油页岩燃烧反应活化能不同求解方法的比较

利用热重分析仪在非等温条件下测得的桦甸油页岩燃烧试验数据，分别采用Coats-Redfern法和等转化率法（KAS法）对油页岩燃烧反应的表现活化能进行了求取，并对结果进行了比较。结果发现，用两种方法得出的活化能都表明油页岩燃烧分为两个阶段，且燃烧前期的活化能低于燃烧后期；等转化率法分析的结果表明，油页岩燃烧是一个复杂的多步反应过程，而C-R法将反应的机理简单假设为遵循反应级数模型，本身就存在问题，所以其得出的活化能值可靠性不高。     

酒糟非等温热解动力学研究

酒糟气化是酒糟高效利用的一种方式。文章对酒糟的热解行为进行了热重分析研究。在高纯氮气的保护下,将10 mg酒糟分别以10,20,30 K/min的升温速率线性升温到923 K。结果显示,酒糟热分解的主要阶段为453～743 K,试样的大部分失重发生在该区域,失重率达67%以上。使用Coats-Redfern模型拟合方法分析酒糟的热解过程,确定了反应的动力学参数。在此阶段,酒糟热分解的级数为2.1级,表观活化能为69.31 kJ/mol,指前因子为4.92×105min-1。此热解动力学模型可以为酒糟的热化学转化有效利用提供基础数据。     

Theory and Applications of Ignition with Variable Activation Energy

The determination of critical conditions for thermal ignition of combustible materials has been traditionally studied by the use of one overall reaction with bounded parameter values for the activation energy and other chemical constants, Significant errors can occur in the values of the threshold parameters for ignition when there are two (or more) simultaneous reactions present with distinct values of the chemical constants. Recent work with simultaneous parallel reactions showed the thresholds for ignition could be lowered in this case. In this paper, motivated by experimental results for forest litter and coal, it is shown that for sequential reactions (different values of parameters in different temperature ranges) that the threshold conditions are changed (safer for lower ambient temperatures and less safe for higher ambient temperatures).The mathematical analysis is summarised and a detailed analysis is given for the forest litter and crushed coal applications. The experimental results show that variable activation energy does occur and that this extension of the classical Frank-Kamenetskii theory is needed. Here the analysis is confined to the slab geometry only but the ideas developed can easily be extended to more general systems, including those involving mass transport, consumption, and phase changes.     

Kinetic modeling of liquid generation from oil shale in fixed bed retort

Kinetics of shale oil generation in a fixed bed retort is modeled using a second order rate equation. Samples from Ellajjun oil shale deposits are tested in 350–550 °C temperatures range. In each run, 400 g are charged to reactor and heated in a range of 2.2–10 °C min⁻¹. Shale oil liquid is condensed at 0 ± 2 °C and its rate measured as function of time and temperature.     

Combustion kinetics of oil shales by thermogravimetric analysis

This study investigates the combustion characteristics of oil shales obtained from two different regions and their blends prepared by mixing them in the proportions of 25, 50, and 75%. To this end, thermogravimetric analyses were performed at an air atmosphere flow rate of 100 ml/min and heating rates of 5, 10, 40°C/min. The kinetic parameters of combustion reaction were calculated using the Coats&Redfern kinetic model.     

Changes of functional groups and gas species during oil shale pyrolysis with addition of pyrite

Oil shale is a potential substitute fossil fuel for petroleum and gas and has attracted much attention in recent years. This study investigated the pyrolysis characteristics of LongKou oil shale in a horizontal pipe furnace, and the gas production and functional groups in coke when different amounts of pyrite were added. The results showed that the organic matrix was decomposed completely in the optimal conditions (a temperature of 500°C, a gas speed of 300 mL/min and a resident time of 40 min). For aromatic hydrocarbon, substitution can be promoted in the direction of H-decrease by the presence of pyrite. For aliphatics, pyrite will inhibit the condensation of macromolecules causing an increase of aliphatic chain length. For O-containing groups, carboxyl was consumed completely and the ratio of C = O to aromatic carbon was decreased. And for gas products, pyrite can promote the generation of CO₂, CO and CH₄ on the whole. But it is worth mentioning that when the content of pyrite is suitable (2%), generation of all gases especially CO and CH₄ is promoted significantly. Considering the pyrite is an important part in untreated oil shale, the results obtained in this research may be able to provide some useful information for desulfurization and gas production in oil shale retorting.     

