HEASUREHENT OF INSTANTANEOUS RATES OF LOSS OF VOIATILE COMPOUNDS DURING DRYING OF DROPS

A novel technique serves to monitor instantaneous rates of loss of a volatile solute from a suspended drop during drying. A highly sensitive electron capture detector is used to monitor concentrations of SF6 released into a flowing gas stream from a suspended, drying drop. Simultaneously, the appearance and morphological development of the drop are monitored with a video camera. This provides the wherewithal of relating instantaneous rates of loss of the volatile solute to particular events during the development of particle morphology.

Initial experiments have been carried out with drops of aqueous solutions of glucose, sucrose, maltodextrin and coffee extract. The results clearly display the onset of the volatiles-retentive selective diffusion phenomenon. There is also substantial loss of the volatile component later in the drying process, when the drops undergo repeated ex ansion, bursting and cratering due to the formation of internaf bubbles. These experiments appear to be the first quantitative demonstration of major losses accompanying changes in drop morphology.     

ON THE PREDICTION OF POROSITY OF BEDS COMPOSED OF MIXTURES OF SPHERICAL PARTICLES†

A semi-theoretical study of porosity of particulate beds composed of mixtures of various size spherical particles has been performed. A model for mixtures of only two particle sizes is developed and is used to identify several dimensionless parameters which are correlated by comparing predictions with the data. The model is then extended to evaluate porosity of mixtures of a large number of particle sizes and distributions. The predictions from the model are found to compare quite well with the data taken in this work and the existing data in the literature when unavailability of a certain fraction of pores formed of largest size particles in the mixture is accounted for.     

ANALYSIS OF RECENT MEASUREMENTS OF THE VISCOSITY OF GLASSES

Viscosity of Simple Soda-Silicate 500° to 1400°C Comparison of the results given by English with those of Washburn, Shelton and Libman, indicates a discrepancy in the absolute values of log₁₀ viscosity amounting to 0.6, those of Washburn et al., being relatively too high. If correction for this is made, the isothermal curves of log₁₀ viscosity as a function of soda content are smooth up to 50% Na₂O, showing no inflection. The observations as a function of temperature T are all represented within accidental error by an equation of the type where all three constants vary regularly with the composition. Change of Viscosity of Glass (6SiO₂, 2Na₂O) due to Molecular Substitution of CaO, MgO and Al₂O₃ for Na₂O The effect is clearly brought out by plotting (from the results of English) the change of log₁₀η due to the substitution as a function of temperature. The curves each show a sharp bend at a temperature between 840° and 1050°C, which is designated the aggregation temperature T_a. If we divide these curves by the corresponding percentage substituted, we get curves for each oxide which are straight and parallel below the aggregation temperatures, the slopes (increase of change of log₁₀η per 100°C) being −0.056 (CaO), −0.055 (MgO), −0.018 (A1₂O₃) per per cent oxide substituted. For substitution of 1/2 molecule the slopes are −0.325 (CaO), −0.23 (MgO) and −0.18 (Al₂O₃) per 100°. At the aggregation temperature the change of log₁₀η per per cent is a minimum, 0.03 to 0.06 for CaO, 0.12 for MgO, 0.07 for Al₂O₃. Evidence of Aggregation in Glasses, from viscosity Measurements The sharp bends in the plots of change of log₁₀η due to substitution of an oxide for Na₂O, suggest the beginning of molecular aggregation at these temperatures. These aggregation temperatures are close to the devitrification temperatures, but the effect on the viscosity curves cannot be due to actual devitrification since it does not change with time. Taking the aggregation temperatures as equal to devitrification temperatures, additional isotherms are roughly sketched into the equilibrium triangle of the system Na₂O-CaO-SiO₂. Change of Viscosity of Glass (4SiO₂, 2Na₂O) due to of Substitution of B₂O₃ for SiO₂ The change of log₁₀η (from the results of English) is plotted as a function of temperature, and also the change of log₁₀η per per cent B₂O₃. The curves are more complex than for the substitution for Na₂O.     

