃(A4)的生成氧化规律和碳烟基本一致, 说明通过分析A4变化可以预测碳烟变化. 添加含氧燃料后, T20燃料中甲苯含量降低是导致PAHs的荧光光谱强度降低和碳烟生成量减少的主要原因; 同时不同含氧燃料本身对多环芳香烃的生成贡献能力也是影响PAHs的荧光强度和碳烟生成的重要原因. 含氧量相当时, 掺混正丁醇后PAHs的荧光光谱强度和碳烟浓度比添加甲醇、乙醇、丁酸甲酯和DMF这四种含氧燃料的更低. 因此从含氧燃料结构来讲, 正丁醇掺混入T20燃料中降低PAHs和碳烟作用最显著.     

Characterization of liquid products of automobile tire pyrolysis

The liquid product of automobile tire pyrolysis and its fractions were studied. The amount of the liquid hydrocarbon fraction is 40–45% of the total weight of pyrolysis products. The hydrocarbon fraction is similar in its characteristics to low-sulfur heavy crude oil. Fractionation of the hydrocarbon fuel was performed. The maximal yield of the light distillation fraction is 39% (temperature interval 180–340°C). The extent to which the characteristics of the light fraction obtained meet the regulations was evaluated. The light fraction of hydrocarbon fuel produced by pyrolysis is recommended for use as a component of diesel motor fuel after additional purification.     

Diesel soot oxidation by nitrogen dioxide,oxygen and water under engine exhaust conditions: Kinetics data related to the reaction mechanism

Experimental studies on diesel soot oxidation under a wide range of conditions relevant for modern diesel engine exhaust and continuously regenerating particle trap were performed. Hence, reactivity tests were carried out in a fixed bed reactor for various temperatures and different concentrations of oxygen, NO₂ and water (300–600 °C, 0–10% O₂, 0–600 ppm NO₂, 0–10% H₂O). The soot oxidation rate was determined by measuring the concentration of CO and CO₂ product gases. The parametric study shows that the overall oxidation process can be described by three parallel reactions: a direct C–NO₂ reaction, a direct C–O₂ reaction and a cooperative C–NO₂–O₂ reaction. C–NO₂ and C–NO₂–O₂ are the main reactions for soot oxidation between 300 and 450 °C. Water vapour acts as a catalyst on the direct C–NO₂ reaction. This catalytic effect decreases with the increase of temperature until 450 °C. Above 450 °C, the direct C–O₂ reaction contributes to the global soot oxidation rate. Water vapour has also a catalytic effect on the direct C–O₂ reaction between 450 °C and 600 °C. Above 600 °C, the direct C–O₂ reaction is the only main reaction for soot oxidation. Taking into account the established reaction mechanism, a one-dimensional model of soot oxidation was proposed. The roles of NO₂, O₂ and H₂O were considered and the kinetic constants were obtained. The suggested kinetic model may be useful for simulating the behaviour of a diesel particulate filter system during the regeneration process.     

Thermal behavior of aluminum powder and potassium perchlorate mixtures by DTA and TG

In this work the thermal decomposition characteristics of micron sized aluminum powder + potassium perchlorate pyrotechnic systems were studied with thermal analytical techniques. The results show that the reactivity of aluminum powder in air increases as the particle size decreases. Pure aluminum with 5 μm particle size has a fusion temperature about 647 °C, but this temperature for 18 μm powder is 660 °C. Pure potassium perchlorate has an endothermic peak at 300 °C corresponding to a rhombic-cubic transition, a fusion temperature around 590 °C and decomposes at 592 °C. DTA curves for Al₅/KClO₄ (30:70) mixture show a maximum peak temperature for thermal decomposition at 400 °C. Increasing the particle size of aluminum powder increases the ignition temperature of the mixture. The oxidation temperature increased by enhance in the aluminum content of the mixture.     

Study of the pyrolysis of municipal solid waste for the production of valuable products

To obtain information on the potential of thermal conversion (pyrolysis) of municipal solid waste (MSW), a thermogravimetric study (TGA) is performed in a stream of nitrogen. Based on TGA results, pyrolysis experiments are carried out in a semi-batch reactor under inert nitrogen atmosphere. Slow pyrolysis is performed up to 550 °C (heating rate of 4 °C/min). Fast pyrolysis is performed at 450, 480, 510 and 550 °C and different input transfer rates (12 or 24 g material/min). The pyrolysis products are studied on composition and yield/distribution and investigated for their use as valuable product.The liquid obtained by slow pyrolysis separates spontaneously in a water rich product and an oily product. For all fast pyrolysis conditions, a viscous, brown oil which contains a poly(ethylene-co-propylene) wax is obtained. Composition analyses by GC/MS of the oil products (slow/fast pyrolysis) show that aliphatic hydrocarbons are the major compounds. The pyrolysis oils have high calorific value (between 35 and 44 MJ/kg), low wt% of water (around 6 wt%) and a low O/C value (between 0.2 and 0.3). The presence of waxy material is probably due to incomplete breakdown of poly(ethylene-co-propylene) present in MSW under study. The optimal pyrolysis conditions, regarding to oil yield, fuel properties, and wax yield is fast pyrolysis at 510 °C with 24 g material/min input transfer rate. The fast pyrolysis gases contain mainly hydrocarbons and have an averaged LHV around 20 MJ/Nm³. ICP-AES analyses of pyrolysis products reveal that almost none of the metals present in MSW are distributed within the liquid fractions.     

