Development of plasma pyrolysis/gasification systems for energy efficient and environmentally sound waste disposal

As more efficient and reliable torches for thermal plasma generation have become available in recent years, the use of thermal plasma as an energy source for pyrolysis/gasification has attracted much interest, and special attention has been paid to waste treatment for resource and energy recovery. Plasma pyrolysis/gasification systems have unique features such as the extremely high reaction temperature and ultra-fast reaction velocity compared to traditional pyrolysis/gasification systems. Plasma pyrolysis/gasification is therefore acknowledged as a novel pyrolysis/gasification technology with great potential in solid waste disposal. This paper gives a comprehensive review on the development of fundamental researches on plasma pyrolysis/gasification systems including direct current (DC) arc plasma system and radio frequency (RF) plasma system with an emphasis on reactor design such as plasma fixed/moving bed reactor system, plasma entrained-flow bed reactor system and plasma spout-fluid bed reactor system.     

Development and application of ferrite materials for low temperature co-fired ceramic technology

Development and application of ferrite materials for low temperature co-fired ceramic(LTCC)technology are discussed,specifically addressing several typical ferrite materials such as M-type barium ferrite,NiCuZn ferrite,YIG ferrite,and lithium ferrite.In order to permit co-firing with a silver internal electrode in LTCC process,the sintering temperature of ferrite materials should be less than 950°C.These ferrite materials are research focuses and are applied in many ways in electronics.     

低温材料及低温钻杆的研发现状

随着目前深井和超深井的发展,以及北方、西北地区高寒地带油气井的开发,越来越多的钻杆要求具有抵抗低温或者超低温度的性能需要.低温钻杆成为目前极有发展前景的石油工业技术之一.文中在综述低温材料研究现状的基础上,阐述了低温材料钻杆的工艺现状及其发展趋势.     

Hardness of materials at high temperature and high pressure

The intrinsic character of the correlation between hardness and thermodynamic properties of solids has been established. The proposed thermodynamic model of hardness allows one to easily estimate hardness and bulk moduli of known or even hypothetical solids from the data on Gibbs energy of atomization of the elements or on the enthalpy at the melting point. The correctness of this approach is illustrated by an example of the recently synthesized superhard diamond-like BC₅ and orthorhombic modification of boron, γ-B₂₈. The pressure and/or temperature dependences of hardness were calculated for a number of hard and superhard phases, i.e. diamond, cBN, B₆O, B₄C, SiC, Al₂O₃, β-B₂O₃ and β-rh boron. Excellent agreement between experimental and calculated values is observed for temperature dependences of Vickers and Knoop hardness. In addition, the model predicts that some materials can become harder than diamond at pressures in the megabar range.     

Effect of outgassing temperature on the performance of porous materials

This work illustrates the consequences of an inadequate outgassing temperature of porous materials of different nature (zeolites and activated carbons) on their performance on gas storage and wastewater remediation. Outgassing at low temperature in thermally stable materials leads to an incomplete cleaning of the porous surface; as a result, the gas storage ability based on adsorption isotherms is underestimated. In contrast, outgassing at elevated temperature in temperature-sensitive materials provokes irreversible changes in their composition and structure, which also affects strongly their stability and performance. Two examples illustrating wrong interpretation data on CO₂ capture on zeolites and wastewater treatment using activated carbons are addressed. The results show how the performance of a given material can be significantly modified or misunderstood after the outgassing pretreatment.     

激光切割脆性材料的温度场模拟

激光切割脆性材料是一个复杂的光致热过程。在综合考虑材料的热物性参数、初始条件及边界条件的情况下,运用Ansys软件建立了激光切割脆性材料温度场的三维有限元模型。采用APDL语言实现了对热流密度的高斯分布和强制对流换热及移动激光热源的模拟。通过设置不同的激光切割参数,对温度场的变化进行了模拟分析。所建立的温度场模拟系统可以对实际激光切割脆性材料的热过程进行前期预测,并能对激光切割参数的选择进行一定的优化,以减少实际切割的盲目性。     

Biomass pyrolysis in pulverized-fuel boilers: Derivation of apparent kinetic parameters for inclusion in CFD codes

