A model of wood flash pyrolysis in fluidized bed reactor

With a view of exploiting renewable biomass energy as a highly efficient and clean energy, liquid fuel from biomass pyrolysis, called bio-oil, is expected to play a major role in future energy supply. At present, fluidized bed technology appears to have maximum potential in producing high-quality bio-oil. A model of wood pyrolysis in a fluidized bed reactor has been developed. The effect of main operation parameters on wood pyrolysis product distribution was well simulated. The model shows that reaction temperature plays a major important role in wood pyrolysis. And a good agreement between experimental and theoretical results was obtained. It was shown that particles less than 500 μm could achieve a high heating-up rate to meet flash pyrolysis demand.     

生物质能的气化能转化及其作用

世界上生物质资源十分丰富,对其进行现代化的利用,有利于减少环境污染、促进能源结构调整,因此引起国际上普遍重视。生物质能可用两种方法转化气化能,微生物法转化生物质能可获得高热值的沼气,而热解法则具有速度快、适应性广的特点。当前两种方法都有广泛的应用,代表着生物质能应用的主流。     

A wide range kinetic modeling study of the pyrolysis and combustion of naphthenes

The aim of this paper is to analyze and discuss the kinetics of the pyrolysis and combustion of naphthenes. The primary propagation reactions of cyclohexane and methylcyclohexane are presented to extend the validity of a semi-detailed kinetic model for the pyrolysis and oxidation of hydrocarbons. Naphthenes are relevant species as reference components in liquid fuels and surrogate blends. A lumped approach is used to reduce the complexity of the overall scheme in terms of species and reactions. Particular attention is devoted to the role of the isomerization or internal abstraction of H atoms in competition with β−decomposition ones. Primary oxidation and decomposition reactions of the cyclohexyl radical are discussed to explain and justify this lumping procedure. The modeling predictions are compared with different sets of measurements. The validation of the low temperature oxidation mechanism of cyclohexane is based on the ignition delay times obtained both in the rapid compression machine at Lille and in closed vessels. Jet-stirred reactors at different pressures and stoichiometric ratios also confirm the reliability of the overall mechanism of oxidation. The comparisons between the model’s predictions and the measurements relating to the pyrolysis and oxidation of methylcyclohexane in the Princeton turbulent flow reactor further support this extension of the kinetic scheme to naphthenes. Finally, the agreement with the oxidation experiments using mixtures of toluene + methylcyclohexane is a primary and simple example of the model’s ability to deal with the combustion of real fuels or surrogate blends.     

Direct synthesis and characterization of spongy CuO with nanosheets from Cu3(btc)2 microporous metal-organic framework

Spongy CuO was successfully synthesized via direct pyrolysis of Cu₃(btc)₂ (btc = benzene-1,3,5-tricarboxylate) microporous metal-organic framework (MOF) in a horizontal tube furnace in the air, in which the Cu₃(btc)₂ was used as the Cu source and complexing molecule precursor. The as-prepared products were characterized by a series of techniques including XRD, SEM, EDX, TEM, and SAED. Results from SEM showed that the as-prepared spongy CuO with average diameter altering from 10 to 20 μm consists of nanosheets with average edge length in the range of 80-200 nm and thickness of about 30 nm, which was also confirmed by TEM analysis. The XRD and SAED results showed that a purity phase of CuO was obtained after pyrolysis. It was also found that the reaction temperature played a key role in the formation of spongy CuO microstructures. The spongy material could be found potential application in various fields such as catalysis, absorption, and gas sensing.     

Conversion of microwave pyrolysed ASR's char using high temperature agents

Pyrolysis enables to recover metals and organic feedstock from waste conglomerates such as: automotive shredder residue (ASR). ASR as well as its pyrolysis solid products, is a morphologically and chemically varied mixture, containing mineral materials, including hazardous heavy metals. The aim of the work is to generate fundamental knowledge on the conversion of the organic residues of the solid products after ASR's microwave pyrolysis, treated at various temperatures and with two different types of gasifying agent: pure steam or 3% (v/v) of oxygen. The research is conducted using a lab-scale, plug-flow gasifier, with an integrated scale for analysing mass loss changes over time of experiment, serving as macro TG at 950, 850 and 760 °C. The reaction rate of char decomposition was investigated, based on carbon conversion during gasification and pyrolysis stage. It was found in both fractions that char conversion rate decreases with the rise of external gas temperature, regardless of the gasifying agent. No significant differences between the reaction rates undergoing with steam and oxygen for char decomposition has been observed. This abnormal char behaviour might have been caused by the inhibiting effects of ash, especially alkali metals on char activity or due to deformation of char structure during microwave heating.     

