HYDRODYNAMICS OF SPOUTED BEDS AT ELEVATED TEMPERATURES

A review of the literature reveals little information on the hydrodynamics of spouted beds at high temperature. Most existing correlations are based upon experiments done at ambient conditions; they have not usually been tested with data at higher temperatures. The present study focussed on obtaining data over a temperature range of 20-420°C. Spouting of three sizes of Ottawa sand with preheated air was couducted in a 156 mm diameter stainless steel semi-cylindrical column with a 60° included angle half-conical base. A transparent wire-glass panel on the flat face allowed measurement of parameters which are otherwise difficult to obtain in a full stainless steel column. In addition to air, helium and methane at room conditions were used as spouting gases. With these two additional gases, it became possible to investigate the effect of changing gas density at constant viscosity and the effect of changing gas viscosity at constant gas density. In general, it was found that the range of stable spouting decreased with decreasing gas density and increasing gas viscosity, hence with increasing air temperature. Existing equations for various spouted bed parameters were tested and, where necessary, empirically modified to fit the new data obtained. @KEYWORDS Spouted bed hydrodynamics, High temperature gas spouting, Temperature effect on spoutability     

MOISTURE MOVEMENT IN SOFTWOOD TIMBER AT ELEVATED TEMPERATURES

The anatomy of a common plantation-grown softwood in New Zealand, Pinna radiata, is reviewed and the differences between the drying behaviour of softwoods and hardwoods are discussed. These differences have significant effects on the paths for moisture movement, and this review of the timber physiology has been used as the basis for a model of the moisture movement at elevated temperatures which distinguishes between the drying behaviour of sapwood and heartwood. It is postulated for the drying of heartwood that liquid flow does not occur within a board due to the aspirated state of the pits, so an evaporative plane at the boiling point of water sweeps through the timber until the centre of the board is reached. In the case of the much wetter sapwood where the pits are not initially aspirated, we assume that liquid flow initially maintains an evaporative plane just below the surface until the moisture is no longer funicular. Thereafter, drying proceeds in a similar way to heartwood. Independent experimental measurements of the temperature profiles at the centre and surface of heartwood and sapwood bkards (100 × 50 mm) have been compared with model predictions, and the close agreement gives some confidence in the model. The model predicts that the drying process for this timber can be divided into three periods, marked by transitions in the gradients of the drying rates when plotted against the average moisture contents. This behaviour has been observed experimentally for Pinus radiata, giving us further confidence that our drying model includes the important physical processes for moisture movement in this timber.     

声悬浮颗粒的加热实验研究

本文介绍了作者为研究是浮单颗粒物理和化学变化过程而研制的声悬浮装置针对加热和温度变化可能造成的影响，详细叙述厂装置的特点,特别是谐振跟踪系统、激光能量调制和谱发射率随区应明显变化的悬浮颗粒的测温方法利用本装置对各种颗粒进行了加热实验研究，结果表明装置各系统工作性能良好，在室温到400℃温度范围内可以长时间悬浮密度不大于铝的各种颗粒、对加热实验中观察到的颗粒悬浮的不稳定现象进行了深入分析，指出加热造成的不利影响虽然很难完全消除，但悬浮稳定性可以通过合理的结构设计和操作加以改善     

高温下兖州煤焦/CO2气化反应性

在常压、温度为950 ℃～1 400 ℃范围内,以二氧化碳为气化剂,用等温热重法研究了我国兖州煤的高温气化反应性.主要考察了反应温度、热解终温和热解速率对兖州煤焦高温反应性的影响,并把兖州煤焦的高温反应性和神府煤焦的高温反应性作了比较.结果表明:随气化温度的提高,兖州煤焦反应性的总体趋势增强;快速热解焦的反应性优于慢速热解焦;热解温度对兖州煤焦反应性的影响甚微;在低温段,兖州煤焦的反应性比神府煤焦略差,但在高温段,兖州煤焦的反应性与神府煤相近.     

ON THE PERMEATION OF SOME GASES THROUGH THE LAMELLAE OF STATIC FOAMS. A PRELIMINARY APPROACH

Basing on the capillary method for the determination of foam bubble size, a method was proposed for establishing values of permeability coefficients of several gases. The permeability coefficients of He, Ar, H₂, N₂, CH₄ through the lamellae of static foam bubbles were preliminarily determined using this method.