The effect of acid treatment on pyrolysis of Longkou oil shale

The effect of acid treatment on mineral removal and pyrolysis of Longkou oil shale were investigated. X-ray diffraction (XRD) and X-ray fluorescence (XRF) indicated that the HCl treatment can remove the calcite, the H₂SO₄ treatment can convert the calcite to CaSO₄, and the HF treatment can remove the quartz and convert the calcite to CaF₂; moreover, all three treatments cannot remove the pyrite in the oil shale. Oil shale was individually treated with HCl, H₂SO₄, and HF before conducted the pyrolysis experiment. The pyrolysis results showed that oil shale treated with H₂SO₄ or HF almost equally enhanced the oil yield, while HCl treatment had a negative effect on the oil yield. Thermogravimetry (TG) analysis indicated that the carbonates had a catalytic effect, sulfates may also had a catalytic effect and the silicates had an inhibitive effect on the decomposition of kerogen. Combining the TG analysis, oil yield and the price of every acid, the H₂SO₄ treatment was considered to be the best method to treat oil shale.Moreover, the carbonate minerals can be removed after H₂SO₄ treatment, so it would reduce the amount of pyrolysis feed to increase production efficiency.     

Comparing product distribution and desulfurization during direct pyrolysis and hydropyrolysis of Longkou oil shale kerogen using reactive MD simulations

The product distribution and organic sulfur removal during direct pyrolysis and hydropyrolysis of oil shale kerogen were investigated via reactive molecular dynamics (RMD) simulations with reactive force field (ReaxFF). Two structural models for direct pyrolysis and hydropyrolysis of kerogen were constructed about kerogen extracted from Longkou oil shale to investigate the impact of H₂ at different temperatures on the product distribution and reaction processes of oil shale. The experimental results show that hydropyrolysis could increase light shale oil (the most important product in shale oil industry), and improve the removal rate of organic sulfur simultaneously. It was found that comparing to the direct pyrolysis, hydropyrolysis can provide more H free radicals to participate in the reaction and therefore promoting the pyrolytic reaction of kerogen. In addition, hydropyrolysis greatly promoted the desulfurization due to the contribution to the production of H₂O molecules, and the transfer of sulfur to the gas products requires the participation of H₂O molecules. This work is an intensive study on hydropyrolysis mechanism at different temperatures at the atomic level. These conclusions could be helpful for the clean utilization technology of oil shale industry.     

The effect of minerals on the pyrolysis and the combustion of oil shale

Oil shale (OS) is a particularly promising alternative fossil fuel source. However, very different from coal, its inorganic mineral content is very high. The organic matters (mainly kerogen) are finely distributed in the inorganic minerals. Therefore, the minerals may affect the processing of OS, whose elucidation is critical to the choice of processing conditions. In this work, different minerals (SiO₂, CaCO₃, and Al₂O₃) were added to OS with different mass ratios of OS to mineral, respectively. Then, the thermogravimetric (TG) technique was employed to analyze the reaction behavior of these different OS/mineral mixtures in N₂ and in air for studying the influence of minerals on the OS pyrolysis in N₂ (i.e., retorting) and on the OS combustion in air. The results show that CaCO₃ and Al₂O₃ have a promoting effect on both pyrolysis and combustion of OS, and they can decrease the reaction activation energy of both kinds of processes. However, SiO₂ has an inhibitive effect and can increase the reaction activation energy for both kinds of processes. It is hoped that the present study can further increase the understanding toward the effect of different minerals on the OS reactions.     

Structural model of Longkou oil shale kerogen and the evolution process under steam pyrolysis based on ReaxFF molecular dynamics simulation

ABSTRACT

The product distribution and reaction mechanism of steam pyrolysis of Longkou oil shale kerogen was researched by molecular dynamics simulation. Molecule structural model used in the simulation was constructed according to the analysis results of a series of detection about kerogen extracted from Longkou oil shale. Reactive force field molecular dynamics (ReaxFF MD) was used to simulate both steam pyrolysis and direct pyrolysis process of the kerogen at the temperature of 1600, 2000, 2400 and 2800 K. The results show that temperature is a critical factor affecting product distribution in steam pyrolysis, and 2000 K is a proper set temperature for studying steam pyrolysis via molecular simulation method. Besides that, adding the H₂O molecules during steam pyrolysis can form complexes with heterogeneous atoms, thus destroying the intermolecular interactions in kerogen. Moreover, as the hydrogen radicals come from H₂O molecules can inhibit cross-linking reactions between small fractions, it can reduce the average molecular weight of organic molecules product. These conclusions could be helpful for rational use of oil shale.     