乙炔/空气预混火焰中CO添加对炭黑生成影响的数值分析(英文)

针对乙炔/空气预混火焰中CO添加对炭黑生成的影响进行了详细的数值模拟.通过对含有不同CO添加量的火焰的模拟结果比较,研究CO添加的温度和化学作用对于炭黑形成的影响.计算结果显示CO添加使炭黑的生成单调下降.炭黑体积分数和成核速率随着温度的升高而增加,到达一个阈值后,再随温度的升高而减少.从炭黑生成的H-萃取角度来看,由于反应OH+CO=CO2+H的向右速率增加,H原子增加以及OH自由基减少,CO添加会激发炭黑生成.从炭黑生成的C-添加机理来看,CO添加减小了C2H2的消耗速率,CO添加也有助于炭黑生成,但CO添加降低了燃料中C2H2的体积分数,使得炭黑表面增长速率降低.     

生物柴油-柴油混合燃料的理化及排放特性研究

对生物柴油-柴油混合燃料的表面张力、运动黏度、抗磨性、氧化稳定性以及碳烟排放等特性进行了测试和研究.结果表明,生物柴油-柴油混合燃料的表面张力随生物柴油含量的增加呈抛物线趋势变化,并随温度升高呈幂函数曲线下降.生物柴油的磨斑直径小于柴油,最大卡咬极限压力大于柴油.生物柴油的质量分数为40％-70％,混合燃料的氧化稳定性...     

Gas-liquid chromatographic determination of the gaseous products of the two-stage pyrolysis of heavy oils

The two-stage pyrolysis of fuel oil and vacuum residues separated from Egyptian crude oil have been carried out using a batch-type reactor technique. In the first stage, feedstocks undergo catalytic cracking in the presence of platinum as a catalyst at temperatures ranging between 380 and 460 °C and 440 and 520 °C for fuel oil and vacuum residues, respectively. Products are carried by argon gas for subsequent pyrolysis in the second stage at temperatures ranging between 700 and 820 °C and 700 and 800 °C for fuel oil and vacuum residues, respectively. The gas yields are about 94.1 and 82.0 wt% of the total products. The gases comprise saturated (C₁----C₅) and unsaturated hydrocarbons (ethylene, propylene, and butenes). By using platinum wire in the pyrolysis of fuel oil, the ethylene yield increases slightly as the temperature of the first stage increases, while it remains almost unchanged in the pyrolysis of vacuum residue. On the other hand, the propylene yield decreases slightly as the temperature of the first stage increases in the two feedstocks. By using a platinum sheet, the ethylene yield is doubled under the same conditions and increases slightly with an increase of temperature in the second stage. On the other hand, the propylene yield varies inversely with the temperature of the second stage by using platinum, whether as wire or sheet, although the yield is higher when platinum sheet is used under the same conditions.     

Kinetics of soot formation in tetrachloromethane pyrolysis

Kinetics of soot formation is studied in tetrachloromethane pyrolysis behind shock waves. The time dependences of macrokinetic characteristics of soot particle growth (the induction period, the soot yield, and the apparent rate constant of soot particle growth) are determined. Based on the experimental data, the quantitative model of soot formation is developed for tetrachloromethane pyrolysis behind shock waves. Special attention is paid to the thermal effects in CC1⁴ pyrolysis.     

On the mechanism of soot particle formation

The results of experiments on the isothermic pyrolysis of acetylene, benzene, and diacetylene in a flow reactor near a low-temperature threshold of soot formation are presented. Diacetylene showed a much higher ability to form soot, coke, and tar than the other hydrocarbons. The threshold temperature of soot formation from diacetylene (800 K) was found to be lower than the threshold temperatures for benzene (1230 K) and acetylene (1200 K) for the same pyrolysis time (0.17 s) and equal hydrocarbon concentrations (on the basis of C atoms). The induction periods of soot formation for acetylene and benzene at 1100–1200 K, which were estimated from experiments, correlated well with literature data extrapolated from the high-temperature region. Invisible soot particles (0.3-0.5 Μm) and particles at different steps of carbonization were found among the products of low-temperature pyrolysis. Experimental data were analyzed and compared within the framework of two soot formation theories presented in the literature (the “acetylene” and “aromatic” theories). The contribution of the process of polyyne polymerization in a gas phase to the formation of a soot aerosol is discussed.     