Biomass combustion in pulverized-fuel boilers is a growing way to produce electricity from a renewable source of energy. Slagging and fouling limit however the reliability of the units that were initially designed for coal combustion. Computational Fluid Dynamics (CFD) codes aiming at studying those phenomena include simplified models of biomass particle pyrolysis, of which the pertinence has already been questioned for the typical conditions of interest. A comprehensive model has been developed to investigate pyrolysis of particles in pulverized-fuel boilers, with sizes ranging from 17 μm to 2.5 mm. The detailed model accounts for internal heat conduction, internal gaseous convection, moisture evaporation and particle shrinkage. It includes a competitive, multi-component kinetic scheme, improved for high temperatures. The discrepancy between the simplified models integrated in most CFD applications and the detailed simulations is highlighted. The simplified isothermal models underestimate pyrolysis time for the largest particles. Moreover, such models delay and shorten the volatiles release. The flame lengths, the local temperature fields and the pollutant emissions might be importantly impacted in global combustion simulations. Apparent kinetic parameters have been derived from the detailed simulations. Their use in existing simplified models improves the behavior of the biomass particles during pyrolysis, and offers therefore an efficient alternative to the integration of complex pyrolysis models in CFD codes.     

微胶囊相变蓄能技术研究现状与进展

微胶囊相变材料是一种新型的复合相变蓄能材料。文中介绍了微胶囊相变蓄能材料的性质,着重阐述了微胶囊相变蓄能材料的制备方法,并分析了微胶囊相变蓄能材料在工业领域的应用,总结了微胶囊相变蓄能材料的发展趋势。     

Differential temperature sensors method for simultaneous determination of thermal conductivity and diffusivity

An attempt has been made to minimize the sources of error involved in the transient probe method for thermal conductivity determination. Two sensors (thermocouples) are mounted parallel to the needle probe at known distances. This modification makes it a device for simultaneous conductivity and diffusivity determination. Thermal conductivity and diffusivity for glycerine, dune sand and mustard seed are determined by this method. Results obtained are compared with those obtained by a calibrated transient probe for conductivity and by a parallel wire method for diffusivity. Analysis of the results prove it to be a better instrument over the traditional ones. The technique can also be used as a direct reading device for conductivity and diffusivity measurements.     

Effects of synthetic routes of Fe-urea complex on the synthesis of γ-Fe2O3 nanopowder

Maghemite (γ-Fe₂O₃) nanopowder was prepared by the thermal decomposition of Fe-urea complex ([Fe(CON₂H₄)₆](NO₃)₃) that was synthesized by various routes including wet and dry synthetic methods. Then the effects of synthetic routes of the [Fe(CON₂H₄)₆](NO₃)₃ on resulting iron oxide crystalline phases and their magnetic properties have been studied using X-ray powder diffraction (XRD) and magnetic measurements. The result of XRD shows that the iron oxide crystalline phases are strongly dependent on the synthetic routes of the [Fe(CON₂H₄)₆](NO₃)₃. When [Fe(CON₂H₄)₆](NO₃)₃ is synthesized in ethanol, thermal decomposition of the compound results in pure γ-Fe₂O₃. When [Fe(CON₂H₄)₆](NO₃)₃ is synthesized either by an aqueous synthetic method or by a dry synthetic method, however, thermal decomposition of the compound results in mixed phases of γ-Fe₂O₃ and α-Fe₂O₃. Magnetic measurements show that resulting iron oxide nanopowder exhibits a ferromagnetic characteristic with a maximum saturation magnetization (Ms) of 69.0 emu/g for the pure γ-Fe₂O₃ nanopowder.     

Thermal radiative properties of carbon materials under high temperature and vacuum ultra-violet (VUV) radiation for the heat shield of the Solar Probe Plus mission

The Solar Probe Plus (SP+) mission will approach the Sun as close as 9.5 solar radii in order to understand the origin of the solar corona heating and the acceleration of the solar wind. Submitted to such extreme environmental conditions, a thermal protection system is considered to protect the payload of the SP+ spacecraft. Carbon-based materials are good candidate to fulfill this role and critical point remains the equilibrium temperature reached at perihelion by the heat shield. In this paper, experimental results obtained for the solar absorptivity α, the total hemispherical emissivity ? and its ratio α/?, conditioning the equilibrium temperature of the thermal protection system, are presented for different kinds of carbon materials heated at high temperatures with or without vacuum-UV (100 < λ < 200 nm) radiation. The synergistic effect of ion bombardment is also presented for one kind of material.     