A rough dependence of the N₂ permeability coefficient through the lamellae of static foam bubbles on the foam wetness and surfactant concentration was also found.

The results obtained lead to the conclusion that the Princen-Mason diffusion model of gas permeation through an isolated soap film was inadequate in the case of permeation through lamellae of bubbles forming a static foam.

A hypothesis that the gas permeation through the lamellae of a static foam is primarily caused by liquid convection in the lamellae core was put forward.     

METHOD FOR DETERMINING TENSILE PROPERTIES OF REFRACTORY MATERIALS AT ELEVATED TEMPERATURES*

Equipment for testing ceramic materials to temperatures of 2000°F. was developed, and a method was devised for evaluating the bending stresses introduced by the test equipment. With this equipment, the tensile strength, stress-to-rupture characteristics, and modulus of elasticity of a sillimanite refractory were investigated at the Cleveland Laboratory of the National Advisory Committee for Aeronautics. The tensile strength varied from a minimum of 8000 lb. per sq. in. at 500°F. to a maximum of 19,000 lb. per sq. in. at 1800°F. Heat-treating the tensile specimens for one half hour at 1800°F. increased the tensile strength 35% at room temperature and 70% at 500°F. No increase in strength was noted at or above 1400°F. The stress-to-rupture in 1000 hours at 1600°F. was 8500 lb. per sq. in. The modulus of elasticity at room temperature was 20.3 × 10⁶.     

SiC和SiC-WC复相陶瓷高温自润滑特性及其机理

研究了SiC和SiC-WC在真空中的自对偶高温摩擦性能。随着温度的升高，SiC／SiC的摩擦系数变化不大，比磨损率(自对偶体积磨损量与接触压力和摩擦路程之比)从20℃到800℃保持为4.0×10~(-8) mm~3／(N·mm)(模式Ⅰ)，从800℃到1 200℃减少(模式Ⅱ)，自对偶的高温磨损机理由轻微的粘着磨损控制，磨损由模式Ⅰ向模式Ⅱ转化，呈现出高温自润滑特性。SiC-WC／SiC-WC显示了较低的摩擦系数，直到1 200℃均不高于0.35，在1 000℃、0.4 MPa压力下自对偶的比磨损率仅为SiC／SiC的比磨损率的50％左右。在600℃SiC／SiC摩擦氧化明显，氧化物主要为无定形的SiO_2，在摩擦表面形成一层由微米或亚微米级无定形平滑薄膜层，这就是样品出现自润滑的机理。     

高温下灰熔融对神府煤焦反应活性的影响

采用慢速和快速两种升温速率,在热解温度为950℃～1500℃范围内制得各种神府煤焦,通过酸洗脱灰处理制得相应的脱灰焦,并采用扫描电镜对原煤焦及其脱灰焦表面灰熔融状况进行观察,结果发现：慢速和快速两种热解条件下,随热解温度提高,灰的熔融状况不同;对原焦样酸洗脱灰处理只能除去表面的部分矿物质;同时,采用等温热重分析法,在反应温度为950℃～1400℃条件下,分别考察了灰未熔融热解煤焦（RP950和SP950）和灰熔融热解煤焦（SP1400和RP1400）脱灰前后的CO2气化反应性．对于灰未熔融热解煤焦脱灰后,其反应活性变化不大,在低反应温时略有下降,而在高反应温度时略有增加．对于灰熔融热解煤焦脱灰后,在整个反应温度范围内,反应活性明显增加,增加的程度取决于反应温度．灰熔融和未熔融热解煤焦及其脱灰焦的气化反应过程都是从低温的化学控制转变到高温的扩散控制．     

电化学方法研究碳钢高温水体系中的氢扩散和渗透

本文应用Devanathan渗透装置的原理,设计了一套能用于测量碳钢-高温水体系中氢在碳钢中的扩散和渗透的实验装置,找出了该装置用于测量的最佳工作参数,并用该装置测量了373—473K下氢在碳钢中的扩散系数和扩散速率,讨论了氢在碳钢上还原的机理。     