Thermochemical treatment of E-waste from small household appliances using highly pre-heated nitrogen-thermogravimetric investigation and pyrolysis kinetics

The EU directive on waste of electrical and electronic equipment (WEEE) 2002/96/EC has set a goal of recovering 70–80% in terms of materials and energy. Nowadays, thermal cracking (pyrolysis) of such waste streams is receiving renewed attention, due to the energy and material recovery that can be achieved and therefore the sustainable waste management. However, it still lacks the kinetic background which is of great importance for a successful design of thermochemical processes. In this study the kinetic parameters of WEEE (originating from small household appliances) pyrolysis using highly pre-heated nitrogen under six different heating rates (1–2.5 K/s) have been estimated using a combination of model-free and model fitted methods. Even though WEEE is heterogeneous material, similar behavior at each of the six different heating rates applied was observed. The activation energy of the pyrolysis process determined with two different model-free methods gave comparable results. Pre-exponential factor and reaction order were determined using the Coats-Redfern method. The estimated kinetic parameters for the WEEE pyrolysis are: E = 95.54 kJ/mol, A = 1.06 × 10⁸ and n = 3.38.     

Non-isothermal kinetics of pyrolysis of Turkish petroleum pitches

Non-isothermal thermogravimetric data of two Turkish petroleum pitches were used to evaluate kinetic parameters of pyrolysis reactions. The article reports the application of Ozawa–Flynn–Wall model to deal with non-isothermal TG data for the evaluation of the activation energy corresponding to the pyrolysis of two different petroleum pitches. Non-isothermal kinetic studies of pyrolysis of the pitches based on the TGA measurements at different heating rates resulted that average activation energy of pyrolysis of pitch B (213 kJ/mol) was higher than that of average activation energy of pitch A (186 kJ/mol). Reaction orders of pitch A and pitch B were calculated as 0.6 and 0.9, respectively.     

远红外辐射涂料节能原理与应用

阐述了远红外辐射涂料的特点及使用方法,分析了远红外辐射涂料强化加热设备传热过程的原理,论述了远红外辐射节能涂料的应用前景。     

Syngas yield during pyrolysis and steam gasification of paper

Main characteristics of gaseous yield from steam gasification have been investigated experimentally. Results of steam gasification have been compared to that of pyrolysis. The temperature range investigated were 600–1000 °C in steps of 100 °C. Results have been obtained under pyrolysis conditions at same temperatures. For steam gasification runs, steam flow rate was kept constant at 8.0 g/min. Investigated characteristics were evolution of syngas flow rate with time, hydrogen flow rate and chemical composition of syngas, energy yield and apparent thermal efficiency. Residuals from both processes were quantified and compared as well. Material destruction, hydrogen yield and energy yield is better with gasification as compared to pyrolysis. This advantage of the gasification process is attributed mainly to char gasification process. Char gasification is found to be more sensitive to the reactor temperature than pyrolysis. Pyrolysis can start at low temperatures of 400 °C; however char gasification starts at 700 °C. A partial overlap between gasification and pyrolysis exists and is presented here. This partial overlap increases with increase in temperature. As an example, at reactor temperature 800 °C this overlap represents around 27% of the char gasification process and almost 95% at reactor temperature 1000 °C.     

Microwave pyrolysis,a novel process for recycling waste automotive engine oil

Used automotive engine oil was treated using a microwave-induced pyrolysis process, with the intention of assessing the suitability of the process in recovering valuable products from this otherwise difficult to dispose of waste. The resulting pyrolysis gases were condensed into liquid oil; the yield and composition of the recovered oil and remaining incondensable gases were determined, and these were compared with those arising from fresh oil. Process temperature was shown to have a significant effect on the overall yield and formation of the recovered oils. The recovered liquid and gaseous pyrolysis products contained various light hydrocarbons which could be used as a valuable fuel and as an industrial feedstock. Our results indicate that microwave pyrolysis shows extreme promise as a means for disposing of problematic waste oil. The recovery of commercially valuable products shows advantage over traditional, more destructive disposal methods, and suggests excellent potential for scaling the process to the commercial level.     