Hydrogen production from biomass coupled with carbon dioxide capture: The implications of thermodynamic equilibrium

In this work we report on the consequences of thermodynamic equilibrium for hydrogen (_H2)$({\mathrm{H}}_2)$ generation via steam gasification of biomass, coupled with in situ carbon dioxide (_CO2)$({\mathrm{CO}}_2)$ capture. Calcium oxide (CaO) is identified as a suitable sorbent for CO₂ capture, capable of absorbing CO₂ to very low concentrations, at temperatures and pressures conducive to the gasification of biomass. The proposed process exploits the reversible nature of the CO₂ capture reaction and leads to the production of a concentrated stream of CO₂, upon regeneration of the sorbent. We develop a thermodynamic equilibrium model to investigate fundamental reaction parameters influencing the output of H₂-rich gas. These are: (i) reaction temperature, (ii) reaction pressure, (iii) steam-to-biomass ratio, and (iv) sorbent-to-biomass ratio. Based on the model, we predict a maximum H₂ concentration of 83%-mol, with a steam-to-biomass ratio of 1.5 and a Ca-to-C ratio of 0.9. Contrary to previous experimental studies, this maximum H₂ output is reported at atmospheric pressure. Model predictions are compared with an experimental investigation of the pyrolysis of pure cellulose and the reactivity of CaO through multiple CO₂ capture and release cycles using a thermogravimetric analyser, coupled with a mass spectrometer (TGA–MS). On this basis, we demonstrate the applicability of thermodynamic equilibrium theory for the identification of optimal operating conditions for maximising H₂ output and CO₂ capture.     

Overlapping of heterogeneous and purely thermally activated solid-state processes in the combustion of a bituminous coal

Mechanistic studies of coal combustion have long highlighted the variety of reaction pathways along which gasification may take place. These involve chemisorption of reactants, formation of surface oxides, surface mobility of chemisorbed species, and product desorption. At the same time, exposure of the solid fuel to high temperatures is associated with solid-state thermally activated processes. Altogether, the course of gasification may be profoundly affected by the overlapping and interplay of heterogeneous oxidation with purely thermally activated solid-state reactions. In the present work the combustion of a South African bituminous coal is analyzed in the framework of a simplified reaction network that embodies heterogeneous oxidative and thermally activated processes (pyrolysis, thermal annealing, coal combustion, char combustion, oxygen chemisorption) active both on the raw coal and on its char. The kinetics of each process of the network is assessed by a combination of thermogravimetric and gas analysis on coal and char samples. The analysis is directed to the determination of the prevailing combustion pathway, established from the interplay of oxidative and solid-state thermally activated processes, as a function of combustion conditions (temperature, heating rate, particle size).     

Carbon nanotube integrated 3-dimensional carbon microelectrode array by modified SU-8 photoresist photolithography and pyrolysis

An integration strategy is devised for a reliable and scalable assembly of carbon nanotubes in photoresist-derived glassy-like carbon microelectrodes. The approach involves UV photolithography process with carbon nanotube monodispersed photoresist followed by high temperature pyrolysis process, and is versatile in yielding various 3-dimensional micro-nano integrated carbon microelectrode arrays. The morphology of the micro-nano integrated structures is characterized. The integrated microelectrodes demonstrate better electrical performance than the blank microelectrodes, showing potential applications in high-sensitive chemical and biological detection systems. The developed method represents a low-cost and facile way to mass production of carbon nanotube-integrated carbon microelectrode array.     

石油与岩石矿物荧光特性的探讨

在录井工作中,部分岩石矿物具有与石油同样的荧光颜色,这就使识别岩样含油荧光更加困难。该文依据分子轨道理论和固体物质的能带理论,对石油及岩石矿物的荧光性成因进行了论述。在此基础上,阐述了利用石油与岩石矿物物理化学特性的差异区别石油与岩石荧光特征的两种常规方法。     

Pyrolysis of brown coal under different process conditions

Pyrolysis tests were performed under laboratory conditions, simulating possible processes in the burning of brown coal mines. These tests focused on gaseous products of thermal decomposition of coal and how their concentrations changed depending on pyrolysis temperature. Results obtained can help to quantify the contributions of particular gases to overall explosiveness of a gaseous mixture and can explain the process of explosive gas release during conflagration.