直链烷烃氯磺酰化反应的光催化动力学研究

本系统采用氯气和二氧化硫作为气相原料，C18－17直链烷烃为液相原料，在光作用下进行气相氯磺酰化反应。由于该反应过程机理复杂，本研究采秀工程研究方法，对过程进行合理简化，导得该反应的动力学速率模型，并采用非线性多响应常微分模型的参数估计方法求得模型参数。模型计算值与实验结果能较好吻合，该模型可用于反应器的设计计算。     

ESTIMATION OF TRANSPORT PROPERTIES OF LIQUIDS

Based on the theory of intermolecular forces and the Hildebrand relation, a generalized equation in terms of refractive index is proposed to estimate viscosity, thermal conductivity and diffusion coefficients of liquid non-polar compounds at various temperatures. Analytical equations are provided to estimate transport properties of n-alkanes in terms of molecular weight. Average deviations for all three properties of various hydrocarbons from C⁵ to C²⁰ are within 1 % for a large number of data points. The proposed equation also predicts transport properties of some polar compounds with a reasonable degree of accuracy.     

微生物对混凝土的侵蚀(英文)

微生物侵蚀会导致混凝土的严重破坏,尤其导致了城市污水收集和处理系统的过早破坏,使其需要提前修复。世界范围内的研究结果表明:处于污水和下水道污泥中的混凝土会遭受由硫酸盐、酸、CO2等导致的严重破坏。评述了混凝土处于利于细菌生长和生物降解环境中时的细菌、微生物侵蚀破坏过程。此外还分析了硫酸产生的机理(硫循环)、用于污水管道系统和农用工业的混凝土的受侵蚀破坏机理以及评价混凝土抵抗微生物侵蚀的方法。     

木糖结晶动力学模型

<正>木糖(D-xylose)是一种新型的甜味剂.其生产原料为农业植物纤维废料,如玉米芯、甘蔗渣、棉子壳、甘蔗髓、稻壳等.中国是农业大国,木糖的原料极其丰富,生产木糖是一个具有较高附加值的二次资源利用项目.国内已有数家企业投入生产,但许多技术问题尚未解决,制约了经济效益,其中结晶工序也是瓶颈之一.本文作为木糖生产新工艺的重要环节,研究了木糖连续冷却结晶过程,并根据结晶动力学的粒数衡算理论(Population Balance)及其连续稳态的动力学测定方法,探索了木糖的结晶动力学模型.国内外迄今尚无这方面的报道.1 粒数衡算理论     

EFFECT OF PRETREATMENT ON KINETICS OF CONVECTION DRYING OF ONION

Onion of two varieties, i.e. Oporto and Blonska was dried by convection at 60°C and 2 m/s. Prior to drying sliced onion was subjected to following treatments: soaking in water, dipping in starch solution, dipping in starch solution supplemented either with ascorbic acid or CaCl₂, and dewatering by osmosis in sucrose solution. Drying of raw onion was taken as a reference.

It has been found that both variety and pretreatment affect the course and rate of drying. Soaking in water and dipping in starch solution either increase rate of drying or have no effect on the kinetics of the process. Supplementing the starch solution with ascorbic acid or CaCl₂ adversely affects the rate of drying. Unfavorable effect on the rate of drying has also osmotic dewatering preceding convective drying.     

COMPARISON OF A PAIR OF THREE PARAMETER EQUATIONS OF STATE

The lattice fluid (LF) equation of state derived by Sanchez and Lacombe from a lattice model is compared to the empirical Peng-Robinson (PR) equation for normal alkane fluids ranging from methane to heptadecane in molecular weight. With respect to vapor pressure predictions, the equations are both good. The LF equation is superior, especially for higher molecular weight fluids, to the Peng-Robinson equation in predicting saturated liquid densities. For carbon numbers less than 6, the PR equation predicts heats of vaporization more accurately, whereas for carbon numbers greater than 9 the LF equation is more accurate than the PR one for temperatures lower than about 95% of critical.     

FUNDAMENTALS OF CONTACT-SORPTION DEHYDRATION OF LABILE MATERIALS

The present study deals with the fundamentals of the contact-sorption mass transfer theory. The criteria used to determhe the rate of a process and the quality indic- es of a product with contact-sorption dehydration of the material are formulated. The methods to calculate a re-quired amount of sorbent are presented, and an estimate of comparative moisture capacity of sorbents is proposed. Examples of the implementation of sorbents in sublimation and vacuum drying, in fluidized bed drying, and in spray- drying are illustrated.     