In situ monitoring of hydrogen loss during pyrolysis of wood by neutron imaging

Hydrogen is an element of fundamental importance for energy but hard to quantify in bulk materials. Neutron radiography was used to map in situ loss of elemental hydrogen from beech tree wood samples during pyrolysis. The samples consisted of three wood cylinders (finished dowel or cut branch) of approximately 1 cm in length. The samples were pyrolyzed under vacuum in a furnace vessel that was placed inside a cold neutron imaging beamline using a temperature ramp of 5 °C/min from ambient up to 400 °C. Neutron radiographs with exposures of 30 s were sequentially recorded with a charge-coupled device over the course of the experiment. Relative absorbance/scattering of the neutron beam by each sample was based on intensity (or brightness) values as a function of pixel position. The much larger neutron cross section for hydrogen compared to carbon and oxygen enables almost direct conversion of neutron attenuation into sample hydrogen content for each time step during the pyrolysis experiment. Target and vessel temperatures were recorded concurrently with collection of the radiographs so that changes could be directly correlated to different states of pyrolysis. The most visible change appeared at the initial phase of the 400 °C plateau as evidenced by strong hydrogen loss and primarily diametric shrinking of the samples. The loss of elemental hydrogen between initial and final states of pyrolysis was estimated to be about 70%.     

固体材料低温热导率的测量

本实验以4.2K二级G-M制冷机为冷源,采用稳态轴向热流法测量了304不锈钢与环氧玻璃钢在低温下的热导率,讨论了样品上初始温差的成因及其影响,给出了热导率真实值所在的区间,并对测量误差以及各种漏热带来的影响进行了分析。     

Influence of ultrasound-assisted extraction on the pyrolysis characteristics and kinetic parameters of eucalyptus

In this study, the influence of ultrasound-assisted extraction on eucalyptus samples with special focus on pyrolysis characteristics and kinetic parameters was explored. Ultrasound and Soxhlet extraction were used to pretreat samples respectively, then samples were assayed by component analysis, TG-FTIR, and kinetic analysis. Ultrasound-assisted extraction did change the physiochemical characteristics of eucalyptus samples, particularly in regards to the quantity of extractives obtained. In TG and DTG curves, ultrasound-extracted samples reflected lower residual weight ratio (17.77%) and higher maximum weight loss rate (−22.92%/min), and were accompanied by a slight shift in the weight loss rate peak to lower temperature (366 °C). The volatiles produced during pyrolysis and the discrepancies of product distribution between experimental and controlled groups were explored based on TG-FTIR spectra. According to kinetic analysis results, ultrasound-treated samples showed higher activation energy at the primary portion of thermal degradation with an average of 206.09 kJ/mol.     

Preparation of well-aligned carbon nanotubes by pyrolysis of phenolic resin in anodic alumina pores

Well-aligned carbon nanotubes (CNTs) of high quality were synthesized by pyrolysis of phenolic resin at 800 °C in anodic alumina oxide (AAO) pores under argon protection. The innocuous source materials and safe operational conditions permit this method to synthesize well-aligned CNTs in large-scale and low cost. The formation mechanism of the synthesized CNTs is also proposed in this work by a series of visual sketches and is proved with obvious evidence. Firstly, phenolic resin nanotubes form in the template pores through the evaporation of solvent. Heat treatment then transfers these tubes into CNTs.     