STUDY ON PERMEATION OF ACETONE/NITROGEN MIXED GAS THROUGH AL2O3 MICROPOROUS MEMBRANES: MOLECULAR DYNAMICS

In this work, by applying Materials Studio 2.2 software package, molecular dynamics (MD) was performed to investigate the dynamic processes of 1:4 acetone/nitrogen mixed gas permeating through different Al₂O₃ microporous membranes. Three systems were modeled by considering different box lengths, microporous sizes, and textures of Al₂O₃ membranes to compare different permeation behaviors. In each system, initial mixed gas contained 20 acetone molecules and 80 nitrogen molecules, and its density was set to 0.1 g/cm³. Analysis on the concentration profiles of nitrogen molecules (N2) and acetone molecules (Ace) in each system at different sampling times was implemented to discuss the permeation behaviors of smaller N2 and larger Ace. The results showed that adsorption and diffusion occurred synchronously but adsorption was dominant for acetone molecules and that the adsorption on the floor surface of the feed gas region more easily reached equilibrium (local equilibrium) than the diffusion and the adsorption on the ceiling of the initially vacuum region. Furthermore, for nitrogen, adsorption followed diffusion. Higher temperature is in favor of the enrichment of acetone on the floor surface of the feed gas region but against the adsorption of nitrogen. The adsorptive layer was found to be a double-layer with COMPASS force field and to be a monolayer with PCFF force field.     

HYDROGEN MASS TRANSFER IN HYDROGEN- METHANE-TETRALIN AND HYDROGEN-ETHANE-TETRALIN SYSTEMS AT ELEVATED TEMPERATURES AND PRESSURES

The volumetric mass transfer coefficient of hydrogen for the systems of hydrogen-methane-tetralin and hydrogen-ethane-tetralin at temperatures up to 650  K and pressures to 7 MPa were studied. Experiments were carried out using an automated hydrogen probe. The volumetric mass transfer coefficient of hydrogen decreased as the methane and ethane partial pressures increased as a consequence of the multicomponent transfer caused by the presence of the hydrocarbon gases. The presence of a second solute has a large effect on the hydrogen mass transfer rates at lower temperatures and lower initial hydrogen partial pressures than at higher values. These results indicate that light hydrocarbon production during coal liquefaction operations could adversely affect the overall liquefaction operation.     

SORPTION,DIFFUSION, AND PERMEATION OF CHLORINATED HYDROCARBON VAPORS THROUGH NATURAL RUBBER,EPOXIDIZED NATURAL RUBBER,AND THEIR BLENDS

The study investigates the transport process of various chlorinated hydrocarbons through natural rubber (NR), epoxidized natural rubber (ENR), and their blends. The effect of structure and morphology of the membranes on the transport parameters has been investigated. Sorption coefficient is found to increase and the permeability coefficient shows the reverse trend with increasing epoxy content. As the mol% epoxidation increases, the polymeric network structure becomes more compact, which leads to a decrease in the diffusion coefficient, which ultimately results in a low permeation coefficient. The morphology of NR/ENR blends has been investigated by combining scanning electron microscopy with permeability measurements. The permeation coefficient is found to be minimum for the NR/ENR 70/30 composition; a 50/50 composition shows the maximum. The heterogeneous morphology of 70/30 NR/ENR blend results in the low permeability coefficient, whereas the co-continuous nature of the 50/50 composition accounts for the maximum permeability. Permeability measurements provide the most useful information about the way morphology is changing with composition of the blends and about the composition corresponding to the maximum level of co-continuity of the two phases.     

GAS TRANSFER THROUGH HUMAN SKIN†

The speed and mechanism by which substances penetrate human skin is becoming increasingly important. Arterial blood gases are now measured transcutaneously, novel skin patches for drug delivery are being offered by various pharmaceutical firms, and inadvertent absorption of toxic substances by this route is a growing concern of many groups. Two models which help in understanding the complex physiology of this process are presented and used to explain several experimental observations.     

BOND STRENGTH MEASUREMENT BETWEEN GLASS FIBRES AND EPOXY RESIN AT ELEVATED TEMPERATURES USING THE PULL-OUT AND PUSH-OUT TECHNIQUES

Pull-out and push-out measurements were performed on glass fibres in an epoxy resin to determine the dependence of bond strength on test temperature and on fibre surface treatment. A comparative analysis of the two techniques was carried out to elucidate elementary processes of polymer-fibre debonding and to determine energy values for adhesional bonds. Differences in bond strength values for pull-out and push-out tests were attributed to failure mechanisms that were either interface-controlled or matrix-controlled. Evidence for the different failure mechanisms characteristic of the two test techniques was provided by an estimation of failure parameters, such as the activation energy for debonding. Failure mechanisms also were manifest in AFM images, showing differences in topography and roughness that depended on fibre surface treatment, test geometry, and test temperature.     