MEASUREMENTS OF INERTIAL DEPOSITION OF AEROSOL PARTICLES IN REGULAR ARRAYS OF SPHERES

Inertial deposition of aerosol particles on single spheres and regular assemblies of spheres was investigated in the range of Stokes numbers from 0.03 to 5. Measurements were carried out on steel spheres suspended from wires in a 100 mm wide flow channel at air velocities from 5 to 28 m s^-1, using monodisperse DES (Di-II-ethyl-hexyl-sebacate) test aerosol in the size range from 1.5 to 15 μm. Experimentally determined deposition efficiencies on single spheres are in very good agreement with theoretically predicted results based on a potential flow field as well as a numerical flow simulation. Results in various types of arrays consisting of up to 12 equal-sized spheres show substantial variation of deposition efficiency from sphere to sphere which are strongly influenced by Stokes number and geometry.     

氧化石墨烯剥离方法的研究进展

用石墨制备氧化石墨是大规模合成石墨烯的起点,也是实现石墨烯大量制备的有效方法之一。目前。制备氧化石墨的工艺相对成熟,而有效剥离出不同尺寸的石墨烯以满足不同的需求,还存在诸多技术难点需要突破。本文着重介绍了氧化石墨烯剥离方法的研究进展,包括热膨胀剥离、超声剥离、机械剥离、静电剥离、低温剥离等方法;最后展望了氧化石墨烯研究工作的发展前景。     

神木煤的主要性质对其水煤浆特性的影响

研究我国大型优质神木煤田12个煤样的主要性质,对其水煤浆特性的影响。实验表明,煤中水分和含氧官能团是主要因素,水分中以最高内在水分与水煤浆浓度呈线性相关,提出以最高内在水分作为评价指标。并研究了煤浆的改性方法,一是加热方法使水分和官能团脱除,煤表面亲水性降低,使煤浆浓度大幅度提高,二是除去煤中可溶无机离子,可使煤浆粘度降低,并添加某些电解质有可能提高稳定性。     

REFINED METHOD OF CONTROL OF CORDINESS AND WORKABILITY OF GLASS DURING PRODUCTION*

Many glass plants obtain daily measurements of the density or specific gravity of the glass in each furnace. Small daily fluctuations of about ±0.0010 density unit are usually taken for granted, while pronounced changes within a two- or three-day period are a matter of concern; but heretofore neither criteria of permissible variability nor rules for interpretation of the data have been in general use. In the present work, the control-chart method of statistical analysis of past data has been applied to data from ten glass furnaces. Small daily fluctuations of density are found to be statistical in character, and the predominant cause of large variations is found to be in the batch house. The rational subgroup sample to be used in analyzing such variations and in operating a control chart is found to be a subgroup of three consecutive daily density values obtained from a particular furnace. Using this subgroup, the average 3-day range of density for the ten furnaces varied from 0.0006 to 0.0023, and the corresponding 3-sigma limits for daily variation from the central line density were ±0.0011 to ±0.0040. A typical value for the average 3-day range of density is 0.0012 and a value no larger than this is a reasonable goal for a glass container plant. The use of control charts for maintaining a state of statistical control of density during production is illustrated for four furnaces over a 2- to 6-month period. Many assignable causes of variation were found in the batch house, usually in the scales; other assignable causes were changes in cullet and in raw materials, changes in firing of the furnace, and laboratory errors in measurement of the density. Present experience indicates that it is difficult to maintain a state of statistical control with the types of batch-weighing equipment in use in some plants. The importance of control, however, was demonstrated for two furnaces in two different plants by the fact that cordiness increased with increasing 3-day range of density. When the density was not maintained under statistical control in one plant, trouble was experienced with checks in the ware. The use of control charts for keeping lack of control within tolerable limits is discussed for one furnace where the variations were small and the control limits narrow. The range was held under control, but the density showed “trends” and went out of control. In this instance, the 3-sigma control limits for variation of daily values from the central line density were ±0.0011, corresponding to ±0.09% replacement of lime by silica. Inasmuch as composition changes in excess of ±0.09% are tolerable in the present state of the art, a modified control limit corresponding to a composition change of approximately ±0.25% is suggested, the corresponding density limits being ±0.0030. When the 3-sigma limits for density are less than, this value, modified limits may be used, although the 3-sigma limits for range are retained. When the 3-sigma limits are greater than ±0.0030, it is most desirable to maintain strict statistical control, and efforts should be made to reduce the variability; otherwise there may be excessive cordiness and other difficulties in fabrication of the ware. In some instances, a reduction in variability will require major repair of batch handling and weighing equipment or a new batch-house weighing installation. Other subgroup methods and other sources of variability are also discussed. Control charts on density are of practical utility to plants. “Assignable-cause” variations are easily distinguished from unimportant, normal variations. The use of 3-sigma action limits keeps investigation of fluctuations to a minimum, and sets troubleshooting, when it is necessary, on the right track. The charts, furthermore, are a useful guide toward a permanent reduction of the variability. They should be helpful to management in striking an economic balance among tonnage pulled, glass quality, and capital expenditures for improvement of batch mixing and handling and other changes. The time required to maintain a chart for one furnace is about one day for past-data analysis, one minute each day for plotting, and not more than one day per month for current analysis, review, and adjustment.     