用单色亮度比较法确定高温黑体的温度

高温黑体温度的测量水平将直接影响光谱辐射度量值的不确定度。我国的高温温标截止于 2 2 0 0℃。确定2 2 0 0℃以上范围内的温度必须进行温度延伸。从Planck公式的定义出发 ,推导出用单色亮度比较法进行温度延伸的原理和方法。在国家光谱辐射度基准改造中 ,该方法被用来确定高温黑体的温度。实验证明 :使用参考灯替代法能够有效消除探测器灵敏度漂移带来的误差。此外 ,旁证实验用来验证该方案的可行性。     

Experimental and computational study of diethyl sulfide pyrolysis and mechanism

The pyrolysis of diethyl sulfide (C₂H₅SC₂H₅), a simulant for mustard chemical warfare agents, was studied in a turbulent flow reactor with extractive gas composition analysis by GC/MS and FTIR. Experiments were performed at approximately atmospheric pressure for four different temperatures between 630 and 740 °C with maximum residence times between 0.06 and 0.08 s. Temperature and species profiles were obtained on the centerline of the reactor. The mixing characteristics in the reactor were determined by using carbon monoxide as a tracer. 80% destruction of diethyl sulfide was observed for the experiment at the temperature of 740 °C and the residence time of 0.06 s. The following species were quantified: diethyl sulfide, ethylene, methane, ethane, acetylene, carbon disulfide, and thiophene. In addition, ethanethiol, methyl thiirane CH₃-(Cy-CH-CH₂-S), ethyl methyl disulfide, and diethyl disulfide were identified but not quantified. A light yellow solid containing sulfur condensed in sampling probes. Thermochemical properties for all species and a detailed mechanism were developed for modeling the reaction system. Thermodynamic and kinetic parameters were based on density functional theory and ab initio calculations using isodesmic work reactions for enthalpies. Kinetic parameters for chemical activation and unimolecular dissociation reactions were determined with multi frequency quantum RRK analysis for k(E) and master equation for fall-off. Important reactions were identified by sensitivity analysis and reaction pathway analysis of the mechanism. Model predictions show overall good agreement with experiment.     

A model of the chemical composition and pyrolysis kinetics of lignin

This study presents a novel approach for the chemical representation of lignin for modelling the reaction kinetics of lignin in lignocellulosic biomass. This methodology relies on the definition of dimeric pseudo-components containing phenolic functionalities, i.e., p-hydroxyphenyl, guaiacyl and syringyl groups, as measured in real biomass and native lignin through wet chemistry and spectroscopic techniques. The reactivities of the lignin pseudo-components are modelled through a series of lumped unidirectional reactions, whose product formation and reaction rate constants are optimised to replicate a comprehensive experimental dataset gathered from several works available in the literature. The new kinetic model contributes to the state-of-the-art by providing a more accurate depiction of the conversion rates, selectivity of char vs. volatiles, and aromatic composition in condensable products in line with the inherent reactivity of lignin functionalities and the empirical observations of lignin depolymerisation and thermal degradation at low (<1?K/s) and high heating rates (>50?K/s).     

The synthesis of multi-walled carbon nanotubes (MWNTs) by catalytic pyrolysis of the phenol-formaldehyde resins

A series of carbon nanomaterials, particularly multi-walled carbon nanotubes (MWNT), are obtained as products from catalytic pyrolysis of the cross-linked phenol-formaldehyde resins with different ferrocene under inert atmosphere. The morphology and structure of the samples were evaluated by TEM and XRD techniques. CNTs morphology is dependent on the iron nanoparticles and their forms (Fe, Fe₃C) resulted from ferrocene decomposition. The amount of nanotubes increases with iron content released from ferrocene catalyst during the pyrolysis process. Fe₃C nanoparticles drive the nucleation and the growth of carbon nanotubes during the pyrolysis process. Long (up to microns) well-defined MWNTs with small defects, ropes and disordered carbon are representatives in the pyrolyzed resins composition.     

基于TG-FTIR的落叶松木材热失重与热解气相演变规律研究

采用热重红外光谱联用分析法考察了落叶松木材在不同升温速率下的热失重特性及气相演变规律,并与其组分模混物的热解特性进行了对比分析。结果表明,落叶松的主要失重区域相对于模混物较宽,落叶松残炭率(18.97%)相对于模混物(29.83%)较低;在低温段,模混物的活化能高于落叶松木材,而在高温段二者差别不大;落叶松木材热解过程经历了水分析出、主成分热分解、后期炭化等阶段,气体析出主要集中在375℃左右;落叶松在热解反应过程中,主要气体产物生成量顺序为CO2>H2O>CH4>CO,随着升温速率的增加,上述气体产物的生成量明显增多;模混物与落叶松木材热解生成气体规律基本相似,但模混物中各气体析出强度均相对较高。