STUDY ON PERMEATION OF ACETONE/NITROGEN MIXED GAS THROUGH AL2O3 MICROPOROUS MEMBRANES: MOLECULAR DYNAMICS

In this work, by applying Materials Studio 2.2 software package, molecular dynamics (MD) was performed to investigate the dynamic processes of 1:4 acetone/nitrogen mixed gas permeating through different Al₂O₃ microporous membranes. Three systems were modeled by considering different box lengths, microporous sizes, and textures of Al₂O₃ membranes to compare different permeation behaviors. In each system, initial mixed gas contained 20 acetone molecules and 80 nitrogen molecules, and its density was set to 0.1 g/cm³. Analysis on the concentration profiles of nitrogen molecules (N2) and acetone molecules (Ace) in each system at different sampling times was implemented to discuss the permeation behaviors of smaller N2 and larger Ace. The results showed that adsorption and diffusion occurred synchronously but adsorption was dominant for acetone molecules and that the adsorption on the floor surface of the feed gas region more easily reached equilibrium (local equilibrium) than the diffusion and the adsorption on the ceiling of the initially vacuum region. Furthermore, for nitrogen, adsorption followed diffusion. Higher temperature is in favor of the enrichment of acetone on the floor surface of the feed gas region but against the adsorption of nitrogen. The adsorptive layer was found to be a double-layer with COMPASS force field and to be a monolayer with PCFF force field.     

JY—801聚酰亚胺树脂的合成与性能

论述了以二异氰酸酯和二苯甲酮四羧酸二酐为原料，在催化剂存在下合成ＪＹ－８０１可溶（熔）性聚酰亚胺的一步法缩聚工艺，研究了单体摩尔比及树脂比浓对数粘度对产品性能的影响，并确定了最佳工艺条件。     

蒸汽渗透法脱除丙烯中微量水分的研究

采用涂敷法制备了CS/PS,PVA/PS,PVA-CS/PS中空纤维复合膜并用于气相丙烯中微量水分的脱除.研究了PS基膜、原料气湿含量、流速及吹扫气流速等因素对蒸汽渗透分离性能的影响.结果表明,这些复合膜均具有良好的分离性能,其中CS-PVA/PS中空纤维复合膜具有最优的蒸汽渗透性能.     

THE ELECTRICAL RESISTIVITY OF SOME CERAMIC MATERIALS AT ELEVATED TEMPERATURES AND A SIMPLE COMMERCIAL METHOD FOR ITS DETERMINATION.1

This paper gives the values obtained by some resistivity measurements of several well known minerals used in the ceramic field. The values for some ceramic bodies are also given. A simple apparatus and method with which these values were obtained are described in detail.     

加压喷动床中细颗粒喷动特性

在内径分别为 186mm和 80mm的加压喷动床中 ,以空气为喷动介质 ,在 10 1～ 70 0kPa的压力范围内考察了几种不同粒度的细颗粒在加压下的喷动特性 .研究结果表明在不同的Re_t 内压力对最小喷动速度的影响不同 .实验还发现 ,随着压力的升高 ,喷动区直径增大 ,稳定操作区域增大 ,加压可明显改善喷动床的操作稳定性     

高温炭化对聚酰亚胺(PI)薄膜结构与性能的影响

研究了在氮气流保护下,聚酰亚胺薄膜在高温炭化过程中结构和性能的变化规律。用X射线衍射和元素分析对在不同温度炭化形成的样品的微晶结构和元素组成进行了研究,并对其导电性能进行了表征。研究结果表明,在1000～1600℃的温度区间内,随着炭化温度的升高,材料的内部结构由杂乱无序的类石墨结构逐渐向有序石墨结构转变,同时碳元素的含量不断升高,氮元素和氧元素的含量不断下降,材料中残留的氮、氧元素进一步脱除。由于有序的石墨态结构的逐渐形成,随着炭化温度的升高,样品的导电性能也不断提高。