制备板状玻璃炭工艺中固化曲线的确定

固化处理是在玻璃炭制备工艺中很关键的阶段．在差热分析和热失重分析的基础上．建立了玻璃炭（GC）固化升温曲线，并与等速升温法作了比较．     

EFFECT OF ADDITIONS OF DIOPSIDE ON PROPERTIES OF WALL-TILE BODY *

Diopside was substituted for both talc and feldspar in a typical wall-tile body. It was found to lower the fusion temperature and to lower thermal expansion when compared with talc and to raise thermal expansion when compared with feldspar. Its effects on firing shrinkage, fired absorption, and moisture expansion were somewhat similar to those of talc.     

四种吸收剂用于煤中硫脱除的研究

采用四种不同的吸收剂作为脱硫剂对煤中硫的脱除进行了比较研究 ,考察了吸收剂用量、煤燃烧温度、时间及催化剂对硫的脱除的影响 .实验结果表明 :在煤燃烧过程中 ,通过吸收剂把大部分的硫固定在煤灰中是一种高效简易的脱硫方法 ,1 #与 2 #的混合固硫剂加少量催化剂的脱硫率可达 82 % .     

THE EFFECT OF SIZE OF GRAIN UPON THE PROPERTIES OF SILICA CEMENT1

A thorough study has been made of the effect of size of grain upon the softening point and linear change of silica cements prepared in the laboratory. The ratio of grain sizes in a cement of constant chemical composition has a distinct effect upon the softening point. The linear change after heating to 110°C and 1300°C was not appreciably affected by variation in grain size. From data obtained by testing a large number of commercial cements it is concluded that, owing to variations in clay content, screen analyses are not definitely related to rate of settle or to softening point. A method for determining “rate of settle” is described.     

COMPARISON OF METHODS OF ANALYSIS OF GYPSUM1

The different analytical methods proposed for the evaluation of gypsum have been subjected to an experimental test. A combination method, consisting of a fusion with KHCO₃ and determination of CaO by KMnO₄ titration, the SO₃ by Andrews method of titration of BaCrO₄ has been found to give very reliable results with the least consumption of time.     

MgSiF_6对铝硅酸溶胶凝胶化的影响及其机理

实验研究了ＭｇｓｉＦ６对铝硅酸溶胶凝胶化的影响，并用２７Ａｌ、２９Ｓｉ核磁共振和ＸＲＤ研究了铝硅酸溶胶－ＭｇＳｉＦ６凝胶的物相组成及Ａｌ、Ｓｉ在其中所处的结构状态。结果表明：在铝硅酸溶胶中加入ＭｇＳｉＦ６会导致Ａｌ３＋离子从溶胶胶粒中溶出，溶胶胶粒结构的破坏，从而引起溶胶胶粒中Ａｌ／Ｓｉ比和Ａｌ、Ｓｉ所处结构状态的变化。ＭｇＳｉＦ６与从溶胶胶粒溶出的Ａｌ３＋、Ｎａ＋离子作用形成水溶性很低的ＮａＭｇＡｌＦ６，从而降低了液相中Ａｌ３＋离子的浓度，减弱了Ａｌ３＋对溶胶的絮凝作用，同时使得铝硅酸溶胶－ＭｇＳｉＦ６系统的Ｎａ、Ｆ溶出率降低。