An experimental study for a combined system of tar sand, oil shale, and olive cake as a potential energy source in Jordan

Jordan is an example of a third world country that is non-oil producing but contains huge reserves of other energy sources such as tar sand, oil shale, and olive cake. Some limited research is available about how to utilize these energy sources in pure form. However, available research does not deal with combinations of these energy sources. This experimental study investigates combinations of these energy forms as potential energy sources in Jordan. The experimental procedure involves characterization of samples by proximate analysis, calorific value determination of different combinations, and a compacting process of the different particles. The best combination, with respect to calorific value, is found to be 20% tar sand, 20% olive cake, and 60% oil shale. Compacting materials either with starch or with heated tar sand up to 110°C for 1 h indicates a feasible process for handling, packaging, and transporting.     

Modeling chemical and physical processes of wood and biomass pyrolysis

This review reports the state of the art in modeling chemical and physical processes of wood and biomass pyrolysis. Chemical kinetics are critically discussed in relation to primary reactions, described by one- and multi-component (or one- and multi-stage) mechanisms, and secondary reactions of tar cracking and polymerization. A mention is also made of distributed activation energy models and detailed mechanisms which try to take into account the formation of single gaseous or liquid (tar) species. Different approaches used in the transport models are presented at both the level of single particle and reactor, together with the main achievements of numerical simulations. Finally, critical issues which require further investigation are indicated.     

Fundamentals, kinetics and endothermicity of the biomass pyrolysis reaction

The paper reviews the pyrolysis of biomass constituents and possible secondary reactions. Biomass pyrolysis yields mostly liquid and solid fuel, easy to store and transport.Relevant working conditions for experiments and large-scale operation are: (i) biomass particles < 200 μm, (ii) a particle heating rate of at least about 80 K min⁻¹ and (iii) a reactor environment where the internal resistance to heat penetration is smaller than the external resistance to heat transfer (Biot-number, Bi < 1).The circumstances of TGA and DSC experiments meet these requirements and fully determine the reaction kinetics and endothermicity of the pyrolysis reaction. The reaction rate constant and the heat of reaction are essential parameters in the design of a pyrolysis reactor. For most of the biomass species tested, the first order reaction rate constant is large and >0.5 s⁻¹. The heat of reaction ranges from 207 to 434 kJ kg⁻¹. All results tie in with literature data, although the reader is cautioned in using literature data since experiments were not always performed under relevant testing conditions.     

Gravity separation of oil shale and low-temperature pyrolysis characteristics of different density fractions

In this paper, gravity separation of Huadian? (HD) and Longkou? (LK) oil shales and low-temperature pyrolysis characteristics of their different density fractions have been studied. The gravity separation results showed that kerogen could be enriched using the gravity separation method. The low-temperature pyrolysis results showed that the highest oil contents of HD and LK were in the density fractions of 1.4–1.5 and 1.5–1.6 g·cm^?3, respectively. Meanwhile, for the low-temperature pyrolysis, the oil/gas ratio decreased with the density increase, indicating higher gas loss and lower oil yield with the increase of density. The mineralogical analysis showed that most of the organic matter were associated with clay minerals, and the organic matter could not fully liberate from the matrix under coarse particles. The migration and occurrence of minerals and organic matter in different density fractions generated various pyrolysis characteristics.     

Comparative study on pyrolysis characteristics and kinetics of oleaginous yeast and algae

The pyrolysis processes of oleaginous yeast and algae were studied and compared using a non-isothermal thermogravimetric analyzer at heating rates of 10–50 °C/min, and the most probable mechanism function and kinetic analyses of the main stage of pyrolysis were carried out by the Popuse method, Starink method, and Fridemen method. The main pyrolysis stage of the samples could be described by the Jander equation and Z–L–T equation and the activation energy of the three biomass was 108–117, 107–121 and 93–108 kJ/mol, respectively. For the three kinds of biomass, the DTG curves were divided based on the four pseudo-components by performing Gaussian fitting which are carbohydrates, proteins, lipids, others, and the weight coefficients of them could be identified. The activation energy of each pseudo-component was obtained in the range of 58.36–140.44 kJ/mol by the Kissinger method. The four-pseudo-component model based on Gaussian fitting provides effective data for the design of oleaginous yeast and algae thermal decomposition systems and the kinetic analysis of the pyrolysis process.