Identifizierung von Pyrolysebeiprodukten in Fließbettruß und Pyrokohlenstoff

In the frame of further development of fluidized bed coated particle fuel for high temperature reactors, both the pyrocarbon desposited on fuel kernels and the soot obtained besides, were investigated to their pyrolysis by-products. Target of the study was to improve the understanding of the mechanisms in pyrocarbon desposition on fuel kernels during the thermal decomposition of lower hydrocarbons. This study was on products formed in acetylene and propylene pyrolysis, the extraction being performed by various methods. The extracts were separated by gas-chromatographic and mass-spectrometric methods. 21 Polycyclic aromatic hydrocarbons could be identified in the soot. Beyond those the pyrocarbon containes polycycles of even higher molecular weights.     

Characterization and reactivity with NO/O2 of the soot formed in the pyrolysis of acetylene–ethanol mixtures

Characterization analyses and soot–O₂ and soot–NO interaction experiments have been performed for soot samples obtained in the pyrolysis of acetylene–ethanol mixtures at different temperatures from 1275 to 1475 K. The objective of these analyses is to address the influence of soot formation conditions on soot properties and structure, as well as on its capability to interact with gaseous compounds.The characterization techniques used are: elemental analysis, transmission electron microscopy (TEM), Brunnauer–Emmett–Teller (BET) surface area analysis, Raman spectroscopy and X ray diffraction (XRD). The characterization of soot samples is useful to increase the database on soot composition and structure and may help to find a dependence of those characteristics with soot formation conditions and the fuel from which soot is formed. From these data it can be observed a certain degree of graphitization for the soot samples formed at higher temperatures and/or from fuel mixtures with a higher content in ethanol.The interaction of soot with NO and O₂ is investigated in order to analyze the capability of soot to interact with gas reactants. Soot samples formed at the highest temperatures are less reactive towards O₂ and NO than those formed at lower temperatures. Soot samples appear to be more reactive when the fuel mixture presents a lower initial volume of ethanol. These observations can be related to the higher C/H ratio, associated to slightly higher degree of ordering, for the soot samples formed in such conditions. Experimental results have also demonstrated that soot samples are more reactive towards O₂ than NO, although the initial concentration of O₂ is lower.     

Characteristics of bicyclic sesquiterpanes in crude oils and petroleum products

This study presents a quantitative gas chromatography–mass spectrometry analysis of bicyclic sesquiterpanes (BSs) in numerous crude oils and refined petroleum products including light and mid-range distillate fuels, residual fuels, and lubricating oils collected from various sources. Ten commonly recognized bicyclic sesquiterpanes were determined in all the studied crude oils and diesel range fuels with principal dominance of BS3 (C₁₅H₂₈), BS5 (C₁₅H₂₈) and BS10 (C₁₆H₃₀), while they were generally not detected or in trace in light fuel oils like gasoline and kerosene and most lubricating oils. Laboratory distillation of crude oils demonstrated that sesquiterpanes were highly enriched in the medium distillation fractions of ∼180 to 481 °C and were generally absent or very low in the light distillation fraction (boiling point to ∼180 °C) and the heavy residual fraction (>481 °C). The effect of evaporative weathering on a series of diagnostic ratios of sesquiterpanes, n-alkanes, and biomarkers was evaluated with two suites of weathered oil samples. The change of abundance of sesquiterpanes was used to determine the extent of weathering of artificially evaporated crude oils and diesel. In addition to the pentacyclic biomarker C₂₉ and C₃₀ αβ-hopane, C₁₅ and C₁₆ sesquiterpanes might be alternative internal marker compounds to provide a direct way to estimate the depletion of oils, particularly diesels, in oil spill investigations. These findings may offer potential applications for both oil identification and oil-source correlation in cases where the tri- to pentacyclic biomarkers are absent due to refining or environmental weathering of oils.     

玉米芯快速热解油特性研究

利用层析法对玉米芯快速热解油进行分析。结果表明,裂解温度对热解油产率及其族馏分构成的影响很大。通过气相色谱(GC)分析表明,脂肪族馏分碳数分布主要在C12~34,在烷烃碳数分布上,脂肪族馏分与柴油相当。并利用傅里叶红外光谱(FT-IR)、核磁共振氢谱(1H-NMR)分析了600℃下得到的热解油特征,表明玉米芯快速热解油作为燃料和高品位化学品原料来源具有潜在的发展前景。